Vintage TMS2764 EPROMs acting strange...  Schrödinger's EPROM? - Page 1
Forum section: electronics / repair

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 05:42:52 am
content: I took two TMS2764 EPROMs out of a piece of equipment, erased them, and programmed them with the latest firmware (with a MiniPro programmer).So the weird thing is - it verifies 100% OK in the programmer... I am able to read the code out and compare on the PC, 100% the same. But the EPROMs don't work in the actual circuit!?!I tried with some Intel EPROMS instead and they work fine. All of the 7 TI EPROMs that I have are behaving the same way as described above...I am struggling to understand how the programmer can read the EPROMS, but the CPU in the equipment they came from cannot?!?

author: MK14
author_rank: Super Contributor
timestamp: February 12, 2021, 06:00:48 am
content: If it was a poor quality programmer, e.g. the proper programming voltages were too low, or not enough time was used, to properly program in the bits. I suppose, the programmer casually (relatively slowly) reading/verifying back the bits, might see the correct values.But a relatively high speed processor (slow, by today's processors), needing rapid from the EPROMS (slow by today's standards, probably) data accesses, might be responding too slowly, because the programming has been done too faintly.N.B. Above is speculation, there are other possibilities.Have you covered the EPROM windows ?Sometimes they can be sensitive to visible light, and stop working properly, without opaque labels on them. Ideal labels, seem to have aluminium (?) strips inside them, for near perfect no light leakage.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 12, 2021, 06:10:04 am
content: Maybe the burn profile is wrong, check datasheet vs programmer voltages? I've heard of programming them twice to really make sure the gates are charged fully, maybe try that.

author: MK14
author_rank: Super Contributor
timestamp: February 12, 2021, 06:19:28 am
content: Also, the access times can vary between different chips (datasheets). Are the 'new' ones fast enough ?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 08:19:09 am
content: The voltages and timing all checked out vs. the datasheet.I got them working by programming them multiple times with the same data, thanks for the ideas.Maybe these devices are just getting old and cranky? They are 30 - 40 years old, after all...They seem to behave more like analog than digital devices!

author: MK14
author_rank: Super Contributor
timestamp: February 12, 2021, 08:25:02 am
content: Quote from: SilverSolder on February 12, 2021, 08:19:09 amEPROMS can be quirky/fussy, in all sorts of ways.My understanding, is they are actually ANALOGUE inside (with digital decoding for the addressing and input/outputs, obviously), with op-amps/comparators, performing the actual readings. There are probably internal reference voltages, for logic '0' and '1', and the comparators then select the most appropriate logic level, based on the analogue voltage from the selected EPROM memory cell.Similar to modern flash memory, but without the electronic 'erase' capabilities. So they use UV light, instead.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 12, 2021, 08:31:49 am
content: hi,it happened to me with AT24C01 eep once before 2000, the programmer said "program ok, verify ok", the eep didn't work in the machine.well, the programmer was right, the machine was right.why? cause programming algo for at24c01 (in fact, atmel and xilinx versions of 24c01 are differents from st24c01 mainstream eep's) is different for ST24C01 algo.you can check datasheetstest with some really serious programmer and we will see after, minipro is for hobby, maybe it' somehow the same problem

author: CJay
author_rank: Super Contributor
timestamp: February 12, 2021, 08:43:11 am
content: Quote from: SilverSolder on February 12, 2021, 05:42:52 amSounds like they needed a slower programming cycle, I'm curious to know if you tried verifying them again after they'd failed in circuit?

author: MK14
author_rank: Super Contributor
timestamp: February 12, 2021, 08:50:39 am
content: Quote from: CJay on February 12, 2021, 08:43:11 amMy partly vague recollection, was that there was essentially 2 extremes of programming algorithms for EPROMS.The original VERY SLOW, but reliable/robust program every memory location, properly. It was something huge like 50mS per location, hence rather/very slow.Various 'fast' algorithms, that did something on the lines of programming a location for 1mS, and immediately reading it back. If it was correct, moving to the next byte, if not, programming it for another 1mS, until it is correct, then moving on and doing that for all the bytes that need programming.So, the wrong algorithm (or a poor quality programmer), wouldn't work out too good.Also, maybe the chips have deteriorated over the decades ?

author: MK14
author_rank: Super Contributor
timestamp: February 12, 2021, 09:06:37 am
content: Quote from: perieanuo on February 12, 2021, 08:31:49 amA while ago, I was reading an article, about the differences between cheap/hobby programmers, and very expensive professional/production ones. I think it was for PIC chips.It was something like the professional/production programmer, used an accurate 5.5V to program, then an accurate 4.5V to read the verification data back, or something like that. To ensure the programming would be robust/reliable for 10+ years, and at differing ambient temperatures, etc etc.So the cheaper hobbyist equipment, can appear to 'work'. But will the device it just programmed, still be working in 10+ years time and/or at min or max allowable operating temperatures, supply voltages, etc.

author: CJay
author_rank: Super Contributor
timestamp: February 12, 2021, 09:30:40 am
content: Quote from: MK14 on February 12, 2021, 08:50:39 amFrom memory some were faster than 1mS as well, they'd hammer the cells with charge until it read correctly then 'overburn' it with a few more for good measure and move on to the next byte, tended to be only lower voltage devices and was generally pretty reliable but I did have a few occasions with second hand chips where it wouldn't be 100% reliable, I rarely ever had a problem with slow programming that I couldn't attribute to a faulty part but some second hand chips (Seem to recall Fujitsu were the worst offenders) would pretend to be erased and then suddenly have remnants of their old contents or just refuse to take new data.

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 10:14:10 am
content: Quote from: SilverSolder on February 12, 2021, 08:19:09 amWell, yeah... Theyaremore like analog devices than digital.

author: Gyro
author_rank: Super Contributor
timestamp: February 12, 2021, 11:05:09 am
content: I do vaguely remember that there was something a bit different about TMS27xx devices. I can't remember what it was - different Vpp / more programming failures, /OE access time or something, but there wassomereason that we used to dodge them when grabbing blank devices from the communal eraser tray. Best to find the specific datasheet and check it very carefully against something like a Hitachi or Fujitsu. Sorry, it really is a very vague memory.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 12, 2021, 12:45:27 pm
content: Quote from: MK14 on February 12, 2021, 09:06:37 amI used in the past programmers better than tl866, like wellon one if I recall right, then smartprog ii and now bategoI recall I had devices bad programmed with wellon, including eproms, then erased and succesful done with smartprogfor me, it's either the programmer either the algorithm, like I said first time.things like tl866 have some flash/eep/eproms in the list they don't really get written with the correct algo specs from memory datasheet imho (but they report verify done)

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 02:41:29 pm
content: Quote from: CJay on February 12, 2021, 08:43:11 amYes, I did try that - they verified 100% directly after failing in circuit! - Perhaps the programmer loads the lines less than the (35 year old) circuit?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 02:55:02 pm
content: Quote from: perieanuo on February 12, 2021, 12:45:27 pmNot only did the programmer (TL866CS - supports 21V) report verify done. I was able to put one of the programmed chips into it, read it into a file on the PC, and compare that file with the original... 100% match.So, it seems that perhaps the amount of loading on the data bus is different on a modern programmer made with modern ICs, compared with the loading that the EPROM sees in the actual circuit? So a "marginal" EPROM works fine when not loaded too much, but fails when some older circuits need more current on the data bus, or some other signal lines?The programming algo for the EPROM appears to be mostly in line with the data sheet:Here are the settings chosen by the programmer:If I try to increase Vdd (write) to 6V as implied by the data sheet, the programming fails immediately with corrupt data, and the chip has to be erased and "done over". It also fails at 5.5V - so I am wondering if this data sheet may have been superceded...In any event, all 6 EPROMs are still working fine in the actual circuits this morning.I did not have these problems with Intel EPROMs, I may source some more Intel ones if any of the TMS ones lose their data...

author: wraper
author_rank: Unknown
timestamp: February 12, 2021, 02:59:45 pm
content: Those EPROMs might be simply faulty/degraded due to their age. There was a thread discussing EPROM outputting some weird reduced high level voltage occasionally.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 03:01:26 pm
content: Quote from: wraper on February 12, 2021, 02:59:45 pmYes, I think they have gone half deaf. But by shouting at them long enough, they got the message!

author: CaptDon
author_rank: Super Contributor
timestamp: February 12, 2021, 03:01:42 pm
content: I have a hand built programmer and I use the full program time allowed per byte. It takes MUCH longer to program but they will always work and retain their data through the worst conditions.

author: wraper
author_rank: Unknown
timestamp: February 12, 2021, 03:03:36 pm
content: Also it's not clear what the circuit is. Maybe it needs faster of slower EPROM to work properly.QuoteSo did it work properly before with the same EPROMs?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 03:06:02 pm
content: Quote from: wraper on February 12, 2021, 03:03:36 pmIt is an 8080 CPU, it runs at a leisurely pace and can add wait states if necessary. These EPROMS are much faster than it needs, so there will be no waits.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 03:09:39 pm
content: Quote from: wraper on February 12, 2021, 03:03:36 pmYes, exactly. The recently purchased "new old stock" TMS2764 chips behave exactly the same way as the TMS2764 devices that were in the device originally.All of them respond to being "shouted at" repeatedly. I've programmed 6 of them now, each one repeated 8x over for good measure... they appear to work reliably after such a therapy session.

author: CaptDon
author_rank: Super Contributor
timestamp: February 12, 2021, 05:12:01 pm
content: I did my programming using just one cycle of maximum allowable length per address/byte. I think the old 2716's were 60ms max, apprx 2 minutes to program, and the 2732/2532 max was around 50ms or nearly 4 minutes to fully program. I think I was hitting my 2764 27C64 at around 25ms single pulse. Never killed one and never had it read or function incorrectly. They have been in several systems for over a decade and still running. I never liked the 'Program it just enough and move on', my stuff was way to critical in its mission.

author: james_s
author_rank: Super Contributor
timestamp: February 12, 2021, 05:19:25 pm
content: I've encountered several situations where a programmer would read an EPROM fine but it wouldn't work in the actual circuit. In one case the ROM in a vintage terminal got corrupted and I was able to read it and then re-write the exact same chip and reinstall and it fixed the problem. Access time can also be an issue and they seem to get slower some time after programming. I once repaired a vintage arcade game board and it looked fine but then after about 30 minutes or so increasing amounts of noise started to show up in the sprite graphics. Eventually I figured out the EPROMs I used were too slow, they would work fine fresh off the programmer but after some time they showed lots of random pixel noise.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 05:35:46 pm
content: Quote from: CaptDon on February 12, 2021, 05:12:01 pmThe max on this particular programmer is 1ms, it doesn't allow any higher setting as far as I can tell. So, repeated runs is the only way to increase the exposure time with this programmer. At least it is able to do that, so there is a solution!

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 05:38:58 pm
content: Quote from: james_s on February 12, 2021, 05:19:25 pmI am learning a lot here... I somehow expected EPROMs to be much more... digital? ... in their behaviour, than they actually are. I guess there was limits to how much they could make out of the circuitry back in the day - clearly, it is not great that the output depends on how "hard" it has been programmed!Clearly, though, if you program them "hard enough" they are obviously able to run for decades with no problem.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 12, 2021, 05:50:53 pm
content: well, I will stop here, but I tell again the story: with some (delicate) devices you need:1. to erase thoroughly the eprom2. to programm it with some serious programmerskipping any of these gets you into 'verify is ok but it doesn't work'

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 06:00:33 pm
content: Quote from: SilverSolder on February 12, 2021, 02:55:02 pmFrom how I read that datasheet, it looks like it should be writing in 1ms bursts until it reads the correct data back (up to 15 times max), then once it gets a good read it is supposed to do a monster "Final Pulse" blast of between 4 and 60ms duration to really set it in stone. Does anyone have any idea if the TL866 is actually doing anything even remotely resembling that?I would expect it to have some settings in that "IC Config Information" where you could specify things like the number of pulse tries or timeout for the prime pulses and most importantly some sort of variable where you can specify what kind of actual final write blast it actually programs with once it figure out how hard to "blast it" by doing the X prime pulses sequence first. In this case the final write cycle looks like it is supposed to be 4 times as long as whatever it took to prime that particular memory location. Is the TL866 actually doing that, what is the actual cycle?

author: mon2
author_rank: Frequent Contributor
timestamp: February 12, 2021, 06:10:35 pm
content: Vintage? Ok, getting old. Need to work on that time machine soon...Forget these EPROMs which are UV-erasable. Love the smell of the ozone after an erasing, not.Replace them with the following and relatively more modern versions that are electrically erasable:https://www.microchip.com/wwwproducts/en/AT28C64BDo compare the pinout but these also work @ 5v Vcc. Have in the past done the same for old farm equipment brought to our shop - we replaced the old UV devices with similar electrically erasable type.Guessing that the read timing is flaky on your TI devices vs. Intel. In either case, you have a realistic work around.Chime back if you need more details but believe it should be a drop in replacement (after you program the firmware).

author: iMo
author_rank: Super Contributor
timestamp: February 12, 2021, 06:43:10 pm
content: Schrödinger's..Btw, you mess with 7 pieces of them in your equipment- do you insert them back into the sockets in the right order?Otherwise they should work ok when the programmer shows data were written ok..

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 06:56:59 pm
content: Quote from: drussell on February 12, 2021, 06:00:33 pmWhen you choose the manufacturer and chip in the application that comes with the programmer, you are (behind the scenes) also selecting the programming algorithm. I'm not sure if it is possible to edit those algorithms or define your own... I'm not familiar enough with the application (which actually seems pretty good, and it supports and amazing number of different devices).Just looking at how it behaves while it is programming, it is definitely "working" on each byte, the total time taken is a lot less if the chip is already programmed (so it needs less repeating cycles, presumably).

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 06:59:24 pm
content: Quote from: perieanuo on February 12, 2021, 05:50:53 pmI believe you are right - any ideas for a "serious" programmer that isn't also a boat anchor, like most programmers from that era seem to be?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 07:00:55 pm
content: Quote from: imo on February 12, 2021, 06:43:10 pmYes, I am old enough to know to eliminate my own stupidity most of the time!Don't forget - the equipment is back up and working now, but I am worried that the EPROMs will start to drop bits soon...

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 07:16:06 pm
content: Quote from: SilverSolder on February 12, 2021, 06:56:59 pmOh, I know... That's what I'm just wondering, if their main database actually has the correct parameters set for the correct algorithm for this chip, since it does not display any information about what it is going to attempt to do other than those limited voltage selections, right? With so many individual parts to try to keep track of, surely there are some errors in the specifics for some chips here and ther, and certain variants of individual parts might need some tweaking to be "perfect" and potentially other even more random things like trying to work with potentially aging vintage parts.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 07:45:50 pm
content: Quote from: drussell on February 12, 2021, 07:16:06 pmObviously, the algorithm could - at least - be improved to the point that I am achieving manually!The algorithm that is there may work with the "sunny day scenario" of a fresh EPROM that ends up in a circuit that doesn't load its signalling pins. But it may not be 'brutal' enough to program an ageing EPROM to the point where it can cope with being loaded down by the bus of an equally ageing host circuit...Also, it seems it matters what make of EPROM it is. The Intel EPROMS that I reprogrammed caused zero issues, they behaved as expected at all times. These TMS ones, on the other hand... there is something going on there. (As a hopeful workaround, I have ordered some more Intel EPROMS to see if the good luck with that brand continues!)I'll take a look at the application that came with the burner and see if the algorithms are defined in a separate file, or something lucky like that...

author: mon2
author_rank: Frequent Contributor
timestamp: February 12, 2021, 08:26:33 pm
content: Confused here, why source EOL UV erasable Eproms from some pulled out equipment when you can order fresh replacements with much more advanced technology?Personally would review the Microchip 2864 Eproms to replace these dinosaurs.

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 08:38:16 pm
content: Quote from: SilverSolder on February 12, 2021, 07:45:50 pmWell the TI and Intel versions of an 8kx8 2764 are totally different internally electrically, aren't they? I though the programming voltage on the TIs were way higher and they used a totally different recommended write sequence?... Maybe I'm misremembering. Oh, this brings back memories...hahahaQuoteIt would be nice if it were in at least a semi-transparent format, but that author is fond of at least weak obfuscation on pretty much everything.

author: james_s
author_rank: Super Contributor
timestamp: February 12, 2021, 08:53:58 pm
content: Quote from: mon2 on February 12, 2021, 08:26:33 pmWhy not reuse existing parts if you have them? It seems silly to buy new parts if you already have something on hand that will work. Anything that uses parallel EPROMs is already a technological dinosaur anyway. What advantage would a 2864 offer in this application?

author: james_s
author_rank: Super Contributor
timestamp: February 12, 2021, 08:57:14 pm
content: Quote from: SilverSolder on February 12, 2021, 05:38:58 pmThe storage of bits is accomplished by way of stored electrical charges, they are used to store digital data but they are really quite analog internally. The line between digital and analog is blurry at times, especially when it comes to data storage and transmission.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 08:59:30 pm
content: Quote from: mon2 on February 12, 2021, 08:26:33 pmI had no idea there were modern mammal replacements for my growing Jurassic Park of EPROMs!Are the 2864 EPROMs drop-in replacements for the 2764 family?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 09:01:09 pm
content: Quote from: james_s on February 12, 2021, 08:57:14 pmModern chips are better at arriving at a clear 1 or 0 solution, though - I can't remember dealing with a chip that seems to think 0.5 is a valid answer in the digital world!Let me see how my setup gets on with the Intel chips from that era - or SEEQ, or any of the other brands. I think the glass topped chips are kind of cool, that's a good enough reason to use them...

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 09:07:00 pm
content: Quote from: drussell on February 12, 2021, 08:38:16 pmYou are right, the algorithms are in a binary format and quite obscure. It is best to view that application as a black box...

author: asis
author_rank: Frequent Contributor
timestamp: February 12, 2021, 10:04:12 pm
content: Hi,If I were you, I would pre-irradiate the chip with ultraviolet light (longer).Then I read it with a programmer in pitching / swing Vcc +/- 10% mode to detect holes in the dump (FF),that is, it rejected/defects. And only then I wrote the data to the chip.Moreover, after writing, I would perform verification several times in read mode Vcc +/- 10%.I've never had such problems with good programmers.In addition, UV EPROMs are quite reliable and less vulnerable to power surges.

author: mon2
author_rank: Frequent Contributor
timestamp: February 12, 2021, 11:19:24 pm
content: I think you have some options. Yes, the AT28C64 can be used to replace the original.Mouser has stock of the Microchip (former Atmel series):https://www.mouser.ca/ProductDetail/Microchip-Technology-Atmel/AT28C64B-15PU/?qs=2VKgqYuc3OvipbcAuBcLow%3D%3Dpn: AT28C64B-15PU (150 ns access)Confirm that your programmer can support this device as it is a standard ('low voltage' - not a high Vpp requiring product) and proceed to load up your code for immediate testing.The pinout matches for each. Just be sure that you do not attempt to program the Microchip device with the TMS configuration otherwise the Pin # 1 will be faced with the high Vpp value of 21V-25v.

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2021, 05:17:45 am
content: Quote from: SilverSolder on February 12, 2021, 09:01:09 pmIf you run the modern chips properly within their specs they are, but even modern stuff can get confused if you set it up improperly or try to run it outside of its rated speed range. The only reason modern storage seems so clearcut is that it contains all kinds of internal intelligence that hides a lot of the gory details from you. An old fashioned EPROM doesn't have any kind of internal programming circuitry so all of the funky voltages and critical timing has to be done by the programmer which has to be familiar with the specific EPROM you're using.The "glass" window is fused quartz, it has to be transmissive to shortwave UV needed to erase the chips.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 13, 2021, 06:12:23 am
content: Quote from: james_s on February 13, 2021, 05:17:45 amI am going to persevere with the old ones - I am going to try some more Intel branded ones since they seem to work better with my entry level programmer, and - given how they work - it seems entirely reasonable that some brands will work better than others if the programmer has limitations. I figure it is cheaper to try a few different brands of chip than getting a "serious" programmer, which I won't use enough to justify.I am also going to try some of the more modern EEPROMs, just for fun. They are probably easier for a "bad" programmer to handle.

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2021, 07:36:59 am
content: I use a TL866, it's rare that I find an EPROM that it won't program properly.

author: m k
author_rank: Super Contributor
timestamp: February 13, 2021, 10:19:01 am
content: I remember a case where I changed away from Intel Fast with Intel chip.That must be with an old ISA board programmer since my MiniPro seems to have max time as 1ms.That is then also a long ago and so chips were not very old.Maybe I remember it wrongly and chips were not Intel and so didn't support Intel Fast.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 13, 2021, 02:54:59 pm
content: Quote from: james_s on February 13, 2021, 07:36:59 amI have 7 of them, LOL. Beginner's luck!Have you ever tried the TMS2764 on yours?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 13, 2021, 02:59:18 pm
content: Success?As an update to this thread, I think the suggestion of programming the TMS2764 EPROM multiple times with the TL866CS appears to have worked.Basically, I (re)programmed each EPROM a total of 8x in succession. (4x was not enough....)They have now been burn-in tested in the target circuits for 36 hours, and appear to be working.

author: m k
author_rank: Super Contributor
timestamp: February 14, 2021, 01:02:51 pm
content: One other recollection is that when dealing with spare EPROMs, if there were options, those bulkier window area ones were thrown away.Next step was to put slow ones to different drawer.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 14, 2021, 04:30:48 pm
content: I don't think the "burn" is completely good the way I did it - one of the meters started only on the second attempt this morning, which I have never seen before...I am awaiting some Intel chips now, which seemed to work better with the TL866CS programmer.Getting a more serious programmer is another option, but I'm loathe to use the $$ and space for a device I use so rarely...

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 14, 2021, 05:28:09 pm
content: Quote from: SilverSolder on February 12, 2021, 06:59:24 pmI can vouch for smartprog ii (or other elnec programmer that supports what you need), batronix, and from cheap ones, maybe wellon. I guarantee for those cause I extensively used those 3 brands, along with old cheap stuff like willem and others 'dyi' but for the last ones I guarantee nothing than hobby-like results

author: james_s
author_rank: Super Contributor
timestamp: February 14, 2021, 06:32:42 pm
content: I'm more inclined to think that your eproms are too slow for the application than any fault with the programmer. I've been using a TL866 for years and never experienced any issues with it. The only time I did run into a problem like you are seeing, I was trying to use a part with too low a speed grade. Also if you bought the chips on ebay you can't always trust that they are what they say they are, they could be slow parts that have been relabeled as faster ones.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 14, 2021, 09:37:36 pm
content: Quote from: james_s on February 14, 2021, 06:32:42 pmI took two TMS2764 eproms out of a working device, erased them, programmed them, and put them back in... and they didn't work (until "overprogrammed" 8x).I programmed two Intel EPROMS (just one time, no overprogramming) and they worked first time with no sign of any issues.I have a batch of five more TMS2764 eproms from eBay, they look exactly like the two original ones when inspected closely through the quartz window so I don't think they are fakes - and they behave like the originals too - they "work" after 8x overprogramming.The circuit these are going into is not speed critical - the original EPROMs are the slowest grade...Somehow, it looks like the combination of TL866 + TMS2764 is not working well for me.

author: Nusa
author_rank: Super Contributor
timestamp: February 14, 2021, 10:25:10 pm
content: Nope, not Shrodinger's EPROM. Might have been, but you looked and ruined it.

author: james_s
author_rank: Super Contributor
timestamp: February 15, 2021, 02:00:46 am
content: I wonder if there's a bug in the profile for that particular EPROM? Maybe there's a hardware fault in the programmer. Have you tried measuring the programming voltage? It would be worth verifying that's going to the correct voltage during the programming process. You might also try connecting an external power supply, I've found a rare few EPROMs needed more power for programming than the USB port can supply.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 02:36:32 am
content: I agree that the best hypothesis is that the programmer struggles to reach the correct voltage, possibly because the chip uses quite a bit of current at that voltage.I programmed some Intel D2764-4 chips, which need 12V to program, and the programmer had no problem with that.I note that the currently sold version of the programmer (TL866II) doesn't support the higher voltage chips at all... maybe they know it was a stretch on the old one?...I might connect the scope and take a look at the waveforms on some of the pins, to see if the theory will withstand contact with reality!

author: retiredfeline
author_rank: Frequent Contributor
timestamp: February 15, 2021, 02:44:24 am
content: Quote from: SilverSolder on February 15, 2021, 02:36:32 amI think they just didn't want to support the higher voltages for a dwindling number of chips. So I'm hanging onto my old model.I doubt if the current is an issue. Boost converters are quite efficient and can supply quite a bit of current. I think the TI chips just aged faster than the Intel ones.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 03:58:36 am
content: I had nothing better to do, so I hooked up the scope and took a look...It seems the programmer is not able to achieve the required 21V on these chips...We are looking at the "gap" between programming events where Vpp falls down towards (but doesn't hit) ground.19.38 volts is as good as it gets....I suspect the new version of the programmer has the same power supply, but a more realistic spec of 18V max!

author: MK14
author_rank: Super Contributor
timestamp: February 15, 2021, 04:29:53 am
content: Quote from: SilverSolder on February 15, 2021, 03:58:36 amSo, it seems the (not) just about good enough programmer, is suffering from at least around 3 or 4 somewhat serious faults.As you just found out, the programming voltage collapses (my understanding is, this is VERY important, otherwise the charge can't properly/fully break into the floating gate (cell bit, whatever it's called), through the insulation layer. Even an apparently small drop in voltage, can be enough to badly hinder the programming process, the datasheets seem to stress the importance of having enough voltage).Also, it should be reporting a 'bad programming' when the voltage collapses like that (ideally).The so called 'verification' process on that programmer, doesn't seem to be very good. It should be detecting the faulty/failed programming attempts, like a professional/production programmer, hopefully would.Where apparently high quality verification mechanisms are discussed, they seem to have sophisticated hardware systems, that can purposely/accurately, raise and drop the Vcc (and maybe other voltages), in order to help the accuracy of the verification. I don't know (so speculation), but maybe decent verification systems, also check that the access times are reasonable, as well. Otherwise the 'charge' maybe too weak to work reliably and/or longer term. As you seem to have just experienced.

author: MK14
author_rank: Super Contributor
timestamp: February 15, 2021, 05:12:56 am
content: Assuming the schematics of your programmer are available, you have the will, and it is not too difficult to open up etc. Maybe your existing programmer can be fixed ?A too weak power supply, doesn't sound too difficult, especially for some of the SMPS (assuming it is that type) experts on here.As other(s) have said, is it simply that a USB power source, is just too weak a way, to power it ?Offhand, I'd have thought there would be enough power 500mA/5V, to be ok, but maybe not, as I don't know the full specifications of what is needed. I suppose it is not going to be able to make 21V at much current, from a weak USB supply, especially if other parts of the programmer, are also going to need power.

author: james_s
author_rank: Super Contributor
timestamp: February 15, 2021, 05:16:23 am
content: It's unfortunate that the newer version doesn't support those chips at all, that makes it inferior to the original, at least for me, I fairly often find myself programming EPROMs that need more than 12V.Is that with a separate power supply plugged into the programmer? If not you should try that, USB is limited to 500mA so some devices require external power connected to the barrel jack to work properly.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 05:58:10 am
content: There is no barrel jack on a TL866, unfortunately.I think it is likely a fine programmer for most things, just not some of these older high voltage (at high current!) parts.I've ordered another programmer to fill the gaps that TL866 doesn't do well - let's see how that works out...https://www.batronix.com/shop/programmer/BX32P/index.html

author: retiredfeline
author_rank: Frequent Contributor
timestamp: February 15, 2021, 06:11:10 am
content: Quote from: SilverSolder on February 15, 2021, 03:58:36 amInteresting, thanks. Maybe I should try your multiple burn trick on some GALs I'm having problems with. Isn't the program pin supposed to drop from Vpp to Vdd, not GND? Or am I thinking of other chips?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 06:20:17 am
content: Quote from: MK14 on February 15, 2021, 04:29:53 amThe biggest Batronix model seems to do all of the above. This level of performance doesn't come cheap... but not as bad as one might have thought either - if I was going to be doing this for business purposes, that's the kind of thing I'd go for, given what I know now!

author: asis
author_rank: Frequent Contributor
timestamp: February 15, 2021, 06:24:06 am
content: All good programmers have their own mains power supply, which guarantees work with the 27XX - series.Elnec made a budget programmer BeeProg2C (from the word Cost) and HONESTLY pointed out this in the specification, offering topurchase an optional embedded PSU to support the 27XX.Advantech has never given up on a full-fledged on-board PSU.I don't know about Xeltek.What do you want from a progammer that is powered only by USB 5V.Why praise a product with an problem.Everything is obvious.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 06:25:50 am
content: Quote from: retiredfeline on February 15, 2021, 06:11:10 amThe multiple burn trick isn't working - after a couple of days, the EPROMs programmed this way are starting to lose their programming, some of the devices they were installed in are behaving erratically... basically, the low voltage seems to be too low to program them properly, even if done repeatedly.Regarding the program pin drop, I am a total n00b here, so I don't really know... The waveform seems to hit neither Vdd nor GND, so I'm not sure what this particular programmer is targeting!

author: retiredfeline
author_rank: Frequent Contributor
timestamp: February 15, 2021, 06:38:49 am
content: Quote from: SilverSolder on February 15, 2021, 06:25:50 amWhich direction are the erroneous bits going, towards ones? Wouldn't that point to inability to retain charge in an old EPROM?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 06:48:02 am
content: Quote from: asis on February 15, 2021, 06:24:06 amI think it should be possible to work from 5V / 500mA, but the programmer might have to work more slowly, breathing deep before each byte programmed, if you see what I mean (i.e. store up energy for use during a single byte cycle).QuoteThey messed up, for sure, by speccing it for 21V.The TL866CS/A model has both good and bad sides. The bad side is that it obviously cannot do the high voltage chips that it claims (at least not without some external help). You can see how they could get fooled, though, as it was able to read back the chip - everything looked good. You actually have to know a lot about this "dinosaur tech" to understand why it isn't working as it should - probably young guys developed this, and fell into a trap for young players?The good side is that it seems reliable on lower voltage chips. Another good side is that it is inexpensive. And supports a large number of devices (even if you eliminate the high voltage ones from the list).It looks like the manufacturer has realized this, and is now selling it with a more honest specification (and a new model name), and they have pulled back all the existing stock of the older models.I'm going to keep my TL866 and just use it within its limitations, and see if Batronix are better at getting the job done at higher voltages.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 06:51:56 am
content: Quote from: retiredfeline on February 15, 2021, 06:38:49 amI can't actually see which way they fail, because the programmer reads the data perfectly... it seems there is something about the timing and/or the loading of the bus in the target system that pushes the EPROM over the edge...Basically, programming devices with voltages that are not to spec is probably a good recipe for a lot of time wasting problems - life's too short, right? Keep in mind also, I have seven 21V EPROMs from different sources, and they all behave (fail) exactly the same way.

author: james_s
author_rank: Super Contributor
timestamp: February 15, 2021, 07:12:14 am
content: Well they didn't just make up an arbitrary number when they specified 21V as the required programming voltage, if you use a lower voltage it's hardly surprising that the chips do not program properly. EPROMs store data in the form of stored electrical charges, if the voltage is low then the stored charge is low, it will behave just like one that has faded over time. The programmer reads it much more slowly than the full operating speed it can support, this is a useful thing since it can let you properly read out an old EPROM that has faded. If you run any component outside of the specifications it should not be surprising when it doesn't work properly.

author: james_s
author_rank: Super Contributor
timestamp: February 15, 2021, 07:15:09 am
content: Quote from: SilverSolder on February 15, 2021, 05:58:10 amWow you're right, I just got mine out and checked. I must be losing my mind, guess I was thinking of the GQ4X or whatever that is that I borrowed from a friend a few times when I had to program a large EPROM that the TL866 doesn't support. I definitely had to plug that one in for the larger chips.

author: james_s
author_rank: Super Contributor
timestamp: February 15, 2021, 07:23:49 am
content: Quote from: asis on February 15, 2021, 06:24:06 amBecause all products have problems, and the best products are not always the best value. I have a TL866 that has served me well for quite a few years. Is it perfect? Of course not, it falls short in a few areas, one of which we are seeing here. Another is the software, it's full of Chinglish, bad enough that I've been tempted to offer to properly translate the strings for them just so I don't have to do it in my head every time I use it. It has the power deficiency discussed here. I still maintain that it's a good product, with certain limitations, it handles a LOT of parts, and it's a very compact little unit that will fit in a pocket and it's very affordable. If you know of a better option in the same price class, or even a whole 50% more then please do enlighten us, otherwise in the real world where budgets are finite and most people who need to burn a ROM here and there are not going to hit them, the TL866 is a very good option. Everybody knows that cheap stuff makes compromises and usually is not as good as expensive stuff, but the cheap stuff is affordable and sometimes the best product is the one you can afford to own that is good enough for at least most of your needs.

author: Moshly
author_rank: Regular Contributor
timestamp: February 15, 2021, 07:31:11 am
content: I have some NOS ST-2716's (never programed)I had to program them 3-5 times to get them to pass in my TOP2011 programmer.In circuit (Apple II clone) they failed.On scoping the data bus, I found they output the correct levels for only a short time and then they go crazy. (high frequency random noise)After more programing cycles they eventually worked (8-12 cycles per chip).I have not tested the clone since but it wouldn't surprise to find them flaky again.I've never had a problem programing 2764/27c64 in this programmer, I don't think any had a VPP over 12.5V tho.

author: retiredfeline
author_rank: Frequent Contributor
timestamp: February 15, 2021, 07:46:37 am
content: Quote from: SilverSolder on February 15, 2021, 06:51:56 amOk, thanks, I'll blacklist my TI 2764s then if they don't work.

author: asis
author_rank: Frequent Contributor
timestamp: February 15, 2021, 08:13:02 am
content: @SilverSolderI am glad that you understand this.The main thing is not to allow yourself to be misled despite such a large number of opinions.Once you have another programmer (no risk), open the TL866 and see what the 5V-> 12-> 21V converter is built on.You can try to power TL866 directly from PSU PC + 5V from MOLEX connector, bypassing + 5V USB circuit.Or from a laboratory PSU, with a reliable GND on the PC.At the moment, if you have a 27XX series with a large volume of 27128-27512 ... you can observe with a scopmeter how the Vpp drawdown occurs throughout the entire PROG cycle.And pay attention to the checksums when reading the chips.@ james_sI am not against all this diversity.Here you need to defeat a specific BUG associated with a power deficit.And as a mechanism for changing Vcc +/- 10% when reading (the same "power deficit") is used for validation.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 01:26:24 pm
content: The schematic has apparently been deduced by @Radioman, attached. It shows the power supply on the last page.It could be interesting to measure the voltage output in the power supply to see if it is getting drawn down.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 15, 2021, 01:48:17 pm
content: for cheap solution, someone already said this, just take pin-to-pin equivalent eeprom, flash the bin and you're up in 2 minsyep batronix, elnec etc. are not cheap, but as I said wellon is really afordable (vp598 or what you find in your area maybe less than 300usd) for a semi-pro programmer, I had one 10 years back, it was reliable with the delicate stuff

author: SilverSolder
author_rank: Super Contributor
timestamp: February 15, 2021, 02:01:45 pm
content: Quote from: perieanuo on February 15, 2021, 01:48:17 pmBatronix has a small model that claims to do the old EPROMs, it seems a relative bargain at EUR 159 if it is really "professional grade".I have ordered one of those, let's see how it performs. I like that it is small, similar to the TL866, so they can sleep together in the same box!https://www.batronix.com/shop/programmer/BX32P/index.htmlLet's see how that works out...

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 15, 2021, 02:44:35 pm
content: Quote from: SilverSolder on February 15, 2021, 02:01:45 pmglad to hear, it won't fail youand the support team is responsive, I had once some issue and they helped me same day or the day after

author: m k
author_rank: Super Contributor
timestamp: February 15, 2021, 06:40:41 pm
content: Quote from: Nusa on February 14, 2021, 10:25:10 pmPrecisely.It was Heisenberg's programmer.And Me dummy have thrown away an EW-704.(just found an old ISA included motherboard, SCSI is also there)

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 16, 2021, 06:21:36 am
content: and what's EW-704?

author: retiredfeline
author_rank: Frequent Contributor
timestamp: February 16, 2021, 06:34:31 am
content: Quote from: perieanuo on February 16, 2021, 06:21:36 amA very old EPROM programmer with an ISA card adapter, full length too, but only XT fingers. I had one. or was it the 701 with one chip socket, but gave it away because I had no more ISA card PCs.

author: mon2
author_rank: Frequent Contributor
timestamp: February 16, 2021, 08:43:28 pm
content: Quote from: perieanuo on February 15, 2021, 01:48:17 pmyep. 2 pages ago.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 16, 2021, 08:56:00 pm
content: I have ordered some EEPROMs to play with, as well.The quartz top chips are like tube amplifiers: cool, but expensive to own!

author: SilverSolder
author_rank: Super Contributor
timestamp: February 17, 2021, 04:24:57 am
content: Quote from: mon2 on February 16, 2021, 08:43:28 pmIf we were talking about one or two EPROMs in one single piece of equipment - you are 110% right, buying an EEPROM is a no brainer.But, here I have ~10 of these high voltage EPROMs, maybe more if you look inside some of the other boat anchors I like to play with. The 10 that I know about would cost ~$50 to replace with EEPROMs. The way I see it, those $50 can be subtracted from the price of a better programmer - one that may quickly solve other problems too, down the road. So, it doesn't seem a cloud cuckoo crazy idea to get a low cost programmer for the dino chips if you have "enough work for it to do" kind of thing.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 17, 2021, 04:36:22 am
content: I've replaced the 21V TI EPROMs with Intel 12.5V EPROMs in four different devices now, and they all seem solid.The TL866CS seems to have no problem programming the 12.5V Intel EPROMs, unlike the high voltage TI chips. The programming worked first time, and worked first time in the actual circuit as well.So, the TL866 can probably still be considered a useful programmer, as long as you realize that the spec for the new model (max 18V Vpp) actually applies to the older models too!

author: asis
author_rank: Frequent Contributor
timestamp: February 17, 2021, 07:20:34 am
content: There are many brands on the EBAY platform and at different prices.Advantech LabTool48XP (UXP).Dataman 48 (XP / UXP) - rebranding LT48 / Elnec.BK precision programmers 8xx-series - rebranding LT48 / Elnec.If you want LabTool48 (no letter) but no LV.The only significant drawback is that for universality (Elnec Xeltek) you have to pay a lot for adapters that are protected from counterfeiting (1-Wire chips Dallas / Microchip).Advantech - they also ask for a lot of money for upgrading 48XP to 48UXP, and then to support new chips, you need to buy a license for 2 years. I suspect that Xeltek has such a policy.You mentioned Batronix here. Are you sure you won't fall into the trap?Be carefull!https://www.eevblog.com/forum/reviews/new-beeprog-2-disappointment/msg285482/#msg285482https://habr.com/ru/post/320870/

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 17, 2021, 10:23:45 am
content: Quote from: SilverSolder on February 17, 2021, 04:36:22 amI expected this outcome, despite some people swearing tl866 is some high-end programmer, it's not, maybe it can be 'tuned' to respect VPP and maybe the algo you neededabout eeprom replacement, I meant if you had some eeproms hidden in your drawers, i have those from spare parts just for this type of situation.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 17, 2021, 10:26:31 am
content: Quote from: asis on February 17, 2021, 07:20:34 amhe ordered bx32, let's stick to the real case. i would bet for the bx48 (i have one it's ok) and the bx32 must be the stripped down version. sw is the same, hw almost the same, so i'm pretty sure he's gonna be satisfied

author: m k
author_rank: Super Contributor
timestamp: February 17, 2021, 12:04:51 pm
content: Where the oven part went, was it another thread.Back in the day the erasing part was more of a concern.My last eraser was a room size.Actually it was a room, an empty one with a meter wide UV-tube on the floor.Other down side was that the process was more than few times forgotten on.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 17, 2021, 02:22:20 pm
content: For the UV eraser, I looked for a used one but could only find very large devices that I didn't really want - I have enough boat anchors already!So I decided to try another product of Far Eastern minimalist engineering... So far, this one has erased all the chips reliably, and fast (the smallest time I tried is 20 minutes, it might be even faster). I would not use it in a professional environment, but it is reasonably small and light.The timer is mechanical, like an old fashioned kitchen timer - you twist it to "3" for 30 minutes, plus or minus quite a few %... and it gets on with its job.I haven't opened it up, because I don't want to scare myself... the whole box is of plastic so unlikely to be dangerous. I just use it and it doesn't cost much more than a UV bulb on its own!

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 17, 2021, 04:06:28 pm
content: i laughed cause i used the bulb inside (some kind of igniter) the 125w sodium light bulbs as UV source for erasing eproms, the tip was for an engineer born in 1945, it really worked and it was FREE (we called it "ram's testicule", ram being male sheep)i guess the igniter was generating ultraviolet in large quantity, the eproms were erased in 10-20 mins, with my watch as timer

author: asis
author_rank: Frequent Contributor
timestamp: February 17, 2021, 08:02:43 pm
content: (we called it "ram's testicule", ram being male sheep)Really - it seems....

author: m k
author_rank: Super Contributor
timestamp: February 18, 2021, 06:43:18 pm
content: Quote from: SilverSolder on February 17, 2021, 02:22:20 pmHackaday had even lighter approach, a single LED.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 18, 2021, 06:49:38 pm
content: I'd have to buy a UV LED and get it shipped - pretty soon you are at 50% of the price of the Chinese minimalist unit - I didn't think it was worth experimenting with.A wise boss once told me, "Never make yourself what we can affordably buy" - at home, you can add "unless you are doing it for fun or education"!

author: srb1954
author_rank: Super Contributor
timestamp: February 19, 2021, 01:16:19 am
content: Quote from: SilverSolder on February 17, 2021, 02:22:20 pmThat timer labelling is highly confusing! My first thought was that 6 mins is not enough to erase an EPROM. They could have made a little bit more effort and printed some zeros after the numbers.I would recommend that you earth the tray holding the EPROMs or otherwise provide for the discharge of any static build-up to prevent ESD damage to the EPROMs.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 03:00:06 am
content: Quote from: srb1954 on February 19, 2021, 01:16:19 amA lot of cost was cut out of manufacturing by not having to expend ink on the zeros - you are dealing with the cost cutting PROS here!Re the anti-static suggestion - is it enough to keep a conductive anti-static mat in the bottom of the tray so all the pins see the same potential? Or does it actually have to be grounded?

author: srb1954
author_rank: Super Contributor
timestamp: February 19, 2021, 04:04:25 am
content: Quote from: SilverSolder on February 19, 2021, 03:00:06 amYes, definitely use the conductive foam in the bottom of the tray.However, that doesn't totally protect the chips in all circumstances. If the tray is plastic pulling it out of the case could build a up a static charge and when you place an EPROM in the tray that static could discharge through the chip pins.You could mitigate this by always wearing a wrist strap and initially touching the foam to discharge any static buildup before picking up any EPROM but you are then you always have to remember to do this each time. Some form of earthing to the tray is good insurance against forgetting to meticulously follow ESD precautions

author: m k
author_rank: Super Contributor
timestamp: February 19, 2021, 12:36:08 pm
content: I've learned that most ESD buildups are from the floor and shoes.Vinyl floor and few steps are mostly guaranteed zap.Quote from: SilverSolder on February 19, 2021, 03:00:06 amIt clearly has an artistical aspect.See how unbalanced that 'ON' is.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 19, 2021, 03:11:08 pm
content: I cut out a piece of anti-static mat to fit the bottom of the drawer. There is no convenient ground or even neutral nearby, so I'll have to use the method of touching the mat before touching anything else...

author: SilverSolder
author_rank: Super Contributor
timestamp: February 20, 2021, 03:26:52 pm
content: I received the baby-Batronix programmer - it took 4 business days to deliver to USA from Germany.The unit looks and feels very solid, metal case, quality socket. It is a similar size to the TL866 programmer.The PC software is intuitive and I was up and running in a few minutes.I probed the Vpp voltage to see if Batronix gets closer to 21V than the TL866. It turns out that the Batronix gets pretty much spot on 21V:I then programmed two TMS2764 EPROMs and put them in the target device - TADAAAA! - worked first time - Winner, winner, chicken dinner!I also programmed two Intel 2764 21V versions. These chips are a lot slower to program than the TI chips. But the Batronix patiently chewed through it, and both worked first time in the target device.A nice thing about the Batronix software is that when you select an IC from its database, it lists every variation of the chip, including the different speed grades (TLS866 only lists the "root name" of the chip). This made it easier to be confident that you have selected the correct chip... I don't know if it makes any actual difference to the programming or verification phase, but it is definitely imaginable that it could make a difference (e.g. if the actual timing is being verified).The whole thing oozes quality and hits the nail on the head, is very compact and easy to store - I feel the EUR 159 was well spent.

author: perieanuo
author_rank: Frequent Contributor
timestamp: February 22, 2021, 08:12:48 am
content: I like also their alu caseI was pretty sure batronix get the job done, now you can sell the other oneglad to hear it's working

author: SilverSolder
author_rank: Super Contributor
timestamp: February 22, 2021, 02:14:46 pm
content: Quote from: perieanuo on February 22, 2021, 08:12:48 amThe TL866 supports so many more devices, I think both are keepers... they complement each other.When they are this small, it barely even qualifies as "Test Equipment Addiction"!

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 22, 2021, 10:12:28 pm
content: Just out of curiosity, how certain are we that this old TL866 is genuine? When and where was it bought? XGecu/Autoelectric claim there are a lot of unlicensed clones of the old A/CS models (which were discontinued in February 2018) out there, not meeting such a prominent specification that helped it become so popular seems like a clue.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 22, 2021, 10:52:15 pm
content: Quote from: BrokenYugo on February 22, 2021, 10:12:28 pmIt was bought several years ago - maybe 3 years ago, or even more, I cannot recall... around the time they first came out.I believe it is genuine, because I recently updated to the latest software and the update went smoothly. My understanding is that if you have a clone, it cannot be updated as the latest software detects clones and bricks them.

author: drussell
author_rank: Super Contributor
timestamp: February 23, 2021, 12:35:32 am
content: Did anyone ever mention these problems with this particular chip series to autoelec?There are really two possible options... Either it is basically just the programming voltage being dodgy (perhaps someone with a TL866II Plus that has modified their setup to inject proper 21V Vpp could elaborate?) or else (more likely in my opinion) they've just got it set in the setup info to use the totally wrong algorithm on these chips.If itismostly an error in the definitions, the original author dude might be able to "fix it" for this series of EPROMs.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 23, 2021, 01:04:21 am
content: Quote from: drussell on February 23, 2021, 12:35:32 amAs you can see from my scope shot earlier in this thread, the TL866CS does not even get close to the correct programming voltage. The spec for the chip says you have to be within 100mV of the target... TL866 is off by more than 1.5V!

author: drussell
author_rank: Super Contributor
timestamp: February 23, 2021, 01:29:22 am
content: Quote from: SilverSolder on February 23, 2021, 01:04:21 amRight, I know... I saw that...The question is whether or not it isjustthe programming voltage.Anyone with a Plus is already instructed that they will need to inject properVPP, it is just a question as to whether that is also the sole issue on the A and CS, for future reference...

author: SilverSolder
author_rank: Super Contributor
timestamp: February 23, 2021, 02:37:05 am
content: Quote from: drussell on February 23, 2021, 01:29:22 amAh, sorry, brain fart, too many things going on today... Even if you mod a TLS866II Plus, the 21V chips have all been removed from the database, I believe?

author: drussell
author_rank: Super Contributor
timestamp: February 23, 2021, 02:48:12 am
content: Quote from: SilverSolder on February 23, 2021, 02:37:05 amCan't you just use something like theminiprosoftware to do whatever you want?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 23, 2021, 03:14:29 am
content: I did look at it, but it looked to me like it was Linux only? ...for me personally, it just seemed like making the TL866 work correctly with 21V parts was too much of a project: fix the hardware, fix the software (i.e. run Linux and minipro or compile it for Windows), then take a chance on the algorithms...If I had to use the TL866 for whatever reason, I'd just go with the 12V equivalent parts which it handles just fine, or an EEPROM (not yet tested, got one on order), and be done with it. If you want to mod the TL866 just for fun, that's a different story obviously. Anything can be justified by the word "hobby"!

author: m k
author_rank: Super Contributor
timestamp: February 23, 2021, 07:34:57 pm
content: I have a Minipro V6.50 for Windows.Is there a serial number or other harware/software limitation?

author: SilverSolder
author_rank: Super Contributor
timestamp: February 23, 2021, 07:43:15 pm
content: I downloaded 6.85 from their web site, it works fine with the TL866CS. I don't know if the old software will work with the new TL866II series though. The software for the TL866II definitely doesn't work with the old hardware...

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 23, 2021, 08:21:10 pm
content: Quote from: drussell on February 23, 2021, 02:48:12 amAs I understand it the gotcha with the TL866 is most of the burn profile stuff is stored and handled inside the programmer without provision for custom profiles or slowly bit banging over the USB cable, at least with the factory firmware. The PC side just selects a chip, fills the buffer and tells it to burn. So to do 21V with a current TL866 you'd need to get lucky that an lower VPP profile otherwise lines up and level shift the VPP pin, as I recall the manual warns that you do that at your own risk, as the rest of the programmer isn't designed to handle it if the chip shorts out or whatever.If you really need cheap (cheaper than used pro grade universal programmers that one can still find software for) 21+V VPP programming it may be better to just build your own.I know some of the bigger EPROMs also have nearly pin compatible flash chips available cheap, e.g. SST39SF040, I've used that one successfully and nearly anything will program it, not sure on availability in smaller sizes.

author: asis
author_rank: Frequent Contributor
timestamp: February 24, 2021, 09:11:51 am
content: Hi,Here is a very simple and effective solution.https://www.dr-bosch.com/volker/umbau/index.html#VppAdapter

author: SilverSolder
author_rank: Super Contributor
timestamp: February 24, 2021, 01:23:29 pm
content: Quote from: asis on February 24, 2021, 09:11:51 amBasically, adding a current amplifier to the Vpp pin?

author: srb1954
author_rank: Super Contributor
timestamp: February 24, 2021, 09:45:28 pm
content: Quote from: SilverSolder on February 24, 2021, 01:23:29 pmNo, this circuit is actually a voltage switch which connects an external 25V Vpp supply in place of the 21V Vpp supply from the programmer, but only when the 21V Vpp is applied to the EPROM.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 24, 2021, 10:21:34 pm
content: Quote from: srb1954 on February 24, 2021, 09:45:28 pmAh, I see, he is actually programming 25V EPROMs... I didn't know they even existed, I thought 21V was the max.That adaptor is actually needed even for 21V EPROMs, since we know that the TL866 power supply is too weak to even get to 21V under load.... would that schematic work at 21V too? I suspect it might not - you might need to load the TL866 down with a resistor or something, to lower its output voltage, or re-design this circuit in some other way.

author: drussell
author_rank: Super Contributor
timestamp: February 24, 2021, 10:48:43 pm
content: You can just try injectingVPPdirectly to the pin on the chip, bypassing the TL866xx altogether:https://pinside.com/pinball/forum/topic/program-21v-25v-roms-in-lower-voltage-programmers

author: SilverSolder
author_rank: Super Contributor
timestamp: February 25, 2021, 12:20:30 am
content: I can see this working on TL866CS, but are the relevant chips still in the database for TL866ii ?

author: drussell
author_rank: Super Contributor
timestamp: February 25, 2021, 12:27:47 am
content: Quote from: SilverSolder on February 25, 2021, 12:20:30 amThe OP in the above referenced pinball forum was using a TL866II Plus.His first post states he tried to purchase a CS mainly for the higher voltage capability but since it was discontinued, was shipped a II+ instead.I thought it was well known that on these programmers you can inject your ownVPPas necessary for a workaround, I'm sure it is buried way, way back in that geinormous TL866 thread here on EEVblog.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 25, 2021, 02:40:07 am
content: Quote from: drussell on February 25, 2021, 12:27:47 amI downloaded the application for the TL866ii and had a look... The chips from the older model appear to still be in its list of supported devices in the new software, so they haven't been removed. Instead, what happens when you select one of them, is that the Vpp dropdown now says "18V" where it said "21V" before (but couldn't actually deliver).Looks like it is indeed possible and worth a try to use the TL866ii with a higher voltage adapter.

author: srb1954
author_rank: Super Contributor
timestamp: February 25, 2021, 08:58:44 am
content: Quote from: SilverSolder on February 24, 2021, 10:21:34 pmThe adaptor circuit may need a minor modification if the programmer is struggling to even provide 21V Vpp. Zener diode ZD1 should be reduced to 15V.Be sure to adjust the auxiliary supply to the correct Vpp voltage before starting programming. Setting a current limit on the auxiliary supply to around 100-200mA is also recommended to prevent damage to the programmer if the EPROM is bad.

author: srb1954
author_rank: Super Contributor
timestamp: February 25, 2021, 09:04:27 am
content: Quote from: drussell on February 24, 2021, 10:48:43 pmYes, but check the datasheet for the chip first and disconnect the Vpp pin from the programmer to prevent excessive voltages feeding back and damaging the programmer.Some of the earlier EPROMs require the Vpp line to be pulsed during the programming cycle. Others require that the Vpp line be reset to 5V during the verify cycle

author: sideburn
author_rank: Regular Contributor
timestamp: March 30, 2023, 06:25:12 pm
content: Hi all, I am having issues as well programming a TMS2764 on a TL866 II Plus programmer.It passes a Blank Check and can do a read but programming it fails every time.I can program a TMS27C64 without any issues just no the 2764...Was it confirmed that the issue is with this programmer and voltage?

author: Bud
author_rank: Super Contributor
timestamp: March 31, 2023, 05:33:27 am
content: TMS2764 need 21V programming voltage. TL866 ii plus only supports 18V max.