Conversion Tektronix TDS500 to TDS700 color oscilloscope - Page 1
Forum section: electronics / repair

author: zxase258
author_rank: Contributor
timestamp: February 02, 2018, 04:11:33 pm
content: In model TDS500B/C/D has been successfully tested.TDS500 and 700 series, in the same model, they have the same firmware and acquisition system, and similar processor board.Only need to add and change some components, you can change TDS500 series to TDS700 series.Before you upgrade, you should first install the color LCD monitor via the VGA out connector.(A similar project (Simmconn Labs) to this topic, he uses FPGA reads display memory, and "color" the data. This solution is too complicated and expensive.)TDS520B -> TDS724ATDS540B -> TDS754ATDS520C -> TDS724CTDS540C -> TDS754CTDS580C -> TDS784CTDS520D -> TDS724DTDS540D -> TDS754DTDS580D -> TDS784DFor TDS500B series(All changes are on the processor board).remove:R12(model ID) R151 & R152 & R153replace:U251 74F04 to U250install:U837 & U835 & U836 & U834 TC528257J-70 Video RAMFor TDS500C/D series(All changes are on the processor board).It has been a long time since I finished this work. I have forgotten which resistors I changed (for the model ID).The following two pictures are used to compare their differences, please try it yourself.replace:U251 74F04 to U250install:U834 & U835 & U836 & U837 TC528257J-70 or M548263-60J Video RAMSoldering SOJ packages is a bit difficult, make sure they are soldered reliably. Otherwise there will be a vertical line or flashing display.enjoy it.

author: Jwalling
author_rank: Unknown
timestamp: February 02, 2018, 08:44:08 pm
content: I always knew this was possible, but I never attempted it as it was way too much work given what these are worth now!You sir, get a high-five!If your scope has an acquisition raw board (700C/D and 500C/D I think) that only has 64Kb SRAMs and that's capable of using 1Mb SRAMS, your next mission could be to replace all the memory and get option 2M!

author: chihaxinh
author_rank: Regular Contributor
timestamp: February 05, 2018, 08:48:03 am
content: Hi zxase258I have one osc 520B like you . Scope have error Display and can't complate boot , can you share me your firmware of TDS 520B ?And when hacking mod 520B to 724A only replace position resistor ?Thank so much !Nam Nguyen Hai

author: zxase258
author_rank: Contributor
timestamp: February 12, 2018, 10:30:18 am
content: Sorry, TDS520B transformation completed in 2015, at that time I do not know the firmware can be backed up. Later this scope was sold by me.Of course, in my experience, the oscilloscope's firmware is rarely damaged. Can you talk about the symptoms?

author: zxase258
author_rank: Contributor
timestamp: February 12, 2018, 10:39:29 am
content: The principle should be feasible, but to solder a lot of SRAM chips, some difficulties, and SRAM prices are not cheap.For the DPO series, fv6.6 firmware (or higher) is shipped from the factory and 2M optional SRAMs are normally installed, so these models can be directly enabled with the 2M option.

author: chihaxinh
author_rank: Regular Contributor
timestamp: February 23, 2018, 09:09:31 am
content: Hi zxase258My scope fail display PCB , i disconnect connector from main pcb to display pcb, and using LCD external . Display in boot process very slow and display green color . No relay clicking , and no led front panel blinking. Boot process not complateMany tks you !Nam.

author: induzer
author_rank: Contributor
timestamp: February 28, 2019, 07:59:32 pm
content: I did a conversion of my TDS540D to TDS754D some weeks ago.I can state the modifications zxase258 wrote to be partly correct, but maybe not complete.Adding the VRAM - soldering was easier I thought.Swapping U251 to U250 - rubbish on CRT (like lost sync, ic handles some picture timing signal, see service manual), no picture on VGA [timing critical part, my replacement ic was some nanoseconds too slow]Swap back 250/251 - i belive it was white blank on CRT, but colour scope screen on VGA.So far, fine.But the scope boots up with one minor error about missing or wrong VRAM registers. Think there is some further action needed.Maybe its missing the circuitry for the NuColor shutter system, a QFP and 3 VRAM-like footprints in the video section are not populated. Factory 745D have them populated.serial boot debug:QuoteApart from that and after replacing a brick CAL-EEPROM and recalibration, the scope works fine with a 19" color screen via the rear VGA port.Lucky me, so I can read the screen without my glasses, which I often set off while debugginggreeting, induzer

author: induzer
author_rank: Contributor
timestamp: February 28, 2019, 10:41:52 pm
content: Had a quick look at the schematics.It's definite the missing frame buffers VRAMs U820 to U822 and the ASIC U2011 (National ADG281)U822 is also called PM011, see my fault code in the last post. Missed that until nowSo the following Parts need to be modified for 540D to 754D conversion (all on CPU board):- CHANGE the ID resistors like shown in picture and table- INSERT U834 & U835 & U836 & U837 + U820 & U821 & U822 == TC528257J-70 or M548263-60J Video RAM- TRY REMOVE U251 == 74F04- TRY INSERT U250 == 74F04 (use fast ic or save U251)(crt picture, see my earlier experiences)- INSERT U2011 == ADG281 == MM9351-VCEIf you can live with error an selftest and are happy with external screen only, leave U2011 & U820 & U821 & U822 open.As far as I can speak for my own scope, it does not affect the meaurement.Maybe someone will proof that I got confused while playing around with U250 / U251 for saving the internal screen functional.induzer

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 03, 2019, 12:38:35 am
content: Do you know any good places to find the vram chips and the ASIC? I guess I could wait and find a fried 754C CPU board on ebay.I also tried just changing the jumper settings without the other mods and it boots up as the 754C with a flashing color screen on the VGA output and a completly white CRT the first time I booted it up, then on the second time I booted it up the CRT was mostly white but had the text on display.

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 08, 2019, 01:29:51 am
content: Okay! I've substituted the TC528257J-70 vram chips with TC528267J-60 and it works just fine. The TC528267J-60 chips where half the price on ebay. As for the ASIC I haven't been able to get one yet. The scope powers on in 754 mode with the built in CRT displaying Text on white background with no waveform, and the VGA out displays full color without error.It does fail the processor self test when run manually but everything else seem to work fine. I guess this might have something to do with the missing ASIC chip. Maybe if someone here has a dead board they are willing to de-solder one of the ASICs and send one my way? Ill buy! Plus beer if your in the DFW area.I guess I would also need U193. Lots of NOS tlc34075 on ebay from what it looks like!I should also add that moving U251 to U250 causes the internal display to go out of sync while doing nothing for the VGA output. So for now I'm just going to leave it at U251. The Internal display is white but the VGA output is still in color. LUCKILY! Putting the jumper resistors back to the 540C config allows it to work fine even after adding the addition ram chips!

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 25, 2019, 02:19:09 am
content: So!! I switched out and installed U193 and now nothing appears on the built in CRT but the VGA out still works.I probably still need the ASIC, probably. I also need U260 which is a 74F08. Weird that they depict it in the schematics as a NOR gate with inverted inputs. Does the same thing though.I went ahead and ordered a couple off digikey and should be here within the week. They can hitch a ride with my LED COB WHT 5600K 95CRI 1214-1267-ND for anyone interested, but that's for another project.Hope this helps anyone else. My goal is to have a converted TDS 754 that still has a functioning CRT with the option of upgrading to a color CRT or LCD swap in the future. I could do an LCD swap now, but that's boring.

author: zxase258
author_rank: Contributor
timestamp: August 20, 2019, 02:48:39 am
content: Quote from: induzer on February 28, 2019, 10:41:52 pmAccording to my tests, the ADG281 is not a required component and it is connected to the TLC34075. The TLC34075 is only used to generate the sync signal required by the NuColor LCD shutter. Even if you do not install ADG281, TLC34075, and VRAM associated with TLC34075, the oscilloscope can PASSED self-test

author: zxase258
author_rank: Contributor
timestamp: August 20, 2019, 03:02:08 am
content: Quote from: PerpetualWalnut on March 08, 2019, 01:29:51 amPlease check your oscilloscope ERROR LOG, if there is something like DsyMem, there are some broken bits in the newly installed VRAM. These chips are very likely to be junk, especially if the sellers selling them are located in mainland China or Hong Kong.I am very sorry that my post was a bit sloppy. I didn't take notes in detail after I worked. It may have some errors, but I can be sure that if the VRAM is not faulty, even if the ASIC is missing, the oscilloscope can pass the self-test.

author: madao
author_rank: Frequent Contributor
timestamp: January 04, 2020, 06:53:08 am
content: A member from here have modified TDS580D to TDS784D with sucess. It is full modification with ADG281 to avoid error message and is capable to driving NuColor-CRT.I have here 4 piece ADG281 left. It came from dead TDS540A.Let me know, if you need it. You can get it for shipping cost and donation. (loc. germany)Spots on one ADG281 is flux oddsgreetingmatt

author: Tantratron
author_rank: Frequent Contributor
timestamp: January 08, 2020, 08:42:59 am
content: Maybe someone could verify this new test I've done.Connected a color external display (DELL) to my TDS540C (black and white) via the video connector.When I boot, both displays show the same thing except during 1 or 2 seconds, the external display shows different colors. Then the external display shifts to black and white but my question, is there a way to block or disable the firmware so the TDS540C with external display becomes a TDS754C ?Thanks, Albert

author: PerpetualWalnut
author_rank: Contributor
timestamp: January 13, 2020, 02:44:37 am
content: Are you still selling those ADG281? I would be more than happy to take one off your hands! I can PM you my address and we can work something out for shipping from there. Thanks in advance!

author: madao
author_rank: Frequent Contributor
timestamp: January 16, 2020, 05:30:35 pm
content: Now is 3 pieces ADG281 avaible.But i must make a notice: Shipping from germany to non EU-contries cost now 16€ (~ US$ 17-18 , german post)

author: madao
author_rank: Frequent Contributor
timestamp: February 04, 2020, 04:59:09 pm
content: Quote from: PerpetualWalnut on January 13, 2020, 02:44:37 amPleas clear your message box, your is full.I answer here: for 16€ shipping from germany to foreign country: no tracking. German post , shame oneself !

author: PerpetualWalnut
author_rank: Contributor
timestamp: February 04, 2020, 05:28:11 pm
content: Got it, thanks again. I cleared my messages.

author: PerpetualWalnut
author_rank: Contributor
timestamp: February 04, 2020, 05:34:31 pm
content: Quote from: Tantratron on January 08, 2020, 08:42:59 amYou would probably have to wire in a switch to get it to do that. I'm currently working on getting my b/w internal display to work properly in 754 mode along with color output on the external VGA port. That's why I wanted the ASIC from madao, I wanted to see if I could get the color sync signals to work with the B/W display. In 754 mode it doesn't appear to generate the proper sync signals with stock hardware for the internal B/W CRT. The advantage to this would be that I could swap in nucolor hardware if my internal CRT ever kicks the bucket along with the option of changing it to a VGA LCD. More options, more reliability. Ill post again when I get the ASIC in the mail.

author: capt bullshot
author_rank: Super Contributor
timestamp: February 15, 2020, 08:48:51 pm
content: Got some promising results - I'm able to use an external VGA monitor in colour (TDS784) mode while preserving the original TDS580C internal B/W display.What did I do:Thanks to madao, I've received a ADG281 ASIC, and some VRAMs (TC528267J-70) from an American ebay seller. Following most of this threads instructions, I soldered the ASIC and seven VRAM chips to the CPU board, replaced U251 to U250, and removed the ID resistor to change the model to TDS784. This works and results in a non-synchronized internal display (as someone pointed out before). Placing U250 back to U251 brought the internal display back to sync, but didn't display a useful picture (as pointed out before). Since I didn't replace U190 by U193 (TLC34075, the RAMDAC for the NuColor internal display), the Display self test results in a failure indicating U193 (go figure).Now, what happens: U199 provides the VGA output for all (colour and B/W models), this works. U190 provides the internal display output in B/W models, and doesn't if a colour model is selected. Turns out, its colour palette registers never get written by the firmware in colour mode (why should the fw do so, since this chip isn't present in colour models). So the palette register have some random content after power on, resulting in an unusable display. Anyway, this leads to simple fix: Remove U190 pin 16 (\WR) from the signal WDAC1*\I and connect this pin in parallel to U199 pin 16 (WDAC2*\I). Now both RAMDACs get written with the same contents, so U190 outputs the same video contents as U199 does to the external memory. In a second step, remove FSYNC/VIDEO*\I from pin 25 (red output) and connect this signal to pin 26 (green output).Voila: The internal display shows a useful picture with the monochrome palette selected from the menu (the external monitor shows all traces in green in this mode). One can edit the colours to display the traces at different brightness levels.As said before, the ADG281 and three VRAMs aren't required for this to work, one requires them if a real NuColor display is to be connected. In this case, one has to replace U190 by U193 also, move U251 to U250 and populate U260. Since I don't have a NuColor display, I cannot verify this.

author: Jwalling
author_rank: Unknown
timestamp: February 15, 2020, 10:51:34 pm
content: Quote from: capt bullshot on February 15, 2020, 08:48:51 pmYou guys are NUTS! (but in a good way...)

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 01, 2020, 02:36:11 am
content: Update on my TDS540Thanks again for the ASIC madao! Works great!I was able to successfully do a full NuColor conversion of my TDS540 to TDS754 scope! I bought a $200 "AS-IS" TDS754 off ebay and used the CRT and LCD shutter out of it to test my board. Unfortunately the ebay listing didn't say anything about a missing CRT driver board... So I got back on ebay and came across 5 CRT driver boards for $20 plus another $20 in shipping! They where AS-IS as well, but for $40 I figured I could get at least one working, but that's for later.The CRTs... The one that came with my TDS754 as badly faded, but the LCD shutter worked. I decided to try the old CRT rejuvenation trick on both of the CRTs that I now had. At first it seemed to work on my 540 CRT, but the 754's CRT was being stubborn. It had a little improvement, but not much. I figured it was toast so I got out the MOT and variac and *POP* there goes the cathode! oopsAt least I got a major improvement from my old CRT. I decided to cut the LCD shutter off the popped CRT and see if I could use it with my old but working CRT. I was able to get that to work by taking the yoke off the popped CRT and putting it on the working one, but the pinout of the working CRT was turned 90 degrees in relation to the popped CRT so I had to improvise an adapter using the connector from my B&W CRT driver board. This worked and I could now fit it into my scope!... The bracket on the face of both CRTs are different. See pics. I did end up swapping by *carefully* cutting both off with a drimmel and using some double sided tape to stick it back on. This kinda works but now the mounting holes don't line up!Anyhow, Ill deal with that later. Right now I want to test my driver boards.3 of them works! 1 only show B&W, and the last one has a short. Not bad for $40! Ill resale them after I repair and test them.As for finishing the 540 to 754 conversion, see pics. There are a few resistors and one or two caps on the BACK of the board that needs to be swapped around or added! And don't over heat your board like I did to mine when I was swapping out U193 with a few different chips because I couldn't figure out why it wasn't work. Turns out it was the resistors on the back of the board... Anyways! Hope you enjoy!

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 01, 2020, 02:39:14 am
content: More PICS

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 01, 2020, 02:40:00 am
content: Even MORE PICS.

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 01, 2020, 02:41:06 am
content: I can only post a few at a time and I've already decreased the resolution so that it's barely usable.

author: madao
author_rank: Frequent Contributor
timestamp: March 01, 2020, 09:34:50 am
content: Good, but, you must trim intensity down. Background shouldn't light and good NuClolor-System hat really black background, as vanta black :lol:Two ADG281 left :-)greetingsmatt

author: PerpetualWalnut
author_rank: Contributor
timestamp: March 01, 2020, 04:40:18 pm
content: Thanks madao. I've since turned the brightness and contrast down. It was kinda hard to get to those pots while it was running due to my test rig. Once I'm done fully testing all of my boards I will reinstall everything and properly fine tune the adjustments.Does anyone know anything about upgrading the acquisition board to 4gs/s? I've heard rumors about it. Is there another thread for that?

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 17, 2025, 02:15:56 pm
content: This is an old thread I'd like to revive but with some restrictions to see if a simpler hacking or transforming method (less chips) is doable.The restriction I have in mind is not using at all any CRT wether monochrome or color A11 board which I intuit to require less chip then connect either an external LCD display on VGA connector or install the LCD kit from SimmCon labs. One reason being that in the past after acquiring two LCD kit from SimmConn labs, the PCB-FPGA sockets into U199 RAMDAC so wether color or mono, there is no need of addition chips (U193, U260, 80 MHz quartz). I understand this chips and parts in my first attached picture in RED are only required to triple the frequency for the Nu color system (CRT and shutter clocked at 180 Hz instead of 60 Hz). So if we go after LCD display then technology I'm interested to know exactly what chips need to be added.Again as a reference for this question, attached 2 pictures of my A11 board from C/D serie: one is monochrome processor and the other is color processor. I put in yellow circle the chips which need to be added or swapped (U251 and U250), same yellow for ID resistor swaping and again in red circle chips which are not necessary for this task since we will not connect any CRT unit.As far as I know, there is no schematics for C/D serie A11 processor board but does anyone has good knowledge of digital video technology to guide or explain which chip do to make color, which chip can be discarded since no CRT color driving.In practice then, either we would connect a VGA-LCD unit from J88 connector (near RED circle zoning) or the FPGA hack into U199 designed by SimmCon labs in USA. Worth noting that some members have succeeded to develop their own FPGA which again is hacking the U199 RAMDAC signal, seethis thread.So in resume, the idea is to drop CRT concept versus reducing added BOM so valid signal are offered to a LCD display.

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 20, 2025, 03:27:14 pm
content: Has anybody colorized any TDS510A processor board and if yes, do you know which ID resistor must be modified ?Attached a picture of my unique TDS510A board, I can make closer view of the specific resistor area to help locating monochrome versus color setup.On a side note, I notice the VRAM's TC528257J-70 of this TDS510A are the same model as on C serie board running with 68040 processor.Thank you in advance

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 20, 2025, 03:44:33 pm
content: Could you advise if it is possible to intermix VRAM's model TC528257J-70 with M548263-60J or rather recommend all the VRAM's in A11 board should be the same part number ?

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 21, 2025, 03:19:34 pm
content: Quote from: Tantratron on May 20, 2025, 03:27:14 pmThanks to private message from member@madaothe solution is to only remove R12 because TDS510A processor board are basically the same as TDS500B serie except firmware.Quote from: zxase258 on February 02, 2018, 04:11:33 pmThe very first post in this thread mentioned R12 for TDS500B.Now I need to find total 2x4 sets of VRAM to resolve the flickering issue on both my TDS500/C/D and TDS510A colorisation process followed by a LCD retrofit so no need

author: ArcticGeek
author_rank: Regular Contributor
timestamp: May 21, 2025, 06:22:41 pm
content: Hello @Tantratron,This post just caught my eye. If I am reading this correctly, you are indicating that if you remove R12 on a TDS510A processor board it allows the external VGA output to be in color, is that correct?I have an old TDS5XXB processor board lying around that I might want to try this on, but you also mentioned you need to update/upgrade the VRAM on the board. Why do you need to increase the VRAM?Thanks,Mike

author: madao
author_rank: Frequent Contributor
timestamp: May 22, 2025, 03:38:41 am
content: Yes, Monitor show on VGA port color, but if TDS510A CPU Board get TDS500B/700A Firmware. (TDS510A is very odd bastard )Short answer: You need more VRAM for color.

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 22, 2025, 03:39:44 am
content: Hello@ArticGeek,Well going from monochrome to color will always require more VRAM so wether a TDS510A or TDS500B or TDS500C/D processor board.Once the specific ID resistor removed depending on TDSxxx model serie, it seems only 4 additional VRAM are required to obtained VGA output color.Normally to have CRT NuColor signal, one needs toadd 4 VRAMs+ 3 other VRAMs + ADG281 chip + replace ADV471KP35 by TLC34075.My opinion is that nowadays best go after color LCD kit internal technology (VGA link or FPGA hacking the RAMDAC) only requiring 4 additional VRAM.Albert

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 22, 2025, 06:15:51 am
content: Quote from: madao on May 22, 2025, 03:38:41 amIndeed as taught in private communication with@madao, I was obliged to flash 4.2.1e into TDS510A processor board initially running with 1.0e in order to obtain color VGA output. This firmware upgrade transforms the special or wierd TDS510A processor programming into any TDS500B/700A processor board latest generation.One test actually consited to interconnect the TDS510A reflashed with my spare TDS784A acquisition board, all works perfect in color.Now remains to decide what intermix VRAM can be used, price and so...

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 22, 2025, 08:05:31 am
content: I've just update 2 pictures with markings to synthetize and visualize which ID resistor must be removed to allow colorization on TDS510A/TDS500B and TDS500C/D

author: ArcticGeek
author_rank: Regular Contributor
timestamp: May 22, 2025, 01:12:26 pm
content: @Madao, @Tantratron,Thanks for the replies. I guess it makes sense that more VRAM would be needed for color; but I was not aware that you could convert a monochrome board into a color board so easily with just a resistor change and additional 4 memory modules.This would be a pretty neat way of making an old TDS500B/C/D into a color model by adding an LCD with a VGA converter board. In my opinion, using an FPGA like the Simconn labs solution is not that elegant because making all the necessary connections is a bit of a kludge. Using a VGA-LCD converter board is a clean approach, and if you really want to keep the VGA out on the scope you could use a VGA splitter.Nice work to all on this discovery.Best,

author: Tantratron
author_rank: Frequent Contributor
timestamp: May 22, 2025, 03:03:56 pm
content: @ArcticGeek,For the moment, I've not decided where to purchase due to high cost the additional four VRAMs to confirm full hack unless omeone has somee spares TC528257J-70. Right now I've 3 monochrome processor boards of different design: TDS510A transformed into TDS500B via firmware upgrade, one C/D serie old design with (5V DRAM with 28F016SA flash) and one C/D serie new design (3.3V DRAM modification with 28F160SA flash). So in practice, I would actually need more additional VRAM to test all processor board revisions. The new design C/D actually uses M548263-60J so still not sure if they can be inter-mixed.Anyway a bit of caution about LCD-TFT size and resolution because most of LCD driver I've tested do not properly decode the native 640x480 resolution from TDSxxx firmware. So you need to use a 800x600 display hence decrease video quality due to the horizontal and vertical rescaling, otherwise you loose part of the image in all the corners. It took me a while to understand and prototype a hack of low cost chinese LCD driver so I really obtain the native resolution on a 640x480 display. You might understand bit more the technical problem in my quick video made few months agoYou'll notice on eBay and other places that most vendors of TDSxxx with color LCD have 800x600 hence small quality problem which explains why SimmConn Labs via its other FPGA hack solved but expensive. This is why that if possible to actually transform a monochrome into color by only removing one ID resistor and adding four VRAMs is a game changerNote that I did learn and study about these chinese LCD driver low level hack because initially, I wanted to colorize a monochrome Advantest R3x61 which took me a huge learning path, see eventually this other video made few months ago

author: madao
author_rank: Frequent Contributor
timestamp: May 28, 2025, 03:22:01 pm
content: I have transform my TDS540C (a scrapyard-find with heavy damaged case) to color with minium amount of needed compoment.I have added four VRAM on location near 4 existed VRAM and removed ID-resistor -> Monitor on VGA Port show colorizied screen without error message.Internal CRT (60Hz) show picture with mismatched "color".No moving of 74F08 on U250/251 position. Keep 74F08 as is.Only four VRAM addition is requiered. (Color Waveform needs 8 VRAM )

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 08, 2025, 08:56:02 am
content: I'm trying to colorized a monochrome CPU board (C/D serie) with only VGA output scenario. After some painful soldering the additional four VRAMs (U834 U835 U836 and U837) and removing ID resistor, it seems to partially work except some strange doubling or quadrupling effect, please see attached pictures.Regarding the F04 chip, some posters previously said to swap between U2501 and U250, other said to not do this swap. In the attached pictures, I've left F04 on U251 but do you think the waveform display problem is related to F04 correct installation ?Otherwise looking at video text plane, it seems to be properly colorize (graticule, readout, cursor and menu).Note the FAIL processor status, the failed test concerns cpuDiagDsyAccess (163 diagnostic test / failure addr = 0x8000000 / expected data 0x101 actual 0x606) whereas before this CPU board work like a charm as monochrome.There were total of 4x40 pins (J form soldered on pad), I've tried continuity test most of them as well as displaying live with the oscilloscope. Maybe some pin are wrong but to my best knowledge, I think they are now properly bonded so I'm curious to understand the role of F04 wether on U251 or U250 spot.

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 09, 2025, 06:30:06 am
content: OK now it works (one vram chip pin19 was shorted with pin 20 so address A4 was always stuck high ar Vcc), many thanks to@madaoinspiration.So it is confirmed if installing LCD from VGA output, only adding four VRAMs, removing color ID resistor, no need to swap U251 with U250 then any C/D monochrome processor board can be colorized.In my case, this is now TDS784C oscilloscope running under 5.2e firmware.

author: satanistik
author_rank: Contributor
timestamp: October 02, 2025, 09:23:45 pm
content: I try to convert TDS540D to color, I add four TC528257J-70 - used from old PCI graphic card. I have colors on screen but on self test I have processor ERROR - some Andres faults. Its cause by missing ADG281 or my ram are damaged?

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 04, 2025, 05:27:46 am
content: What are the model part name of other VRAM which were installed on TDS540D processor baord ?What is the firmware version of your TDS540D: 6.x or 7.x ?Can you make picture of ERR log file to see more details of processor board error ?

author: satanistik
author_rank: Contributor
timestamp: October 04, 2025, 06:35:00 pm
content: Originally I have OKI M548263-60J Vram installed, I add 4x Toshiba TC528257J-70. It's hard to find spare parts for old devices. I have FV 6.2.1e installed. In log I have ERROR: Diagnostic test failure dsyPM011RegMem. **addr=0x75ed808 exp data = 0x7f00....(this part is not visible).

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 05, 2025, 07:04:22 am
content: The error is reported from address space 0x700 0000 which corresponds to the TRISTAR processor (DSP space). If the issue was related to one failed VRAM, the address space would have been 0x800 0000 (display space). However it is not easy to conclude in your case, ideally more information fromConsole Port or GPIB would help.

author: satanistik
author_rank: Contributor
timestamp: October 05, 2025, 07:30:01 am
content: Ok, if i solder select resistir back to BW mode, this error goneI donta have ADG281 soldered - not available in market.This IC is connected to system bus and probably have same registers.

author: madao
author_rank: Frequent Contributor
timestamp: October 05, 2025, 10:19:36 am
content: Do you have move IC on U251/250 position -> they can reason for failure messageI haven't moved 74F08, let as is.greetingsmatt

author: satanistik
author_rank: Contributor
timestamp: October 11, 2025, 05:57:02 pm
content: I add second 74f08. Do you have no errors after modyfing without ADG281? ADG281 is interesting ic, It have more that one function in this scope and inputs to select one of this.

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 12, 2025, 04:26:30 am
content: There is absolutly no need to add neither swap the 74F08 chip.Just leave them as they are from a monochrome processor board, it worked for madao, I made same as instructed by madao.