Bought TTi EL302P off ebay, dead display - Page 1
Forum section: electronics / testgear

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 06:38:06 am
content: Sure others might have saw this listing:http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380545309157Figured it's a great power supply, and if it's got a dead display (only), it's still a great supply. Hoping I'll be able to fix. Anyone have any suggestions (haven't gotten it yet) on where to start, or should I just try contacting TTi to see about replacement parts? The fact BOTH are dead obviously leads me to think it's a common component rather than just one of the panels.I'm in the states, btw. I did manage to find the service manual online.Guessing I'm going to get "wait until you have it". =) I do plan to test output voltage and current immediately. But for $86 with shipping, it's still a darn good price even with the dead display (assuming everything else works)... isn't it?

author: free_electron
author_rank: Super Contributor
timestamp: April 11, 2013, 06:49:56 am
content: Probably some i ternal voltage that is missing. These meters needto float. I would not be amazed if it is a simple fuse or rectifier that popped internally. Could even be the connector coming fro. Transformer that popped loose. They use those moled idc connectors inside.Some ttis have an additional transformer for the comtrol circuitry.... Could be the fuse there..Most likely it is very simple to repair.

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 06:51:44 am
content: That's what I figured.Once I have it in hand I'll take a meter to it. The service manual seems extremely well written and detailed.Thanks!

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 06:59:44 am
content: I guess big question is... think the fault will be visible, or am I going to be hunting? Looks like, from the service manual, they're all largely single sided pcbs (well, think there might be some caps on the back of the ICs but seemingly nothing major).Thanks!**What am I doing?! wait until you have it in hand!

author: amspire
author_rank: Super Contributor
timestamp: April 11, 2013, 07:06:18 am
content: Quote from: staze on April 11, 2013, 06:38:06 amIt has LED 7 segment displays, so you are right - it is unlikely to be the displays that are faulty. It may be that it is basically a analog power supply with a micro added to do the RS232 and remote voltage and current settings. When in remote mode, the front panel controls are locked out, and with the coarse and fine knobs, it just looks like conventional pots on the front.So it is possible that the whole digital board has a problem, and probably the worse case scenario would be a custom programmed micro chip has died. You would have to get a replacement from the manufacturer for that. But the fault is probably something else, and it could easily be a simple fix.If you need to talk to another owner, IanB has one:https://www.eevblog.com/forum/testgear/tti-el302p-power-supply/

author: ve7xen
author_rank: Super Contributor
timestamp: April 11, 2013, 07:11:40 am
content: Almost got this myself a couple weeks ago. It's been on there a while. Ended up getting an E3610A instead for less. Good buy though I think, I'd guess it's something in the floating supply too.Looking forward to your report on the easy fix.

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 04:06:56 pm
content: Quote from: ve7xen on April 11, 2013, 07:11:40 amOh, so that was you that got that E3610A! =)There's another one on there too that I was keeping an eye on. I've been watching the TTi for a bit now, and figured I'd just pull the trigger given it's range, and RS232 (worst case the screen is dead dead, I can write up some software to display the info, albeit slowly).Yeah, I'll just have to take a look. I hope it's easy... I'm pretty new to most of this stuff (done some cap replacements in monitors, but heck, that's EASY when you can see they're blown). I'll no doubt be back with questions on where to probe to check things out. But I'm heartened by how detailed the service manual is.

author: krivx
author_rank: Frequent Contributor
timestamp: April 11, 2013, 04:49:01 pm
content: I also almost bought this supply, the fact that it was a 230V version caught my eye. I ended getting a E3615A for about the same price that was listed as not working but turned up working just fine.

author: free_electron
author_rank: Super Contributor
timestamp: April 11, 2013, 05:37:17 pm
content: the TTI's are switchable to 110 volt. open case , swap two straps , close case. I've done this on plenty of machines. i had like 50 of their supplies in europe. bought through farnell.the tti machines use icls7107's to readout. not a micro in sight.the remote control is a micro driving a few multiplying dac's ( essentially r-2r ladders ) that takes over for the potmeters.only the new TTI's with the keypads are microcontroller driven

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 05:55:58 pm
content: Quote from: free_electron on April 11, 2013, 05:37:17 pmJudging by the block diagram, and I have no clue which version of the PCB it is yet, the readouts share a HC574 and a ULN2003A to do readout. But I can't figure out where the displays are actually powered from (basically, are the IC's not getting power and not driving the panels, or are the panels not getting power). The fact that the controls are encoders vs pots, and it supposedly has output, makes me think that the 5V rail must be working (obviously the PIC is working if the encoders are working).I'll just have to wait and see... but it's so much fun to guess... =)

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 05:59:16 pm
content: What's most interesting is looking at the block diagram, I can see a lot of similarities to what Dave designed in his PSU videos... which I'm STILL watching... so, much, material.

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 06:19:02 pm
content: so one other question... what would be the best/easiest way to test amperage output on this guy? voltage I'll just hook up my meter, but amperage, I'd need a load, and since I'm starting out my ability to really put a load on something...Obviously building a adjustable load would be good... but I'm not sure about throwing something together that fast.just set it to like 5V, buy a 10W load resistor, and set it up to 2A, or should I really try to test the whole range of voltages? Figured I also have some 12V halogen bulbs that I could use for load as well...Thoughts?

author: ve7xen
author_rank: Super Contributor
timestamp: April 11, 2013, 06:51:43 pm
content: Quote from: staze on April 11, 2013, 06:19:02 pmIf you're just looking to test out / calibrate the meter readings and maximum current output, just put your meter directly across the outputs. The calibration instructions (HP's anyway) usually have you connect a low value resistor (0.1R or something) across the output and measure V across it in CC mode, which is exactly what your meter is doing in current measurement mode.If you want to do a load test, either a power resistor or rig up a power device in linear mode with a pot as an active load. CC mode probably makes the most sense for the load. It's just a couple parts on a breadboard, hardest part will be thermal management.12V halogens are a decent and cheap test load for high-ish powers that can be a pain to deal with otherwise.

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 07:12:32 pm
content: yeah, testing voltage is no problem.Testing current is the issue. Dave has a video on building a load, but ordering parts, etc would take time. Ideally I'd love to just throw something together from local parts store (alas, that means Radioshack, or a local store that has some stuff).Any places you can point for building up an adjustable load? only needs about 60W. I have no shortage of heatsinks that I can drill and tap for thermal management. Again, just learning all this stuff, so any help would be greatly appreciated. I just want to test this thing when it shows up so I know if it actually works, or if it's only outputting like .1A at 15V and that's it.Thanks!

author: gerrysweeney
author_rank: Regular Contributor
timestamp: April 11, 2013, 07:29:21 pm
content: I would second @Ve7xen suggestion, use a 50W 12V halogen lamp which if you don't have one you can get from any DIY store or supermarket. Connect the lamp in series with your meter in current mode and the PSU. The lamp will draw a spike of current +5A and then drop back to 1-2A once the filament is warm. It takes about 30 seconds to reach its operating temperature so you get a slowly decreasing current draw. Watch your multi-meter and the PSU current meeter and see that they track and are accurate. It's simple, cheap and reliable and you don't need to do anything. I use these lamps all the time despite having a 150W fully programmable load on my bench.Gerry

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 07:32:21 pm
content: Makes sense. In my case, I can't watch the PSU display since it's not working, but at least I'll be able to tell if it's putting off a full 2A.I guess my biggest question is, if a power supply can put out 2A at 12v, does it follow that it most likely, give it's specs, should be able to do the same at 30v, or do I need to test the whole range?The supply is a 30v 2a model, so I'd even think a 12v 35W bulb would work as well... which I think I may already have.

author: ve7xen
author_rank: Super Contributor
timestamp: April 11, 2013, 08:07:02 pm
content: Quote from: staze on April 11, 2013, 07:12:32 pmTesting current isn't either. Just use your meter's current range; you don't need a load to calibrate the meter readings.Where it gets trickier is when you want to test the power supply under load; the issue is then the same regardless of whether you want to test CC or CV mode. You can use an adjustable constant current load for either purpose.60W is quite a lot of power to dissipate. All you really need though is a constant current sink with adjustable current. The lowest part count way to do that I know of is to use an LM317 or similar regulator and adjustable resistor - it's in the National datasheet. But you won't get 60W out of this (safely anyway). Otherwise you need an error amplifier and pass device - this can be done with any opamp and a power MOSFET or BJT. In a pinch you can use a signal transistor as error amp. Probably you have something usable in your junkbox, or you should be able to get this stuff at RS.Getting something that works down to 0V is tricker, but you shouldn't need that to test a power supply.

author: staze
author_rank: Frequent Contributor
timestamp: April 11, 2013, 08:44:10 pm
content: Quote from: ve7xen on April 11, 2013, 08:07:02 pmYeah, but it's better than an old Pentium 4.Don't really have a junk box as of yet... working on that. But yeah, looking at something like this:http://stevecoates.net/cc_load/or Dave'sit seems like it should be doable. Probably don't need the panel meter though. =P And his only goes up to 1A-ish.Think I'll just try to use some 12V halogens. Put two in series and that should let me test at 24V... wonder what they blow at... like, could I put 15V into one. =)

author: staze
author_rank: Frequent Contributor
timestamp: April 12, 2013, 07:30:20 am
content: So, question.If I picked up a 100W, 1? resistor (for example), and the power supply is a 30V 2A supply, then it resistor should be able to carry 30A at 30V, no? So it should easily be able to take the 2A I'm giving it... and the total heat dissipated would be 60W (still within spec of a 100W power resistor. If I just wanted to draw the 2A, then a 15? would be the "proper" value... but anything less than 15? should be able to draw the full 2A without breaking a sweat.That seem right?

author: Balaur
author_rank: Unknown
timestamp: April 12, 2013, 07:43:52 am
content: Quote from: staze on April 12, 2013, 07:30:20 amIf you pick a 1 ohm resistor and try to connect it to a 30V 2A PSU, the source will likely limit the current to 2A, with a lowered output voltage of 2V. The power dissipated by the resistor is a total of 4W.Now, if you really have a 30V, 30A PSU, then the power dissipated by the 1 ohm resistor will be 900W; the resistor will go up in smoke.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: April 12, 2013, 08:16:09 am
content: heysimply buy irfp250N and op07 ,0.1ohm 10W resistor , 2.7K 1/4W resistor , 10K 10 turn pot and lm336 , then let me know when all parts has arrived , when they will . I'll post schematic . build it - I'll work you for sure , oh and intel H.Slinks :*resistor :http://www.ebay.com/itm/New-OHMITE-0-1-OHM-1-10W-1KV-Ceramic-Resistors-/250780281927?pt=LH_DefaultDomain_0&hash=item3a63ab6c47*IRFP250N :http://www.ebay.com/itm/IRFP250-IRFP250N-Power-MOSFET-N-Channel-30A-200V-/250833367462?pt=LH_DefaultDomain_0&hash=item3a66d571a6*lm336:http://www.ebay.com/itm/LM336Z-5V-LM336-Shunt-Voltage-Reference-Diode-/400312200958?pt=LH_DefaultDomain_0&hash=item5d34776efe*op07:http://www.ebay.com/itm/1pcs-original-DIP8-OP07CP-DIP-8-OP07-TI-LOW-OFFSET-VOLTAGE-Op-Amp-IC-/370745511569?pt=LH_DefaultDomain_0&hash=item5652278e91* 10K 10 turn pot :http://www.ebay.com/itm/110968872239?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649* intel H.S :http://www.ebay.com/itm/NEW-CPU-Heatsink-fan-Cooler-cool-for-Intel-Core2-LGA-775-to-3-8G-NEW-A-/140912841026?pt=UK_Toys_Games_Outdoor_Toys_ET&hash=item20cf0f5142and some 1.9 or 1.95 m'm drill :*1) :http://www.ebay.com/itm/10-Pcs-Lot-1-9mm-Micro-HSS-Twist-Drilling-Bit-for-Electrical-Drill-/290644511691?pt=LH_DefaultDomain_0&hash=item43abc34bcb*2) :http://www.ebay.com/itm/5pcs-Carbide-Micro-Drill-Bits-1-95mm-Shank-Diameter-1-8-inch-3-175mm-/160767392654?pt=LH_DefaultDomain_0&hash=item256e7bbb8efor the screw of course !P.S , I'll open thread on my 1000W electronic load soon( actually I'll use 200~300W tops but he's capable of 100A 150V 1000A )Cheers !

author: staze
author_rank: Frequent Contributor
timestamp: April 12, 2013, 04:54:38 pm
content: Quote from: Balaur on April 12, 2013, 07:43:52 amokay, that makes sense.So a 15? resistor should get the PS to output 2A at 30V, and it would dissipate 60W, yes?

author: eevblogfan
author_rank: Frequent Contributor
timestamp: April 12, 2013, 05:00:05 pm
content: yup

author: staze
author_rank: Frequent Contributor
timestamp: April 12, 2013, 05:13:04 pm
content: Quote from: eevblogfan on April 12, 2013, 08:16:09 amokay, going to check local shops for this stuff before ordering (since stuff from China takes forever).figure 10x 1? 1W resistors should work, a single turn pot (for now), and the op amp and lm336 should be easy enough.not sure about the mosfet. quick hints about what might be a substitution?

author: eevblogfan
author_rank: Frequent Contributor
timestamp: April 12, 2013, 06:04:01 pm
content: 10X 1ohm 1W 1% will doas for the mosfet , IRFP250N and IRFP064N are good choice for that linear task since they have good SOA ratings in the linear regiontry to get the IRFP250N because of it's high voltage rating ( no need to fear from spikes of 40~ 80V )good luck

author: staze
author_rank: Frequent Contributor
timestamp: April 12, 2013, 06:31:22 pm
content: K, will post back results from local shopping. =)Guess the big question... I think the local shop carries NTE components... do you know if there is equivalents? I'm checking their cross reference, but not seeing anything for the IRFP250N, or the OP07. =/Will have to see the actual store stock. Maybe they have some other stuff.

author: staze
author_rank: Frequent Contributor
timestamp: April 13, 2013, 01:44:31 am
content: Up, local places had nearly none of that stuff... and what they did have was hella expensive. sucks.Anyway, ordered the stuff off ebay. guessing a couple weeks unless something has changed since I ordered a bunch of 1/4w resistors from china a few weeks back.For now, I guess when I get the PSU, I'll do basic testing with a halogen bulb for load.Will post back once parts are here, as well as once I have the PSU in hand. Still need to look at fixing the displays. =)

author: IanB
author_rank: Super Contributor
timestamp: April 13, 2013, 03:50:44 am
content: If you have a serial cable you can control the power supply from a computer using any convenient terminal program. The supply uses a very simple set of commands for control and read back that you can enter by hand.

author: amspire
author_rank: Super Contributor
timestamp: April 13, 2013, 04:10:50 am
content: Quote from: eevblogfan on April 12, 2013, 06:04:01 pmI didn't think these parts had any DC SOA specification.What that means is that these parts could work fine, or they could fail in linear DC mode. The manufacturer is not giving any opinion, so it is up to you to experiment. It is very likely the designers of these parts did not design them to be suitable for DC linear mode operation.An example of a device specified for Linear DC operation is the IXYS IXTH24N50L. With the case at 60 degC, it can safely handle something like 5A up to about 35V. It will do 10A up to 20V. The package is 400W at 25 degC so you might be able to get 200W out of the device on a great heatsink.There are others - IR have devices with linear DC SOA specs - but it is not easy finding them. Look for devices with gate turn on voltages (Gate Source Threshold Voltage at 250uA) over 3V. The higher the gate turn-on, the more chance the cells will share current evenly allowing the device to handle DC. Also the devices with a higher Rds are more likely to have a DC SOA rating then the devices with a low Rds (given the same power rating for the two devices).Richard.

author: mariush
author_rank: Super Contributor
timestamp: April 13, 2013, 04:30:18 am
content: I've built a constant current load using the circuit here:http://www.sleepyrobot.com/?p=136But I've used a FQP50N06 :http://www.fairchildsemi.com/ds/FQ/FQP50N06.pdfIt works OK, maxes out at somewhere under 1A if the voltage is below 3-5v or so, above I tested it up to 2-3 amps with my linear power supply (which does max 3a) and it worked great.My prototyping board soldering skills aren't that great, I've used network cable wire to make connections, soldered the decoupling cap directly on the opamp power pins, works just fine.

author: staze
author_rank: Frequent Contributor
timestamp: April 13, 2013, 05:47:20 am
content: Quote from: IanB on April 13, 2013, 03:50:44 amYes, saw that. do you know if it just works with a standard serial cable?It looks like you can just feed it very simple commands followed by an LF and it responds... so that should be easy enough. =) Big reason I bought the supply... worst case, if I can't get the display working, at least I have an easy way to read output... just write something to update on my screen every 20ms or so (according to the manual, you have to wait about 10ms between commands). =)Thanks IanB!

author: staze
author_rank: Frequent Contributor
timestamp: April 13, 2013, 06:22:43 am
content: Quote from: mariush on April 13, 2013, 04:30:18 amI actually saw this design earlier. Great design actually. I bought a 10turn 50k pot just so I could build that design if this one doesn't work. =Pbought duplicates of the opamp and mosfet as well.guess this is how we build parts bins...Your soldering skills look fine given it's perfboard.Anyway, should be easy enough to pick up those extra parts and breadboard. The previous version should work with a 50k 10turn I'd think. I ordered the couple missing pieces I didn't have real quick, and I'll just pick up the ceramic caps locally... because finding the .1uF is spendy. Guess I could just order from Mouser. Shipping is the killer though on something like that.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: April 15, 2013, 06:13:03 am
content: hey amspierI've bought 10 IRFP250Nthey indeed don't state the SOA in datasheet , but have a look , they do specified the max current and max voltage , plot it into the current SOA and you'll get the DC SOA ,no need to spent big $$$ on special mosfet when silly irfp250n can do the taskas for the op , you did well , it's fine any circuit that you've build is okay , the reason I gave you that list was because I built that circuit and it works fine with no oscillation up to few amps . and has -3DB of around 87Khz ( if modulation needed )Cheers

author: amspire
author_rank: Super Contributor
timestamp: April 15, 2013, 07:08:22 am
content: Quote from: eevblogfan on April 15, 2013, 06:13:03 amIt doesn't work that way unfortunately.Most power mosfets have no DC safe operating spec because their design does not share current evenly between individual mosfet cells in the mosfet in the linear mode. The current sharing is fine when the mosfet is fully on - that is no problem as the Rds defines the current sharing.Most power mosfets are not made as a single mosfet device - they are an IC containing a large number of small parallel mosfet devices. The larger the silicon die, the more mosfet cells are in parallel. This is one of the reasons it is easy to scale a design from a low current version up to a high current version - just make the chip bigger and add more cells.In the linear mode in most power mosfets, the sharing tends to be defined by the gate sensitivity which has a negative temperature sensitivity. What that means is that the hotter an individual cell gets, the more sensitive the gate becomes, so the harder that cell turns on. So in linear mode, if one cell in the mosfet gets a bit hotter then the other cells, it turns on even harder and gets hotter until thermal runaway occurs shorting the cell and destroying the mosfet. Mosfets that are good at linear mode often have a high enough channel resistance so that it starts to dominate over the gate sensitivity before thermal runaway occurs. Mosfets designed low low Rds switching usually do not have this safety mechanism.There is no possible way to deduce a mosfet DC SOA from voltage and current specs. Mosfet manufacturers never leave a DC spec of the SOA curves by accident. If there is no DC curve, the designers are not prepared to specify any safe level of DC in linear mode for that device.As I said, you can try the irfp250n and if you are lucky, it may work fine. It will likely work fine up to a point - perhaps an amp or to. Beyond that it is a gamble. If it blew up and you told IR, they would shrug their shoulders and say "What do you expect - it is not designed for linear DC use". If you were going to make a current load product to sell, you would not touch the irfp250n. You would definite go for a device like the IXYX device I mentioned or the FQP50N06 that mariush mentioned.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: April 15, 2013, 07:22:02 am
content: I tried the IRFP250N and I can report it held 150W for 24/7 , It may not hold 150W for high MTBF but it may hold okay at the 100W region ( based on my approch to that , it should be SOA max at 110W or so )please tell me, 30A rating , what is that telling you >?for me It says that up to 30A the internal arry will shear fine the current , since that's 250V mosfet , it should hold up to 250V peaks at 30A switching , obviously the duty factor of the spikes should be very low , so the AVJ power dissipated will not exceed the 110W I've mentioned , now since I've tried that IRFP250N I can recommend him for that purpose ,please note BK8500 uses that mosfet for 45W continues maX , I believe you can use this for up to 110 and you should hold good margin so I believe 80~90W continues will be okay for very long MTBFas per the construction of fets , amspier , I am awear of that , but thank you for bothering writing that long and detaild post , I appreciate thatCheers

author: staze
author_rank: Frequent Contributor
timestamp: April 16, 2013, 12:21:29 am
content: Forgive the n00b question here, but with a 3 post power supply (neg, ground, and pos), if I am hooking up a load, or say, a multimeter, should I be hooking to pos and neg, or pos and ground? If I understand correctly, if I hook from pos and ground, I'd get say +15v (for example). Same as hooking between pos and neg. But if I hooked up between neg and ground, I'd get -15v?Basically, if I'm not needing anything with a neg rail, I should just hook up between pos and neg, and forget the ground, yes?

author: ve7xen
author_rank: Super Contributor
timestamp: April 16, 2013, 04:57:23 am
content: The positive and negative are the floating supply outputs. The ground is mains earth. If you want a floating supply, ignore the ground lug, but sometimes you will want to tie part of your circuit to earth ground. Sometimes you'll see the negative output strapped to earth. It's not a power supply output though, just a convenient connection to the mains earth pin on the input power cable.You should get no current between + and ground (unless you've strapped - and ground together, of course).If you want a +/- supply, you need a second supply. Because they're floating, you can connect them in series and use the centre node as ground.

author: staze
author_rank: Frequent Contributor
timestamp: April 16, 2013, 06:02:22 am
content: okay, that makes sense. Guess I'm still a bit fuzzy on "floating", but I'm getting there.Thanks!

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 02:37:01 am
content: Sooooo....Power supply arrived, and looks like the attached photo. =(Postal system seem to have completely destroyed it. We shall see what the seller and/or ebay do. Doubt it was insured by the seller.*sigh*

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 02:38:43 am
content: That said... anyone got any recomendations for similarly spec'd power supplies for not a whole lot different price (sub-$100, output toggle, 0-20v+, 2 or so amps with either 10turn or encoders?)*bummed*

author: Monkeh
author_rank: Super Contributor
timestamp: April 17, 2013, 02:43:34 am
content: .... Insurance or not, that's totally unacceptable.

author: IanB
author_rank: Super Contributor
timestamp: April 17, 2013, 03:01:41 am
content: Quote from: staze on April 17, 2013, 02:37:01 amWTF? How was it packed, exactly?

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 03:12:31 am
content: it was actually packed pretty well. it was in bubblewrap, then in a good 4 inches all the way around in peanuts.The box was pretty destroyed too. USPS at its finest I guess.Sad really. If it turns out I don't have to ship it back, I'm obviously going to try to repair. The front looks like it's in good shape, but I have no idea how the inside looks at this point. =( And of course today is when I started receiving parts for my adjustable load...Guess I'll be looking at E3610a's...

author: ve7xen
author_rank: Super Contributor
timestamp: April 17, 2013, 03:17:14 am
content: Quote from: staze on April 17, 2013, 02:38:43 amThe Power Designs stuff is ancient, but well designed and stable and can be had for well under $100. I don't think they have output toggles though. Decent examples can be had for under $50. e.g.this. The older HP 62xx series fits the bill too, just be careful you pick a model with constant current and with the output voltage/current combo you need, there are lots of different ones.If you keep your eyes open you should be able to get an E361x for around $100 too. My E3610A was $85 and that was on the high end of the spread for a guy selling a dozen of them over a week or two. Just keep your eyes open for them or set up e-mail notifications.Or you could go new, the Mastech stuff is supposed to be decent and some of their models can be had for around $100.http://www.mastechpowersupplies.com/Also that is REALLY RIDICULOUS. Someone clearly threw it off the loading dock onto concrete. Absolutely not acceptable. Sorry for your loss.

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 03:20:51 am
content: Quote from: ve7xen on April 17, 2013, 03:17:14 amThink it was machinery. Given how the box looks, I don't see how a fall could have done that. This was crushed.Sad.

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 05:12:10 am
content: So seller fully refunded. Didn't want it back....Sooo... I've pulled it all apart at this point, and THINK it's salvageable. Innards all look intact except one wire that goes between the RS-232 interface, and the front board. Easy enough to replace.Going to pound the case back into shape this week(end) and see what I can get. Wonder if TTi would just sell me the casing. =D

author: KJDS
author_rank: Super Contributor
timestamp: April 17, 2013, 08:36:49 am
content: I'm glad I don't ship stuff round the states if that's what happens to them. It's been a long time since I've seen anything that badly damaged and the box on that occasion had a set of lorry tire marks across it. That has suffered a lot more than a drop, it's either fallen off a moving vehicle or been in one that's been crashed, or possibly driven over.Good luck getting it working.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 17, 2013, 02:21:20 pm
content: Agree that it looks crushed, not merely dropped - but, ouch!Looks likethis Tektronix 'scopecould have been in the same container!

author: free_electron
author_rank: Super Contributor
timestamp: April 17, 2013, 03:05:07 pm
content: Quote from: grumpydoc on April 17, 2013, 02:21:20 pmWow that's the best looking tek scope i have ever seen. Must be the salvador dali edition...

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 04:31:32 pm
content: IanB (or free_electron),Any chance you could confirm the transformer in yours is wired like this?Mine still seems to still be wired for 230V, which makes me wonder if that's what causes the display issue. Currently it's wired to the two outside lugs, and then a jumper between the middle ones.I THOUGHT it would just be unplugging, but it looks like soldering is involved (which is completely fine). I just want to confirm the wiring before doing it. Guessing in 230v config, the middle winding is unused, and in 115v, you are just adding that winding to up the voltage/current on the output side of the transformer.

author: IanB
author_rank: Super Contributor
timestamp: April 17, 2013, 04:40:41 pm
content: When you look at the transformer you should see lugs corresponding to two primary windings. The windings are put in series for 230 V operation and in parallel for 115 V operation. The diagram you showed should match this. When I examined my unit it looked very much like the diagram in the operating manual.When I get home I can scan and post the exact instructions from my operating manual if it would help.

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 04:57:16 pm
content: Oh, already have that. And that makes more sense. You bought yours from a US supplier though, yes? So it came that way, and marked for 115v?Mine is wired like this currently, so 230v. So I just need to change it, which is some basic soldering, but no problem.I've got the manual though, it was just a bit ambiguous since it mentions changing the connections... I thought they'd just be push-on connections. =P

author: IanB
author_rank: Super Contributor
timestamp: April 17, 2013, 06:31:13 pm
content: Yes, my unit was configured for 115 V on delivery and the connections to the transformer were done with solder and heat shrink tubing. There is a sticker on the back that shows the expected input voltage. I don't think they expect this to be changed very often. Once a unit is in a given country it is likely to stay there.

author: staze
author_rank: Frequent Contributor
timestamp: April 17, 2013, 06:34:17 pm
content: Makes sense.Guessing the original owner must have been using it with 208v or maybe 240v. Interesting though is whether the seller was testing it with 115v (120v), and the unit was "almost" powering up. e.g. could that be what was causing the "bad display" if it wasn't getting enough voltage/current on the output side.I know first hand what happens if you plug in a 120v supply to 208v (bang!), but what is likely if you plug in a 230v into 115? I'd guess nothing really since it's all way under-volted.

author: staze
author_rank: Frequent Contributor
timestamp: April 18, 2013, 04:37:38 am
content: So....After two nights of banging with a rubber mallet and a vice, below is the result.Yes, it's the same unit. Yes, it's a little worse for wear, but it works. And yes, the displays work. Guessing the "no display" was due to it being configured for 230v and being tested on 115v.Tested with a simple 35w 12v MR16 halogen bulb, and yes, it does work. =)I'm happy! Especially for free. =D

author: ve7xen
author_rank: Super Contributor
timestamp: April 18, 2013, 04:44:21 am
content: Great score. Nice work.

author: IanB
author_rank: Super Contributor
timestamp: April 18, 2013, 05:17:20 am
content: Cool. You should definitely replace the label on the back with "This unit is configured for: 115 V", or someone will plug it into 230 V and it will smoke...

author: staze
author_rank: Frequent Contributor
timestamp: April 18, 2013, 05:20:25 am
content: it's not a label, it's silkscreened. but yes, I do plan on mark it. =) maybe just a label, or sharpie.Thanks! Guess I answered the question about what happens if you plug a 230v into 115v... it lights some leds, but nothing else works. =)

author: IanB
author_rank: Super Contributor
timestamp: April 18, 2013, 05:29:09 am
content: Ah, on mine they just put a sticky label over the top of the 230 V.

author: staze
author_rank: Frequent Contributor
timestamp: April 18, 2013, 05:30:33 am
content: That makes sense... okay, will just do that. =)

author: staze
author_rank: Frequent Contributor
timestamp: April 18, 2013, 08:15:40 pm
content: So, question.Looking at buying some banana to banana leads, but not sure about length. What do you all generally find most useful? Was thinking 3' at first, but realized that's a bit short if my PSU is on a shelf. So maybe 5'?Was looking at the pomona banana-banana jack ones here:http://www.pomonaelectronics.com/pdf/d_b_1_01.pdfThen probably picking up some banana to pin adapters to plug into breadboards, etc. Like these:http://www.mouser.com/ds/2/159/d3561-3563-3565-4691_100-65890.pdfI know I'm going to need crap-tons of leads in the future, but for now, figured I'd start with a good general purpose set (so long-ish cables, but not so long they're coiled up on my bench).Thanks!

author: staze
author_rank: Frequent Contributor
timestamp: April 28, 2013, 05:14:54 am
content: Quote from: eevblogfan on April 12, 2013, 08:16:09 ameevblogfan,All parts have arrived. Would love to try schematic. Also thinking about trying the sleepyrobot one since I have the parts for it too.Thanks!

author: IanB
author_rank: Super Contributor
timestamp: April 28, 2013, 05:52:54 am
content: By the way, I've never been quite sure about the idea of using active loads like constant current, constant power, constant voltage to test a lab power supply.You essentially have a control system in the power supply attempting to regulate voltage or current to a set point, and now you have a load also trying to regulate voltage or current to some other set point. It seems to me that this is creating a scenario where oscillation or other forms of instability might occur where different control loops interact with each other in unplanned ways.Best in my view to test a lab power supply with "normal" loads that represent applications foreseen and planned for by the power supply designers.

author: staze
author_rank: Frequent Contributor
timestamp: April 28, 2013, 06:00:11 am
content: Quote from: IanB on April 28, 2013, 05:52:54 amMakes sense. I just planned to set the PSU to 30v, 2a and use the dummy load to test that. I don't really have anything that I can use to test that. Best load test I've done with it so far is a 35w 12v bulb. =/ Which did draw the full 2A at that voltage, but it would be nice to confirm the full 2a at 30v. *shrugs*Also, a nice little project to build... since I'm still learning this stuff.

author: staze
author_rank: Frequent Contributor
timestamp: April 28, 2013, 06:29:45 am
content: That, and it'll make a nice hand warmer. =)

author: IanB
author_rank: Super Contributor
timestamp: April 28, 2013, 06:36:37 am
content: I have not tested my supply up to 30 V either, I'm just taking it on trust so far that it will do it.One thing you could do is look for 6 V bulbs (motorcycles?). Put five of them in series and you get a 30 V load with a known current draw. For example, 6 V 12 W bulbs would give you the maximum load.

author: staze
author_rank: Frequent Contributor
timestamp: May 06, 2013, 11:03:15 pm
content: IanB,Have you ever cracked your EL302P? I'd be curious what caps (brand and size) are on the driver board. Mine are CapXon's (ugh), but there's reference in the service manual to them having changed a couple of the caps between Rev 1 and Rev 2 to resolve an issue with the output apparently engaging on power off (or something like that).Also, does your's remember the output setting? If I have the output on, then turn the whole unit off, the output will be enabled when I switch the unit back on. Kinda thought the output should be "off" by default on power up, no matter what.

author: IanB
author_rank: Super Contributor
timestamp: May 06, 2013, 11:18:56 pm
content: I can take a look for you later and let you know. I have not tested what happens if I switch it off with the output on.

author: staze
author_rank: Frequent Contributor
timestamp: May 06, 2013, 11:28:43 pm
content: awesome, thanks!

author: IanB
author_rank: Super Contributor
timestamp: May 07, 2013, 01:38:49 am
content: The main big caps on the driver board are Jamicon, 1000 µF 63 V 85°C (four of them). All the other caps are Jamicon too except for one little purple ELNA cap.Perhaps it's disappointing they didn't use a top brand in a premium quality item, but neither should the caps be heavily stressed in a linear supply, so maybe not too bad.My unit remembers all its settings when you switch it off, including the output setting. If the output is on when you operate the main power switch, then the output is on when you turn it back on again. So I guess your unit is behaving as designed.

author: staze
author_rank: Frequent Contributor
timestamp: May 07, 2013, 06:40:24 am
content: Quote from: IanB on May 07, 2013, 01:38:49 amAh, excellent to know. Haven't heard of Jamicon before... but that doesn't mean much. I KNOW I've seen blown CapXon's (monitor repairs). I think mine had some small ELNA's in it as well, can't recall. Guess if mine ever blow (which I doubt given their size, and the adequate airflow), I'll replace them with some Rubycon's or something.The reason I asked is there's a note in the Service Manual that says: "C21 and C22 (C121 and C122) on the Driver pcb are now both 470uF to prevent the output from occasionally turning on briefly when the mains power switch is turned off." C21 and C22 aren't any of the big ones, but rather two more in the center line of the board. See picture. According to the parts list, the 470uf's should be a 35V (C21), and a 16V (C22). *shrugs*I believe this revision was made after mine was produced, since my control board is all through hole (the change to surface mount was with Rev 2). But I can't say I've seen the output switch on on power off. Maybe once I have a scope I'll test this more thoroughly (maybe compare to your graphs in your other post as well).Also good to know about the output setting. Do wish it defaulted to off. Guessing they had a reason for it.