Author Topic: Bought TTi EL302P off ebay, dead display (Read 18400 times)

staze · « **on:** April 11, 2013, 06:38:06 am »

Sure others might have saw this listing:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380545309157

Figured 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?

free_electron · « **Reply #1 on:** April 11, 2013, 06:49:56 am »

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.

staze · « **Reply #2 on:** April 11, 2013, 06:51:44 am »

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!

staze · « **Reply #3 on:** April 11, 2013, 06:59:44 am »

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!

amspire · « **Reply #4 on:** April 11, 2013, 07:06:18 am »

Quote from: staze on April 11, 2013, 06:38:06 am

Sure others might have saw this listing:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380545309157

Figured 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.

It 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/

ve7xen · « **Reply #5 on:** April 11, 2013, 07:11:40 am »

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

.

staze · « **Reply #6 on:** April 11, 2013, 04:06:56 pm »

Quote from: ve7xen on April 11, 2013, 07:11:40 am

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 .

Oh, 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.

krivx · « **Reply #7 on:** April 11, 2013, 04:49:01 pm »

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.

free_electron · « **Reply #8 on:** April 11, 2013, 05:37:17 pm »

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

staze · « **Reply #9 on:** April 11, 2013, 05:55:58 pm »

Quote from: free_electron on April 11, 2013, 05:37:17 pm

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

Judging 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... =)

staze · « **Reply #10 on:** April 11, 2013, 05:59:16 pm »

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.

staze · « **Reply #11 on:** April 11, 2013, 06:19:02 pm »

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?

ve7xen · « **Reply #12 on:** April 11, 2013, 06:51:43 pm »

Quote from: staze on April 11, 2013, 06:19:02 pm

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...

If 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.

staze · « **Reply #13 on:** April 11, 2013, 07:12:32 pm »

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!

gerrysweeney · « **Reply #14 on:** April 11, 2013, 07:29:21 pm »

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

staze · « **Reply #15 on:** April 11, 2013, 07:32:21 pm »

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.

ve7xen · « **Reply #16 on:** April 11, 2013, 08:07:02 pm »

Quote from: staze on April 11, 2013, 07:12:32 pm

yeah, testing voltage is no problem.

Testing 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.

staze · « **Reply #17 on:** April 11, 2013, 08:44:10 pm »

Quote from: ve7xen on April 11, 2013, 08:07:02 pm

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.

Yeah, 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's it 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. =)

staze · « **Reply #18 on:** April 12, 2013, 07:30:20 am »

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?

Balaur · « **Reply #19 on:** April 12, 2013, 07:43:52 am »

Quote from: staze on April 12, 2013, 07:30:20 am

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?

If 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.

eevblogfan · « **Reply #20 on:** April 12, 2013, 08:16:09 am »

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 !

staze · « **Reply #21 on:** April 12, 2013, 04:54:38 pm »

Quote from: Balaur on April 12, 2013, 07:43:52 am

If 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.

okay, that makes sense.

So a 15? resistor should get the PS to output 2A at 30V, and it would dissipate 60W, yes?

eevblogfan · « **Reply #22 on:** April 12, 2013, 05:00:05 pm »

staze · « **Reply #23 on:** April 12, 2013, 05:13:04 pm »

Quote from: eevblogfan on April 12, 2013, 08:16:09 am

simply 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.S

okay, 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?

eevblogfan · « **Reply #24 on:** April 12, 2013, 06:04:01 pm »

10X 1ohm 1W 1% will do

as for the mosfet , IRFP250N and IRFP064N are good choice for that linear task since they have good SOA ratings in the linear region

try to get the IRFP250N because of it's high voltage rating ( no need to fear from spikes of 40~ 80V )

good luck


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Author Topic: Bought TTi EL302P off ebay, dead display (Read 18400 times)

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