Bought TTi EL302P off ebay, dead display

[IanB]

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.

[staze]

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

[IanB]

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.

[staze]

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.

[staze]

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

[ve7xen]

Great score. Nice work .

[IanB]

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...

[staze]

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. =)

[IanB]

Ah, on mine they just put a sticky label over the top of the 230 V.

[staze]

That makes sense... okay, will just do that. =)

[staze]

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.pdf

Then 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.pdf

I 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!

[staze]

hey

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

eevblogfan,

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!

[IanB]

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.

[staze]

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.

Makes 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.

[staze]

That, and it'll make a nice hand warmer. =)

[IanB]

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.

[staze]

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.

[IanB]

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.

[staze]

awesome, thanks!

[IanB]

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.

[staze]

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.

Ah, 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.