Thermo electric pcb power supply

[Aaron The Tinkerer]

Re: Thermo electric pcb power supply

Alright...I think I'll just use an inverter when I want to use it on the road or off-grid, even though I lose some efficiency. I may be jumping in to the deep end too soon. There's obviously much more I need to learn before I mess with this.

Thanks anyway, guys.

[Agent24]

Re: Thermo electric pcb power supply

Probably a good idea to have a look here: http://www.smps.us/power-supply.html and http://en.wikipedia.org/wiki/Switched-mode_power_supply

[stj]

Re: Thermo electric pcb power supply

i will start by saying your lucky to be n the u.s.
because if you had real mains like Europe / Australia your meter would have done a lot more than gon "kaput".

the mains goes through the filter choke that looks like a transformer.
then it gets rectified into dc.
120v rectified is closer to 190v i think. in Europe it would have been about 370v!!!

that then gets converted into very high frequency pulses and fed into the "real" transformer.
the output voltage is controlled by altering the pulse frequency.

i dont think you should be messing with this if you dont understand the principle of how they operate!

[Aaron The Tinkerer]

Re: Thermo electric pcb power supply

That's not a transformer, just a line filter. Those diodes output rectified line voltage, NOT 12v.

Thanks. That's probably why my meter went kaput! Learning as I go...

I'm guessing the big transformer is where the stepdown takes place, so the diode(s) should be after that, right?

[Agent24]

Re: Thermo electric pcb power supply

That's not a transformer, just a line filter. Those diodes output rectified line voltage, NOT 12v.

[Aaron The Tinkerer]

Re: Thermo electric pcb power supply

Hi, I know this is an old thread but I just joined because I'm trying to convert my thermoelectric fridge to be able to run on 12VDC input and this is the thread I found when searching for info. related to servicing the PSU boards that run these things.

I have one of those Chinese boards made by Hanny (part no. S126AM14-5), like the ones found in Haier, Avanti, and Chefmate thermoelectric refrigerators and wine coolers. This particular one was salvaged out of a countertop water dispenser and is being used in a custom 0.7 cf homebuilt top-loading fridge box. If anyone can point me in the right direction, I'm looking for a point to tap in a 12 volt lead. I'm not very well-versed in electronics but I know some of the basics. At what point on this board would I get 12 volts? I'm told it's after the Schottky diode but I see several such diodes. It appears that after the main AC power comes in, it goes to that first transformer which is then followed by two small diodes but my little cheapo meter went on the fritz when I touched it to the leads.

[kc8adu]

Re: Thermo electric pcb power supply

area around the topswitch looks like a spill/cap leak.
those surface mount caps may have leaked.
edit!
zoom in on the area around u4.looks like an arc between pins.

[sawbones]

Re: Thermo electric pcb power supply

Has anyone had an experience with the 500W power supply for the ThermoTek Vascutherm 2? Board has number OP8A500PPS on it. Here is the picture:

[budm]

Re: Thermo electric pcb power supply

That is why this place is called BADCAPS.NET, so many bad caps in all kind of products.
Great job fixing it.

[epkoncept]

Re: Thermo electric pcb power supply

Eureka, got it to work at lunch time today.
I managed swap out the remaining electrolytics, 1, 4.7, 22 uF caps. There were about 6 small caps to replace. I replaced 4 of them and it worked. I noticed that the caps were between 1/2 to 1/10 the rated capacitance. Just for peace of mind I also changed two more caps which I think were used for the snubber for the switching transistors.

Doing an aging test tonight.

Thanks again. Funny that it turned out to be bad caps.

Peter

[Behemot]

Re: Thermo electric pcb power supply

I think KY's are not bad at all, I mean, like there is not even much more better lytics on market. They are cheap, but hey, I noticed in DigiKey similar Nichicons (HE/HD IIRC) are even cheaper. Datasheet-wise, both are very good with great ripple and long lifetime.

[sam_sam_sam]

Re: Thermo electric pcb power supply

connected ? OCP ? I wonder if the bulk caps are degraded so they can's support the inrush current requirements ?
Peter

I have also seen this as well

I just replace all of the cap with FC / FR / FM<...... If money is no problem

KY I think this is the right one KME <........If money is is a problem

This works most of the time

Here is what the problem with this drive was when it cooler in the AM the drive would go in to an ground fauilt alarm every time you would start the the drive to run the motor

I just had to repair a Variable Speed Motor Drives (AC ) that is 12 years old it had two bad cap on the current senseing board 47 uf @ 16 volt in this case I used FR cap in it

But here is the funny part of this.....>
One cap had a ESR reading .57 @ 80 *F but at about 60 *F then it when to .75 and going higher the other cap was .51@ 80 but at about 60 *F then it when to .70 and going higher

The FR caps 47 uf @ 25 volts I put in I did the same test and had a ESR reading .47 @ 80 *F but at about 60 *F then it when to .51 and stay there

If this power supply have been around for a while and used a lot or it sits for long periods of time not being used I would replace ALL CAPS in it

I hope this helps

[sam_sam_sam]

Re: Thermoelectric PCB power supply

Budm:

I did notice one odd trait. I had to push the probes pretty hard to get continuity ? However, i did not see any evidence of any conformal coating ?
Peter

I have seen this before as well

What I do is take my desoldering gun and remove the old solder and put new
solder and then you do not have that problem more

[epkoncept]

Re: Thermo electric pcb power supply

Budm:

I did a quick visual.
Looked pretty normal, but I did notice one odd trait. I had to push the probes pretty hard to get continuity ? However, i did not see any evidence of any comformal coating ? Wonder why ?

Peter

[budm]

Re: Thermo electric pcb power supply

Just to be sure, you have already inspected all the solder joints?

[epkoncept]

Re: Thermo electric pcb power supply

Tom:
Changed the input bulk caps( 120uF 200V) and the output filter cap( 220uf 16V) of the+12V line and there was no change in the operation. I wonder what to do next ?

Should have asked if anyone ever managed to find a schematic of this ps ?
p

[tom66]

Re: Thermo electric pcb power supply

Startup cap or main output caps could be a possible cause of the problem.

[epkoncept]

Re: Thermo electric pcb power supply

Update: disconnected the peltier, then plug in the AC power, fans run. While still plugged in, I re-connect the peltier to the ps, and it continues to operate fine. Left it for 2 hours Works great. I wonder what causes the system to
output basically 0 volts to the peltier if started up with the peltier connected ? OCP ? I wonder if the bulk caps are degraded so they can's support the inrush current requirements ?
Peter

[epkoncept]

Re: Thermo electric pcb power supply

Hi:

just joined today. I have a problem.
The interior LED turns on, but hte cooler and fans are dead.
checked the sw tr's, diodes and serires resistors and all seem fine.
Does anyone have any hints ?
Or better yet a schematic of this supply ?
Peter

[Behemot]

Re: Thermo electric pcb power supply

Man Yue makes Samxon RT in this long life/high voltage segment. Also you can take small RTs with parameters similar to Nichicon PW/HE.