Wine Fridge Power Board

[keeney123]

Re: Wine Fridge Power Board

I believe the IC's are op amp LM358P, PulseWidth Modulator AZ494AP-E1. The input line Transformer that is being used as a inductor is either ET-24 or EE-25 both GP brand. The two big electrolytic caps are 330UF. The cap across the line and neutral is possibly 0.22 uF at 275 Volts. C16 is a 1uF 20% tolerance 200 volt. The big transformer is a ERL-28. Perhaps acornish can look at the board and confirm and possible add the voltage of the big caps. Once this is done I will continue to look up parts and draw rest of schematic

[keeney123]

Re: Wine Fridge Power Board

acornish if you pull off the quality control sticker from the transformer I circled in white we could find out what number it is. Also if you could try and clean the top of the ICs. first try some water, lightly. Then use at least a time 5 Diopter magnifier to look at the chip numbers. If that does not work use some isopropyl alcohol. Let me know what numbers you come up with.

[keeney123]

Re: Wine Fridge Power Board

I made it a diode because it had Dxx on it. You also,missed R36. You had circled the end points of it, but you didn't put symbol in. This is a schematic Primary side with the correct component numbers as the board. I put the two components in that were in question to what I believe you referred to. I can values of resistors from what I can see. If you think something is wrong let me know. I will try and look up the transformers later on to get the correct pin number and voltage value. I found they usually go by the part number so if there is a ll-19 it usually means 19 volts.

[budm]

Re: Wine Fridge Power Board

Sure like to know what that part is inside that tubing, and the Value of that resistor.

[budm]

Re: Wine Fridge Power Board

Yes, that one looks like it has shrink tubing on it (with Dxx printing next to it) and is connected between incoming AC L and another end goes to the junction of those two filter cap not to the primary DC negative as I have drawn. The resistor next to it looks to be connected between the circuit GND and the junction of the two filter caps.
Your brightened picture shows a lot better than the original

[keeney123]

Re: Wine Fridge Power Board

BudM I notice something at little different in your component layout. I have adjusted the exposure and circled the area in question. To me it seems where you have a resistor there is a diode. That would be the resistor going back to the line . The other thing I noticed is the resistor I have circled does not appear in your component layout.

[keeney123]

Re: Wine Fridge Power Board

Originally Posted by acornish
The chip marked IC3 has no markings on it and my guess is that it proprietary.

You can usually tell what it is as to what it is connected to. Many times to safe guard a design manufacturers will wipe off the chip name and number. I have seen it done on programmed chips. This chip could be program one time chip to behave a certain way, that is only speculation though.

Also, I did use a roller to paint. The roller made a bigger mess then the brush that I used for the trim. This was paint the Manager of the apartment gave me. They use this on all the apartments. The paint I put on several years ago was good quality paint. Yes Dr. Kriesler was a good teacher and he was Head of the Department and Head of Graduate Emissions. He would work from 6:30 AM til past 9:00 PM He was in the applied Physics side.

[Agent24]

Re: Wine Fridge Power Board

budm, the capacitance of C16 is 0.97 uF, and it is rated at 1.0uF
The other large capacitors on the board:
C20 = 0.070 uF, rated at 0.1 uF (capacitor near fuse)
C15 = 118 uF (rated 120)
C12 = 123 uF (rated 120). These are the units mentioned by kenny123 and are "near" C16.

These caps have not been replaced, but appear to be "close" to their rated values. Is "close" good enough, or should they be exact..

Because of material variances and manufacturing process variances, not all components will be exactly the same. That is why they are specified with a tolerance value in percent, which shows how much the part may deviate from the marked value.

If your 0.1uF capacitor is rated at 10%, then it can be anywhere between 0.9uF and 1.1uF and still be considered OK. They do not have to be exact.

If a part is outside its specified tolerance, it's either bad quality, damaged\faulty, or has drifted with age. In all cases it should be replaced.

Last thought on TR1, I have tried "finding" it online, but the numbers on it "HEC0809/A EE-19" seem elusive. Any thoughts on what this might mean? I would replace it if I could find it. The only thing I have found is the attached data sheet for an "AEE19-3460", but I don't understand the specification enough to determine its step down ratio. I see that the 5th specification indicates that PRI:SEC = 1:1, but that doesn't make sense either. What would be the point of a 1 to 1 input to output ratio?

Finding replacements for SMPS transformers is hard as they are often custom designed for each supply. There are some exceptions though (yours might be a "standard" EE-19 (Don't quote me on that!) but in any case, the transformers practically never fail, so it's not the first part to suspect as faulty by any stretch - unless it's visibly damaged.

A transformer with a 1:1 ratio would be used for isolation\coupling. Some SMPS designs might use a 1:1 transformer for part of a feedback loop for example.

The chip marked IC3 has no markings on it and my guess is that it proprietary.

Could be, but often they use standard parts and scrape the numbers off so you don't know what they used, so you can't copy the design (or realise they've ripped yours off!)

[keeney123]

Re: Wine Fridge Power Board

Those electrolytic along with the associated diodes appear to be in the reverse order. The negative side appears to be connected to the positive side voltage. That is why I suggested to ohm them out not the value of them but where are they in the circuit. If you look at my schematic you can easily follow them back to the B+ voltage.

[budm]

Re: Wine Fridge Power Board

The AC Voltage reading low can be due to low bandwidth of the meter AC function, the AC frequency on this board can be from 50KHz to 80KHz which most meter cannot measure accurately.

[acornish]

Re: Wine Fridge Power Board

There are 13 electrolytics cap, lots of small one on the secondary side.

True enough and as the forum's name suggests that sure could be the problem. I will replace them next week and see what happens.

Any thoughts about my Transformer 1 concern?

acornish

[budm]

Re: Wine Fridge Power Board

There are 13 electrolytics cap, lots of small one on the secondary side.

[acornish]

Re: Wine Fridge Power Board

This is just how we did it in the olden days. No need to thank me. Just remember to also use post 82 component layout assignment as it corresponds with the schematic as I was not sure what number components it had to do. Understand that the cooling of the unit will be limited. I had to paint two coats on my apartment to cover the underneath paint and the apartment building uses very running paint, to a point one has to wait for the paint to stop dripping off of the brush. It took me 24 hours to paint everything. When I used my paint the first time I painted everything in 16 hours with two coats. I live in subsidized housing so I will have to wait until an apartment opens up in North Adams MA. What do you do at the University? In 1980 I use to work for UMass at Amherst as a research assistant for the High Energy Physic Dept. My boss was Prof. Kriesler. Hardest working man I know.

keeney123, Yikes! That paint sounds like quite a challenge. I have painted before around the house but it usually dries in an hour or so. It is pretty dry where I live and I am sure that makes a difference, but it also sounds like your paint might be a bit watered down. You mention using a "brush", might a roller have helped? That is what I usually do, only using a brush to "cut in" the edges. I have been lucky enough to get some good advice from the painters here on our campus it sure has helped the projects at home.

With respect to the University I work at, my back ground is Molecular Biology and Microbiology (DNA and Bacteria), but I also look after old surplus equipment. It was my frustration with throwing out perfectly good equipment that often only needed a new fuse (yes, Researchers often don't check even that) that started me repairing stuff. It had started almost as a "work hobby" but so far I have actually managed to fix a number items. The two 30" monitors that I currently use on my office computer were "garbage" unit, with the help of this group, I fixed the power supply and got them working. I just needed a couple of $3 chips from China and I was back in business.

This fridge has been a tougher nut to crack, but I am learning a ton of stuff and the fact that it even now works is quite satisfying. If I, with your help and the help of others like budm, I can get it working properly, I will be pretty happy. That and I can keep my lunch cool!

As for Prof. Kriesler, a quick Google search makes it look like he has retired, but from his "rate-my-prof" page it sounds like he was a great teacher.

Thanks again for your help and again good luck with the move. My fingers are crossed that something comes available for you soon.

acornish

[acornish]

Re: Wine Fridge Power Board

Please check the capacitance of the polyester film cap C16 next to the big transformer.

budm, the capacitance of C16 is 0.97 uF, and it is rated at 1.0uF
The other large capacitors on the board:
C20 = 0.070 uF, rated at 0.1 uF (capacitor near fuse)
C15 = 118 uF (rated 120)
C12 = 123 uF (rated 120). These are the units mentioned by kenny123 and are "near" C16.

These caps have not been replaced, but appear to be "close" to their rated values. Is "close" good enough, or should they be exact.

When I start looking at voltages, the whole system starts fine at 120V AC, but by the time we get to the large transformer (TR2) near C16, the input voltage across #1 and #2 is only 82V AC with on output voltage at pins 7 and 5 or 8 and 5 of only 9.7 volts. When a peltier unit is attached to the system this voltage drops to under 1 volt.

Similarly on Transformer 1 (TR1) the voltage across 3 and 5 is 38V AC with an output at various combinations of 6, 7, and 8 of under 1 V AC. The voltage across 4 and 1 is about 70 V AC, but again out is under 1 V.

Does this suggest that TR1 is the problem? If the out put of TR2 is about 1/10 of the input, shouldn't the output of TR1 be more than 1 V? The section of circuitry around TL494, which does appear to be an oscillator seems like an amplifier. The datasheet for TL494 indicates that the VCC can take up to 41V, with a min-max range of 7 to 40 V. If TR1 putting out less than 1 V, then does it make sense that TL494 is not "energized" to the point where is can self-oscillate and get the process going? Any suggestions on how to test TR1 to see if it is "healthy"?

Last thought on TR1, I have tried "finding" it online, but the numbers on it "HEC0809/A EE-19" seem elusive. Any thoughts on what this might mean? I would replace it if I could find it. The only thing I have found is the attached data sheet for an "AEE19-3460", but I don't understand the specification enough to determine its step down ratio. I see that the 5th specification indicates that PRI:SEC = 1:1, but that doesn't make sense either. What would be the point of a 1 to 1 input to output ratio?

The IC marked IC2 is an LM358P chip that, as near as I can tell is an two channel amplifier, but in this case is only being fed 1 channel as pins 5, 6, and 7 are not connected to anything. My thoughts are here is that it amplifies the weak signal coming from the thermocouple and potentiometer inside the fridge.

The chip marked IC3 has no markings on it and my guess is that it proprietary.

I have attached an updated version of your drawings with some labeling in yellow to help match my descriptions above.

Thanks again for your help.

[keeney123]

Re: Wine Fridge Power Board

keeney123

Wow! Thanks for doing so much work on this. I have also been busy at the University I work at and have not had a chance to do anything with this. I will check out the capacitors and work through you schematic in post #85. I really appreciate the time you have put in to this for me-"Thank you" just seems inadequate.

I will post back as soon as I can.

I hope the move and the painting are going well. I have done similar work at home recently myself and although gratifying when finished, it is a lot of work.

Take care-Acornish

This is just how we did it in the olden days. No need to thank me. Just remember to also use post 82 component layout assignment as it corresponds with the schematic as I was not sure what number components it had to do. Understand that the cooling of the unit will be limited. I had to paint two coats on my apartment to cover the underneath paint and the apartment building uses very running paint, to a point one has to wait for the paint to stop dripping off of the brush. It took me 24 hours to paint everything. When I used my paint the first time I painted everything in 16 hours with two coats. I live in subsidized housing so I will have to wait until an apartment opens up in North Adams MA. What do you do at the University? In 1980 I use to work for UMass at Amherst as a research assistant for the High Energy Physic Dept. My boss was Prof. Kriesler. Hardest working man I know.

[budm]

Re: Wine Fridge Power Board

I cannot easily see the designators for each of the components to make it easier to guide as which component to check, I.E. Check the DCV of Cxx.
But from looking at the board I can kind of see how it works.

[keeney123]

Re: Wine Fridge Power Board

The thread is getting long so I am not sure if you replace all those electrolytic caps or not.
I updated what I can see on the board, from looking at it when the power is first applied to the board, it goes into self oscillation and supply its own power to produce the VCC for pin 12 of TL494, once it start running then the TL494 will start regulating the circuit to maintain 12V Output.

Bud M did you see my post 85 schematic on your component layout? The schematic corresponds to Post 82 component layout assignment. As I did not know which actually numbers corresponded with your component layout. The values could be placed in to the schematic. If I get some spare time I will draw a schematic of the rest of the board.

[budm]

Re: Wine Fridge Power Board

The thread is getting long so I am not sure if you replace all those electrolytic caps or not.
I updated what I can see on the board, from looking at it when the power is first applied to the board, it goes into self oscillation and supply its own power to produce the VCC for pin 12 of TL494, once it start running then the TL494 will start regulating the circuit to maintain 12V Output.

[budm]

Re: Wine Fridge Power Board

Please check the capacitance of the polyester film cap C16 next to the big transformer.

[acornish]

Re: Wine Fridge Power Board

keeney123

Wow! Thanks for doing so much work on this. I have also been busy at the University I work at and have not had a chance to do anything with this. I will check out the capacitors and work through you schematic in post #85. I really appreciate the time you have put in to this for me-"Thank you" just seems inadequate.

I will post back as soon as I can.

I hope the move and the painting are going well. I have done similar work at home recently myself and although gratifying when finished, it is a lot of work.

Take care-Acornish