Norcold DE-251E repair

[PSteward]

Hello,

It seems my Norcold stopped working for 12V input and I was wondering if anyone had a repair manual for the power supply (16011396007)?
I pulled it apart already and relays work, the fuses are good, the diodes are good, the caps seem fine (visually) so I'm not sure where the failure is and as my boat is being wrapped I don't have access to the fridge (wouldn't fit to remove....).

I read that the compressor was 28VAC (?), but need to verify, worst case I could make a new power supply or just get a small inverter (need 120v .4A) to deal with the DC load...

Thanks,

--Phil

[Coolerking]

Is it a dual voltage unit (ac/dc)?

[PSteward]

Yes, it supports AC/DC. The issue seems to be on the DC input.

Thanks,

--Phil

[Coolerking]

If it runs on ac power, then you likely have an issue with the wiring condition, or battery voltage under load.
Have you tried to disconnect the fan and run it on 12vdc?

[Richard Kollmann]

Originally Posted by PSteward

Hello,

It seems my Norcold stopped working for 12V input and I was wondering if anyone had a repair manual for the power supply (16011396007)?
I pulled it apart already and relays work, the fuses are good, the diodes are good, the caps seem fine (visually) so I'm not sure where the failure is and as my boat is being wrapped I don't have access to the fridge (wouldn't fit to remove....).

I read that the compressor was 28VAC (?), but need to verify, worst case I could make a new power supply or just get a small inverter (need 120v .4A) to deal with the DC load...

Thanks,

--Phil

That unit is dual voltage AC DC 26 or 28 volts 60 cycles. The power transformer has two separate output field coils one for each power source. If unit cools on AC and not DC the DC converter boosting 12/24 volts to 60 cycles 26-28 volt AC is produced at compressor.

If over heated transformer smell is detected one of the three coils inside has failed.

When both AC and DC power is good at unit the DC is automatically turned off by a two position relay.

[PSteward]

Hello,

I tested the whole thing including the transformer and it produces 23VAC on 120v power. On DC I hear the relay switching (and switching "off" when I have both connected), there is a three pin connector that interfaces with the large transformer, the middle pin brings 12v, and the other two I'm not to sure as I cannot read anything there. What is the intention of the main transformer? I see 7 leads, two are the 120v in, two are the 23vac out (to compressor), and the remaining three are from the DC feed (2 unknown pins, plus a 12v pin).

Thanks,

--Phil

[PSteward]

As a workaround, I've tested (without the fridge, just the PS) an inverter and it operates fine, voltage fluctuates a bit more (22.8-23.2 vs 22.7-22.8 VAC) then on straight AC but it works.
If I can't resolve the DC part of the board issue I'll build an AC driven relay board to cut out 12v to the inverter when there is dock power and switch to that as a source instead.

[PSteward]

It appears the circuit is similar to this:


Which implies that the oscillator chip has failed on the board if nothing is being received at pins 1 or 3. Pin 3 should output an inverted wave of Pin 1.

If I create a separate board to output a 60hz wave on pin 1, inverted 60hz wave on pin 3 and 12v on pin 3 and re-interface to the new board I think it would resolve the issue.....

[PSteward]

Does anyone know if the original circuit output a square wave or a sine wave?

Thanks,

--Phil

[PSteward]

Anyone have any ideas? This is to run the 23VAC compressor, I can swap in a quick circuit that provides a 300w square wave but am worried if the original made a sine wave, however it is challenging to determine not knowing the chips on the board since they are unmarked or covered.

Thanks,

--Phil

[Richard Kollmann]

Home electrical is sign wave. The Norcold swing compressor power sources I am familiar with use a transformer to decrease AC and increase DC voltages to 20 to 28 volts at 50 to 60 cycles to pulsate vibration of compressor magnet.. A transformer's requires clean sign wave home power.

Refrigeration techs carry a standard 110 volt to 24 volt transformer to connect direct from standard AC outlet and to these compressor for a quick test. Swing compressors are not all the same voltage some are designed for only 20 volts power transformers.

[PSteward]

Hey Richard,

My plan was to use to use a circuit that converts a 12v signal to a 12v signal that has an inverted square wave at 60 hz. The circuit uses an oscillator to make and flip the wave and then it's put into the original transformer which brings it from 12VDC (oscillating 3 leg) to 23VAC.
My only concern was if the original circuit made a pure sine wave output at 12vdc before it was sent to the transformer and this seems to be done traditionally with BJT level shifters, unfortunately there are two ICs (or so I think) covered up that I assume is at the very least providing the oscillation but I don't see what would be fixing up that inverted square wave on the original board.
Is there a circuit diagram for that power supply?

Thanks,

--Phil

[DeBe]

The 12V circuit is square wave & the compressor is quite happy with that.

[DeBe]

This is the wave form on the transformer windings to feed the compressor on 12V DC. These compressors basicly use Engel fridge system (its 50HZ aprox here as this is an Australian model)

[DeBe]

Bit more details. Drive to the switching MOSFETs.