Old Toshiba aircon unit

[FloodGoose]

Thanks for explaining. I did that and, once I made sure to plug in the molex connectors, I was able to get continuity from Live and Neutral to L01. Could you tell me the next step I need to take please?

Thanks

[electrofix]

next step is to check R1

if that ok we can say C02 should charge to 300v DC

we now need to know if the power supply is operating so we need to check the voltages on the smaller caps

you should get 7 12 and 35 volts on the caps

if you get nothing then the power supply unit is not working

Dave

[FloodGoose]

Thanks for the reply. What am I checking on R01, just continuity from one side to the other?

And, presumably to check the capacitors, that means connecting the power first and testing while the power is on?

And finally, by power supply unit, you mean IC01? SO if there’s nothing coming from the capacitors at this point, it means replacing that?

Sorry for all the stupid questions, it’s just new to me and I don’t want to mess anything up!

[electrofix]

yes resistor will be low value poss 47 ohms or so so if its thousands its gone

the capacitors are the dc voltages that feed the circuits and yes if you get nothing and R01 is ok i would suspect the IC01

as a last double check you can check voltage on C01 which should be 240v AC
and the voltage on C02 which should be 300v DC or there abouts

just remember to take care and be careful measuring live circuits

Dave

[FloodGoose]

Thanks a lot.

One quick question, the power lines feeding the unit aren’t very long, and there’s not a ton of space, so I’m not sure if I can connect the power whilst having the PCB accessible, and not shorting anything out. Any tips?

Also, I guess stand on a rubber mat, wear rubber gloves, and handle the probes by the insulated parts for best practice. Anything else?

Thanks again

[electrofix]

well if it was me i would power it up on the bench, but that is more difficult as you would have to solder wires to the board to get mains power to the correct place.
we need to find out if the board power supply is ok

to do this by the way the only connectors you need are where the power comes in, looks like P04 and CN04 the rest dont need to be connected to test power supply

you can leave boards hanging out on test provided you make sure it cant touch anything. I have used bits of cardboard etc to hold the board during test

Dave

[FloodGoose]

Hi again, No, I didn’t electrocute myself and die! I was waiting on some crocodile clips for the multimeter! When they came, I checked the power lines into the unit (the 3 wires coming in, not the 4 wires that go to the outside unit) and was surprised that I’m getting a 0L reading (00.1 when I use the 10A port). There certainly was power going to it before, hence the fuse on the PCB popped, and there’s still power on the circuit, because it shares it with an outside power outlet than runs a CCTV camera (which requires 12V). But it looks like, somewhere, it’s not getting to the a/c unit.
I’m not really sure where to look. There’s no isolator switch for the unit, or any other switch or anything like that, but given the issues I mention, I presume that somewhere between the circuit breaker and the unit, something is going wrong. Is that reasonable to assume? Any ideas how I can track that fault down?

Thanks again for all your help

[electrofix]

OL on a meter normally means overload or the meter is on a lower voltage scale then the voltage on the circuit

if your measuring sully voltage from the mains to the board you need the meter on AC volts and a scale above 250

Dave

[FloodGoose]

Ah, ok. I feel a bit silly! Yes, once I turned it up, it’s showing fine for the power.

So, I need to test the caps, as you said, but I’m not certain I can do it. Can I test them from the soldered, back side? I got some crocodile clip probes, but I doubt they will be able to grip, so it’s back to the standard probes. But, I can do that from the back side, right, I don’t need to get between the caps and the PCB?

[electrofix]

you need to connect to the solder pads on the caps. you dont need much of the wiring in to do it just the mains and the cn04 connector. get the board as stable as possible
what i am hopiing is you get no power which make it poss ic01 is the fault

Dave

[FloodGoose]

Ok, so I grew a pair and did it, and you were absolutely right. I was getting voltage from some places on the board, but those were totally dead. SO I guess it’s replace the Power supply. I will report back when that’s done. Thanks so much, I’d have been lost without your help!

[electrofix]

so all the low voltage side did not work ?

if yes change chip and see what happens

Dave

[FloodGoose]

So, I just got the unit back with the power supply changed and, oh boy, it works! So thank you so much for your help, I couldn’t have done it without you.

But, 2 related issues have become apparent:

1. It turned itself on, and was running, and I can hear the compressor running outside, but the fan isn’t turning on. THe air was cool for a couple of minutes, but then warmed up, presumably because the fan isn’t taking the heat away. ANy idea why?

2. The remote has also stopped working. The display wasn’t coming on, but if I squeezed it, I could just about see the temperature etc.. change, but now nothing an dno response from the unit. ANy ida how I can try and fix it before dropping the cash and more importantly the time to get a new one?

Thanks again

[electrofix]

check connector CN 27
thats where the fan connects to the board

Dave

[FloodGoose]

Just to update you, I couldn’t get the outside fan working, as I couldn’t afford to take it back to the shop, but I rednecked a solution by disassembling a box fan and strapping it backwards to the outside of the outdoor unit! So, just as we’re at the peak of a heatwave, we’re enjoying lovely cool, dry air! You really saved out bacon, which would have been crispy fried otherwise! Thanks again!

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