Old Toshiba aircon unit

[FloodGoose]

Hi everyone. I have a very old toshiba ras-10skh-e aircon unit that was in place when I moved in. We’re moving soon, but need to get through a hot, humid summer here, whilst packing up the house. The unit stopped working and when I opened it, I found a roast joint of mouse on the circuit board.

I took the board to a local (well, the most local, 90 minute drive each way!) repair place, who replaced the part that was fried. I brought it home and installed it but, probably due to my shoddy installation, the fuse on the PCB blew straight away. Another 3 hour round trip and the fuse and one capacitor were replaced, so this time I was extra careful. I put extra insulation tubing around all the power wires, made sure to check nothing was touching anything it shouldn’t be, and when I turned the circuit breaker back on…nothing.

I disassembled it again, and the fuse was still fine. I took a multimeter and tested every path on the PCB that I could find, including the junctions where the power cables enter and exit, and any wires that connect the mainboard to the small peripheral board etc… and everything shows continuity.

I reconnected it, making sure every connector was firmly in etc, turned it back on, and still nothing.

It’s so old I can’t get any replacement parts for it, so I have to find a way to fix it myself.

So, my question is, if the PCB seems to be fine and didn’t blow it’s fuse, but it did the previous time which shows there is still juice going through the line, where else can I look for the problem?

THe circuit breaker for the unit is functioning gine as far as I can see, snaps nicely back into the on position, and because of how the unit was installed, I can’t see any other point where there’s a fuse of circuit breaker etc…

Thanks so much for any help

[electrofix]

would need a look at the board and to know which parts fried to try to come up with a why

the service manual is online to help you

Dave

[FloodGoose]

Thanks for the reply. The guy who replaced the initial problem, and then the fuse and capacitor did check the board, and, as I say, I checked every single path on the PCB for continuity.

But, I can take a picture of the board as it is now and post it here if that’s helpful?

Thanks again

[electrofix]

if all the components are ok then it should work

you need to find a reason why the fuse blew. was it a board fault or an external component that caused it

I can find board overlays but not a board circuit diagram and dont know what components blew or why so its difficult to come up with a theory

yoes post some pics but the is a size constraint so you may have to host elsewhere and post public links

Dave

[FloodGoose]

Thanks again Dave,

I’ve uploaded an album here. In the final image, I circled in red the initial part that he replaced, he also replaced, on the second visit, one of the brown cylindrical capacitors(?), the one on the far left of the image with the brown top, and the fuse that blue (which he fashioned from spit and sawdust, lol)

https://imgur.com/a/vfn5MYU

[electrofix]

well you need to check on power

diagrams shows power come in the board then it goes out to 2 77 degree thermal fuses

you need to find and check them shows on connector cn04

Dave

[FloodGoose]

THanks a lot. SO they’re on the board? And they may be damaged even though the multimeter shows continuity? SO maybe they were also samaged at the same time as the othe rfuse (that was replaced?)

[electrofix]

this is a switch mode power supply to work they take 240v and rectifiy it to make DC at about 300v on the big cap

but in the circuit are 2 thermal fuses that are on equipment in the unit.and connect ot connector CN04. you need to see if you have a circuit across the CN$ plug, if these fail then there is no power to the power supply

my first job on a dead unit is to see if you have 300v DC on the main cap. if not we need to figure out why

Dave

[FloodGoose]

Thanks so much. I’ll have a look in the morning and see if I can figure that out.

I’m really grateful as it’s already humid and muggy, and getting hotter, and the missus is already feeling unwell.

I’ll let you know how I get on (or more likely be back to ask more questions!)

[electrofix]

be careful your dealing with high voltage DC

and if the capacitor is charging you can get a shock when its off in certain circumstances

Dave

[FloodGoose]

Thanks for the warning. Before I go ahead, I wanted to check I’m looking at the right part. The wires from the power input connect to two black oblongs. Are they the fuses? And I should put the multimeter probe into the leads to check the voltage? I’ve attached an album below. Thanks again for the help and advice
https://imgur.com/a/vogVrun

[FloodGoose]

Also, in terms of precautions, I guess standing on a rubber mat, wearing some rubber gloves, and holding the probes by the insulated part should be ok?

[electrofix]

first what i think i would do is find component L1 on the board

then with all the plugs connected you chould get continuity from the plug, both live and neutral to this component. this is where the power goes to the power supply on the board

this can be done with no risk with a 9v test meter

Dave

[FloodGoose]

Thanks again. So, I tested it by putting a probe on each of the 3 cables that lead from the two terminal blocks, and the other probe on the backside of the PCB, and there was continuity on them all the parts RY01 and RY02. But, they seem like switches, so I couldn’t get anything from them to L01, which is a kind of induction coil just next to them, but I don’t know if that’s just because one or both of the switches are open.

So, could you advise me on the next step?

Thanks

[electrofix]

live comes in and goes to term 3 on ry01. it then leaves the board on CY04 term 1 and goes to 2 thermal fuses. it then comes back to the board on cy04 term 3 and goes to L01

neutal comes in and goes to RY02 term 3 it then goes straight to L01

you need to find both circuits from plug to L01 first

Dave

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