Electronics > Repair

Please help in saving this WORKING power supply

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administr4tor:
Hello,



I have an old furnace in house and this is its working control module.

How can I collect information/date/readings/measurements from this working module so in case if something happens to this working module  I can cross check from the information noted down and find broken component easily.

Should I take diode mode measurements of all the soldered pins on the GREEN SIDE OF THE board?
Any other ideas?

I am not too good electronics troubleshooting :(





thankyou

fzabkar:
If it were my device, I would trace the circuit.

The coil would be some kind of custom wound ignition coil. Thyristor THY1 would be the ignition switch.

The IC is made by Hitachi, but I can't find any information about it. I'm thinking it may be a custom uC, possibly 4-bit or 8-bit, but I can't remember if there was anything of this kind way back in 1975 (assuming 7518 is week 18 of 1975). I can't see a crystal, so that makes me think I'm wrong.

I see references to an NEC uPC3605CA, but this turns out to be a 3-terminal regulator. :-?

james_s:
I wouldn't mess with it, if it does fail some day it's probably going to be fairly easy to troubleshoot, usually the issue is bad solder joints, bad capacitors and occasionally a bad relay.

That looks very old though, what kind of furnace is it? Personally if it's more than about 15 years old I'd just replace the whole furnace if it fails. Last year I put a new furnace in my brother's house, the old one was only 70% efficient, the new one is 98% efficient and has a much quieter variable speed blower and modulating burner, it's a vast improvement.

administr4tor:
yes, its an old furnance and old house, I dont want to spend too much money for furnace now, I am ok with 70% efficiency until it fails. As cost of new furnace is insane now a days. I have upcoming expenses for roof next year :(

administr4tor:

--- Quote from: fzabkar on December 07, 2022, 12:40:56 am ---If it were my device, I would trace the circuit.

The coil would be some kind of custom wound ignition coil. Thyristor THY1 would be the ignition switch.

The IC is made by Hitachi, but I can't find any information about it. I'm thinking it may be a custom uC, possibly 4-bit or 8-bit, but I can't remember if there was anything of this kind way back in 1975 (assuming 7518 is week 18 of 1975). I can't see a crystal, so that makes me think I'm wrong.

I see references to an NEC uPC3605CA, but this turns out to be a 3-terminal regulator. :-?

--- End quote ---
how do I trace the circuit? I dont know how to trace it. can you help me?

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