Technics SU 8080 relay
- Thread starter EC1
- Start date
duncan
flâneur in training
Yes, but it's unusual for a relay to fail in that way. It's unclear to me whether you've eliminated the possibility of a shorted TR405 as @avionic suggested.
Can you float the base pin of TR405 (desolder it completely so it doesn't make contact with the board)? Then see if the amp still makes sound. That will "cut the problem in half" for us without requiring measurements.
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Normal operation at power on is a small time delay before the relay " sets" or clicks. This allows the regulated power supplies to stabilize before connecting the speakers to the amplifiers.
I apologize if my stupid questions upset anyone. Just trying to understand it before I start touching it. As I mentioned:
1. It Powers up
2. Pop right way, instantly from speakers.
3. Then it operates as normal
Assume the relay stays close all the time or instantly close when power up.
Will try to inspect through the relay box to see does it open up when power down, or click when power down, doubt I am able to see it or hear it.
Next I will replace the TR405 as suggested as my first attempt assuming I can get the board out.
Thanks.
1. It Powers up
2. Pop right way, instantly from speakers.
3. Then it operates as normal
Assume the relay stays close all the time or instantly close when power up.
Will try to inspect through the relay box to see does it open up when power down, or click when power down, doubt I am able to see it or hear it.
Next I will replace the TR405 as suggested as my first attempt assuming I can get the board out.
Thanks.
duncan
flâneur in training
In the absence of more information, it's a strong suspect. But it could be something earlier in the circuit that turns the transistor on and off. Another possibility: I'm not smart enough to glance at a schematic and be absolutely sure of the function of each part, but if the intended delay is implemented with some variant on an R-C timer, then a bad capacitor could kill that delay. i.e., C402 and C403 deserve a look.
Still... if you want to go straight to replacing parts (kinda like the Dr. House method of diagnosis-by-treatment, right?) then sure, the TR405 is a good place to start.
Yes, I am aware of that, some other member mentioned that in earlier posts already. I only have spare KSA992 in hand but not those capacitors. And I don't want to pay $8 shipping just for 2 capacitors. That is also why I will try to replace TR405 first. Another question, will bad C402 or C403 if that is the case, kill my to be installed new KSA992 once it is installed? I have like zero knowledge in this basic electronics. Just have to ask.
Swap TR405 out with KSA992
. No change. Relay still close instantly at the power up. Now need to get part for C402 and C403. Do I need to get the face plate off to access the protection board. I was lucky not doing that since TR405 is right at the edge of the board and somehow I manage to insert the KSA in.
. No change. Relay still close instantly at the power up. Now need to get part for C402 and C403. Do I need to get the face plate off to access the protection board. I was lucky not doing that since TR405 is right at the edge of the board and somehow I manage to insert the KSA in.
