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Need help with Pioneer SX-750 power amp board

jpreza

jpreza

Active Member
Hey fellow Pioneer audio enthusiasts!

I'm restoring a Pioneer SX-750 receiver. I'm currently working on the power amp board AWH-046. While pulling it out, I noticed that one of the connectors going to the heatsink from the D3 diode is snapped. Does anyone know if there is a replacement part for this? It's labeled 70B on the connector.

Thanks in advance! JP70B connector.jpeg
 
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That is a STV-4H diode. Its purpose is to regulate the bias to the output transistors based on temperature.IIRC they are no longer manufactured and are very hard to find. I have read here that it is possible to grind away a little bit of the casing and carefully solder the lead back together.
 
That is the Varistor STV4H.:yikes:
DON’t power up the unit with this broken part. :thumbsdown: :thumbsdown: Otherwise you will destroy even more. :no::no::no:

There are hardly no NEW parts available.If you are lucky, someone from Audiokarma can repair it for you.
Second choice is a workaround, just search for that STV 4H
 
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Don't power it on, the amp will self-destruct!!

That is the dreaded thermal diode broken wire.

Your bad luck is that it is a STV-4h diode, unobtanium. As such, salvaged parts on ebay will command (and get) exorbitant prices.
There is a thread or two on this forum about fabricating acceptable replacements...

one member (myself) excavates to the wire stub, solders on replacement flexible wire and holds it all together with epoxy.
It's been a while since I've been able to do some, ( need more appropriate tools and materials) and they have piled up.
 
jpreza said:
Hey fellow Pioneer audio enthusiasts!

I'm restoring a Pioneer SX-750 receiver. I'm currently working on the power amp board AWH-046. While pulling it out, I noticed that one of the connectors going to the heatsink from the D3 diode is snapped. Does anyone know if there is a replacement part for this? It's labeled 70B on the connector.

Thanks in advance! JPView attachment 2782818
Click to expand...
Anything on the other side? Mine are 64C but still screwed on.
 
MegaHurts said:
Anything on the other side? Mine are 64C but still screwed on.
Click to expand...
The diode on the other side is OK. That said, it looks like my best bet is going to be:
1. use an exacto knife to dig leads out of the connector that goes to heatsink
2. solder a couple of extra capacitor leads I have (i.e. flexible wire)
3. epoxy everything using nail polish :beerchug:
 
jpreza said:
The diode on the other side is OK. That said, it looks like my best bet is going to be:
1. use an exacto knife to dig leads out of the connector that goes to heatsink
2. solder a couple of extra capacitor leads I have (i.e. flexible wire)
3. epoxy everything using nail polish :beerchug:
Click to expand...
I meant anything written on the back side of the broken one.
 
jpreza said:
It's the same value as the other one '70B' if that is what you're referring to?
Click to expand...
I just thought that the if the front had 70B that the back might have something different since the front side of mine shows 64C it may have been a manufacture/batch code and not the diode id. I see someone else has replied about it.
 
MegaHurts said:
I just thought that the if the front had 70B that the back might have something different since the front side of mine shows 64C it may have been a manufacture/batch code and not the diode id. I see someone else has replied about it.
Click to expand...
The back side on both have no other markings. The only other marking is a yellow dot on one of the sides (which you can see in my picture)
 
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