5000a running extremely Hot

[aje123]

Hey all,
Was making a trade for a Sansui 5000a today.
Had unit operating 10 minutes and 1 possibly 2 heat sinks on back Extremely Hot. I burned finger,hot.
Opened up unit. It has the updated 6013 boards. But large caps next to boards- 2 are 1500uf. And 2 are 2200uf
Looks like the 2200uf were changed way back when. All the other pics I saw of large caps were gray Nichicon, these 2200uf are silver??
What could be heat sink getting that hot?
Measured heat at 190 deg. Thank You

 

[MIJ_Pioneer]

An incorrect bias (current) can cause this and should be checked/adjusted. Procedure is noted in the service manual under the adjustments section. Does it have the original trimpots to adjust the bias? They could be failing, keep an eye for that. Bias too high = outputs blow.

 

[maxhifi]

You sure the boards are updated? This is exactly how the old boards fail.

 

[aje123]

Yes it has the 6013 boards not the 1040 boards that the original schematic shows. Thanks

 

[Skywatcher]

Yes it has the 6013 boards not the 1040 boards that the original schematic shows. Thanks

But what about the BIAS diodes? The LV-2 are known to get funky. The very first thing I would to is like @MIJ_Pioneer suggests. Check the BIAS current and monitor it over time. It may not be regulating itself down.

 

[Hyperion]

I recommend only running the unit for very short periods until you can find the issue and correct it.

 

[Orwell84]

I recommend only running the unit for very short periods until you can find the issue and correct it.

It probably wouldn't hurt to power it up on a dim bulb until the problem is found either.