Well here is the latest item for a fix and slight restore. This is a Rotel RB-850 2 channel amplifier that outputs 50w @ 8ohms or 150w @ 8ohms mono. The THD is 0.03% and damping factor of 280. As you can see it is basically 2 amps in a single chassis. This particular example had a open solder joint issue that caused the left channel to drop out anytime you moved the amp. I cleaned up the amp and addressed the solder joint issue. As a side note – Not sure what those transformers are made out of but they are deceptively heavy. Unicorn horn maybe??
Since the amp is 30+ years old I figured I should also remove the heat sinks and mica and add some new thermal paste. The old stuff was definitely dried out and needed replacing. As you can see this is a pretty simple amplifier without a lot of components and definitely no IC’s. This amp could live forever if you have a soldering iron and know how to find mouser.com.
I checked the DC offset and bias 4.0mv and it was spot on after warming it up for about 15 minutes. Also nice that the manual and service manual are available on Hifiengine.com and you don’t have to read the super small fine print to find the bias settings.
The unit has some light rash on the front top edge from living in a cabinet I assume but its certainly not bad (way better than what I have seen on fleabay and CL). As you can see in the pictures this amp can be used in stereo (50w) or mono (150w) modes. Sorry no balanced XLRs here but that is expected on this type of amplifier. I ran this for a few hours to heat cycle and ensure that were no issues and all looks and sounds great. This one is going up for sale and should be a solid low cost performer.