Newly unearthed 800C with cap repair inside?

absolve2525

absolve2525

Super Member
I just picked this up yesterday. Price was right, owner says it doesn't work. Power tubes are cooked, preamp and phase inverter tubes all test good. I finally opened it up to find this repair. This large loose Mallory cap was bracketed but not screwed down inside. Any ideas what's going on here and how to proceed? The owner inherited it. Thanks!
 

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I use HH cans, add IBBM, install a modern rectifier, and replace all the typical capacitors so they last another 50+ years.
 
If you have the space and energy I will also recommend an EFB board and the volume buffer board both as designed by Dave Gillespie. They both made nice improvements to a 400 and a 500c as well as a 500c power amp that I built.
 
Update! I put in 10ohm safety resistors, CL-80 Thermistor, replaced selenium rectifier with modern silicon. It turns on, both the front lamps light up, preamp tubes light up, but after a few moments there was smoke coming from somewhere. I didn't get to see where from exactly before shutting it off. This was with all power tubes removed and speakers hooked up. Fuse doesn't blow or the thermistor. I wonder if maybe a phase inverter pot is fried? I cleaned all switches and knobs including those. I tested coupling caps and they all measure good.
RS Steve said:
I use HH cans, add IBBM, install a modern rectifier, and replace all the typical capacitors so they last another 50+ years.
Click to expand...
 
Last edited:
absolve2525 said:
Update! I put in 10ohm safety resistors, CL-80 Thermistor, replaced selenium rectifier with modern silicon. It turns on, both the front lamps light up, preamp tubes light up, but after a few moments there was smoke coming from somewhere. I didn't get to see where from exactly before shutting it off. This was with all power tubes removed and speakers hooked up. Fuse doesn't blow or the thermistor. I wonder if maybe a phase inverter pot is fried? I cleaned all switches and knobs including those. I tested coupling caps and they all measure good.
Click to expand...
Check to see if any of the big cans are showing as shorted. Are you using a dim bulb tester?
 
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