Ampeg Reverberocket R-12R

[dkirk]

Found that there is 0.0 volts at "C" and working backwards, found 0.0 volts at "F". Have 373 volts at "A". Thus, it is now obvious that the 1K, 10W resistor has failed. Have a new one ordered from Antique Electronics Supply. Will report back when resistor is installed. Thank you Hangman for your guidance. Having the correct schematic is very helpful.

[dkirk]

The good news - got the 1K 10W resistor installed and the amp is now operational! Reverb works as it should, and vibrato works perfectly. Tone control functions normally too.

The bad news - there is very little output to the speaker with volume control at 100%. Is there a specific area that I should now be focusing my attention? Power tubes?

[dkirk]

My Ampeg Reverberocket is now repaired and fully operational. Reason for the low volume was poor conductivity due to oxidation in the preamp tube sockets. Pulled all preamp tubes, cleaned socket contacts with cleaner and small brush, straightened and cleaned pins on tubes, and this restored full performance.

The real culprit was the 10W 1K resistor which doesn't look quite OEM but at least it works:

   

Got the amp reassembled today:

   

   

The amp works perfectly with the outstanding reverb that Ampeg is known for. Tremelo operates as it should. At full volume idling, there is barely any discernible hum. The tone is very bright - tone control is barely off of the bass setting. I'm using a Gibson ES-175 for a signal generator, and this tone setting is just about right for a good archtop sound. The amp is not very powerful - compared to the Clark I have with a 5Y3 circuit, the Ampeg falls short in volume, but the clarity of tone is quite amazing. It reminds me of playing through a hi-fi system versus a guitar amp.

I hope what I've discovered in bringing this one back helps others with similar problems.