Sunn 1000S Head & Cab

[retrorod]

A frind of mine has a Sunn 1000S head and cab. GREAT sounding amp. All of a sudden it is dropping down in volume after 10-15 minutes play time at moderate volume. I have done a lot of amp work on Fender,Marshall and others but not much (any ) work on Sunn. I don,t find much on the 'net about the 1000S. It is dated '69 and is a BEAST....Very round and full sound. Any help?? It has all original components. A cap job is is order for longevity. I plan on trying new tubes...Any suggestions or input?
 I guess, I should say, Thanks for any info...I am new to this forum but not new to forums in general. I like like-minded comeradery...Rod

[mckinnon audio]

   Hi there,you're right on track about the cap job and re-tubing.You might want to check out all the tube sockets,(clean them and retension the pins if necessary),clean all controls and jacks and check for bad solder joints,you'll end up with a great amp,Mel.

[retrorod]

Thanks Mel, Just did a cap job on the Sunn. Everything was original to the amp. Amazing that it was still running after 40 years. Date in chassis is 4/69....'summer of love'....cool! Someone had put a 10amp fuse in her...yikes! !! I am in the process of checking current flow in the the old tubes and trying some re-issue Tung-Sol 6550' in it. While checking the old GE's that came in it, I find that the plate voltage varies when firing the amp up. One time its running about 480V and another time, its 505V. Could this be a rectifier issue? It has dual 5AR4's that are different brands, but both test well on my tube tester.
 Another subject!.....Those Oregon boys weren't scared to put any iron on these amps were they..!  This has got to be one of the fattest,warmest guitar tone I have hear....I love the trem too..Rod

[mckinnon audio]

  Hi there,if you haven't replaced the rectifiers,I'd give that a try.Very few tube testers can actually test a tube (esp.rect.)with circuit like conditions,so it may read fine on the tester and work differently in the amp.Good luck,Mel.