New to this forum and new to the Sunn Amp. I own a few amps both SS and Tube.
Brief description of the trouble with my Sunn Beta lead amp I just bought. Tested it out at a small local music shop and played it low vol in clean and then loud without any problems for about 15-20 minutes.
Got it home and set it up to tinker with (clean up). Worked fine for about 5 minutes, turned it off then back on then out of no were had this horrible loud hum as if it was grounding out. Waited a minuet for the my body shock to dissipate then tried turning it on again with the same result, very loud hum, turned it off fast. Looked around the cab at the wires witch looked to be a mess but nothing were grounding would be an issue.
So gritted my teeth and switched it back on, no loud hum? Looked at the wires again no grounding or loose wires. Later on without any sound problems other that a continuous hiss sound that gets louder with reverb turned up it was fine, then I by accident I smacked the top of the cab above the head and all hell broke loose again, very loud hum.
I do a lot of recordings and like the sound when working properly of this amp so I decided take it in to a guitar/amp shop that has a person that works on tube amps ans SS amps. So far he has no idea what is causing this problem that comes and goes. But he just stated looking at it but had some other work to do before a full focus.
This may or may not be horribly inportant but it may, a day ago while the amp head was out of the cab at the shop, I decided to clean up and replace the speaker wire as it was not pretty. This being a 4 x 10" 16 ohm speaker cab with a 4 ohm output head I was setting it up for new Parallel wiring. By my fault when I was at the end of removing all the old wires from the speakers I was at the last bottom row and noticed that it had one black wire crossing over from the Pos lower left speaker to the lower right speakers Neg and that was it. I should of taken a picture of the wiring before removal but I failed to do so so I now am not to sure it it was a Series/Parallel setup at 8 ohms or 16 ohms instead of 4the required 4 ohms.
also I noticed that the pigtail 1/4 jack for the head to cab was not a speaker cable but a short instrument shielded cable. I have no idea how long the amp has been in this configuration nor haw loud it was played. The amp played okay before all this and now after the new speaker wiring and a new speaker wire 1/4 jack I don't know if the speaker sound has change for the better and maybe resolved the issue. The only other thing notice on the PC board was a cement resistor that looked not that great - see photo. The tape around the wiring harness was temp to see if it was picking up RF, was temp and has been removed.
My apologies for a long winded description but being a law enforcement officer I learned that any and all information is critical.
With that said should we be looking into the power amp and the output transistor(s) for a possible problem area or??
Any help or guidance is more than welcome.
