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First Re-cap. Lost Noob...Help!


mgreene300

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Well I couldn't leave well enough alone and went ahead with the cap job on the 67 Skylark GA5-T. While I was at it, I changed the output transformer to a Mercury magnetic GA5-0, removed the death cap, and changed the 3 wire cable for a 3 wire detachable cable socket. I turned it on, got sound, and didn't burn my house down yet, but that's where the good news ends.

 

Now there is no steady hum, but there is a hum (that increases with volume) until I touch the strings. Is this something to worry about? I tied the negatives of the Sprague Atoms together and jumpered them to the same spot where the original can cap was grounded (a tab surrounding a tube socket). Should I have just grounded them to the chassis screw where the power cord is grounded instead?

 

On top of everything else, my tone doesn't seem nearly as good now. In some of the comparison videos I've seen of upgraded OTs in other amps, the tone improves in most cases, and there is always a volume increase. If anything, I think I may have slightly less volume now. Could it be that I bought the incorrect OT? The new one is about 25% smaller than the original and has an extra set of speaker wires (that you'll see hanging in the pic because I didn't know where else to put them.)

post-44567-072993300 1341716807_thumb.jpg

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There a quite a few guys in the forum who are very knowledgable about working on tube amps. maybe if you post pictures of the area with the sprague atoms, someone might see something that could help. Make sure there are no cold solders or loose connections. Sounds like a cool amp. I am sure you will prevail against the unwanted hum.

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  • 2 weeks later...

Wow, not sure how I skipped right over this and answered your last thread instead!

 

I have the same issue with mine since the repairs. Actually, I also have the issue with my 78 Peavey Classic VT; the previous owner broke out the ground pin so I had to replace the plug. Since both repairs, the buzz has reared it's annoying head through both amps.

 

It has something to do with the ground loop I believe. Someone can correct me if I'm wrong but from what I've read, by grounding the amp there are now 2 paths to ground (one through the amp and one through the guitar). This causes that annoying buzz that stops once you make contact with anything on the guitar that is wired.

 

I probably did the same as you, though I grounded the plug to that little tab where the death cap used to reside, I wonder if switching to the chassis bolt would make a difference. I grounded the cap to wherever the black wire went, after discharging I clipped and stripped the old wires and just soldered to those. Maybe today after work I'll open mine back up and try it, I agree it's an annoying thing and makes the Skylark seem like it would be an issue to record.

 

I'm not too sure about the OT, maybe someone else could be a better help regarding that.

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