Recapping Gibson G-10 questions

[52 Bill]

Still concerned if I'll need to jumper the leads where the death cap was connected, since it goes through the PCB. If all that did was go from V+ to the chassis (ground) then I think I'm OK.

Removing the cap is all you needed to do. No jumpers.

The amp, after changing out just the large, 2000uF filter cap, was whisper quiet. Now that I've updated it to a 3-prong, grounded line, I have that hum/buzz. It's not "too bad", but a bit annoying. It increases/changes with both volume and treble increases. Any tips? [/B]

If you turn down the volume control on your guitar does the hum go away?

[Brazen]

Removing the cap is all you needed to do. No jumpers.


If you turn down the volume control on your guitar does the hum go away?

Hey Bill!

It matters not. Whether my guitar is connected or not, the hum is there as soon as the power is turned on, and isn't influenced by the guitar or numerous known good cables, house receptacles, etc.

I have to correct myself from above.... the hum doesn't change with volume, but does sound different with treble and bass tone control adjustments. So power on, volume at 0 or 10, instrument connected to either input or not, there is no fluctuation in hum/buzz. It's not "too bad" and tolerable especially for an antique, budget amp..... I'm just curious since it "only" appeared after my 3-wire conversion. Before that, I replaced just the one 1500uF filter cap with 2x 1000uF in parallel [see pic], and it was literally whisper quiet with the 'ole OEM lamp cord.

Also, it matters not which receptacle in the house I use, AND my lil test area is where I've been doing all the repair work so I'm sure it's not that. I also checked the house receptacles with my tester.... all good. (I'm a building contractor) The cord I used was a nice, newer 12ga stranded copper extension cord I hacked the female end off of, and I did check "polarity and continuity" of the cord before using... just to be thorough.

So in conclusion, this noise only appeared after the 3-wire conversion AND death cap removal, and I did it exactly as suggested here. Safety first! lol
Thanks again!!!!!!!
Jimmy

[g1]

It is likely that the cap you removed was killing the hum. That was it's original purpose, they are removed because they are unsafe if they go bad when an amp is plugged into an ungrounded outlet.
There is a modern equivalent which is safe, called a class X capacitor. Some manufacturers use them in the same position as the one you removed.

[Brazen]

It is likely that the cap you removed was killing the hum. That was it's original purpose, they are removed because they are unsafe if they go bad when an amp is plugged into an ungrounded outlet.
There is a modern equivalent which is safe, called a class X capacitor. Some manufacturers use them in the same position as the one you removed.

I was thinking that myself. Since I snipped it at the same time I 3-wired the chassis, it's hard to tell. I followed 52 Bill's recommendations above and agree via the amp's schematic & parts list that this cap [C12] is what some might refer to as the "death cap" on this amp. It was soldered through the PCB since this amp has the combo power/volume pot, not a SPST toggle switch. You can see before and after pics of my progress above, as well as the amp's schematic and the disc cap I snipped. As usual, the cap removed [C12] was .01uF 150VAC but my parts list specs .04uF 500V. LOL [see pic added below, C12)

Forgive me for my lameness, as I am a simple contractor and hobbyist, but what would be a recommended modern replacement cap if I were to decide to install one? Should I stick with a .01uF value that worked well "before" grounding the chassis, or use Gibson's spec'd .04uF value? And.... LOL.... could this be placed elsewhere in the line..... say across the + and - transformer leads at the terminal strip provided? [see pics above, left-front of chassis]

Thanks again guys..... all of you for all the assistance!
Jimmy


PS: and upon further reading, if this "C12" was a "to ground" cap.... wouldn't it require a Y-type cap for replacement?
"Class X capacitors are used in “across-the-line” applications where their failure would not lead to electric shock. Class Y capacitors are used in “line-to-ground” (line bypass) applications where their failure could lead to electric shock if a proper ground connection were lost." Excerpt from the article at: ABC's of Safety (Interference Suppression) Capacitors for Tube Radios

[g1]

You are correct, it should be class Y from line to ground. .01 should do, the .04 may have been a typo.

[gbono]

Check out this discussion .......Gibson G 30