Pittbull 45 noise, mod questions

Amps & Cabs Pittbull 100/CL
1

Howdy. I just picked up a (my third) Pittbull 45 last week and have a few questions. Mine has EF86 reverb driver, a 5AR4 and a full-feature loop. Serial number TSD020347.

It sounds wonderful, but has a sort of static-type sound that occurs sometimes after a note is played, sometimes when it’s idling, and pretty much always when I tap on the middle preamp tube after playing for a while. Oh, and pretty consistently on startup.

I’ve swapped in known good tubes and am not getting any static or trouble from the loop.

My guess is that some pieces parts and/or traces near that tube socket have gotten melty, but I haven’t looked inside yet. Sure sounds like it when I tap around the area (but, interestingly, not when I do the fist pound to the top of the cab; maybe because it’s so stout).

Any suggestions for further troubleshooting or a possible remedy?

Is it possible to reduce the amount of gain in the boost mode?

I’m half the man I used to be, apparently. Is it possible to reduce the wattage with a smaller transformer? If so, can I buy a transformer from Fryette?

If I’m a classic rock/alt-country guy looking for more touch-sensitivity and a little less throaty Hi-Watt-type tone, would the Torn mod be advisable?

Anybody had success with any particular alnico speakers in one of these? I’m thinking about trying a Fane A60 I have lying around. Seeking some lower headroom, I’m trying a WGS ET65, which sounds really good, but it’s a bit boxier still (which would be perfect for pure Brit tones).

Thanks for any input you care to share; nice to be back.

John

2

Anybody…? Any suggestions for other forums or avenues I should try to get answers? Thanks

3

Welcome to the forum and apologies for the slow response.

Sometimes a bit of a crackling sound that isn’t solved by replacing tubes can be a loose PCB standoff. In that case the offender would be on the power amp board, which makes a ground connection to the chassis.

looking inaside the chassis with the front panel facing you, find the mounting screw on the corner of the board nearest to the middle of the amp on the far right.

Loosen that screw and tighten the standoff under the board. We use a right angle pair of pliers to get under the edge of the board and get a good grip on the standoff. Turn the standoff clockwise. If that’s the issue, you’ll feel it move. Don’t over torque it. Just make it snug. Replace the screw and tighten gently to you don’t snap the screw head off.

The traces around the tube sockets may appear discolored but they don’t melt, so you can ignore those.

Best thing to do to reduce the boost gain is to back off on the guitar volume. There is a resistor value that can change to reduce gain, but I’d have to look it up.

The Torn Mod will increase sag a small amout and increase ghost notes, but it won’t affect volume much.

The amp is already on the bright side, so I’m not sure if the A60 which has a huge magnet will do the job. It might though. It’s a great sounding speaker. Kind of a smoother Celestion Blue.

Hope that helps.

Dave

1 Like
4

Thanks, Dave.

I tightened the board supports – one might have been a little bit loose, if so, it didn’t move much. In any event, noise remains, though maybe a teeny bit better.

Pencil-tapping around the board yielded the noise, particularly around r8, 9, & 10. I reflowed them and things got appreciably better, but not gone entirely. Noise seems to be specifically localized to r8 & 9 at this point.

Any additional suggestions?

Thanks

5

Any thoughts? My window to return it to GC is closing and I don’t want to hold on to it if I can’t sort it out. Thanks!