help with volume rise and fall when channels jumped

[Nick-O]

I have an ok tube amp.

The tone is best tamed when I jump the channels, otherwise its way too bright.

The volume started to drop and rise and maybe get a little muddy.

I removed the bugera S-1, checked cords and wirelesss, various guitars, no change.

When I plugged back into the main channel, thus far the symptoms have not returned.

Anything obvious?

Sorry to ask perhaps a simple question, but my tube amps have never given me grief.

Perhaps i've just been fortunate.

Thanks in advance....

 

[Mr French]

I've had similar issue with volume and turned out it was the preamp tubes. More like a single tube but I replaced all 3 of them while I was there.

 

[cooljuk]

If you're getting a problem when you have the channels jumped and not when you are only in one channel, how about when you are only in the other channel?

 

[Nick-O]

If you're getting a problem when you have the channels jumped and not when you are only in one channel, how about when you are only in the other channel?

well....the main channel, such as it is has all the gain and drive....the other channel is just volume and tone....sounds like a dry biscuit, but you're right, I should check that first.

not a fan of this amp builder, really not a fan but it does the one trick it was designed to ok.

thanks....

 

[Nick-O]

Just to update if any amp doctors are reading, but it does it on the main channel unjumped.

I played the clean channel for a while but it was too uninspiring to play for long.

I only get a short chance to plug in and play and hate to waste time playing a channel I never dick with unless I'm jumping it.

If anyone can point me in the right direction, much appreciated.

Otherwise I'll drag it to Charleston and let it disappear into the abyss of the only amp repair guy within 75 miles of the house.

 

[Big John]

What make/model is this amp?

 

[Nick-O]

this thing, with EL84s

 

[ARandall]

Its funny.
I have this sort of amp - but with an EF86 second channel.....and it does not work with channels jumped.

 

[Nick-O]

hmm.....interesting.

i'm ok with the amp in the main channel, but obviously something's up.

 

[Big John]

You sure the channels are in phase with each other? Also, number one rule with tube amp problems...always check the tubes.

 

[Nick-O]

jumped it the way the "builder" advised....worked amazing for a year.

tubes will be replaced once it makes it to the shop.....be months from the sound of it.

 

[Big John]

Months to replace tubes? You don't have any spares sitting around? If anything, swap around the ones that are already in the thing. Take the PI and swap it with #1. If you have a set of tubes handy, throw them in. Shouldn't take more than 48 seconds.

 

[ARandall]

Just be aware OP that in some of these 18W designs that the PI is V2 and not V3.....the Ceriatone build I have uses V2 for the PI for all TMB versions.

 

[Nick-O]

thanks....i don't have any tubes on hand and there is no schematic/chart on the inside of the cabinet to guide.

i thought tubes had to be biased to change/replace with new.

i always took my amps in memphis to strings and things.

haven't had any tube issues in years now, and i'm in the musical backwoods of sc now.

if its simply a swap, i'm up for that.

 

[Big John]

If your amp is a Marshall 1974 knock-off, then it's power tubes are cathode biased. No bias adjusting needed. So all your tubes are "swap at will". Get you some glass, get in there, and do it.

 

[Nick-O]

cool.....thats what i needed to hear.

 

[ARandall]

This is the Ceriatone version.
The PI section on the board is just to the right of the big 16uF capacitor. Trace the two red wires from the bottom of the board back and you get to V2

 

[Central Scrutinizer]

@Nick-O hopefully this will get cleared up soon for you.

When I say the following, it is not a reflection on you! It also is not my Christmas brag letter that gets sent with my Christmas Card.

I used to restore and build custom motorcycles, HD and Indian, at times, one a year. On two separate occasions I built 2 choppers starting with just the cases and a title.

Every time during the process, I would just hit a wall and have absolutely no idea on how to get over what seemed like a tremendous hurdle, he it wiring, shimming the transmission, boring cylinders... This would set me back, sometimes for weeks. I would be as a savant stumbling around the problem, letting it frustrate me to the point of staring at my 16# sledge in my shop and thinking how fun it would be to pound it like a cheap steak.

What worked was to walk away from the situation, forgetting about it for a bit, putting it totally out of mind. Then I would approach it with a fresh set of eyes and thoughts and find a simple solution to the problem.

You will get this figured out!

Good luck.

EDIT: spelling seamed/seemed.

 

[Nick-O]

thanks brother!

sound advise.

i got some advise from a wise soul last weekend, took the guts out and now waiting on some parts.

taught me i need a better back up amp, so its nice to be looking for a new addition.

i tend to you settle in to an amp or two and play....

much peace my friend