Can a bad cap in a guitar..

robgilmo · June 2019

Make it sound as dull as dish water then after around an hour of playing sound as it should? I am having this issue with my Epi 56 GT , when I start playing it sounds dull , boomy, neck pick up especially sounds way out of where it should be, sounds dull, boomy, and way way higher volume than the bridge, then after about an hour it all sounds bright and clear and balanced. It sounds like all the treble is being sucked out, like the treble nobs are at zero.

My first thoughts were the amp ( peavey deuce) taking its time to warm up but my Tele sounds pretty good from the off set.

Then I thought my amp may not like the P90's much but I cant see it really, could it be a cap in the guitar failing?

It has a temperamental switch that isnt right but Im still not convinced that is the cause because it fixes itself after a while.

Any ideas?

robgilmo · June 2019

Just to add, ive set the pick up height and although it changes the sound it doesnt lift the veil or add treble, so its not that.

ICBM · June 2019

No. Even if the cap was faulty, having the tone control at 10 removes it from the circuit almost completely.

It’s more likely to be something to do with the amp, most likely valves, that just isn’t as sensitive to the less bassy Tele.

robgilmo · June 2019

When it happens again I will try the guitar in my Vox and see if the problem crosses over. Could the switch be at fault? Its a bit temperamental, it will crackle if I shake it, lose contact sometimes, but will it suck treble if its dodgy? I did clean the contacts but that didn't help.

The valves I cant vouch for, it has two JJ's that the previous owner put in there before I bought it and two older sovtek? valves, I did notice the JJ's glow brighter than the other two.

ICBM · June 2019

Nothing in the guitar can *add* bass like that.

The brightness of valve filament glow is no indication of performance at all. I did notice in a previous photo that both the JJs are on the same side of the power amp though - while it’s not a good guide to performance either, it would probably be better to have one on each side.

thegummy · June 2019

Maybe there's a build up of wax in your ears and the sound waves causes it to vibrate and liquefy over an hour but it's solidified again by the next time you come to play?

Funkfingers · June 2019

ICBM said:

Nothing in the guitar can *add* bass like that.

+1

The effect of a dirty or corroded pickup selector switch would be subtractive. It would reduce the strength of the signal(s) leaving via its output terminal.

It is remotely possible that both of your tone pots are defective. The type with a flat underside to the chassis case can be deformed by impacts or overenthusiastic pushing down of replacement plastic knobs onto the splined shaft. This impairs the contact between the wiper and the resistance track.

If the polepiece screws on a P90 are raised too close to the strings, it can lead to “Stratitis”.

I cannot recall whether the Deuce gets its overdrive from cascaded pre-amp valve gain stages or an IC.

Direct substitution might help to track down which valves need attention. There are plenty of other things that wear out in an elderly valve amplifier. Who better than a professional repairer to explain them to you?

prowla · June 2019

A simple way of eliminating the caps would be to disconnect (ie. de-solder) one end of each, but with the tone on 10 they're bypassed anyway.

Do the pots crackle as you turn them?

Have the pots or jack socket (or pickup selector) ever been loose and needed their fixing nuts tightening up? (That can lead to frayed wires.)

The best way to eliminate the amp question is to plug it into another amp!

Corvus · June 2019

Jacket socket touching screened cavity? Had that once, lower output less balls etc. In one orientation it was hitting the wall.

robgilmo · June 2019

Thanks guys, the amp is apart at the moment but I will do a comparison tonight between the two amps I have, that should narrow things down a bit.

EvanEvanNorth · June 2019

I would say that one or more of its 4 power amp valves are causing this.
The deuce has a solid state pre-amp and valve power amp.
Further to this, these amps are rather elderly and would need a good testing/service/revalve by a qualified tech.

robgilmo · June 2019

I had the amp apart today (new grille cloth) and when putting it back together I reseated the valves, I tried it briefly and it sounded Ok, I will have a better play with it when I get the kids off to bed but it did seem better. Could it be bad contacts on the valves? I had it apart last week end too and didn't really use it much throughout the week.

robgilmo · June 2019

Switching amnpos didnt make a difference, apart from the different tonal quality's of the amps. I switched the guitar to the neck pick up and it sounded very dull and very quiet, back to bridge, sounded fine, back to neck and nothing, no sound at all, fiddles with the switch and the neck became loud and booomy! So my guess is the switch is kaput! Or at least its a good place to start. Any recommendations for a switch to fit an Epi Les Paul?

Funkfingers · June 2019

Post a photograph of the selector switch in its cavity. The contacts of Asian short chassis, sprung leaf toggle switches can be cleaned.

The selector switches with their moving parts enclosed inside a metal box are utter shite. Replace A.S.A.P.

NOTE: Mark the three cables before detaching them from the switch contacts. (B, N and OUT.)

robgilmo · June 2019

Its a mechanical type, I cleaned it and bent the contacts a little but the plastic ball thing has worn so its not right, it works now but will need replacing. The neck pup still sounds boomy though, bridge sounds good. Neck sounds louder and all the height adjustment in the world isnt changing it. I did read somewhere that the 56 pickups were matched and not balanced.

Funkfingers · June 2019

If Epiphone has stayed true to 1956 Gibson specifications, the two pickups should be of equal output. If they are set at equal distances from the strings, the greater string excursion above the neck/Rhythm position will always generate a stronger signal than the bridge/Treble position unit.

On genuine vintage Gibson instruments and "authentic" replicas, the traditional solution is to set the bridge pickup as high as you dare without it getting floppy on the springs and screws. Then, set the neck pickup low enough to achieve balanced volume output from the two positions.

robgilmo · June 2019

Thank you, I will have another play with the pick up heights and report back.

robgilmo · June 2019

So, I had a play with it and the tone control for that pick up is scratchy, but its only scratchy when a string is being played, if the strings are silent so is the pot. Also its scratchy no matter what position the selector switch is in, again only when a string is being played. Surely thats not normal?

jaymenon · June 2019

Do the pickups have braided shielded wires - and are those wires touching the metal legs of the capacitor?

That'll give you a 'dull as ditchwater' tone

normula1 · June 2019

Is your hand rubbing on the pickup cover?

My LP special used to crackle like a b*stard when my hand caught the cover until I attached an earthed bit of copper tape to the underside.