Epiphone Valve Special

SlopeSoarer

I've just acquired an Epiphone Valve Special and only being the second amp I've owned (first being a Vox VX II) I want to learn a bit about it from any that have had experience.

Is a bit of hum normal when turned on?

When being turned on there sometimes is a popping sound, as if in an empty hall (if that makes sense), is that normal or indicative of something?

I guess it is around 12-13 years old, would there be any benefit from changing the tubes? If yes what and where is good to source them from?

Other than the above I'm very happy with the sound (but don't have any experience of tube amps to compare with) and do like how it can be played pretty quietly with without the depth of sound being affected too much.

Getting ahead of myself now (can't help tinkering) I assume the two silver cylinders contain tubes... how does one remove the cover/cylinder?

ICBM

A bit of hum is normal. It's hard to describe how much isn't, if you're not familiar with valve amps... but this is a single-ended amp, so it will hum a little more than some others. It can also be a sign of a worn valve (usually power).

A popping sound when turning on is usually nothing to worry about. If the source of the pop or something it affects is upstream of the reverb, that will give a 'hall' sound.

The power valve - the EL84, the one not under the covers - is likely to need changing I think. Although it's hard to be sure it's not a photographic artifact, the discolouration at the top of the valve (bottom in the pic) doesn't look right and it it does actually look like that in reality, is the sign of a very worn valve.

You get the silver covers off by turning them until the 'bayonet' lugs line up with the two small notches you can see. It's usually hard to turn them because the rubber o-ring grips the chassis and the cover. The preamp valves are under them, but probably won't need changing, at least not just because of age/use - they can last a very long time.

Does that help?

SlopeSoarer

ICBM said:

A bit of hum is normal. It's hard to describe how much isn't, if you're not familiar with valve amps... but this is a single-ended amp, so it will hum a little more than some others. It can also be a sign of a worn valve (usually power).

A popping sound when turning on is usually nothing to worry about. If the source of the pop or something it affects is upstream of the reverb, that will give a 'hall' sound.

The power valve - the EL84, the one not under the covers - is likely to need changing I think. Although it's hard to be sure it's not a photographic artifact, the discolouration at the top of the valve (bottom in the pic) doesn't look right and it it does actually look like that in reality, is the sign of a very worn valve.

You get the silver covers off by turning them until the 'bayonet' lugs line up with the two small notches you can see. It's usually hard to turn them because the rubber o-ring grips the chassis and the cover. The preamp valves are under them, but probably won't need changing, at least not just because of age/use - they can last a very long time.

Does that help?

Absolutely!

The valve does look like it does in the photo, so I will replace it. Any particular brands/sources I should look at/avoid?

Thank you very much for the reply: )

Phil_aka_Pip

FWIW if the mains i/p is connected to the 230V tap on the transformer, move it to the 240V tap. I had a VJ that ate o/p valves for breakfast until that modification. Bother ye not with the standby.

ICBM

SlopeSoarer said:

The valve does look like it does in the photo, so I will replace it. Any particular brands/sources I should look at/avoid?

JJs are the most robust of the modern EL84s. Karltone does them singly and cheaply.

Phil_aka_Pip said:

FWIW if the mains i/p is connected to the 230V tap on the transformer, move it to the 240V tap. I had a VJ that ate o/p valves for breakfast until that modification. Bother ye not with the standby.

Yes, if it has a 240V tap then do that - it will run the valve cooler.

Using the standby switch is fine on this amp, since it doesn't have a valve rectifier.

SlopeSoarer

Thanks again for the advice and I'll have a look at the transformer.

Phil_aka_Pip

ICBM said:

Using the standby switch is fine on this amp, since it doesn't have a valve rectifier.

Can't a silicon bridge get killed by an inrush of current? Or is the switch after the reservoir caps?

ICBM

Phil_aka_Pip said:

Can't a silicon bridge get killed by an inrush of current?

Not really - the current rating of even a basic 1N4007 is high enough that there's no risk. In fact, these are exactly the type of amps where a standby switch *is* useful, by avoiding applying the full HT before the valves have warmed up - this is actually more of an issue for the filter caps than the valves, especially the ones further down the chain.

Phil_aka_Pip

ylsned