Amp techs Help! Spider Valve issue.

[Metal Overload]

A friend called me today to help him with a spider valve combo amp that some guy is selling (for good price) But!, the amp isn´t working, first thing, the preamp tubes are missing, so my friend connected a rockmaster preamp in the effects loops to use the power amp section but it doesn´t work, the amp makes no sound at all, so when i look into the power tubes, it seems like they are blown, but i don´t know they have this two round silver stains in the glass, at first i thougt the amp may be all blown (my friend told me that the speaker was disconnected) but the amp turn on and the power tubes glow.

Any suggestions on what it could be?? i want to use two spare power tubes and preamp tubes i have here and check if the amp is fine, but it may also blown those.

Here`s a pic of one of the power tubes

 

[Omega_Void]

...when i look into the power tubes, it seems like they are blown, but i don´t know they have this two round silver stains in the glass...

Patches of silvery-coloured deposits inside the glass are a normal side-effect of the manufacturing. Does not indicate any problem with the tubes.

....at first i thougt the amp may be all blown (my friend told me that the speaker was disconnected) but the amp turn on and the power tubes glow.

The power tubes will glow if there is current supply to the heater filaments. That does not mean the valve is intact.

It may be a simple as a blown fuse in the high-voltage supply. It may be as serious as a trashed output transformer.

Probably need to have a tech look at it.

 

[Metal Overload]

THanks Omega Void

Damn i think is the second thing you mentioned (trashed output transformer) since the disconected speaker. it seems like the owner doesn´t care to much about his gear. I checked the fuse and it doesn´t look blown, unless there is another one inside the amp.

 

[53Crëw]

The silver color inside the glass tube is a "flashed getter". It absorbs residual gas to help maintain a good quality vacuum.

I don't know the Spider Valve specifically, but generally, tube amps with an effects loop use a tube buffer. If the preamp tubes are missing and you plug into the effects return, you will not get any sound because the tube for the effect loop is missing, and any tube that follows it.... i.e. the phase inverter drives the power tubes. So if that is missing too.... again no sound. Essentially, plugging into the effects return still relies on the preamp tubes.

Put some tubes in it and try it out.

 

[Metal Overload]

Ahhh thanks a lot dude! gonna try that tomorrow, phew! im thinking on buying this amp he wants about $250 for it.

 

[TheWinterSnow]

I don't know the Spider Valve specifically, but generally, tube amps with an effects loop use a tube buffer. If the preamp tubes are missing and you plug into the effects return, you will not get any sound because the tube for the effect loop is missing, and any tube that follows it.... i.e. the phase inverter drives the power tubes. So if that is missing too.... again no sound. Essentially, plugging into the effects return still relies on the preamp tubes.

The Spider Valves Triodes are post preamp, the FX send is tube buffered and the FX return is buffered as well as the fact that the phase inverter lies after the FX loop tube. So basically if there are two pre tubes missing, then the FX loop is nothing more than a very expensive open circuit, because its the tubes conductance that completes the circuit from one point to the next.

Get some preamp tubes in the amp and give it a run. There's is only one rare fault in an amp that would cuase it to blow your tubes if you put them in, and the chances of that happening in a brand new (or newer) amp are slim to none.

 

[Sloan]

Dude, since it doesn't work, talk the guy way down in price. Almost anything and everything can be fixed. I'm guessing the most expensive parts will be buying new tubes.

 

[Metal Overload]

Hey Guys Thanks a lot for your help, Sloan that´s what im thinking to do, and it seems like this guy haven´t the slightest interest on this amp anymore so probably gonna be selling for a good price considering it´s condition.

 

[Sloan]

that's how i got my 333xl for $200 with a carrying bag! one of the best deals ever!