Loud Hum, No signal

[Smilie]

Hello,
I am very new to tube amps and am a veritable noob on anything tube related. I only know enough to keep me from dying.

I recently purchased an amp of unknown origin(eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices)

I replaced the cord with a grounded cord , plugged my guitar in, and there was a very loud hum.
There was a notiable second of guitar signal after it is switched off and powers down

what is the problem?

P.S. any info on the amp's maker, or model is greatly appreciated

[Jazz P Bass]

Did you try the amplifier before you replaced the power cord?

[52 Bill]

Made in Japan, appears to be line powered (no power transformer).

Are you saying that when you turn it on it just hums and doesn't pass any signal until you turn it off, and then you hear the guitar as the power supply discharges?

[Smilie]

Yes I did try it out, there was a fair amount of crackling and hissing but guitar came through on all three inputs

and @ Bill yes thats exactly what happens

[Jazz P Bass]

If this amp is indeed a "Widow Maker", then I do not know if, at this point, you should have the safety ground wire hooked to the chassis.
There were all sorts of permutations of this type circuit.
With really bizarre grounding schemes.
First of all, you need to verify if the amp has a power transformer or not.
If there is a number on the rectifier tube, please tell us what it is.

[Smilie]

I don't know which one is the the rectifier tube but the two larger ones are 50c5 552 and 35W4 339

I don't think there is a power transformer.

[Jazz P Bass]

Yup.
Widow Maker.
These amps are deadly to say the least.
Your best bet is to buy a separate transformer.

[Mark Black]

Smilie -

Judging by the tube complement (50C4, 35W4) you have now become the proud owner of an amp of a design which has a long and storied history on this as well as other forums.

If you do a search here in this forum on "50c5 35w4" you will begin to get an appreciation of how these amps are viewed.

In a nutshell these type amps are regarded as trouble-prone and even deadly amps due to their design, which has no power transformer to create line isolation and furthermore has one pole of the incoming AC Line Voltage tied to the chassis. In other words they were cheap to make (no power transformer) and dealt pretty loosely with safety concerns.

I would consider these to be somewhat above the "veritable noob" stage so far as achieving a safe and satisfactory outcome. No offense at all intended...

[Smilie]

No offense taken,
Is this amp worth my effort to learn how to fix it and fix it
or should i just count my losses and take it as a good lesson on
buying on impulse and try to sell it?