Hot Rod Deluxe - First issue after all these years - help needed

[Big Alex]

Hi Folks,

Have just registed!!

Yesterday I arrived at my weekly GIG, took the amp from its box (Yes I still have the original box with all the styrofoam corners), set it in a chair in the stage, power it up and waited it warm a little while my band mates were doing the same with their gears.

Then we started the soundcheck, and as soon as I turned the stand by switch on, I heard a strange noise coming from the amp. Something "like" an egg being fried.. shhhhhfrrrshhhhhfrrrrr. I could even play the amp since the noise was not that loud, but as soon as I stopped playing there it was.... Then I plugged the guitar off and started investigating... The noise is there as soon as the stand by switch is flipped. It happens in both normal and drive channel (even in the more drive). Turning the reverb knob down also doesn't help. Rotated all the knobs and nothing helped.

So I took the back cover and pulled all the tubes, reinserting them firmly hoping that a bad contact would be the cause of the problem. Nothing happened it is still there...

Later at home I swapped v1 with v3 and after that v3 with v2 with no results what leads me to think that a bad pre amp tube wouldn't be an issue. The tube sockets seems to be tight enough.

Just ordered a full retube kit from Eurotubes hoping that this will fix the problem.

I would appreciate any inputs that I should look for before sending the amp to a technician. I hope that this could be something easy to fix like for instance dirt in the sockets or something like this.

Thanks in advance,

[MWJB]

Power down and remove V3, the preamp/phase inverter next to the power tubes. Power up, is the noise still there?

[Big Alex]

Can I do this without harming the amp? You mean just take it off and power up?

If the noise continues I would guess the problem would reside in the power section (probably a power tube) right?

Thanks for the prompt response.

regards

[StratTone]

Yeah it won't hurt anything. Just give it a try. I would always try tubes first and go from there. It is definitly in your preamp. Now these amps as im sure you have ready have a tendancy to have cold solder joints on the ceramic wire wound resistors and that could be your problem.

[Big Alex]

I think inserting a patch cable in the power amp in would do the trick as well... wouldn't it?

[MWJB]

You might get hum from the free end of the cable?

Pull out V3, you cannot damage the amp by doing this, in fact you can pull out all the tubes and not damage the amp...it obviously won't make any sound though.

We're pulling out V3 to eliminate the power section as the cause of your noise, plugging an unterminated cable into the power amp in might introduce noise/complicate the issue.

As Stratone says, the symptoms you describe suggest preamp/tube noise in the absence of any other cause, so let's rule them out first. Do you have a spare known good 12AX7 to sub for the current tubes?

[Big Alex]

Well I understand.

I don't have a spare set of pre amp tubes (just ordered a full retube kit from Eurotubes and it will take a white to arrive).

But I did the swap between v1 and v3 and afterwards v3 and v2 and nothing happened (the crackling and popping continues as soon as I flip the stand-by switch), what makes me think that probably the problem is related to the power amp section. Since the amp was purchased in 2002 it could be a good bet :-)

Hope it is just tubes.....

[StratTone]

More than likely it is the 2 resisters I was referring too. It is a very common problem and easy to fix.

[52 Bill]

The sound that you describe could also be a failing plate resistor.

Did you try powering up the amp without V3 installed, as MWJB suggested? If you do, you will know if the problem is in the pre-amp or the power amp section.

[StratTone]

The sound that you describe could also be a failing plate resistor.

Did you try powering up the amp without V3 installed, as MWJB suggested? If you do, you will know if the problem is in the pre-amp or the power amp section.

I totally agree. I think he is just a little nervous about turning the amp on with the V3 out for some reason.

[Big Alex]

jeesusss

[Alex R]

jeesusss

He would have had no hesitation pulling the PI tube out.

[Big Alex]

Ok.

IŽll do it. IŽŽll take v3 out. I will report the findings soon.

Lord have mercy

[Alex R]

Take it easy in there. Don't use your teeth.

[Big Alex]

Update

Removed the v3, powered the amp up , flipped the stand-by switch and there it is. So I shall assume the problem is located in the amp power section, right? New tubes or something more....