'62 Fender Tremolux hum

[arnauddd]

Hello to all,
i'm new to this forum, just stumbled onto it by accident.
I own a '62 Fender tremolux amp, and some years (i know it's a shame) ago, it started doing a huge hum randomly when i was using it.
The hum usually starts low then gets louder and louder (really LOUD) as the sound from the guitar goes down. After 5 to 10 mins, the amp might pop and then hum would dissapear completely.
I also noticed that playing with the volume know changes the hum volume, and that turning them (bass, treble) can change, or even stop it too.
I sent the amp to 2 different tech guys who changed my tubes, but told me it was working perfectly each time.
Do you guys have an idea of what could cause this? if it needs recaping or something like that, i'd definately get it done, but i don't want to send the amp again to a tech guy to have it not fixed so a clue might be interesting.
Thanks in advance.

[MWJB]

Firstly, a tech should give you a resume of the work carried out (I've heard of guys local to me who charge for "looking" at an amp, and I mean just looking...no measurements are taken, no sonic evaluation, nothing!). A retube will normally include a charge for biasing on an amp with non-adjustable fixed bias (like your amp), sometimes the tech will get lucky & have some tubes that bias up in range through substituting different pairs (though this can take time & may also be chargeable)...if the bill looks like it's going to be big (hundreds of $) then you should be made aware in advance.

If the amp hums, it's not working "perfectly".

If your amp is a '62 and has never had a cap job, it's about time that it did. The hum could be down to several things but you wouldn't necesarily trouble shoot until you had taken care of the basics, like the electrolytic filter caps (that eliminate hum from the power supply & bias supply) and the cathode bypass caps (smaller electrolytic caps on the circuit board).

It's still possible that a duff preamp tube might be responsible for the hum, but the caps are way past their best & it's best to change them before they change themselves.

You might be looking at a couple of hundred dollars, depending on what else is wrong, but that will last you at least 10, usually 20 years (excepting any typical retubing in that time).

[arnauddd]

Wow thanks for the fast and complete reply!

So i guess i'll just have to find a really good (better than the two others) amp tech in my area.
i find it sad to leave that amp sleeping in a corner of one room.
Thanks for your advice, i'll try to find someone to get the basics covered and hopefully the noise will start up in front of the guy so he can have a better idea of what it happens.
Thanks again