Tube Amp Archive

Stevem wrote: ↑Mon Nov 15, 2021 11:30 am Yes, I have worked on many of them and you can power them up with no speakers hooked up, just tape off the ends so they can't short to each other or the chassis.

Thanks!!

Some recommendation to fix it?

Hi, I have a Roland JC120 and the chorus doesnt work, some recommendation to fix it?

could I turn on to check it without speakers? (I mean is a transistor amp)

Thanks everyone

I replace it with 500pF on the volume pot, also I replace the resistors and wires

Now it´s okey guys

Thanks again

I replace the resistor and it´s look like some noise go away but when I push presence and trebble to 10 and I turn up a little bright volume make noise

(I try it without any guitar plug in)

https://drive.google.com/file/d/1q69HTE ... sp=sharing

If swapping the tubes did nothing then one of the two plate load resistors for that channels tube may be going bad. These are 20 cent parts that take two minutes to unsolder and replace with a new one. If you do so then up grade them from 1/2 watt up to 1 watt for even less noise and longer life! I...

johnnyreece wrote: ↑Wed Oct 06, 2021 11:54 am Is this a new noise, or has it been this way since you got it? Have you tried swapping in known good tubes?

I try new tubes and the noise still there.

Stevem wrote: ↑Wed Oct 06, 2021 11:49 am C5 is a coupling cap and needs to be there to block DC voltage and pass just the audio signal on down stream just like C2 does for the other channel.

If I reduce this C5 the hiss could dissapear?

Inside the amp the green wires going to each preamp tube are grid wires and the should get raised up above the other wires as much as possible. There’s also a purple wire going to the presence control. This should be moved away from the preamp section as much as possible also, in fact it’s a good i...

The noise still there with any cable connected

Hi! I have one marshall 1987x with noise when I turn up high treble volume, some ideas about this problem?


Thanks

Here is the noise (it´s very anoying)

https://drive.google.com/file/d/1xf6d90 ... sp=sharing

The amp is working now.

The rectifier was bad, HT Fuse too and one resistor was open.

Thanks you guys

It sounds like one of the 4 output tubes are bad and since you do not have a tube tester or another amp to prove them out in all you can do is to order up a new quad of them. Today I changue the fuse and now it doesnt blow any fuse Rectifier is working good and everything is working, but still gett...

mI can turn on and play a little but it blow fuses every 40 seconds.


Every time it blow one fuse a Blue Shine come from tubes

Stevem wrote: ↑Tue Aug 10, 2021 10:03 pm Yes, and the JJ is of a better internal construction then then Sovtek.

I changue it and It´s works and sound, but every 40 seconds or If I turn off and on quickly it blow the Main Fuse. (Not HT FUSE)

Stevem wrote: ↑Tue Aug 10, 2021 7:43 pm That amp is very hard on rectifier tubes!

Be sure to but one that has the glass the same diameter as the black plastic base.

Other ones not made as such are not real 5AR4 / GZ34 tubes, but glorified 5Y3GT tubes.

I had Sovtek 5AR4, if I use JJ GZ34/5AR4 It would fit?