Tube Amp Archive

Well two new sockets in without the need for jumpers ( miracle ! ) like the 3 that had already been worked on before me. Two of the dammed nylon board standoffs busted due to age so I need to work around that. The amp now works but has low distorted output on both clean and lead channels. It only ha...

I took in 1987 Highwatt 50, you know the era with the circuit boards 😣 In all of these years of doing this repair stuff this is only my second time into one of these and someone has already been into this jumping out preamp tube circuit traces to get the peice of crap to work again, and now it needs...

Why are you in need of testing them, because of a precived problem with the amp?

As the current Output of any given PT starts to reach its limit then the tone of the amp will start to change. The point where the power supply voltage starts to sag is where you have maxed out the current available from the PT. This is also the point where the filament voltage will sag with the res...

A bag helps, but it’s not a necessity because it’s really just to keep crap out when it mounted to the bottom. In many Ampeg combo amps they were mounted vertically on a side wall and with no bag. The main thing for having a low 60 hz noise floor is to keep the output side of a tank as far away from...

Good question.
I guess that they wanted to limit the total current thru each side of the OT and those two screen resistors let them do that while still having only one bias setting on pin 5 for all of them.

Me neither, but just wondering what the idle noise floor looks like in a fixed bias amp that just for the second part of the test you convert to cathode bias, of course with the PI tube pulled out so your just looking at the noise floor of the output section . Output sections don’t have much gain so...

Do you have a scope?

Besides that, it’s making multiple post of just one post.

I would start by ohm checking all the ground paths by looking for a high resistance. Just because the amp might’ve been recapped even just 3 months ago does not mean that one can not be going bad, so if all the ground paths check out then I would jump out the filters one at a time. If this issue is ...

I would start by ohm checking all the ground paths by looking for a high resistance. Just because the amp might’ve been recapped even just 3 months ago does not mean that one can not be going bad, so if all the ground paths check out then I would jump out the filters one at a time. If this issue is ...

Yes, and he still needs to check, but I posted this because I have used this PT from Hammond in a echo twin and one sold by Fliptops for a replacement in the same model as his PT he is questioning.

In both cases of replacement PT’s the white was the heater CT.

So you can put this to bed here’s what that white wire is on a new replacement PT.

They’ll be back.

They were taken to another earth like planet.

To them when they get back it will seem like they have been gone for 5 minutes, but us…….. who knows how long!

Then simply don’t use that white wire, just shrink tube it off and roll it up in a loop and cable tie it.