The Amp Garage

thanks again for the suggestions I will try them out when I get back ltr this evening, yes the plate? that got me thinking the only place AC could come in is via the OT secondary but it only happens when signal is applied - makes sense? I recall testing the OT primary and secondary for shorts but I ...

Guys, thanks for the help and a couple of things to highlight: a) The problem stays with the socket rather than the tube i.e. V4. If i swap tubes the same thing happens in the same socket. I have done this a few times so I am confident it is not the tubes. b) I have documented all changes etc that I...

Thansk Guys I will try some screen resistors and get back. The feedback loop resistor was measuring down to 4.4k? where it should have been 100k (according to the schematic) Ill let you know how I get on and I am getting the scope out to see if I can find anything else... Cheers Sean ________ Motorc...

Guys, I have a 1978 Marshall 2204 that I have been fixing up and when I got it had a number of minor problems all of whihc I fixed but I have found the following problem with V4 - power tube which ahs me foxed. When the amp is switched on and idle, all the tubes come up as normal and everything look...

Guys, I have a 1978 Marshall 2204 that I have been fixing up and when I got it had a number of minor problems all of which I fixed but I have found the following problem with V4 - power tube which has me foxed. When the amp is switched on and idle, all the tubes come up as normal and everything look...

Guys thanks for the suggestions and the help with the LED's. I will get round to these over the next day or so. I should have mentioned I have not installed the FET board in this build, but I also dont recall that I have added an additional 150k simulation resistor? excuse my ignorance but why is th...

Sean, looks like something is wrong with your PI tube. You should be well over 300V with the 360 tap and I'd expect around 290-300V on the plates with the 330 tap. Dogears a big thank you & spot on... just changed the tube for a spare one I had and the voltage is now showing 290 with cathodes aroun...

Hi everyone, I have recently built a dumble clone based on the ceriatone kit parts including building all boards myself etc however I have the following differences. 1. Used spare bassman type PT, OT and choke (5H/100ohm) that I had from a previous build not completed 2. Used my own steel chassis et...

Yes i understand that hence being careful. Some more information. I have 3 ground points in the amp. 1 - Earth ground to the chassis (reads 0 volts) 2- Star Ground A - Bias, OT ground, power cap, power tube grounds (reads 0 volts) 3. Bus bar B - pre amp signal ground, input jack ground etc - reads 0...

Guys Being a 'newbie' to amp building I have been doing OK for my first 4/5 builds but I have a problem that has started on this one that has foxed me. The symptoms are very simple with all tubes pulled the B+ voltages look correct to the plates on all sockets. No voltages showing up on cathodes etc...