The Amp Garage

Usually power transformer is last thing to fail..almost impossible in good wound transformer.. Also fuses should be burned before the transformer..

Hmm it is strange thing.. Does PT has normal voltages in operation? Pls retest IN OPERATION all the voltages, and write here.. If they are normal, and current consumption is normal.. And transformer is hot.. then is undersized for this application..

otherwise, making only V1 DC supply for heaters is simple.and cheap(7812) and fixing all of the problems.. V1 matters only, sometimes V2

the problem in the power transforner should be overtaken by making electrostatic shield between secondary and heater winding, which need to be located at the top (last winding), and gnd this winding

Lead dress is causing oscillations in higher gain... oscillations are positive feedback, and cable connected to sensitive grids is acting like an antenna.. Whatever this cable picks up, it is getting amplified. grid is multiple turn of small wire so it is real antenna.. In guitar amp there are many ...

for the added fuse, check what is this and why is there

all electrolytic capacitors needs replacement.. another critical point are film capacitors after the PI to the output tubes, they need to be replaced too.. all those moves are preventive and cheap..all elcos are too old and can fail anytime in the future. on other positions film caps should be measu...

connecting mosfets in parallel can easily lead to a silicone pop-corn

Im just reading feedbacks on FB Tube Guitar Amplifiers group..not looking good..reliability problems?

https://www.facebook.com/groups/724815140961013/
posts down

Well you've got at least one dud there. Have you considered using thermistors for a soft start instead of a standby switch? not really , because you need to hold high voltage at least 20-30 seconds and if not.. all of the Ub line caps will be on max voltage .. You need something like 500k. So or Au...

Stephen1966 wrote: ↑Fri May 10, 2024 10:07 am
The ticking is some kind of internal arcing?

Yes, and the voltage drops are there too in the same time.. on variac if i lower the input voltage, then in one moment is ok situation, but on nominal looks like is going to the white smoke.

Chasing the ghost

faulty caps video:
https://drive.google.com/file/d/18ELqsP ... sp=sharing

Here is something what happened after in the amp.. failure on 450V elcos in the preamp section (they were new Kemet - Long life - ex Rifa) ? Very strange, i didnt measure wall voltage before.. maybe little bit over 230? Looks like caps took surge voltage during cold start (power and standby switch p...

For the past weekend we had some festival dedicated to vinyl and tubes, where was amp played.. i took nude and rude version without box.. Very nice experience.. maybe little bit too fatty/creamy sound with 1x12" Alnico Cream.. room and people damped the heights so better in the start to have more mi...

I wonder if anyone can actually call out a tube by hearing it. not possible.. also there is wide range of manufacturing types and shapes..but you can hear the differences.. and NOS are at least 30% better than modern tubes.. Altough i have good luck with 12AX7 JJ, often they are good enough-till-gr...