The Amp Garage

Thanks for all the replies, I'll try to address everyone's points in order: -Electrostatic shield would definitely be effective in combating this issue. Unfortunately I don't know of anyone making off the shelf PT's with them included. I'm at the point now where I could fairly easily design my own ...

it is ok.. also there is wide range of usable impedances for all the tubes.. nothing to worry about..in datasheets yu can find distortion vs load impedance , this is changing, also little bit he character.. but is it ok

PP or SE?

I had the same problem in one amp, when inside the box.. chassis and power transformer were extremelly hot.. while outside on the table, chassis and PT temp was just moderate, nothing to worry about... Then i discover that there is no sufficient air circulation in the cabinet, and tubes were heating...

I only have one fuse, 3 amp slow on input power. In Operate 118vac wall voltage 320-0-322 vac secondary. 320vac leg is also feeding bias circuit. B+ 414vdc Bias -360vdc at 5mA PT's biased to 27mA with -49 volts. if this is in operation all looks ok.. temperature is ok also little bit hot, 45 deg C ...

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/
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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...