my 5f1 stopped working

February 27th, 2012, 04:54 PM
I have a Marsh Amps Tweed Champ that has been working great. I turned it on a couple of days ago and no sound. I have power, the caps and resisitors all show they are still with me, the 12ax7 and 6L6 are glowing. the rectifier 5y3gt has no glow when I checked the 3 and 4 outputs I had 350vac If I remember correctly and 1.120 vdc at the 2 and 8 pins. I pulled all the tubes and tested again at the 5y3gt and got the same readings. would this suggest that my power transformer has passed on?


February 27th, 2012, 05:15 PM
With due care and Multimeter set for high voltage AC, with tubes removed, check for high voltage AC at pin 4 of rectifier tube socket.

If you have high voltage AC on pin 4, you should have high voltage DC on pin 2 and 8 when rectfier tube is installed. (Change meter to DC High Voltage setting). If you have high voltage AC on pin 4 (and 6) your PT is good.

If waht you say is accurate, your description foretells a bad rectifier tube.

February 27th, 2012, 09:23 PM
I just double checked my voltages as my original post was from work. I removed the 5y3gt turned the amp on and checked pin 4 and 6 and I have 349.3 vac. then I reinstalled the 5y3gt and checked pin 2 and 8 I have very low voltage 1.125 vdc. That confirms your diagnosis and I will pick up a new 5y3gt. thank you for your help. :grin:

February 27th, 2012, 09:31 PM
Go NOS or JJ!