Search found 6 matches
- Wed Jun 07, 2023 6:07 pm
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
Re: jtm 45 build issues
Finally got some time to sit down and work on the amp, as per tube depots recommendation, I replaced the filter caps( even though I knew they tested fine, which they did once tested after removal) Rechecked for any off value resistors or caps and re flowed most of the connections on the amp incase o...
- Mon May 01, 2023 1:40 am
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
Re: jtm 45 build issues
checked the mix resistors on pin 2 of the second 12ax7 they are in spec, I added a 100pf cap across the NFB 27k resistor with no real notable change, then I switched it for a 66k resistor and it helped some but still has oscillation, I also re flowed a few joints that I thought might be suspect, its...
- Sat Apr 22, 2023 4:52 pm
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
Re: jtm 45 build issues
All the Voltages in post 1 look good. With all pots set to 5, touching a DVM probe (other probe grounded) to the Grids (pins 2 or 7) of the 12AX7s should produce a clicking or hum through the speaker. Touching 2 and 7 of the PI should produce loud clicks. I can't help but think you may have a short...
- Fri Apr 21, 2023 9:08 pm
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
Re: jtm 45 build issues
I may be wrong, but have you tried to reverse the OT primary plate leads. I don't know if you have NFB connected. If you do not have it connected then disregard. ah yes I forgot to mention I have tried that with no change, I got slightly better results now after swapping the mica cap that bridges t...
- Fri Apr 21, 2023 5:05 am
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
Re: jtm 45 build issues
thanks for the suggestions so far, I checked the input jacks and speaker jacks , wired correctly and ohm out proper values aswell, decided to rebuild using only the tube depot jtm45 layout except I left out the NFB mods and the solid state rectifier, with the new layout the voltages are still within...
- Tue Apr 18, 2023 1:21 am
- Forum: Marshall Discussion
- Topic: jtm 45 build issues
- Replies: 18
- Views: 4513
jtm 45 build issues
Im trying to finish up a jtm style build built off the tube depot and ceritone jtm45s, currently I get sound from the amp but super super low volume even when fully cranked on all knobs and fully cranked it is pretty distorted , the tone stack dosent do much but does alter the tone somewhat current ...