This is a newer reissue version. Amp sees a lot of usage. Customer states the HT fuse is blowing.
I tested all tubes (test good), tested OT (test good).
Ran the amp in 50W mode for a few minutes with no issue.
Switched to 100W mode, played for a minute and then heard a subtle noise (like something switched) and then saw the current spike. Powered down before HT fuse (T1A) could blow. Waiting to hear back if this mimic the original issue.
Tested again, chop stick everything in sight. Wiggled all tubes, no issue.
Amp is drawing around 1A at the wall plate until it spikes.
All tubes appear to be original Marshall branded. I suspect a tube(s) may be failing after a few minutes of usage.
Looking for suggestions before I try new tubes.
I have attached a schematic but I do not think this is the latest/correct version as I see some rectifier diode numbering not matching the circuit board. Anyone have a schematic?
Thank you, Mark
marshall_25aniv_silverjubilee_50_100w_2555.pdf
![Click image for larger version
Name: 20240816_161533.jpg
Views: 81
Size: 1.84 MB
ID: 1002880](filedata/fetch?id=1002880&d=1723841853&type=medium)
I tested all tubes (test good), tested OT (test good).
Ran the amp in 50W mode for a few minutes with no issue.
Switched to 100W mode, played for a minute and then heard a subtle noise (like something switched) and then saw the current spike. Powered down before HT fuse (T1A) could blow. Waiting to hear back if this mimic the original issue.
Tested again, chop stick everything in sight. Wiggled all tubes, no issue.
Amp is drawing around 1A at the wall plate until it spikes.
All tubes appear to be original Marshall branded. I suspect a tube(s) may be failing after a few minutes of usage.
Looking for suggestions before I try new tubes.
I have attached a schematic but I do not think this is the latest/correct version as I see some rectifier diode numbering not matching the circuit board. Anyone have a schematic?
Thank you, Mark
marshall_25aniv_silverjubilee_50_100w_2555.pdf
Comment