|Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum|
Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
||Thread Tools||Search this Thread|
|29th January 2007, 03:20 PM||#1|
Join Date: Jan 2006
Location: Northern Virginia, USA
Marshall 100v 8100U Guitar Amp Hums
I'm guessing somewhere out there is a forum for guitarheads that like to work on gear, if anyone knows of one, please let me know.
Amp is 1995 vintage. This guy came with broken volume and contour pots, pretty beat up. I replaced with identical Marshall parts and I think I did this right, at least the hi and lo values match up with the others. The only other thing I did was add solder to C62, it looked like there wasn't any on one of its legs.
I don't play guitar and do not have the proper connectors to test. I used walkman headphones in both the line out and rear output jacks all I get is a hum/buzz. I plugged a microphone into the input jack, no result on the outputs, same noise. I adjust all controls and push buttons, no effect, just hum/buzz. Am I just testing this wrong?
What is the function of the send/return jacks?
I did take a dc measurement at the output jacks, got steady 18mv.
The schematics are here, the pdf files are easily expanded and they look pretty good actually:
Three General Questions:
1. The tube is there, it is original and lights up. Is there any way by looking at it to determine if it is operating properly? I do not have a spare tube.
2. I hear talk of filter caps, are these C61 and C62 and usually close to the transformer? These checked out with the esr meter, they are good. Note comment about added solder.
3. I also hear there are "coupling caps", how do you find these on the schematic? Do they come in pairs like filter caps?
|Thread Tools||Search this Thread|
|Thread||Thread Starter||Forum||Replies||Last Post|
|Guitar amp problem (marshall 8080 valvestate)||Palmu85||Instruments and Amps||3||26th September 2011 10:33 PM|
|Marshall guitar amp. Upgrade IC's recommendations||Joelg||Solid State||8||23rd January 2009 12:48 AM|
|SERIOUS TROUBLE: Marshall Valvestate 100v 8100||RevDEAD||Solid State||1||2nd March 2006 08:59 PM|
|FS: 82000uF/100V; 56000uF/100V||gengis||Swap Meet||0||6th July 2005 04:17 AM|
|turning an ibanez guitar amp to a marshall||electro samurai||Instruments and Amps||0||5th June 2004 09:33 AM|
|New To Site?||Need Help?|