Help needed, amp won't work

GuitarRock04 · Not So Newbie Joined: 29 Jan 2007 Posts: 5

I am modding an old gibson 10" combo, a Maestro M-201. I have replaced the electrolytic caps, and added a tone stack from a champ schematic. I have also replace the output transformer and speaker.

Here is the original schematic:

And here is the modded schematic:

I tried it out last night, and got nothing more than a very faint hum. (I have the original speaker in it now, because even though it has a tear in it, i wan't to make sure everything is in order before i hook up the ridiculously expenzive new one.) When i switched it off though, you could suddenly hear what i was playing, though still faint, it was there for a second then faded.

Does this symptom set off any obvious areas to troubleshoot? Is there something wrong with my circuit design? Any help is appreciated.

roverjohn · Sea Monkey Joined: 11 Feb 2007 Posts: 14

have you tested all the old tubes to make sure thay are OK? and did the amp work before you modded it? Adding a tone stack reduces gain but usually not to the point where you have none.
John...

GuitarRock04 · Not So Newbie Joined: 29 Jan 2007 Posts: 5

Actually, yes, the amp did work previously and I have tested the tubes in another amp and they work just fine. But here's the thing: in the other amp, the power tube has no problems. But when I put it in this amp, it becomes horribly microphonic. Tapping on it with a screwdriver comes through quite loudly, even though i've got no other output... This mean anything to you?

gnappi · Tadpole Joined: 13 Aug 2006 Posts: 18

roverjohn · Sea Monkey Joined: 11 Feb 2007 Posts: 14

owwdatune · Posted: Thu Feb 15, 2007 2:45 pm Post subject:

first of all...put a speaker in it that is 100%......check all the solder points...the ones you did as well as the rest..if unsure, simply resolder...check all connections to be sure they are as should be (while working on it you could have messed something up)....use your multi-meter to check all readings/connections as well as continuity.---- i don't have the time to check out your handiwork--perhaps someone else can ??---but if the amp worked previously..then the problem has to be with what you did in your mod......goodluck & let us know what you find & how you fixed it. #Scramble

_________________
~T~...Live a little >crank it up< ...

--> SAVE A LIFE - ADOPT A SHELTER/RESCUE PET <--

owwdatune · Posted: Thu Feb 15, 2007 4:31 pm Post subject:

i've used this in the past to help me figure a thing or two out---maybe it's something you could utilize as well >>> http://www.duncanamps.com/tsc/index.html
_________________
~T~...Live a little >crank it up< ...

--> SAVE A LIFE - ADOPT A SHELTER/RESCUE PET <--