Traynor YGM-replaced filter caps/NF mod and now volume works strange...

[bbrownsbrick1]

Hello again,

I replaced the filter caps on my Traynor YGM-3, and it sounds killer, while I was at it I removed the .1 capacitor that was wired to the Negative Feedback resistor. I took a chance and fired it up, here is what I noticed

a lot of hum; i flipped the ground switch and that issue was quickly solved

as i turned the volume knob it seemed to get its loudest at 5, staying stagnant til 8 and 8 with a ton of headroom and suddenly gets very compressed and distorted from 8 to 10, a sudden jump.

I'm now wondering, did I wire something wrong in the filter section or is it the NFB that I altered doing this? The original schematic called for 4 40 section of filtering but I have 32/32 for the preamp and 50/50 for the power...I really hope I got this right...

Another thing (maybe needs a new post), but im looking to install a 3 prong and bypass the circuit reboot and ground switched and add a bias pot. I have added a bias pot to my non reverb BF princeton with great results using the torres method, but how would I go about doing this on this amp? I assume bias resistor attached to ground/chassis or back of pot, wiper coming from bias supply on tagstrip and outer tab attached to where the bias resistor used to be? I still want to have the tremolo which is bias powered as well...

sorry for all the questions...help me get out of noob hood!

[Enzo]

it would be gentlemanly to link a schematic.

http://www.schematicheaven.com/barga...rmate_ygm3.pdf

Why did you remove that cap?

Volume issues? Your amp might be going unstable, oscillating at high frequencies. That might explain the sudden onset of distortion. and that could be involved with the NFB parts.

[Robert M. Martinelli]

+1 on what Enzo said.

When present, a NFB loop is there for a purpose, and fiddling with it ( for fiddling sake? ) might shatter the amp's stability.

I would classify this thread under the "B.U.M. syndrome" ( Blind Urge to Modify ) category; if the amp sounded killer, why on earth did you remove that cap altogether?

Aside from the safety concerns normally associated with working on tube amps, one should never attempt to modify them without a real need, or without weighing beforehand all the pros and cons of performing a certain mod IMHO.

JM2CW

Best regards

Bob

[bbrownsbrick1]

Sorry for lack of schematic, I cant find one that is accurate to my make of YGM-3 online. I was using the one attached to the chassis for reference.

I modified the NFBL because I wanted it to respond more to the speaker, like my Deluxe Reverb. Sound and feel are two completely different things IMO, i've had amps that sounded great and felt terrible, like this late 60's tweed Peavey....

Ill post some pics after work.
Thanks a bunch

[bbrownsbrick1]

Reversed the mod: and the results...

Well, needless to say the volume/distortion onset is as smooth as can be, HOWEVER it is now making crackling/faint squeeling in the background. I reinstalled the .1 Mustard in parallel with the NF resistor. I read that this can be from poorly dressed leads, how does one dress a lead (it makes me think of putting ranch dressing on the connections of a resistor)? I know this is a stupid question, but im just getting into this type of thing.

Here are pics, just to make sure im doing an OK if not substandard job. The last pic is an example of how I grounded the filter cap...is it ok?