Traynor YGM4 Tremolo Problem

[ianmarks]

I've got a Traynor YGM4 where I don't think that the tremolo is reaching full intensity. I have seen a couple videos on youtube where it definitely sounds "choppier" than what mine does. It is a bias modulating tremolo seen at the bottom of this page:

Bias Modulating Tremolo Circuits

I have replaced all the caps, checked the pot, switched tubes, but no change. Any ideas before I take it to a tech would be appreciated!

Here is a link to the full shcem:

Prowess Amplifiers - Traynor - Schematics - Guitar Mate Ygm 3 and Ygm 4

[Jazz P Bass]

Bias tremolo circuits have the "most" intensity at a lower volume.
You will not get much if the amp is dimed.
Just a thought.

[Gtr_tech]

Output section bias setting has alot to do with how well bias trem works. If the output tubes are idling too hot, the effect will be less. I actually use the trem to set the bias in most amps with bias trem if the customer is really into using it. Just set the trem to max intensity and dial bias back until it sounds as it should. Idle current normally ends up on the conservative side

[ianmarks]

Gtr_Tech - I am assuming R39 is the bias resistor. If I raised this value should I be able to hear a difference in the trem intensity? I went up to 30k and didn't hear a difference. Maybe I should use a larger value pot?

When I switch the amp into standby, I hear nice trem action for about 2 seconds....

[Gtr_tech]

You could replace R39 with a 15k in place of it and a 25k pot in series with that. Should give a good adj range.

What wattage are your output tube plates idling at?

Double check all the resistors in the trem osc circuit, especially the 820 K resistor. You *did* replace the 25u bypass cap right?

I have a YGM3....later version with bumper trim and round knobs.

[ianmarks]

I found the problem and it was due to my ignorance. I had replaced c28 and c29 when I first got the amp and recapped all the electros and did not pay attention to the fact that their + goes to ground.

Anyway, swapped them around, adjusted bias to -17 and have a fabulous sounding tremolo.

Mine is an earlier three input version. I've done "parkhead's" mods to mine and have found it to be much more usable. I am interested to see how much this will effect the tone at loud volume, but baby is sleeping.

Thanks for the help!!

[Gtr_tech]

You may think about replacing those bias filters. They may have been damaged by the rev polarity. Cheap insurance. If one shorts, there goes yer bias, and there goes yer output tubes.....

[ianmarks]

Yeah, that was my thought as well. I've got cheapos in there until I get everything sorted out. Gonna experiment with a tone stack bypass switch, too. Gotta love these amps for DIY as they are so easy to tinker with!