Ampeg Micro-CL modding

[mybreathyourlung]

Hi,

I’m going to attempt the repairs mentioned here:

https://music-electronics-forum.com/...stortion/page3

This is my first foray into this kind of electronic work and I’ve already hit a stumbling block: when purchasing the resistors and capacitors what wattage and voltage should I be choosing, respectively? The schematics for the amplifier doesn’t provide this info. Thanks, all.

[Jon Snell]

A schematic on what you intend to do would help. Eg, replace C104 to 47uF, stuff like that.
If we get a list of your intentions, we can advise on wattage of resistors and voltage ratings of capacitors etc.

[mybreathyourlung]

Replace C106 with a 680pf, replace R6 for a 62k, replace R24 and R18 with 22k and 100k respectively, add a 2200pF cap in parallel with 100k R6 resistor.

[Jon Snell]

Resistors; No high power resistors are required so any 1/4W or 1/2W MF, MO or CF 5% or better will be fine.
Capacitors; No high voltage capacitors are required so 63v 10% will be fine.
Your mods will make it sound different, as C106 will slow the HF response down in the power stage and a capacitor across R106 may cause instability.

[g1]

Replace C106 with a 680pf, replace R6 for a 62k, replace R24 and R18 with 22k and 100k respectively, add a 2200pF cap in parallel with 100k R6 resistor.

This is incorrect. The 2200pF goes across R18, not R6.

[mybreathyourlung]

I’m simply going off what was suggested and seemed to improve things based on the other thread I linked. Do you have any suggestions or different changes? I’m new to this so I’m all ears. Thanks for the information.

And yes, I was incorrect with the placement of the 2200pf, I didn’t have the schematic with my notes on me. Thanks for the reminder!

[mybreathyourlung]

Resistors; No high power resistors are required so any 1/4W or 1/2W MF, MO or CF 5% or better will be fine.
Capacitors; No high voltage capacitors are required so 63v 10% will be fine.
Your mods will make it sound different, as C106 will slow the HF response down in the power stage and a capacitor across R106 may cause instability.

Instability in what way?

[g1]

Instability in what way?

He said it would cause instability if you placed it across R6. But that was a mistake. It goes across R18 and will not cause instability there.

[Helmholtz]

In the context of amps instability means a tendency to self-oscillate.