Thanks for the explanation. I am having a hard time locating it on the board...Helmholtz wrote: ↑Tue Jan 13, 2026 2:39 pm Explanation for my proposal regarding C20:
This cap forms a resonant circuit together with the inductance of the reverb transducer resulting in a treble boost of the reverb signal.
Fender started using this method to brighten up the reverb with the SF amps.
Very weak channel and intermittent Tremolo !
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Re: Very weak channel and intermittent Tremolo !
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Re: Very weak channel and intermittent Tremolo !
It should be the ceramic disk wired across the 1M resistor which goes from pin 7 to ground.
Re: Very weak channel and intermittent Tremolo !
About those yellow rectangular caps, why did they choose those ? they are using mustards everywhere in the amp, why not for those locations ?
Re: Very weak channel and intermittent Tremolo !
Those yellow rectangular caps are quality Philips MKC 341 caps, available with a voltage rating of 630V (Mustard caps were only available up to 400V).
Also used in Marshall amps around '68.
What about the reverb sound?
Also used in Marshall amps around '68.
What about the reverb sound?
Re: Very weak channel and intermittent Tremolo !
Hello --
It would be unsurprising if the amp originally had "Mustard" film caps and those molded Philips were used for repair. Traynor amps were widely used for rentals in Canada, and those got heavy use often bordering on abuse.
What speakers did this come with? Some of the Traynor OEMs were of dubious sonic quality and possibly the perceived "highs" could be a product of Marsland "thinness".
Perhaps post a fresh gut shot showing the details of electrolytic refresh. Before attempting to diagnose more obscure problems it's key to fix the obvious stuff.
Best .. Ian
It would be unsurprising if the amp originally had "Mustard" film caps and those molded Philips were used for repair. Traynor amps were widely used for rentals in Canada, and those got heavy use often bordering on abuse.
What speakers did this come with? Some of the Traynor OEMs were of dubious sonic quality and possibly the perceived "highs" could be a product of Marsland "thinness".
Perhaps post a fresh gut shot showing the details of electrolytic refresh. Before attempting to diagnose more obscure problems it's key to fix the obvious stuff.
Best .. Ian
Re: Very weak channel and intermittent Tremolo !
Here is a fresh pic of things as they stand. All electrolytics replaced. Still have not removed the ground switch. Not sure what the best route is for A.C. There are many ground points to chassis here.
Also here is a pic of one of the speakers,not working. I have one Tone Tubby Red installed in place and will likely replace the other with a G12 65 creamback unless someone has other recommendations.
Lifting the .001 cap has a subtle but pleasing effect on the reverb.
The tremolo works when I first turn the amp on then stops as it warms up. Would this be pointing to a defective coupler ?
I also noticed the filter caps seem to drain as soon as the amp is turned off. Suggestions on bright cap value ?
Also here is a pic of one of the speakers,not working. I have one Tone Tubby Red installed in place and will likely replace the other with a G12 65 creamback unless someone has other recommendations.
Lifting the .001 cap has a subtle but pleasing effect on the reverb.
The tremolo works when I first turn the amp on then stops as it warms up. Would this be pointing to a defective coupler ?
I also noticed the filter caps seem to drain as soon as the amp is turned off. Suggestions on bright cap value ?
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Re: Very weak channel and intermittent Tremolo !
The work-in-progress is coming along. Still encourage getting a few eyelet zip tie downs. Adhesives don't cut it.
A TT Red removes any concern the speakers are the issue. And even the OEM speaker looks like one of the better Traynor selections.
I note on the schematic the coupling cap off the reverb recovery is a 0.001uF. Increasing it should let any bottom end that's made it through the signal path fill in a bit -- try a 0.01uF? There is a 560pF cap feeding the driver, and that's also has spectral shaping affecting the input.
No easy obvious advice on why the tremolo is misbehaving. The optocoupler could be at fault, though doubtful. Perhaps others can help with this along with other issues.
..
A TT Red removes any concern the speakers are the issue. And even the OEM speaker looks like one of the better Traynor selections.
I note on the schematic the coupling cap off the reverb recovery is a 0.001uF. Increasing it should let any bottom end that's made it through the signal path fill in a bit -- try a 0.01uF? There is a 560pF cap feeding the driver, and that's also has spectral shaping affecting the input.
No easy obvious advice on why the tremolo is misbehaving. The optocoupler could be at fault, though doubtful. Perhaps others can help with this along with other issues.
..