An Essay about bad filter caps – or My tremolo is not working!

Hi everyone,

I just came across an interesting thing which I want to share with you guys: A friend of mine came to me and asked me to get the tremolo in his blackface bandmaster working again. When the amp sat here on my bench, I realized that first, the tremolo ticked and secondly the effect was weak. So the good news was, the tremolo was oscillating, the bad news was, that the effect was not really there.

Ticking needed anyone?

To deal with the ticking I tried a 0.022 cap over the 10M resistor in the oscillator circuit which is the same for about any silver and blackface amps with great result. The Ticking stopped and the effect of the tremolo became really strong. After I told my friend, that I repaired the tremolo and that he might not need to change the filter caps, I started wondering.


I recently had to deal with a strange problem on the preamp of a blues deluxe amp, which I repaired changing the filter-caps for that stage. What happened was crosstalking from the first to second stage due to old filtercaps. So I thought about it and found out that the tremolo effect in that actual might be weak because of bad filtering. The HT for the light-bulb had the high voltage only filtered by that double 70uF Caps. I thought if those were old, almost no filtering happened on the HT for the tremolo circuit. How should the tremolo (light bulb) work if theres so much ripple on the HT?


I tried to new 70uF Caps in parallel with the old one and tadahhhhhhh! The Tremolo worked great!

RULE: If the tremolo oscillates, you see the light bulb blinking and there’s almost any tremolo effect, it’s most likely bad filter caps on the first stage. So if your amp has that sickness, bring it to your favourite repairman and let him change your filter caps.

Have a great first advent evening.



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