Fender Twin Reverb (1972, CBS) - suggestions for “refurbishment”

[ccaudle]

I've found values as high as 47uF, 25v.

I found the data for that specific combination:
https://www.murata.com/products/productdetail?partno=RDEC71E476MWK1H03B
You can see that at 10V DC the capacitance is already around half of the rated value:

Just something to be aware of when using ceramic capacitors.

 

[Alva Goldbook]

That datasheet does not have a graph for capacitance vs. bias voltage, but you might be able to find that in a sheet for the specific part number (that datasheet covers a family of parts).
This page describes the effect:
https://www.murata.com/en-us/support/faqs/capacitor/ceramiccapacitor/char/0005

Well, if I recall correctly, the bias voltage was about 1.3VDC, so it should have a negligible effect. Within the tolerance range of most components.

 

[Alva Goldbook]

I found the data for that specific combination:
https://www.murata.com/products/productdetail?partno=RDEC71E476MWK1H03B
You can see that at 10V DC the capacitance is already around half of the rated value:
View attachment 142781
Just something to be aware of when using ceramic capacitors.

Interesting. So these will work fine for most bias arrangements for 12ax7s, but for 12au7’s, 12at7’s and other high current triodes, this effect will have to be considered. Thank you for letting me know!