PT Snubber

[C Moore]

I guess "snubber" is the correct term.
The cap(s) you see across the PT secondary of many older amps.

Do they act like a phase inverter fizz cap.....causing phase cancellation above a certain frequency.?
Are they "necessary"...still used today.?
Thank You

http://www.prowessamplifiers.com/schema ... C_100.html
http://www.prowessamplifiers.com/schema ... /1986.html

[Stevem]

They help with the noise hash made from the diodes turning on and off, in latter Fender amps they put a .01 cap across each diode in the bridge.
If you build or change over to fast recovery type diodes you do not need them.

[C Moore]

OH...OK.
Thanks.

Round numbers...if my DMM measures 700 VAC across the secondary.
Would I need a cap with a V rating of 700 x 1.4= 980V .?
(I guess that is why Marshall use 2x 630V cap in series.?)
Thank You

[Cliff Schecht]

OH...OK.
Thanks.

Round numbers...if my DMM measures 700 VAC across the secondary.
Would I need a cap with a V rating of 700 x 1.4= 980V .?
(I guess that is why Marshall use 2x 630V cap in series.?)
Thank You

If you are measuring voltages that high with your multimeter, make double sure that the peak-to-peak voltage you are putting in is within your meters limits. I fried a high dollar Fluke (not mine thankfully) testing some unknown transformers and one of them was putting out nearly 1200V p-p. Poor Fluke never stood a chance .

[Stevem]

Yup, a 1000 volt cap.

[C Moore]

Again...Thanks for the answers and the info.
I am sure it CAN very a lot, from one amp and power supply to another...but generally speaking...do you guys use this cap(s) across your PT secondary.?
Assuming "normal"...general purpose diodes...do you guys notice some switching noise without a cap.?
Thank You