If rectifier tube fails do filter caps get damaged?

[Dingleberry]

The subject was my question I was wondering.
Does anyone know?

-T

[FYL]

Common failure modes don't hurt the caps. Some rare types of shorts could lead to AC applied to the caps and dead caps.

If in doubt, remove the caps from the amp and check their capacitance, ESR and leakage.

[tubeswell]

One of the R.G. keen immortal amps series of articles has a tip on tube rectifier short protection - 1 x 1000V1A diode in series with each side of the HT winding and the rectifier tube's anodes (diode's banded end/cathode pointing towards the tube's anode). This means that the SS diode is doing the initial rectifying, but you still get the voltage drop expected with the tube rectifier, until the tube rectifier shorts (at which point you get the voltage drop expected with the SS diode). This helps ensure that high voltage AC never gets a chance to destroy the filter caps, or by implication, your PT either.

[Dingleberry]

You mean like this Tubeswell?

I've got some BY228's (1500V/3A) and BY448's (1500V/2A) lying around. They both will probably do the job well?

-T

[rp]

One of the R.G. keen immortal amps series of articles has a tip on tube rectifier short protection - 1 x 1000V1A diode in series with each side of the HT winding and the rectifier tube's anodes (diode's banded end/cathode pointing towards the tube's anode). This means that the SS diode is doing the initial rectifying, but you still get the voltage drop expected with the tube rectifier, until the tube rectifier shorts (at which point you get the voltage drop expected with the SS diode). This helps ensure that high voltage AC never gets a chance to destroy the filter caps, or by implication, your PT either.

Do you loose the gradual warm up if you do this?

[Structo]

I wouldn't think so because the tube still has to heat up before it will conduct much.

[tubeswell]

You mean like this Tubeswell?

I've got some BY228's (1500V/3A) and BY448's (1500V/2A) lying around. They both will probably do the job well?

-T

Yup

[tubeswell]

One of the R.G. keen immortal amps series of articles has a tip on tube rectifier short protection - 1 x 1000V1A diode in series with each side of the HT winding and the rectifier tube's anodes (diode's banded end/cathode pointing towards the tube's anode). This means that the SS diode is doing the initial rectifying, but you still get the voltage drop expected with the tube rectifier, until the tube rectifier shorts (at which point you get the voltage drop expected with the SS diode). This helps ensure that high voltage AC never gets a chance to destroy the filter caps, or by implication, your PT either.

Do you loose the gradual warm up if you do this?

Depends what tube rectifier you are using. directly heated tubes (like the 5U4G) warm up faster than indirectly heated tubes (like the 5AR4)

[Dingleberry]

The amp I'm servicing right now is a JMI AC30 treble.
It has GZ34 rectifier, so the diode protection mod will probably perform well in that circuit. I really would like to make it as reliable and safe as possible yet keeping it as original as I can. If there will be no (major) change in sound and operation I will install the diodes.

-T

[tubeswell]

If there will be no (major) change in sound and operation I will install the diodes.

Sound-wise - makes no difference