5AR4 diodes added

[Prairie Dawg]

Any idea whether this is worth doing? It's supposed to offer some protection from rectifier tube failures.

If there's an EE in the house an explanation would be nice. Mark?

200S Diode Mod

[pdf64]

See
http://www.geofex.com/tubeampfaq/TUBEFAQ.htm#ampmods
Recommended mod #8. Pete.

[mooreamps]

Any idea whether this is worth doing? It's supposed to offer some protection from rectifier tube failures.

If there's an EE in the house an explanation would be nice. Mark?

Well, if someone does it, perhaps it's for a good reason. I've not seen a rec tube go bad in this way, but since you can mount the diodes directly on the tube socket, it's like why not...

Basically each solid state diode is in series with each internal plate of the rec tube, in the event the internal plate should short to the filament, the external diode will still keep the A/C voltage from passing through the rec tube, and thus mitigate the A/C from taking out the filter caps...

-g

[Rhodesplyr]

Basically each solid state diode is in series with each internal plate of the rec tube, in the event the internal plate should short to the filament, the external diode will still keep the A/C voltage from passing through the rec tube, and thus mitigate the A/C from taking out the filter caps.

It seems to me like this would make more sense when dealing with directly-heated rectifier tubes like 5U4s and 5Y3s where the filament can potentially break and short directly to the plate, but I guess plate-cathode shorts do sometimes happen in 5AR4s.

[R.G.]

Well, if someone does it, perhaps it's for a good reason.

Hmmm. Maybe:

See
http://www.geofex.com/tubeampfaq/TUBEFAQ.htm#ampmods
Recommended mod #8.

from a couple of hours before your post, which also tells you the reasons why it's good. It's almost like reading the references would be useful, isn't it?

BTW, the Tube Amp FAQ at GEO dates from the mid 90s, and was posted to usenet from before a time when there was a world wide web to browse. It's still a useful thing to read, I think.

[mooreamps]

Tube amps in the environment take a beating.. I remember when I got one of my loaner amps back from Seattle from FedEx, and they slammed the amp so "hard" one of the power tubes was physically broken inside.. and yes it was shipped insured and yes we did file a claim....

-g