Adding A Rectifier Tube/Diode Switch

[jaster55]

I recently added a tube rectifier to a Frankenstein Bassman... I decided to add a switch and diodes to the tube socket following following a Rob Robinette mod I found. The project turned out great and it's nice to have the best of both worlds. In reading more about the mod I found that some techs add diodes to the rectifier tube socket for added High Voltage protection in case the rectifier tube fails. I also read that wiring the socket using the Robinette method could cause problems if someone down the road were to plug a different type of rectifier tube into the modded socket. All the articles I read about the subject caused me to have an Ah Ha moment and I thought why cant I do this instead.
This Ah Ha idea I had may already be out there and patented. I'm just trying to find out if there is any reason why I shouldn't do this. I'm attaching a drawing geeked up earlier today.

Any help would be appreciated.

[sluckey]

If you draw each in schematic form you will see that the circuits are the same... except you have two unnecessary diodes.

[cboysen]

I recently added a tube rectifier to a Frankenstein Bassman... I decided to add a switch and diodes to the tube socket following following a Rob Robinette mod I found. The project turned out great and it's nice to have the best of both worlds. In reading more about the mod I found that some techs add diodes to the rectifier tube socket for added High Voltage protection in case the rectifier tube fails. I also read that wiring the socket using the Robinette method could cause problems if someone down the road were to plug a different type of rectifier tube into the modded socket. All the articles I read about the subject caused me to have an Ah Ha moment and I thought why cant I do this instead.
This Ah Ha idea I had may already be out there and patented. I'm just trying to find out if there is any reason why I shouldn't do this. I'm attaching a drawing geeked up earlier today.

Any help would be appreciated.

By Different rectifier, you mean one that utilizes pin 3 and 5 I assume? I can't think of any common pinouts that would use those?

In anyway, there is no apparent difference in your and Robs design, besides the added cost (2 extra unnecessary diodes) and labortime by your design. Also you may introduce a bit of noise if those AC wires are runing far and wide. In any case, it's good practice to figure out how a circuit works, and try to come up with different ways to do the same job, it gets the brain going.

kind regards
Christian

edit: sluckey beat me to it

[pdf64]

As a side note, be aware that the 2 protection diodes (ie 1 in series with each tube plate) should have a rating >1kV.
As they’ll have 1046V across them (320x2x1.414)

[kagliostro]

As far as I can know protection diodes purpose is to avoid AC to reach the circuit if a vacuum diode short

and also (as a side effect ?) to increase the max voltage allowable by the vacuum rectifier diodes

the max vacuum diodes allowable voltage is summed to the max allowable voltage of the Solid State diodes

so, on the Solid State diodes you have the same effect that you have on the vacuum rectifier diodes

the voltage seen by the single pair of diodes is less

Franco

[pdf64]

Sorry I should have specified that the protection diodes will have >1kV across them in the case of the tube rectifier shorting.

[sluckey]

As long as you are tinkering, change all 6 diodes to 1N4007 and connect like this...

[jaster55]

Thanks for all the responses...
I should of pointed out that the six diode SS circuit is existing so my plan was to save time by not adding diodes to the tube socket. The diodes are 5408's.
I like the idea of tapping in at the second set of diodes... Thanks Sluckey

So... From a safety standpoint,  does adding the diodes to a tube rectifier a good idea?
And... Does it change the characteristics of the tube rectifier sound, response, sag, etc

Thanks Again To All...

[kagliostro]

SAG will be the same

1N5408 are more than fine, if they are UF5408 also better

Franco