Grundig H&B 6007 tube power supply - Repair or gut for parts?

[GloBug]

Each cell drops about a volt.

How many cells in the Selenium?

[the_manta]

I have old german tube-radio radio here often playing some music. The original selenium rectifier working just fine.
As long as none of them has failed, I wouldn't change them. Compared to mercury or other heavy metals, selenium is harmless. As long as you don't crush them and inhale the dust.
I have been working with equipment which has selenium rectifiers in them since I was 16. The same with asbestos (transformer heat cover). As long is you don't disassemble these things, everything is fine.
When you want to change them so bad, you should at least keep them as spares for vintage tube gear. But as I said, when you see selenium as a problem, then you should be scared to death by mercury vapor rectifiers :-)

There is no problem with resistors. Selenium doesn't have a higher threshold only a higher differential inner resistance.
And since this PSU is regulated, every drop before the regulation shouldn't matter.

[overtheairbroadcast]

Do you have anything comparable (my friends father has two tube testers, a stack of volt meters for tube amp building, and volumes of printed material), in that you will not be missing such a fine piece of equipment? If you don't want it, then sell it or take it apart for parts. If however, you like the unique look and history of it, then keep it. This definitely is something you don't find often.

I'd keep it and fix it. If not using, fix it still, and then sell.

[Rodeodave]

You're right, overtheairbroadcast. I have looked into some projects that could be realized with this PSU and if I can get it to run it will become very handy.

I very much distrust selenium rectifiers, thus they will all be replaced with a 1000V (V_RRM) 8A (I_F) rectifier bridge (GBU8M from General Semiconductor). Maybe I'll ad dropping resistors after the rectifier bridges. I think they should be on the order of 100R and rated 3W (Vishay Phoenix PR03).

I will also replace the bleeder resistors of the EL156 circuit with 220k 3W Vishay PR03 resistors, the old ones are bent and possibly damaged. I will see how the caps perform when slowly firing up the PSU with a variac, maybe they can be reformed to a certain extent.


I have two questions:

Can I safely increase the capacitors at the regulators' outputs (C5, C14, C21; originally 0.1uF 350V) to 1.5uF? I have several Arcotronics MKP C.4G 1.5uF 850V capacitors and would like to use them. Do I risk damage or instability by adding so much capacitance?

Is it possible to wire the two EL156 circuits in series to create a +/- 150V bipolar HV supply? It looks like the circuits themselves are not referenced to ground, so it should be possible...

http://www.jogis-roehrenbude.de/Bast...g-H&B-6007.gif (Thanks again for the link, Simon!)

[overtheairbroadcast]

Originally Posted by Rodeodave

You're right, overtheairbroadcast. I have looked into some projects that could be realized with this PSU and if I can get it to run it will become very handy.

Glad I could be of some assistance, hope it turns out well for you and that you have fun doing it!

And don't forget to post pictures along the way.