SS 83 again

[v4lve lover]

if you want a constant voltage drop of 10 volts or 15 for a 83 mercury rect can you put a few 1n4007 in series and it will produce the same voltage drop ? i was thinking about this when i saw posts about 83 replacement in certain hickock testers

the mercury doesnt really change its voltage drop over load . 1n4007 a bounch of them wouldnt change over load to ?

[HollowState]

Well, with a 0.7 volt per silicone diode, you would need 21 diodes for a 15 volt drop. Make that 42 for full wave. Not very practical.

[kevinkr]

In tube tester service you might consider a high power zener (15V/5W or more) in series with the 1N4007 - noting that this is a no no if there is any significant amount of capacitance after the rectifier..

[SpreadSpectrum]

I was considering the series zener plan for a tube tester that I was about to calibrate. I figured the diodes would be better balanced with better long term stability than a tube. Of course, I am going to put some power resistors to load the filament winding as well.

[HollowState]

Originally Posted by kevinkr

In tube tester service you might consider a high power zener (15V/5W or more) in series with the 1N4007 - noting that this is a no no if there is any significant amount of capacitance after the rectifier..

Considering that a lot of tube testers don't use any electrolytic capacitors at all, except maybe one across the meter movement, a zener is a viable idea. Such testers, your Hickok 539B included, work from the haversine pulse peak like a transistor curve tracer does.

[Defiant]

Capacitance causing oscillation is only an issue if the zeners are being used as a shunt regulator. If they are being used as a series dropping element then the capacitance is only limited by the peak current capability of the diode, just as it is with the regular rectifier diodes.

I would only run SS if you need a replacement rectifier. If the merc rectifier still works then there is no compelling reason to replace it IMO. The things seem to last darn near forever in tube testers.

[Cobra2]

This worked for me (on a Hickok 750)

Arne K

[v4lve lover]

42 1n4007 in series is still cheaper than the power resistors you need to load the fillament whit

[dgta]

Originally Posted by kevinkr

In tube tester service you might consider a high power zener (15V/5W or more) in series with the 1N4007 - noting that this is a no no if there is any significant amount of capacitance after the rectifier..

What part of that is a no-no and why?

[kevinkr]

Originally Posted by dgta

What part of that is a no-no and why?

Just have to be careful to make sure that the ripple current does not exceed the zener current rating, and that the overall dissipation is acceptable as well. I think most 5W zeners may be OK with a reasonable sized input cap - just check the ratings of the proposed zener to make sure. (I have not tried it with a cap input filter, hence the caveat.)

FWIW I have a 539B and will continue to use the 83 rectifier until it fails - which may not be in my life time given the limited use it receives.