B&K Dyna-Quick Model 500 Tube Tester

Hi everyone,

This is my first post, so please bear with me.

I recently acquired an old B&K model 500 tube tester.
It has several issues, and I am trying to figure out if it is worth salvaging.
It has two loose sockets, which I can replace.

The main problem is every tube I test comes up as "?" on the Gm test.
Every tube lights the neon short indicator very dimly.

The manual and schematic I have shows a 6AT6 and an 83 tube.
There is no calibration procedure.
http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Roe-Pruefer/B&K-500/bk500_manual.pdf

My unit has a 6AT6 and a 6AX5 , making it a later version.
Can't find the schematic for it.

I have checked all the resistors, I can't seem to find any that have really drifted.
The two selenium rectifiers appear to be OK, in that I read a positive voltage from one and a negative voltage from the other with power applied. But without the schematic and calibration procedure, I am at a loss here.
I can replace the rectifiers with 1N4007 diodes, but then I need to know what resistors need to be changed to get the proper voltages.
I don't even know at this point what the voltages are supposed to be.

There is also another thread in this forum that contains an adjustment procedure, but it seems to apply to the old version of this tester, since it references a pot that I can't find.

Any help or ideas would be greatly appreciated.

Thanks for your time.

Bob Savino
Bergenfield, NJ
 
Finally got my hands on the proper schematic, with the 6AX5 replacing the 83 tube.

I have two burned up resistors in the voltage bridge for the bias circuit.
The schematic only lists R numbers, no values.
So we have
R10 - ? 10 M ?
R11 - 1K
R12 - 560
R13 - burned to a crisp

If anyone could please tell me the values of R10 and R13, I might be able to salvage this tube tester.

Bob Savino
 

Hezaug

Member
2016-05-25 9:58 pm
Finally got my hands on the proper schematic, with the 6AX5 replacing the 83 tube.
I have a B & K 500 but the schematic is that was with it is wrong. It says I have an 83 tube which I don't - I have a 6AX5. Now if we could help each other, I would like to have a copy of the schematic and I could locate the resistors or at least try to using the resistor values and number you indicated. Think we can strike a deal? If not, how much for a copy of your schematic or where can I get one?
 

Hezaug

Member
2016-05-25 9:58 pm
Bob,
I have a B & K 500 but the schematic is that was with it is wrong. It says I have an 83 tube which I don't - I have a 6AX5. Now if we could help each other, I would like to have a copy of the schematic and I could locate the resistors or at least try to using the resistor values and number you indicated. Think we can strike a deal? If not, how much for a copy of your schematic or where can I get one?
 

AmadeusMozart

Disabled Account
2009-10-08 10:29 pm
New Zealand
A late reply but just in case someone else finds this thread.

I was going to build my own but life changed all of that and I finished up picking up a B&K 500 that I am restoring.

The schematic for the 6AX5 is almost identical as the one with the 83 tube. It is best to modify the 6AX5 version to one that mimics the 83 version as it is more accurate. Obviously the transformer does not have a separate filament winding for the 83 and the solution is to replace the 83 with attached rectifier schematic. (It took a year for someone else to come up with that solution.) Then add three resistors in the high, medium and low bias connections.

I've also attached the notes that I made while searching for more information, enjoy.

Something like Elmers wood hardener can be used to stabilise the wooden base and then you can put a new finish on it with a nice piece of canvas that is glued down with some PVA glue, mod-podge or contact adhesive out of a spray can.

I expect this is my last post here, last year I had triple bypass surgery and recently diagnosed with left bundle branch block. Best wishes to all and enjoy the hobby.
 

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PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> recently diagnosed with left bundle branch block. Best wishes to all

And best wishes to you with that.

Medical jargon may be different. My sources say LBBB is a real complication to reading ECGs but is not itself an illness. "People with bundle branch blocks may still be quite active, and may have nothing more remarkable than an abnormal appearance to their ECG." However most BBB is a result of serious heart trouble. You have the scar to prove it. Of course if your life has turned and you prefer to go fishing, or sky-diving, go for it! And best wishes on that.