Rpg4/3

[Funksammler]

I picked up this picture from Ebay, showing a plugboard with full legend:



Note that distribution of contacts I to IX is slightly different to what I said earlier. This seems to follow the schematic of the earlier Funke W18 model:



So before doing any measurements, better check which version you have...

regards,

Funksammler

[BTaylor]

Funksammler -
Knowing that the test points on the schematic are accessed from the plugboard is very helpful. Taking a closer look at mine I could see where someone had scratched in fte Roman numbers there.
My board looks more like the first photo you sent. I through V on the left and VI through XI on the right. One difference. On the top row of Anode voltages - AC - mine goes through 100 V and the following plug is 500 V D.C. (Checks out)
As far as I have checked, all voltages check out within 5% or less, closer for heaters. It seems capable of putting out proper direct and alternating current voltages.
When D.C. voltages are checked through the meter, it indicates, and moves farther across the scale as higher voltages are introduced. This is the first that I have ever seen the meter move, so that was a plus. (May not mean anything, but the meter drops below 0 and bottoms out with the dial set to "1" even with no pins in the board.)
Unfortunately, with a jumper between VI and VII, as you seem to suggest, no movement appears on the meter, and the AC voltages do appear to be there.
So the rectifier bridge is not working? I doubt if that can be repaired.
I had to remove the meter to repair some of the physical damage caused by shipping, but nothing seemed out of place or electrically disturbed.
Reached an impasse. Could open the meter, but not in total ignorance.
As you say, it would be nice to see the schematic for the meter.
I will post a few photos of my RPG soon, probably today.
In any event, thanks again.
BTaylor

[BTaylor]

Here are some photos of my RPG when purchased and after some cleaning and repairs. Damage points on the meter mounting are indicated after repair. Bakelite frame for the meter glass was in multiple pieces.

[BTaylor]

More Photos

[BTaylor]

More Photos

[BTaylor]

More Photos

[Funksammler]

Well, at least the meter is alive, so congratulations are in order. Don't worry about the AC part, I will have another look at the meter circuit next week, a rectifier should be simple enough to fix. In the current state I suspect you should be able to test most Wehrmacht valves without problems.

regards,

Funksammler

[BTaylor]

Funksammler -
Thanks again for the generous efforts made on behalf of all of us!
Meter seems to indicate properly on the "12 -13" test settings with a known good tube set up for testing.
No movement at all through the 1 to 11 test settings, however. I have been checking continuity in the vicinity of the meter. Everything seems to check out so far. 500 ohm and 50 ohm on the Ktratzgerausche transformer check out.
Will keep testing and thinking. Somewhat optimistic at this point. Learning a bunch - usually a good thing.
BTaylor

[Funksammler]

This is normal, the meter will normally only indicate on 12 and 13. The other steps indicate particular faults within a valve, so can only indicate with a faulty valve. For example, a broken filament will cause the meter to indicate left at step 1 (the same effect can be had by taking the valve out of the valve tester). Steps 2 to 11 will indicate short circuits of particular components within the valve, with the sturdy Wehrmacht type valves these faults are extremely unlikely to occur, so nothing to worry about that you do not see any indications at these steps.

regards,

Funksammler

[BTaylor]

Outstanding!
The meter does in fact indicate left when no tube is present (only).
So I may be trying to fix something that is virtually unbroken. I was looking for a "Gut" indication with positions set 1 through 11. I need to take another, closer, look at my RPG4/3 booklet, I think.
A grand new year to everyone on the forums!
BTaylor

[Funksammler]

The switch legend on my RPG4 is a bit more informative in that respect:



It shows schematically the different components in the valve that are tested. On 1 - 11 the tester works as a Ohm meter, if the resistance is under 200 KOhm the meter will deflect left as an indication of failure.

As I said before, Wehrmacht valves will generally not fail because of internal short circuits, normally they fail due to Cathode degradation or a burned out filament. Cathode degradation occurs over time and causes the current from Anode to Cathode to decrease. This is what you measure at setting 12. If the current drops below a certain value due to degradation, the valve is deemed "Nicht Brauchbar". On 13 the steering grid voltage is removed, causing the current through the valve to drop. By switching between 12 and 13 a few times, you effectively test the amplification factor of the valve, so the bigger the difference, the better...

Hope this helps,

Funksammler

[BTaylor]

Funksammler -
Helpful as always...
I think I have also seen photos of RPG4/3 units with these symbols in addition to the 1-13 numbering, although they are subject to wearing away until they are hard to decipher.
I translated the booklet but didn't read it very carefully. It all makes sense now and agrees perfectly with your comment.
I got my lovely bright blue capacitor permanently installed. The original metal box style unit was long gone and had been replaced with a (now way out of tolerance) cardboard cylinder type.
I actually tested a batch of RV 2 P 800 and RV 12 P 4000 tubes last night. Most all were right in the "Gut" range. One had nothing at No.12 or 13, and a couple went to "fail" at No. 1 and these were set aside right away without additional checking. As far as I could tell, the tester performed perfectly, much to my satisfaction.
I have some RL 12 P 35 tubes I will test eventually. A little different to hook up, but I see how it is done. Tubes for my Fusprech F will also be checked.

Many thanks.
BTaylor

[Funksammler]

Glad it all worked out in the end.... Still working after 70-odd years, try that with modern digital rubbish!

regards,

Funksammler