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Old 08-13-2017, 12:57 AM
tubetwister tubetwister is offline
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Join Date: Oct 2010
Location: west blue coast conservative
Posts: 163
Quote:
Originally Posted by Electronic M View Post
I have seen 2-3 AA5 sets with field coil electrodynamic speakers, not common, but some did it.

What matters with the output grid is that it be negative with respect to the cathode. One thing you can do is connect a large cap (.22-10uF) between the output grid and signal ground to bypass any hum from proceeding stages to ground, then put the meter common lead on the grid and the hot lead on the cathode...That should give you a positive voltage indicating the cathode is positive WRT the grid and that the grid is negative WRT cathode.


I think I saw some electromagnet speaker AA5 photos . I amassed a huge old radio web image collection with actually thousands of images but I'm not so sure there were many or any of those electromagnet speaker AA5 past the 1936 reference AA5 revision but if they were I may have the image trus`me


That other thing may be something if its off spec. with a (correct uf capacitor to output tube cntrl. grid we don't have now ) . so maybe that should be shelved for now. especially if we look at the cap uf in there at output tube contrl. grid as opposed to spec that may be bigly over volting output tube cntrl. grid now like I think it is and I see +6V on my DVM .


I can verify so far the 50C5 output tube control grid input is indeed +6V and the output tube 50C5 GE tube data spec is specifically 0 to neg volts with no mention at all about the cathode only at a brief glance of pin out volts .

AVC /First Audio and Output tube and first IF amp tube heater and plate volts are fine.


I did not read the diode plate voltages at the 12AV6 First Audio AVC Duplex Diode Triode that are wired to each other in the radio and the VOL pot is not deaf anyway so probably nothing to see there given the vol pot is ranging normally and phone volume is normal but lots of distortion that may be something else ,a tube or one of the caps I ordered .

I am sure if I had the parts and tubes like you surely have in your workshop this radio would be done ,

So that where it ends for me until I get my NOS tubes and or the caps on order, beyond that ,maybe tomorrow now the clever one at a time tube pull with alligator clip tube pin heater leads you mentioned I have the leads here at the ready

Edit:

oh you have any photos here or at the usual spots of your hoarders conflagration of electronics refuse or is it a nice tidy 200 radio collection?

Last edited by tubetwister; 08-15-2017 at 07:10 PM.