[BC] Tips to repair a CCA AM 1000D

[wernerl@tutopia.com]

I just want to get some tips on the reparation of one CCA  AM 1000D. 
as possible for your knowledge ,, I'm new in the tube technology.. my 
field is on the Transistors, Fets on  FM and AM Power transmitters.


Today  I just found no modulation at all in my transmitter .The power 
still looking fine but not the modulation at all.

I checked the tubes on the front of the transmitter and I found the 
rear left to be smoked inside. I change that tube , but I really 
didn't know which are the Modulation tubes from the front .. I 
supposed that the rear right is the V3 ,,  I don't know where is the 
V4 but I suppose that is rear left as Schema didn't show crear.

The handbook said that when is 16mA on the V3, V4 meter the state is 
Idling,, I just have 10mA on both scales.

The V1 and V2 are wrong too ,, the V1 is on 16mA and V2 is on 42mA 
,,  when its value has to be between 20-30 mA

At the point that I increase the Low power Input audio Control , I 
became to get some modulation around 5 to 10% ,, but is all.

I checked the resistors on the 1M network and still fine ,,, some of 
them are around 600K Ohm  , others around 800K,, but that's it.  I 
test all  resistive components around the modulation circuit and the 
two 27K resistors that sum the audio modulation on the 4-400 tube.


Please Let me know which side of the modulation circuit I will check.



Thanks very much for your attention.


Sincerely,

Werner
Sorry my english, my native is spanish.