[R-390] Re: Solid State Ballast 'quirks'?

[Drew Papanek]

Mike wrote:

>I have a Collins 390a that has a solid state ballast
>replacement that I got as part of the restoration.
>Sometimes, while listening, the station will suddenly
'>go away' and just have static.

(snip...)

... should I zero in on the solid state ballast first - I suspected that
unit since the only thing that seems to go away is the tuning/bfo
- any one seen this before??

Mike,

If the ballast is causing trouble you will see that the BFO tube (V505) and 
the PTO tube (V701) will go
dark.

If those tube heaters are dark, it is also possible that one of those tubes' 
heaters is thermally intermittent .  Either of those tubes could be swapped 
into another 6BA6 socket (IF stage); failure to light (perhaps after waiting 
for the radio to quit) would indicate a defective tube.

Similarly, if during testing neither of those tubes goes dark in another 
location (and tubes taken from the IF sockets and installed at V505 and V701 
do go dark), suspect the ballast.

Replacements for the ballastube are myriad and controversy-generating.

For a wealth of information on the topic, go to r-390a.net      Click on 
references, Pearls of  Wisdom.

Drew

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