[Hallicrafters] SR-400A - no output

[Roger K8RI]

Don't rule out the disc ceramic coupling and bypass caps in the SX117, 
HT-44, and SR series of transceivers.  I had to replace the bypass caps in 
the driver and final as well as the coupling cap between the driver and 
finals.  I also had to replace all of them in one of the states in the 
SX117, but I don't rember which one that was now.  I'd assume they ended up 
with a bad batch of caps, but who knows how many ended up in rigs before 
they were caught, if they were.


Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
> Hello,
>
> Thanks for reading this.
>
> I recently acquired an SR-400A that seems to work ok on receive but
> does not producing any real output. There is no indication of ouput or
> plate current on the meter (it actually drops a tiny bit when I key the
> transmitter).
>
> Here's what I've found so far:
>
> - V11 defective - replaced
> - V5 possibly defective - will leave for now since I don't have
>  a replacement
> - C180 and R110 missing from V18 (driver screen grid) - replaced
>  (someone was working on this before me!)
> - bias sets ok
> - SSB and CW can be heard on a nearby receiver
> - in transmit (CW or tune) the following peak-to-peak RF voltages
>  were measured on 80 metres with the RF level control set at maximum
>  - V11 pin 7 - 2V with V4 removed (het osc only), 8V complex
>    waveform with V4 installed
>  - V11 pin 9 - 8V
>  - V18 pin 2 - 2V
>  - V18 pin 6 - 8V
>  - antenna jack - 4V
> - DC voltages at V11 pin 6: 13
>                         7: 0.22
>                         8: 231
>                         9: 244
> - DC voltages at V18 pin 2: -13
>                         6: 229
>                         8: 213
>
> As you can see, I'm not getting much amplification in the driver
> chain although operating voltages appear to be ok. I've tried peaking
> L11/L34 but that didn't help. I tried a 6CX8 for V11 (no other spare
> 6AW8A) but that didn't help either. I don't have a spare 7558 for V18
> and don't know of any substitute.
>
> Can anyone give me some advice about what might be the problem?
>
> 73, Don
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