[ARC5] Deaf BC-454

[J Mcvey]

The AGC is effectively shorted out at max volume on the BC-454. 
I once encountered strange issues with an ARC-5 radio, which was traced to a mis-wired front panel plug-in.The gain control ground ran through the audio output winding!  This caused poor gain, distortion and oscillation.
Did you restore the "capacitor pots" ? don't remember ever finding a bad half watt resistor in one of those radios, just bad "paper caps" in the "pots"I cut them open with a pipe cutter and replace them with ceramics, then solder the pot back together. Looks "legit".
The 7K /10W wire wounds are often bad, which provides screen voltages could cause gain issues too.

If you have a scope and RF generator , you can check divide the problem in half by checking the IF chain.
Maybe it's just a bad RF or MIxer tube? 


 

    On Sunday, September 25, 2016 4:27 AM, Brian <brianclarke01 at optusnet.com.au> wrote:
 

 Hello Dave,Thanks for the thought. That’s exactly what was wrong with a Navy R-1051G I have - but not this BC-454-B. I checked the banana plugs for the RF coil set and all the IFTs – they were all OK. When I wrote yesterday, I had only aligned the IFTs and gotten uneven response across the spectrum. So, today I did a really thorough alignment of the front end, with the result that 100 uV at the antenna post gives 1 mW audio output across the whole spectrum of 3 to 6 MHz. So, the set is about 20 dB deafer than all the other Command receivers I have aligned. This set is still approximately linear up to 300 uV antenna input, but after that the audio output doesn’t increase. What next? Over-active AGC?Cheers, Brian, VK2GCE. On Sunday, September 25, 2016 3:23 AM, you suggested: Remove the RF coil pack and I F transformers.  Check the contact pins to see if any of the banana plugs is missing the "leaf" contacts, causing that contact tone open.  Seen that.  If so, let me kniw and will talk about how to fix it.   
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