[Collins] 75A3 front panel and power supply

[Dr.Gerald N. Johnson]

----- Original Message -----
From: C E [mailto:catman351 at yahoo.com]
Sent: 6/7/2006 5:57:29 AM
To: collins at mailman.qth.net
Subject: [Collins] 75A3 front panel and power supply

> All:
> Just wanted to know your thoughts on these questions:
> 
> On the first, I recently swapped for a 75A3. I'm
> repainting the cabinet as well as rebuilding the
> speaker. The front panel is in nice shape *except*
> that some prior owner drilled out four holes to
> accommodate front panel handles (now long since gone
> but the holes remain). I think I can put front panel
> mounting screws in there place to put it in the
> cabinet but I can also JB Weld them and send the front
> panel out for rescreen/repaint. The A3 has been
> slightly modified.
> 
> 
> The next is the power supply. Transformer gets warm,
> REALLY WARM/BORDERLINE hot! The filter cap also seems
> warm and there is a trace of hum on the audio.

A warm filter capacitor with hum in the audio is a pair of pretty good signs the
filter capacitor is leaking a LOT and could explode. Believe me, you don't want to clean up after that happens. You can check that by pulling the rectifier tube to see if the transformer runs hot with no B+ load. The transformer can run hot from excess line voltage or damage within the windings or from the leakage load of a very bad filter capacitor.

Bucking the voltage is not a bad idea and a bit of fan may help keep the cool, but will add fuzz and grunge to the radio.

 I'm
> going to do a cap replacement but I was also
> considering bucking the voltage down and installing a
> quiet muffin fan to cool down the entire rx
> (modification bolt in and easy to remove). Your
> thoughts? 
> 
> 
> Thanks and looking forward to your feedback.
> 
> Cal, N6KYR/8
> 
 73, Jerry, K0CQ, Technical Advisor to the CRA.
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