[ARC5] BC-453 B dynamotor hum

[J Mcvey]

I just tried changing the 12A6-same problem!I got lucky on last couple of ham fests and found quite a few ARC 5 receive tubes including the 12SR7, 12SF7 and 12A6 most were NOS and inexpensive. Not too many people know what they belong to any more. Most old rigs use 6V tubes.
It would have been nice if I found some output transformers, too. Anybody got one to sell?
 


     On Sunday, November 1, 2015 11:30 AM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
   

 On 1 Nov 2015 at 15:24, J Mcvey via ARC5 wrote:

> The problem only occurs when the radio gets warmed up.
> Uh-oh could this be a bad output transformer arcing internally? There isn't much
> else to the 12a6 circuit! HELP!!!

Hmmm....I too have yet to find a "bad" 12A6. 

But audio transformers are one of the particularly unreliable elements in the 
ARC-5 receivers, so that is a possibility. In fact, in my hacked-up pile of 
rejects, bad, or completely missing, audio transformers show up regularly. I 
would guess that at least 1/3 of the receivers I have here have bad audio 
transformers.

However, one of the easiest and quickest checks you can perform is to 
simply try a new 12A6. Doing so would eliminate that from concern.

Do you have any extra 12A6s? If not, I can send you one. I have a box of 
NIB tubes for the receivers which I received in that estate that was given to 
me many years ago. The only tubes in that pile which are "rare" are the 
12SF7s....of course... :-(

Ken W7EKB
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