[Hammarlund] Weird problem with my HQ-129-X.

[Bob Camp]

Hi

The most common way this happens is when a wire gets crushed under a 
terminal strip or a mounting bolt. That gives you a nice solid short to 
ground. The wire pretty much does as you describe. The insulation burns 
off fairly quickly and the wire sits there glowing a red / orange color 
up to the point it burns out.

The simple way to find the short is to look for what's left of the 
insulation and for the color of the wire. If the entire wire is the 
same color and all the insulation is gone then you had a short at the 
far end of the wire. If so check the leads off of the tube socket and 
see if any of them are a bit close to a ground.

I don't think it applies in your case but if you have a piece of number 
28 wire feeding a piece of number 18 then the 18 can short and the 28 
will be the one that catches fire. I have never seen that in a 
production radio, but a previous owner might have done something odd 
....

	Enjoy!

		Bob Camp
		KB8TQ


On Sep 25, 2004, at 1:26 PM, Ken Hickman wrote:

> Hi Fellows,
>
> I am working over a 129-X I got thru Ebay. The previous owner had made 
> many
> changes in the circuits.
> While going thru stage-by-stage to restore to original schematic, I 
> had a
> fire occur in the filament wire
> that runs from the ungrounded side of the filament transformer. A 
> single
> wire running from the filament
> tie-point to the 6V6 burned up turning cherry red and emitting copious
> quanties of smoke. The 6V6
> tests fine. The only thing I have been able to come up with is that 
> the wire
> shorted to the chassis.
> The socket shows no leakage to chassis. First time I have had this 
> kind of
> thing happen!
> Anyone have anything similar happen? Comments?
> Take care,
>
> Ken   N5CM
>
>
>
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