Hw-12 PROBLEM...

[Morris]

I'm not familiar with that particular rig but my approach is to clean it up,
replace the obvious paper caps and electrolytics, check the tubes and then
start the troubleshooting.  I also do a quick resistance check of the old
carbon resistors (without first disconnecting) since that even in circuit
they should not read higher than 10% or 20% over, depending on their
tolerance rating.  Don't assume that they are all good because they do
change value when of the quality used by Heath.  Usually they gain in value
and have to gain that much to cause a problem.  Sometimes it's easier to do
preventive maintenance than to troubleshoot multiple problems.  Even if you
found the problem outright you would probably want to go over it completely
anyway.  Others may disagree but that's just my take.  Good luck with it.

73

Morris ki4iua


> -----Original Message-----
> From: Heathkit Owners and Collectors List [mailto:HEATH at LISTS.TEMPE.GOV]
> On Behalf Of Alexander N. Gerli Sr.
> Sent: Wednesday, November 03, 2010 10:37 AM
> To: HEATH at LISTS.TEMPE.GOV
> Subject: Hw-12 PROBLEM...
> 
> Hi, gang,
> 
> I've got a HW-12 on the bench that has some problems...
> 
> Firstly, on powerup, it seems to be stuck in transmit. I haven't loosened
> and retightened all the bolts holding the circuit board to the chassis
> YET,
> but that's on the list based on experience. Probably gound-loop city.
> 
> So far, I've cleaned all the switches and pots with DeOxit.
> 
> One weird thing is the two dial lamps: the one for the dial is nice and
> bright. The one for the S-Meter is half-bright. Seems like a short
> somewhere
> in the filament chain, as the two bulbs are in series across that 12V
> line.
> Yeah, I have two identical #47s in there.
> 
> Also, I get about 25W on Tune into my dummy load. And, the Carrier Null
> pot
> doesn't null - it gives the full output at one end of rotation, and a
> carrier minimum at the other end. No spot that's a true null.
> 
> I've subbed tubes from my stock that I know are OK.
> 
> Don't see any burned or broken resistors anywhere. Disc ceramics look
> normal
> 
> This was a $20 boneyard bargain which looked complete and wasn't otherwise
> messed with. And, I love challenges anyway! So, how about some suggestions
> for me??
> 
> 73 and thanks!!
> 
> Sandy AC1Y
> 
> Alexander N. (Sandy) Gerli, Sr.
> 5805 Newhall Road
> Durham, NC  27713-2615
> 919-489-9638
> 
> CCA # AC9800001
> 
> A Scotsman drinks 40 gallons of alcohol each year.
> A Scotsman walks 900 miles each year.
> Scotsmen get about 25 Miles Per Gallon.
> 
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