[Hallicrafters] HA-1 issues...

[Kenneth G. Gordon]

On 4 Jun 2008 at 8:03, jeremy-ca wrote:

> Ken, I believe there are 2 versions of schematics. Its been awhile but
> a past experience with the HA-1 sort of jogged a few brain cells.

Well, that sort of figures. So, I wonder which schematic I 
need, then? 

The schematic in the BAMA appears to be OK. It is just the 
voltage chart that appears to be off....which makes it rather 
difficult to trouble-shoot.

Thank you, Carl, for letting me know about the possibly two 
different schematics. I should have suspected such, given 
Hallicrafter's penchant for making significant changes in 
their circuits over time.

And thanks to Roy Morgan for his insights too. Many of the 
resistors in various parts of the circuit are quite high 
values...up in the 2 meg range or higher. I suspect many of 
them are WAY out of spec.

It is somewhat difficult to work on this thing: Halli workers 
used the old method of securely wrapping EVERY wire 
through and around the connection point before soldering.

Plus, the wiring looks like a rat's nest, with unnecessarily 
long wires in places, nothing done in any apparent order, 
etc.

I may just simply "reverse-engineer" it to get the schematic, 
and then completely rebuild it.

When it was working correctly, it was LOADS of fun to use!

I am keying an HW-101 with it. Voltage across the key is 
around 50 volts, and the current is only about 2 mA., so the 
snubber is not really required in this case.

The sub for the 12AU7 is a 5963, which, when compared 
with normal 12AU7s are vastly cheaper from AES: around 
$5.00 each as compared with $15.00 to $45.00 each for 
"real" audio-phool quality 12AU7s.

Thanks for the help, Guys.

Ken W7EKB