[Hallicrafters] diodes +HA-1 problem

[Roy Morgan]

At 09:36 AM 10/10/2005, jh7hc at juno.com wrote:
>Picked up a HA-1: ... Are there documented mods applied to this unit?

No mods that that I know of.  I seem to remember a change in some resistor 
values, but I don't know of any ham-generated upgrades or fixes.

>Any help on the dash problem appreciated.

Replace all tubular capacitors.
Replace all high value resistors. Test all of them, the 470 K and one meg 
and up  may well have drifted.  There are two 2.2 meg and two 5.6 meg ones 
that I bet you will find very drifted, and maybe open.

These things use a mercury relay.  You need to have the unit positioned 
upright for operation.. the mercury relays don't like being on their 
sides.  Troubleshooting the thing upside down can be an adventure!  An 
extension cable - octal to octal - for the relay to be upright while you 
work on the underside can help a lot.

>  Also,  any substitute for the 1n1763A--or a good cross reference 
> sight????

That thing is a silicon diode used in a switching function.. I would try 
anything I could lay hands on as long as it was silicon and had enough PIV. 
Switching speed is not important.  It seems to be a one amp 400 volt diode. 
Try a 1N4004 or something like that.

Roy

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