[Heath] HW-101 VFO

[David Goncalves]

I think, aside from one thing, this is what I did. I invented NOTHING here.
My theory was that if the best minds in the hobby couldn't make it work
over the last 40 years, that I'd take it out and replace with a highly
filtered DDS VFO.

Refer to these: http://www.ultrawebb.com/OHP/SERVICE.htm
 http://www.ultrawebb.com/OHP/NRWILLIAMSON.pdf

0. Replace all resistors with new 1/2W 5% carbon film resistors (bought
good stuff from Digikey), except change R947 to 1k (per service bulletin
HW-101-2)
1. Check PN of coil in VFO, change it according to HW-101 service bulletin
HW-101-1 (mine did not need this)
2. Change C947 to 47pF NP0 per service bulletin HW-101-19 and C951 to a
10pF N750 per Williamson (I have perhaps ONE to spare).
3. Install a heavy wire per service bulletin HW-101-27.
4. Hot-glue C946 per service bulletin HW-101-42.
5. Verify that peaking of VFO coil is correct per service bulletin
HW-101-45 and N.R. Williamson.
6. If you find the VFO stops working in CW/USB on the upper end of bands,
change R947 back to 470 Ohms (per service bulletin HW-101-52).
6. Get the verniers working well. I ended up buying a new set from Jackson
Brothers (see here: http://www.mainlinegroup.co.uk/jacksonbrothers/4511.htm)
and get Model 4511DAF. Machine the shaft to the length of your original
set, and install for that original 70's feel.
7. Make sure your supplies to the VFO are stable. Particularly, upsize some
of the resistors on the Power board (I'm getting to those notes soon!!).
Make sure to redo your HP-23.

That is what I did, and it works very well. I really think you have to go
through the radio completely to really get everything stable and running
sweetly. One could argue that some of these changes have more impact than
others - and given the difficulty of finding N750 caps one might have to
evaluate that - but I found that all the rest was easy and just did them
all.

Best of luck,

David Goncalves

On Thu, May 10, 2012 at 11:05 AM, Janusz Juryk <ve2zhp at yahoo.ca> wrote:

> Greetings everyone,
>
> I'm rebuilding the VFO from a HW-101 and there are certain components that
> need changing. The crystal diode is one and need to know what equivalent
> could be used.
>
> Cheers
>
> Janusz  ve2zhp
>
> _______________________________________________
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>
>


-- 
David Goncalves
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