[Heath] HW-16 update and additional question (11 MAR 14)
wrcromwell at gmail.com
Wed Mar 12 11:21:10 EDT 2014
Have you tried reversing *one* set of leads on the transformer. If the
feed back route is through there that will turn a regenerative circuit
into a degenerative circuit. It might help and it won't hurt.
On 03/11/2014 01:13 AM, John Klingelhoeffer wrote:
> Thanks to all who responded and gave comments and suggestions to the
> questions regarding the HW-16 refurbishment. Most were very helpful.
> I still have a locked slug in the 15M het oscillator coil form in the
> receiver that I may have to break out and retune with an external
> capacitor. Silicone spray was not the answer. That 15M LO level is a
> lot lower than 40 and 80 M. On the transmitter side, I seem to get
> 50-60 watts out on all three bands so I'm happy, happy, happy about that.
> The comments I have seen previously on the reflector about carbon
> composition resistors increasing in value on this old equipment is
> very important to heed. So far, of those removed or tested, all have
> been 15-20% high in value. Some also had very little 'headroom' in
> their dissipation. The order to the electronics parts place is
> already in process.
> Okay, so I won't say this is the last problem I'll post, but it is so
> far a vexing one. At even moderate audio levels, a strong station
> will cause something - I think the audio output tube - to regenerate
> the received tone. It sounds like the tube is oscillating in
> synchronization with the incoming CW and producing a strong keyed tone
> - sort of like a locked oscillator. It ends up being a LOT louder
> than the signal level.
> The troubleshooting instructions in the manual talk about the output
> transformer plate (blue) lead being too close to the PCB (and hence
> the grids of the audio amp tube) and causing 'howling'. I would not
> characterize this as howling (unrestrained audio feedback) - the
> oscillation only happens when the strong CW signal is there and ceases
> between dits and dahs. It's a keyed audio oscillation.
> Just in case, I moved the blue transformer lead all the way to the
> edge of the chassis per the troubleshooting hint, and I also shielded
> it with the braid from of a piece of RG-59 cable. However, no joy.
> Still as bad as ever. Also tried to replace the audio tube cathode
> electrolytic capacitor since I wasn't sure I'd changed that recently.
> No change. I performed the tube socket voltage tests and all were
> within a couple of percent.
> Until this gets fixed, I'm not going to attempt any of the increased
> gain mods for the IF and RF amps as they would be counterproductive.
> But, it needs to be fixed else the radio will be pretty useless.
> Anyone seen this before and found a fix for it? I don't remember
> this sort of thing happening on the one I assembled and used back in
> Should I just take a piece of insulated solid #16 buss wire, bring it
> up absolutely vertically from the PCB plate connection, and then route
> it over to the vicinity of the transformer before connecting to the
> blue transformer wire on a terminal strip under the transformer
> mounting screw? I can't think of any way of getting it any more
> quickly away from the PCB and putting space between it an the tube
> grids. I could use Teflon coaxial cable to make this a shielded run
> as well. Other thoughts?
> Thanks and 73 John... WB4LNM
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