[Heath] HW-16 update and additional question (11 MAR 14)

[Bill Cromwell]

Hi John,

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.

73,

Bill  KU8H


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 
> 1968-1970.
>
> 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
>
>
>