[Heathkit] Heathkit HW-100 nightmare

[Dick KF4NS]

Sure hate to do this but if I do not include the entire first message, 
some will not know what I am talking about. Sorry about the bandwidth 
and will trim it down next post.
So many replies and advice. Will have to just send to entire group.

I am using both the 100 and 101 manual to be sure I get things right. 
Besides, I have all the 101 mods installed anyway. I also have all the 
bulletins and mods ever promulgated, from Heathkit and all the many 
individuals, including magazine articles. It is quite a library.

Another point I must make is the fact that the radio had been working 
great since I first built it 1970, up to the time of the power supply 
debacle.

I have swapped cables and power supplies with no change in status.

I may have a slug coming and yes, I know they are hard to find but if 
I am correct, any slug from any of the early Heathkit series use the 
same slug in all of the coils. It is only the windings of the coils 
that differ so any parts rig would be a source for the slug.

It is not very likely that the pots mentioned are a source of the 
trouble, not just because I tested them but I found that I can load up 
fine on 20M and 15M now. Only 80 and 40 (due to the missing slug and 
this coil must be complete for the two bands to work) and all of 10M. 
The bands unaffected by the missing slug all seem to be holding fine 
at the operational HET OSC level but I did find that I must keep the 
settings at/above -1.8vdc or one or the other drops out.

Oddly enough, the level of bias set by the bias pot does not align 
with the mark on the meter but rather must be set to just above the 
zero marking. At that point I read -65vdc on pin 5 of the finals in 
recv and grounding the mic key lead drops it to -62vdc, both of which 
are in the specified levels on the recv/xmit voltage charts. Both the 
47ohm and 2.2ohm resistors in the metering circuit have been replaced 
and the two on the meter are yet to be replaced, one is +17% and the 
other -15% so that may help.

I cannot neutralize the finals until I can get 10M to tune at more 
than 3watts. That is where the relays start to chatter I and hear a 
horrible buzzing out of the speaker. By the way, I always neutralize 
by first removing the plate and screen supply from the finals. I still 
doubt that the trouble is anything related to the finals or 
neutralization. Both finals are 6293 (6146A).
73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!


----- Original Message ----- 
From: "Dick KF4NS" <kf4nsradio at verizon.net>
To: <heathkit at mailman.qth.net>
Sent: Saturday, March 06, 2010 11:20 AM
Subject: Heathkit HW-100 nightmare


>I have NEVER given up on a repair but this disaster has me climbing
> the walls. There have been so many snafus that I could not count 
> them
> all. The first thing happened when the HP-23A went into the
> self-destruct mode with the rig setting on the bench in RECV mode
> while I was out of the room. The breaker in the PS failed to trip 
> and
> took out the ICL (current limiter), the diodes in the HV, B+ and LV,
> leaving the supply in the shorted condition. (I since replaced the
> breaker with a slow blow 3A fuse).
>
> I restored the HP23A using upgrades for everything. The damage done 
> to
> the rig is still being traced after two weeks working on it. I never
> saw so many complex, seemingly endless number of
> associated/unassociated troubles. (not counting pilot error)
>
> First the rig lit up but nothing worked. I found 3 shorted and/or 
> grid
> emission conditions in the tubes. Another 4 were just plain weak. 
> All
> were replaced according to all known criteria. Next thing I found 
> was
> that the BIAS could not be set, adjusting the pot (which tested 
> good)
> would only give me about 30ma max, then it started pegging the 
> needle.
> All xmit tests made in tune mode, finals ok but swapped anyway, 
> level
> pot at full ccw and pot ok. Neutralization was not touched. Then the
> RF gain indication on the ALC meter started dancing around. The pot
> could be set at full ccw and still have full RF gain. The pot tested
> ok. Trying to trace out the bias is a very difficult route and a
> total nightmare. It is like a maze, going everywhere. I realized the
> connection between the bias and the RF gain trouble so that 
> explained
> that coincidence. I then decided to do lots of voltage tests and
> resistance tests from the charts in the manual. Nothing too unusual. 
> I
> started the alignment of the receive section and quickly discovered
> that there was a major defect somewhere when the het. osc. alignment
> would not hold as I switched from band to band. It is there and then
> it is not there as set and read at TP1. I cleaned all the band 
> switch
> contacts again and made sure all contacts were making good contact. 
> If
> I jiggled the 3 coil boards and there was surely an intermittent.
> Found one coil lead loose, one wire lead to the driver plate board
> loose and resoldered both.
>
> I began looking for anything in the huge bias string but no luck. 
> Then
> I began checking all wire and component leads everywhere for bad
> solder connections. Then a further inspection and some voltage
> and resistance checks in the coil areas. I accidently shorted out 
> the
> 100 ohm that runs external and connects between the driver 
> grid/driver
> plate boards, with my meter probe. Sparks flew and the resistor 
> split
> in two and I did a dirty in my pants. My bad, as the kids say.
> Replaced that resistor.
>
> Then I decided to get back to the receiver section again and aligned
> the het. osc. coils again. They seemed to be holding. Heard some
> crackling in the audio. Banged on everything from tubes to pots and
> variable caps. Kept getting closer and finally realized that the CXR
> null pot was the culprit. Got a new one from the parts box. Now the
> receiver was really playing good, very low noise and good strong
> signals. I decided to try tuning up again since the rcvr was working
> fine. As soon as I raised the drive level, the relays began
> chattering. Ten watts was all it would allow. This again points to 
> the
> bias situation.
>
> Next, the evil black cloud over my house appeared again. As I turned
> the rig on it's side to measure the actual bias voltage on the 
> finals,
> sparks flew from the power cable connector on the back. Turned
> everything off and found that the ground female pin in the cable 
> broke
> and shorted to another pin. Repaired the cable and glued the cable 
> to
> the connector so no more twisted cable breakage. Turned the rig over
> again and some pieces of black material with threads on it fell out.
> Oh no, a broken coil slug! It is the het osc coil for 80M. With the
> top slug missing, it will not tune up on 80M or 40M. Nothing but 
> relay
> chatter and full drive even with the mic/cw level pot full ccw.
>
> I QUIT, I AM GOING TO BED! Anyone have a spare slug laying around 
> for
> my  80M het osc coil?
>
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>