[Hammarlund] Hammarlund Digest, Vol 201, Issue 9

[wes Bolin]

Years ago I had a HQ-140 that would arc in the phenolic bandswitch. .  I
had used DeOxit on it.  I finally solved the problem by cleaning the
phenolic with distilled alcohol several several times.....as said before,
DeOxit ONLY on switch contacts.  I had to take an X-acto knife and dig out
the carbon path.  Once no carbon and clean phenolic, the switch worked fine
and I didn't have to replace the wafer, a big job.
You might look into this method after you eliminate the cause of the arc.
Wes

On Fri, Mar 20, 2026 at 3:22 PM <hammarlund-request at mailman.qth.net> wrote:

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> Today's Topics:
>
>    1. HQ-170 Repair Saga (Elmore, Kim)
>    2. Re: HQ-170 Repair Saga (fernan)
>    3. Re: HQ-170 Repair Saga (manualman at juno.com)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 20 Mar 2026 13:43:00 -0500
> From: "Elmore, Kim" <cw_de_n5op at sbcglobal.net>
> To: Kim Elmore via Hammarlund <hammarlund at mailman.qth.net>
> Subject: [Hammarlund] HQ-170 Repair Saga
> Message-ID: <b6bd2724-3020-450a-a846-ab4a333bc2c2 at sbcglobal.net>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Well, following up on my foray into my HQ-170: I kept getting very
> confusing reading when I checked for shorts to ground meaning I simply
> couldn't reliably isolate the issue. I'd check for shorts to ground
> through the cold side of R9 and find it open: no shorts. Sometimes, I'd
> see wildly fluctuating resistance readings, but they'd quickly resolve
> is I jiggled the test leads. This puzzled me, but I ultimately became
> convinced that something else was happening, such as fingers on probes,
> etc. It's a Fluke 79 so pretty responsive.
>
> Following an earlier suggestion, I decided to measure the current though
> R9 using a 1500 ohm 5W resistor simply because I had one. The idea was
> to simply get a glimpse of what I'm dealing with. I put the test leads
> in series with it and gingerly turned on power keeping my fingers art
> the ready to turn it off. I saw about 170 mA.
>
> 0.17 * 1500 = 255 V. That's essentially the B+ value. A short *clearly*
> exists somewhere.
>
> But when I did this I INSTANTLY saw arcing in the front wafer of the
> band switch. Power on to power off spanned 1-2 s. I removed tubes in
> case there's an intermittent interelectrode short. Same result. With
> power off, I moved the band switch and tried again. Same result.
>
> Two things are now irrefutable: the problem is in C134, a 2 pF 500 WVDC
> mica coupling capacitor between T1 and T2 that I have yet to locate. But
> the other, more ominous issue is that the front wafer of the band switch
> was damaged when C134 shorted in the initial episode that incinerated
> the original R9. At that point it was destroyed for all practical
> purposes. C134 is the only capacitor I have not been able to find and
> test that is in the path through the band switch. It has to be the
> source of the problem. Now, if I could only find it C134...
>
> The damage to the band switch prevented me from making reliable
> measurements.: the voltage used by the ohmmeter was insufficient to
> bridge the damage to the switch. But, at 250-300 V it's bridged easily.
> In one sense, I'm fortunate that it's the front wafer because it's about
> the only accessible one. The band switch is the heart of the radio and
> the entire thing is literally built around it. Yet, the only way I can
> repair that switch is to find a front wafer from a donor HQ-170. Even
> then, I'm not entire convinced I can get enough access to do the job.
>
> This particular HQ-170 has considerable sentimental value to me because
> it was my dad's and so was my very first receiver as a Novice. It is
> cosmetically perfect and was aligned almost perfectly, a job that took
> me couple of days to perfect. I admit that I'm emotionally attached to
> it. That said, I am not left without a receiver: a good friend gave me
> his HRO-60 in perfect electrical condition with ALL the coil sets, and I
> also have an electrically perfect Drake 2A. Performance-wise, both of
> these are superior to the HQ-170 in many respects.
>
> So, I'm in no hurry. I'll look a bit more at my '170 to find C134. If
> anyone has a front wafer for an HQ-170 band switch, please contact me.
>
> 73,
>
> Kim N5OP
>
> --
> Kim Elmore, Ph
>
> Kim Elmore, Ph.D. (Cooperative Institute for Severe and High-Impact
> Weather Research and Operations, Adj. Assoc. Prof., OU School of
> Meteorology, CCM, PP SEL/MEL/Glider, UAS, N5OP, 2nd Class
> Radiotelegraph, GROL)
>
> /?I am no weather master, nor is aught that goes on two legs.? ? Tom
> Bombadill, ?Fellowship of the Ring?/
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 20 Mar 2026 14:54:50 -0500
> From: fernan <ve4feb at gmx.ca>
> To: "Elmore, Kim" <cw_de_n5op at sbcglobal.net>
> Cc: Kim Elmore via Hammarlund <hammarlund at mailman.qth.net>
> Subject: Re: [Hammarlund] HQ-170 Repair Saga
> Message-ID:
>         <CALDPdrrqOF7fwRsiDUFUrshG9be11m=gSoNw=
> TwhXFUR2TWwFQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Hi
>
>   I'm at work, so I haven't read the messages completely yet. I just wanted
> to mention something similar happened to me. A resistor blew and there was
> arcing on the bandswitch wafer. The issue was that the wafer was soaked
> with contact cleaner. After washing the bandswitch wafer and replacing the
> resistor, everything returned to normal. This occurred on my main receiver,
> the HQ145A.
>
> Regards
> Fernan
>
> On Fri, Mar 20, 2026, 13:43 Elmore, Kim via Hammarlund <
> hammarlund at mailman.qth.net> wrote:
>
> > Well, following up on my foray into my HQ-170: I kept getting very
> > confusing reading when I checked for shorts to ground meaning I simply
> > couldn't reliably isolate the issue. I'd check for shorts to ground
> > through the cold side of R9 and find it open: no shorts. Sometimes, I'd
> > see wildly fluctuating resistance readings, but they'd quickly resolve
> > is I jiggled the test leads. This puzzled me, but I ultimately became
> > convinced that something else was happening, such as fingers on probes,
> > etc. It's a Fluke 79 so pretty responsive.
> >
> > Following an earlier suggestion, I decided to measure the current though
> > R9 using a 1500 ohm 5W resistor simply because I had one. The idea was
> > to simply get a glimpse of what I'm dealing with. I put the test leads
> > in series with it and gingerly turned on power keeping my fingers art
> > the ready to turn it off. I saw about 170 mA.
> >
> > 0.17 * 1500 = 255 V. That's essentially the B+ value. A short *clearly*
> > exists somewhere.
> >
> > But when I did this I INSTANTLY saw arcing in the front wafer of the
> > band switch. Power on to power off spanned 1-2 s. I removed tubes in
> > case there's an intermittent interelectrode short. Same result. With
> > power off, I moved the band switch and tried again. Same result.
> >
> > Two things are now irrefutable: the problem is in C134, a 2 pF 500 WVDC
> > mica coupling capacitor between T1 and T2 that I have yet to locate. But
> > the other, more ominous issue is that the front wafer of the band switch
> > was damaged when C134 shorted in the initial episode that incinerated
> > the original R9. At that point it was destroyed for all practical
> > purposes. C134 is the only capacitor I have not been able to find and
> > test that is in the path through the band switch. It has to be the
> > source of the problem. Now, if I could only find it C134...
> >
> > The damage to the band switch prevented me from making reliable
> > measurements.: the voltage used by the ohmmeter was insufficient to
> > bridge the damage to the switch. But, at 250-300 V it's bridged easily.
> > In one sense, I'm fortunate that it's the front wafer because it's about
> > the only accessible one. The band switch is the heart of the radio and
> > the entire thing is literally built around it. Yet, the only way I can
> > repair that switch is to find a front wafer from a donor HQ-170. Even
> > then, I'm not entire convinced I can get enough access to do the job.
> >
> > This particular HQ-170 has considerable sentimental value to me because
> > it was my dad's and so was my very first receiver as a Novice. It is
> > cosmetically perfect and was aligned almost perfectly, a job that took
> > me couple of days to perfect. I admit that I'm emotionally attached to
> > it. That said, I am not left without a receiver: a good friend gave me
> > his HRO-60 in perfect electrical condition with ALL the coil sets, and I
> > also have an electrically perfect Drake 2A. Performance-wise, both of
> > these are superior to the HQ-170 in many respects.
> >
> > So, I'm in no hurry. I'll look a bit more at my '170 to find C134. If
> > anyone has a front wafer for an HQ-170 band switch, please contact me.
> >
> > 73,
> >
> > Kim N5OP
> >
> > --
> > Kim Elmore, Ph
> >
> > Kim Elmore, Ph.D. (Cooperative Institute for Severe and High-Impact
> > Weather Research and Operations, Adj. Assoc. Prof., OU School of
> > Meteorology, CCM, PP SEL/MEL/Glider, UAS, N5OP, 2nd Class
> > Radiotelegraph, GROL)
> >
> > /?I am no weather master, nor is aught that goes on two legs.? ? Tom
> > Bombadill, ?Fellowship of the Ring?/
> > ______________________________________________________________
> > Hammarlund mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/hammarlund
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> >
> > List Administrator: Gary Harmon, K5JWK
> > ** For Assistance: gharmon at idworld.net **
> >
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 20 Mar 2026 16:20:30 -0400
> From: <manualman at juno.com>
> To: hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] HQ-170 Repair Saga
> Message-ID: <AABW55MCNA5CCNMJ at smtpout01.vgs.untd.com>
> Content-Type: text/plain; charset=utf-8
>
> I haven't read the history of this Hammarlund HQ-170 repair yet but this
> is one of the reasons why I also mention that Deoxit should never be
> sprayed on to the paper phenolic switch wafers which were quite common on
> many receivers, transmitters, etc. in the 50's and 60's.
>
> The Deoxit is absorbed into the wafer  material and the chemical agents
> that bond the paper phenolic together react with the composition
> chemicals of the Deoxit and can form minute resistive streaks in the
> material and can often short one switch contact with another. If voltage
> gets presented on a wafer terminal where there an internal resistive
> streak has formed, maybe to another terminal, it's possible to  pass
> smoke from the switch wafer.
>
> Deoxit should be applied minutely to the actual terminal carefully and
> not sprayed on the entire wafer.
>
> Pete, wa2cwa
>
> > On Fri, Mar 20, 2026, 13:43 Elmore, Kim via Hammarlund <
> > hammarlund at mailman.qth.net> wrote:
> >
> > > Well, following up on my foray into my HQ-170: I kept getting very
> > > confusing reading when I checked for shorts to ground meaning I
> > simply
> > > couldn't reliably isolate the issue. I'd check for shorts to
> > ground
> > > through the cold side of R9 and find it open: no shorts.
> > Sometimes, I'd
> > > see wildly fluctuating resistance readings, but they'd quickly
> > resolve
> > > is I jiggled the test leads. This puzzled me, but I ultimately
> > became
> > > convinced that something else was happening, such as fingers on
> > probes,
> > > etc. It's a Fluke 79 so pretty responsive.
> > >
> > > Following an earlier suggestion, I decided to measure the current
> > though
> > > R9 using a 1500 ohm 5W resistor simply because I had one. The idea
> > was
> > > to simply get a glimpse of what I'm dealing with. I put the test
> > leads
> > > in series with it and gingerly turned on power keeping my fingers
> > art
> > > the ready to turn it off. I saw about 170 mA.
> > >
> > > 0.17 * 1500 = 255 V. That's essentially the B+ value. A short
> > *clearly*
> > > exists somewhere.
> > >
> > > But when I did this I INSTANTLY saw arcing in the front wafer of
> > the
> > > band switch. Power on to power off spanned 1-2 s. I removed tubes
> > in
> > > case there's an intermittent interelectrode short. Same result.
> > With
> > > power off, I moved the band switch and tried again. Same result.
> > >
> > > Two things are now irrefutable: the problem is in C134, a 2 pF 500
> > WVDC
> > > mica coupling capacitor between T1 and T2 that I have yet to
> > locate. But
> > > the other, more ominous issue is that the front wafer of the band
> > switch
> > > was damaged when C134 shorted in the initial episode that
> > incinerated
> > > the original R9. At that point it was destroyed for all practical
> > > purposes. C134 is the only capacitor I have not been able to find
> > and
> > > test that is in the path through the band switch. It has to be the
> > > source of the problem. Now, if I could only find it C134...
> > >
> > > The damage to the band switch prevented me from making reliable
> > > measurements.: the voltage used by the ohmmeter was insufficient
> > to
> > > bridge the damage to the switch. But, at 250-300 V it's bridged
> > easily.
> > > In one sense, I'm fortunate that it's the front wafer because it's
> > about
> > > the only accessible one. The band switch is the heart of the radio
> > and
> > > the entire thing is literally built around it. Yet, the only way I
> > can
> > > repair that switch is to find a front wafer from a donor HQ-170.
> > Even
> > > then, I'm not entire convinced I can get enough access to do the
> > job.
> > >
> > > This particular HQ-170 has considerable sentimental value to me
> > because
> > > it was my dad's and so was my very first receiver as a Novice. It
> > is
> > > cosmetically perfect and was aligned almost perfectly, a job that
> > took
> > > me couple of days to perfect. I admit that I'm emotionally
> > attached to
> > > it. That said, I am not left without a receiver: a good friend
> > gave me
> > > his HRO-60 in perfect electrical condition with ALL the coil sets,
> > and I
> > > also have an electrically perfect Drake 2A. Performance-wise, both
> > of
> > > these are superior to the HQ-170 in many respects.
> > >
> > > So, I'm in no hurry. I'll look a bit more at my '170 to find C134.
> > If
> > > anyone has a front wafer for an HQ-170 band switch, please contact
> > me.
> > >
> > > 73,
> > >
> > > Kim N5OP
>
>
>
> ------------------------------
>
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>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> End of Hammarlund Digest, Vol 201, Issue 9
> ******************************************
>