[R-390] ssb stand alone product detector
W2xj
W2xj at w2xj.net
Mon Jan 20 00:56:22 EST 2020
I use a CV-157 ISB adaptor. It’s simple plug and play.
Sent from my iPad
> On Jan 19, 2020, at 3:15 PM, jm <josemic at gmail.com> wrote:
>
> I have seen on ebay an external product detector without make or
> manufacturer signs. It is identified as SSB-1A Product detector.
>
> It is one of the several devices that I've found to connect to the IF
> output of the r390a. Until now I have seen similar circuits that needed an
> external audio amplifier to perform their function.
>
> This one is different because the connections are marked as Diode load and
> IF out. It surprises me that one of them should be an input to the r390a. I
> thought (erroneusly perhaps) that both diode load and If are outputs of
> the receiver.
>
> I don't find out what the way of operating on this configuration is
>
> This is the link
>
> https://www.ebay.com/itm/SSB-1A-Product-Detector-for-R-390A-Receiver/283743872204?hash=item421073e4cc:g:FeEAAOSw1kpeHhZn
>
>
> Someone could shed some light about?
>
> Regards
>
> Jose
> EA8DCP
>
>> El vie., 17 ene. 2020 a las 13:45, <r-390-request at mailman.qth.net> escribió:
>>
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>> Today's Topics:
>>
>> 1. Re: [MRCA] Working on the R-392 (David Olean)
>> 2. Re: Working on the R-392 (David Olean)
>> 3. Re: Working on the R-392 (Larry H)
>> 4. Re: [MRCA] Working on the R-392 (Charles Steinmetz)
>> 5. Re: Working on the R-392 (David Olean)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Thu, 16 Jan 2020 16:16:52 +0000
>> From: David Olean <k1whs at metrocast.net>
>> To: J Mcvey <ac2eu at yahoo.com>, R-390 Forum <r-390 at mailman.qth.net>,
>> "MRCA (Military Radio List)" <mrca at mailman.qth.net>
>> Subject: Re: [R-390] [MRCA] Working on the R-392
>> Message-ID: <2569aa3b-c8c9-63a5-35cb-ed17fc0f9680 at metrocast.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> I live in Maine and heat build up is not a great problem here. The joke
>> here is that our summer runs from July 1 thru July 6. I have run my
>> R-392s in their case and temps seem OK.? If I lived in SC or Florida, I
>> might come to a different conclusion.? I actually had a MIL 26A7 SS
>> replacement that I inherited from my army days. I sold it on EBay before
>> I ended up with three R-392 receivers. Two of the R-392s had small
>> diodes in the 12AU7 tube.sockets. I left them there except that I fitted
>> gold plated pins from a DB-25 plug to each diode lead for a 100%
>> positive fit to the tube socket. Maybe I will replace the audio amp at
>> some point. You are sure right that it does get warm.
>>
>> I saved the little 2000 pf mica cap for posterity.? It was a good
>> learning experience for me. Looking at the circuit, it was in the 1st RF
>> output stage. It had 28 volts DC on it, but the capacitor was floating
>> and not referenced to ground. The only voltage across the capacitor was
>> that developed by RF signals and the plate swing of the 1st RF tube.?
>> I'll bet there are plenty more of these silver mica caps getting ready
>> to quit.
>>
>> 73
>>
>> Dave K1WHS
>>
>>
>>> On 1/16/2020 2:51 PM, J Mcvey wrote:
>>> The problem components always seem to hide in the most inaccessible
>>> places, don't they?
>>>
>>> Did you solid state the 26a7 yet?
>>> The R-392 runs a lot cooler without the 15 watt 26A7 heater !
>>>
>>> I replaced the 12au7s with 1n4148 diodes also. Works fine. only one of
>>> the 12au7 sections is used as a triode and that is the IF output
>>> buffer for the front panel.
>>> I replaced that section with a fet.
>>> It was relatively easy to solid state the detector, audio section and
>>> oscillators, but the IF and RF sections are a lot more challenging, so
>>> I have let them alone for now.
>>>
>>> On Thursday, January 16, 2020, 2:17:36 AM EST, David Olean
>>> <k1whs at metrocast.net> wrote:
>>>
>>>
>>> I finally figured out that my severe distortion was only affecting one
>>> band. Any strong station in the BC band between 1 and 2 MHz was
>>> distorted. It was interesting that stations between 500 and 1000 kHz
>>> were fine.? I had originally thought that my AGC circuitry must be bad.
>>> I traced the problem to some noise coming from the tuned coils after the
>>> first RF stage. I used a dual trace scope to ferret out the noise and
>>> used the R-392 RF stage test points for connecting the scope probes. The
>>> correct one with noise was Z-208. I took the tuning rack apart and
>>> removed the RF coil. Inside were a couple of silver mica postage stamp
>>> caps and the coil. I tested each cap with a Fluke DVM. each cap showed
>>> infinite resistance. I put some DC voltage across the 2000 pf postage
>>> stamp and saw almost all of the DC voltage show up on the other end. It
>>> was shorting out.? At first, I thought I hooked it up wrong. I couldn't
>>> believe my eyes. It was leaking so badly, it was almost a complete short
>>> at 50 volts. I then tried low voltage across it, and saw the cap worked
>>> fine up to about 8 volts DC. Then a little DC started to leak through.
>>> It was only when I ramped things up to 12 or 14 volts and then it broke
>>> down and allowed almost all the DC voltage to pass through! What was
>>> strange was that I could blow on the capacitor and the leaking voltage
>>> would drop to almost zero! This was shorting out when strong BC stations
>>> were going through the RF stage. No wonder I was having problems.? I
>>> only found it due to the static noise it was making occasionally as it
>>> was sitting there in the circuit.
>>>
>>> So all the Sprague Vitamin-Q caps were fine, and it was a silver mica
>>> postage stamp type capacitor? inside an RF transformer that was giving
>>> me grief!
>>>
>>>
>>> 73
>>>
>>> Dave K1WHS
>>>
>>> ______________________________________________________________
>>> MRCA mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/mrca
>>> Help: http://mailman.qth.net/mmfaq.htm
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>>>
>>> This list hosted by: http://www.qsl.net
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>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Thu, 16 Jan 2020 16:31:40 +0000
>> From: David Olean <k1whs at metrocast.net>
>> To: Charles Steinmetz <csteinmetz at yandex.com>, r-390 at mailman.qth.net
>> Subject: Re: [R-390] Working on the R-392
>> Message-ID: <1ede737e-d223-acd5-ab08-343960c3f25f at metrocast.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> Thanks for the comments, Charles,
>>
>> Yes, I think I will be replacing many of those postage stamp types as
>> time goes on.? I like the term "hoe".?? Many of the rigs I have been
>> restoring were obtained from Land Air Communications. I am not sure if
>> the previous work that I have seen on this gear was done there or the
>> units were like that when Land Air received them.? All I know is that
>> the work was shoddy and I spent much time undoing damage caused by
>> previous repairs. Garden tools sounds about right.? Another term that I
>> recall was from Glen, K1GW who described his repair acumen as akin to
>> using blow torch and boxing gloves.
>>
>> 73
>>
>> Dave K1WHS
>>
>>> On 1/16/2020 8:06 AM, Charles Steinmetz wrote:
>>> David wrote:
>>>
>>>> So all the Sprague Vitamin-Q caps were fine, and it was a silver mica
>>>> postage stamp type capacitor? inside an RF transformer that was giving
>>>> me grief!
>>>
>>> In the ~60 years I've been playing with radios and other electronic
>>> gear, I can only recall finding one bad Vitamin-Q -- and there is a
>>> very good chance that one was damaged by the hoe who tried to fix the
>>> radio before me.? [For those who haven't heard the term before, "hoe"
>>> refers to someone who leaves electronic equipment looking like it was
>>> worked on with garden tools.]
>>>
>>> By contrast, postage-stamp micas are dying like flies now.? The time
>>> is nearing -- if it isn't here already -- when they should be replaced
>>> shotgun-style, like plastic-cased paper caps.
>>>
>>> Epoxy-dipped silver micas have generally been very reliable unless
>>> they had spent time underwater, but old ones have started to show EOL
>>> failures over the last 20 years or so.? I expect this trend to
>>> accelerate as they age further.
>>>
>>> Best regards,
>>>
>>> Charles
>>>
>>>
>>> ______________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/mmfaq.htm
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>>
>>
>> ------------------------------
>>
>> Message: 3
>> Date: Thu, 16 Jan 2020 18:03:55 -0800
>> From: Larry H <larry41gm at gmail.com>
>> To: David Olean <k1whs at metrocast.net>
>> Cc: R-390 Forum <r-390 at mailman.qth.net>
>> Subject: Re: [R-390] Working on the R-392
>> Message-ID:
>> <
>> CAOSJ_nuG9xYXiJn80+J8joNmUaWiT4SWnhDbBpKNsR3kjyKb7Q at mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>>
>> Dave, Nice work. Thanks for letting us know what and how you found it.
>> It's good to hear the blow by blow story. Sadly, I have been relegated to
>> fix the noisy bath exhaust fan. I'd rather by R-390(x)ing.
>>
>> As Charles said, we are seeing more and more silver micas bite the dust.
>>
>> Regards, Larry
>>
>>
>>> On Wed, Jan 15, 2020 at 11:17 PM David Olean <k1whs at metrocast.net> wrote:
>>>
>>> I finally figured out that my severe distortion was only affecting one
>>> band. Any strong station in the BC band between 1 and 2 MHz was
>>> distorted. It was interesting that stations between 500 and 1000 kHz
>>> were fine. I had originally thought that my AGC circuitry must be bad.
>>> I traced the problem to some noise coming from the tuned coils after the
>>> first RF stage. I used a dual trace scope to ferret out the noise and
>>> used the R-392 RF stage test points for connecting the scope probes. The
>>> correct one with noise was Z-208. I took the tuning rack apart and
>>> removed the RF coil. Inside were a couple of silver mica postage stamp
>>> caps and the coil. I tested each cap with a Fluke DVM. each cap showed
>>> infinite resistance. I put some DC voltage across the 2000 pf postage
>>> stamp and saw almost all of the DC voltage show up on the other end. It
>>> was shorting out. At first, I thought I hooked it up wrong. I couldn't
>>> believe my eyes. It was leaking so badly, it was almost a complete short
>>> at 50 volts. I then tried low voltage across it, and saw the cap worked
>>> fine up to about 8 volts DC. Then a little DC started to leak through.
>>> It was only when I ramped things up to 12 or 14 volts and then it broke
>>> down and allowed almost all the DC voltage to pass through! What was
>>> strange was that I could blow on the capacitor and the leaking voltage
>>> would drop to almost zero! This was shorting out when strong BC stations
>>> were going through the RF stage. No wonder I was having problems. I
>>> only found it due to the static noise it was making occasionally as it
>>> was sitting there in the circuit.
>>>
>>> So all the Sprague Vitamin-Q caps were fine, and it was a silver mica
>>> postage stamp type capacitor inside an RF transformer that was giving
>>> me grief!
>>>
>>>
>>> 73
>>>
>>> Dave K1WHS
>>>
>>> ______________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:R-390 at mailman.qth.net
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Fri, 17 Jan 2020 02:16:05 -0500
>> From: Charles Steinmetz <csteinmetz at yandex.com>
>> To: r-390 at mailman.qth.net
>> Subject: Re: [R-390] [MRCA] Working on the R-392
>> Message-ID: <5E215F35.3010603 at yandex.com>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> David wrote:
>>
>>> Maybe I will replace the audio amp at some point.
>>> You are sure right that it does get warm.
>>
>> Getting rid of the heat is certainly a good idea, but an even better
>> reason to do something about the 26A7 output amplifier is that it
>> improves the audio quality by about a million percent.
>>
>> There is a very simple modification that works extremely well, my "super
>> simple audio mod." Documentation is posted at
>> <http://www.ko4bb.com/getsimple/index.php?id=manuals> [file name "R392
>> 26A7 super simple audio mod.pdf"]. Whether you want to do this mod or
>> not, it may be worth a read -- this file explains what is wrong with the
>> existing 26A7 amplifier and why it sounds so very, very bad.
>>
>> The best fix, IMO, is to replace the 26A7 with two power MOSFETs as
>> drawn by someone named "S. Johnson" in 1991. That schematic, with my
>> annotations, can be downloaded from
>> <http://www.ko4bb.com/getsimple/index.php?id=manuals> by searching for
>> the file named "R392 26A7 MOSFET replacement Johnson annotated
>> updated.pdf." [NOTE: there is an older file posted there that does NOT
>> have "updated" in the file name. You want the updated file.]
>>
>> An annotated schematic of the stock audio amplifier is posted there as
>> well, for reference [file name "392 audio amp schematic V606 607 608
>> annotated.pdf"].
>>
>> Best regards,
>>
>> Charles
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 5
>> Date: Fri, 17 Jan 2020 13:45:07 +0000
>> From: David Olean <k1whs at metrocast.net>
>> To: Larry H <larry41gm at gmail.com>
>> Cc: R-390 Forum <r-390 at mailman.qth.net>
>> Subject: Re: [R-390] Working on the R-392
>> Message-ID: <ee6eb8d6-dde2-a450-8857-79ce72f64007 at metrocast.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> Hi Larry
>>
>> Well, the project isn't quite over.? I have noticed that the AGC sags as
>> the set warms up. A -25 dBm BC signal will drive the AGC up to about
>> -2.7 volts, but after an hour or so, it only rises to about 1.7 volts. I
>> checked two receivers, and both are doing the same thing.? It must be a
>> leaky cap. I need to buy some freeze mist to find it. If the AGC sags, I
>> start to hear a bit of distortion on strong signals.
>>
>> Dave K1WHS
>>
>>> On 1/17/2020 2:03 AM, Larry H wrote:
>>> Dave, Nice work.? Thanks for letting us know what and how you found
>>> it.? It's good to hear the blow by blow story. Sadly, I have been
>>> relegated to fix the noisy bath exhaust fan.? I'd rather by R-390(x)ing.
>>>
>>> As Charles said, we are seeing more and more silver micas bite the dust.
>>>
>>> Regards, Larry
>>>
>>>
>>> On Wed, Jan 15, 2020 at 11:17 PM David Olean <k1whs at metrocast.net
>>> <mailto:k1whs at metrocast.net>> wrote:
>>>
>>> I finally figured out that my severe distortion was only affecting
>>> one
>>> band. Any strong station in the BC band between 1 and 2 MHz was
>>> distorted. It was interesting that stations between 500 and 1000 kHz
>>> were fine.? I had originally thought that my AGC circuitry must be
>>> bad.
>>> I traced the problem to some noise coming from the tuned coils
>>> after the
>>> first RF stage. I used a dual trace scope to ferret out the noise and
>>> used the R-392 RF stage test points for connecting the scope
>>> probes. The
>>> correct one with noise was Z-208. I took the tuning rack apart and
>>> removed the RF coil. Inside were a couple of silver mica postage
>>> stamp
>>> caps and the coil. I tested each cap with a Fluke DVM. each cap
>>> showed
>>> infinite resistance. I put some DC voltage across the 2000 pf postage
>>> stamp and saw almost all of the DC voltage show up on the other
>>> end. It
>>> was shorting out.? At first, I thought I hooked it up wrong. I
>>> couldn't
>>> believe my eyes. It was leaking so badly, it was almost a complete
>>> short
>>> at 50 volts. I then tried low voltage across it, and saw the cap
>>> worked
>>> fine up to about 8 volts DC. Then a little DC started to leak
>>> through.
>>> It was only when I ramped things up to 12 or 14 volts and then it
>>> broke
>>> down and allowed almost all the DC voltage to pass through! What was
>>> strange was that I could blow on the capacitor and the leaking
>>> voltage
>>> would drop to almost zero! This was shorting out when strong BC
>>> stations
>>> were going through the RF stage. No wonder I was having problems.? I
>>> only found it due to the static noise it was making occasionally
>>> as it
>>> was sitting there in the circuit.
>>>
>>> So all the Sprague Vitamin-Q caps were fine, and it was a silver mica
>>> postage stamp type capacitor? inside an RF transformer that was
>>> giving
>>> me grief!
>>>
>>>
>>> 73
>>>
>>> Dave K1WHS
>>>
>>> ______________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:R-390 at mailman.qth.net <mailto:R-390 at mailman.qth.net>
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>>
>> ------------------------------
>>
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>>
>>
>> End of R-390 Digest, Vol 189, Issue 3
>> *************************************
>>
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