[R-390] R-390 Digest, Vol 180, Issue 5
jm
josemic at gmail.com
Sat Apr 6 18:54:01 EDT 2019
Hi everybody. This is my first post and it is about the carrier meter.
Has somebody made a scale with the equivalent values in terms of S based in
the carrier meter 0-100 indications?
I am confused. In some threads of the reflector it is mentioned that S9
corresponds to a reading of 34 in the scale. But, is it correct that
S9+10 would be 44 and so on?
I read every issue and I am very impressed with the technical level.
Sorry for my poor English.
Jose
EA8DCP
El sáb., 6 abr. 2019 a las 23:29, <r-390-request at mailman.qth.net> escribió:
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> Today's Topics:
>
> 1. R 390A Audio Upgrade - Again (Perry Sandeen)
> 2. 17 MHz AGC pulling problem (Perry Sandeen)
> 3. Re: knobs- availabiity (Gary I. Biasini)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 6 Apr 2019 16:41:42 +0000 (UTC)
> From: Perry Sandeen <sandeenpa at yahoo.com>
> To: r-390 at mailman.qth.net
> Subject: [R-390] R 390A Audio Upgrade - Again
> Message-ID: <1865383702.17702173.1554568902860 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> Yo Bubba Dudes!
> There have probably been as many *A* audio upgrades as any other mod. Some
> are more successful than others but most have limitations as they just do
> some mods to the existing circuit which for long term listening: just suck.
> BTDTGTTS! The Achilles heal of all the mods is that they still used the OEM
> audio output transformer. Although in Chuck Felton's mod he did use some
> negative feedback.
>
> The best mod (and yes it is not reversible so *purists* can stop reading
> now) is the one done by Bill Kleronomos SK who did them for a side business
> until he passed.
> What made this the best by far is that it used a Hammond true Hi-Fi P-P
> output transformer with negative feedback.
> That said IMNSHO there were seveal shortcomings to his design.
> First he used a Amperex 6360 9 pin dual heptode(?) mounted in place of the
> last 6AK6 tube used for the local audio output. This tube runs very, very
> hot.
>
> Secondly he changed the line output stage to a 6AH6 as the 1/2 12AU7
> driver for the 6AK6 tube was removed because of the need for a 6DJ6 phase
> inverter.? The line audio stage and its associated precision resistors are
> used in the A's calibration.
> Thirdly, he left unused OEM audio output transformer in place and mounted
> the new audio transformer where the squelch circuit would be installed.
> I started to improve on this by relocating the under chassis dropping
> resistors to the top of the chassis and in their place install new
> Panasonic electrolytics so that the OEM filter cap sockets would be
> available to use for P-P 6AQ5 audio tubes.? With a little fitness I was
> able to remont the OEM filter chokes in the space behind the power
> tanformer.? An alternate plan was to use the Hammond 1.25 Hy chokes from
> Triode Electronics and up the filter caps to 330 uF each.? This would give
> the same or better attenuation as the OEM ckt but take far less space. I
> also planned to do as W. Li did so well was to do a star ground sustem.
>
> I added another 9 pin tube so there would be the same 12AU7 driver so the
> 6AK6 line driver circuit would remain the same.
> Then I screwed up big time.
> I felt the 800 narrow filter was useless and cut it out.? That left me
> with a huge mess of wires that I never got straightened out.? Waiting for
> *more quality bench time* never happened.
> I believe that the improvements I started would combine the best on
> chassis audio with the best reliability.
> I would be delighted to email all of my circuits, notes, pictures and an
> unpublished experimental article to all who might want to do this mod.
> If one leaves in the narrow filter I believe doing the mod is not too
> difficult.
> BTW my audio module had the $#^%&^( MFP.? I found that a simple engraving
> tool was great for removing it from solder terminals.? Wear a mask and
> don't inhale it.? it's still hazardous even at 60 years old.
> Regards,
> Perrier
>
>
>
>
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 6 Apr 2019 17:51:12 +0000 (UTC)
> From: Perry Sandeen <sandeenpa at yahoo.com>
> To: "r-390 at mailman" <r-390 at mailman.qth.net>
> Subject: [R-390] 17 MHz AGC pulling problem
> Message-ID: <959952909.824422.1554573072374 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> Yo Bubba Dudes!
> A challenging problem for solving by those with cold logic and a hot
> soldering iron.
>
> One of the puzzling mysteries of the a is the 17 crystal oscillator drift
> caused by the application of AGC to the first mixer. This can be 300 - 450
> Hz from the findings of Chuck Felton.
> Collins went to the trouble of putting the crystal in an oven so why not
> solve this problem.? Best guess.? They knew about it BUT it wasn't in the
> required stringent spec's so engineering, knowing the cost of solving the
> problem, just kept quiet.
> Now for causal AM listening Chuck noted that it probably wouldn't make any
> difference.? However e are interested in listening to the continuous sound
> of the 100 watt station in flea fart from Fiji, or something similar.
> But for us true believers in getting the ultimate performance from our
> beloved A's this intolerable technical gaffe must be remedied, if not,
> we'll become the laughing stock of those heathen rice box lovers.
>
> I started to investigating methods for solving the drift.
> The? major difficulty is that the oscillator is located on the RF chassis
> making simple access impossible.
> Also finding a 17 MHz crystal or a harmonically related prove futile
> except for SMD. Ugh
>
> An outboard metal box approach using a SS method led to using a 10 MHz and
> a 27 MHz 1/2 crystal can oscillators feeding a Minicircit passive DBM then
> using a tuned 17 MHz LC circuit.? This would be fed through a very good
> .01uF/1KV ceramic cap into to pin 5 of the 6AK5 oscillator tube V207 after
> removing B+ resistor feed R211.
> OPS! pin 5 goes to tuned circuit T207.? Square wave into LC circuit, not a
> good idea.
> Feed the new 17 MHz through P221? Perhaps.
> Plan two was to remove the 17 MHz crystal, make a new oscillator circuit
> then feed it into the grid pin 1 of V207 utilizing it as a buffer.
> Would this work? I don't know.
> This is just a starting point for others as I will never be able to pursue
> this.? Good luch to any who will even try (and post there results on the
> list.
> Regards,
> Perrier
>
>
>
>
>
>
> .
>
>
>
>
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 6 Apr 2019 14:49:19 -0600
> From: "Gary I. Biasini" <gary.biasini at shaw.ca>
> To: "'Lester Veenstra'" <m0ycm at veenstras.com>, <r-390 at mailman.qth.net>
> Cc: wb3fau55 at neo.rr.com
> Subject: Re: [R-390] knobs- availabiity
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Sorry, it was right beside the last drawing.
>
> Here is what I found on the non-tuning knobs - large, small and small
> without line.
>
> Regards,
>
> Gary
>
> -----Original Message-----
> From: Lester Veenstra <m0ycm at veenstras.com>
> Sent: April 6, 2019 8:36 AM
> To: 'Gary I. Biasini' <gary.biasini at shaw.ca>; r-390 at mailman.qth.net
> Cc: 'Barry' <n4buq at knology.net>; wb3fau55 at neo.rr.com
> Subject: RE: [R-390] knobs- availabiity
>
> Interesting, and the little knobs?
> That would be an easier starting point
> Have to get some bigger Al blanks for the main knobs
>
> Lester B Veenstra? K1YCM M?YCM W8YCM 6Y6Y
> lester at veenstras.com
>
> Physical and US Postal Addresses
> 5 Shrine Club Drive (Physical)
> HC84 452 Stable Ln (RFD USPS Mail)
> Keyser WV 26726
> GPS: 39.336826 N? 78.982287 W (Google)
> GPS: 39.33682 N? 78.9823741 W (GPSDO)
>
>
> Telephones:
> Home:?????????????????? ? +1-304-289-6057 US cell???????????????????
> +1-304-790-9192 Jamaica cell:?????????? +1-876-456-8898
> ?
>
> -----Original Message-----
> From: Gary I. Biasini [mailto:gary.biasini at shaw.ca]
> Sent: Saturday, April 06, 2019 1:09 AM
> To: r-390 at mailman.qth.net
> Cc: 'Lester Veenstra'; 'Barry'; wb3fau55 at neo.rr.com
> Subject: RE: [R-390] knobs- availabiity
>
> Lester,
>
> Here is what I found. I am looking for more.
>
> Regards,
> Gary
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On
> Behalf Of Lester Veenstra via R-390
> Sent: April 5, 2019 3:09 PM
> To: 'Barry' <n4buq at knology.net>; wb3fau55 at neo.rr.com
> Cc: r-390 at mailman.qth.net
> Subject: Re: [R-390] knobs- availabiity
>
> Anybody got drawings? I have a cnc mill that should be able
>
> Lester B Veenstra? K1YCM M?YCM W8YCM 6Y6Y
> lester at veenstras.com
>
> Physical and US Postal Addresses
> 5 Shrine Club Drive (Physical)
> HC84 452 Stable Ln (RFD USPS Mail)
> Keyser WV 26726
> GPS: 39.336826 N? 78.982287 W (Google)
> GPS: 39.33682 N? 78.9823741 W (GPSDO)
>
>
> Telephones:
> Home:?????????????????? ? +1-304-289-6057 US cell???????????????????
> +1-304-790-9192 Jamaica cell:?????????? +1-876-456-8898
> ?
>
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of Barry
> Sent: Tuesday, April 02, 2019 10:29 AM
> To: wb3fau55 at neo.rr.com
> Cc: r-390 at mailman.qth.net
> Subject: Re: [R-390] knobs- availabiity
>
> Yes, Dan is an SK.
>
> I think he offered knobs that were machined from solid aluminum and
> powder-coated. They were quite nice.
>
> Thanks,
> Barry - N4BUQ
>
> ----- Original Message -----
> > From: wb3fau55 at neo.rr.com
> > To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
> > Sent: Tuesday, April 2, 2019 9:18:40 AM
> > Subject: [R-390] knobs- availabiity
> >
> > Gang- some time back, i heard Dan Arney had built die-cast molds for
> > 390 knobs. i guess he is SK? What became of the dies or molds? 73s
> > Russ wb3fau
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