[R-390] R-390 Digest, Vol 85, Issue 11
Luc Vlecken
vlecken at hotmail.com
Fri May 20 02:33:24 EDT 2011
Dear Listmates,
I have a R-390A/URR serial 299 MOTOROLA 14385-PC-58 with an IF without the Collins filters also.
Would this also be a R-725 then?
This set performs extremely good in CW indeed, no ringing at all, smooth as silk.
Thanks for info and greetings to all from over here.
Luc Vlecken ON4ALV
Zerkingen 34
3800 Sint-Truiden
Belgium
GSM: + 32 (0) 473 201 069
Tel Home:+32(0)11 68 72 64
mailto:vlecken at hotmail.com
QUAERO ET TEGO
> From: r-390-request at mailman.qth.net
> Subject: R-390 Digest, Vol 85, Issue 11
> To: r-390 at mailman.qth.net
> Date: Thu, 19 May 2011 12:01:21 -0400
>
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> Today's Topics:
>
> 1. Re: R390 NON A IF deck mods in ER (David Wise)
> 2. Re: R390 NON A IF deck mods in ER (Tom M.)
> 3. Re: RF Module Adjustable Slug Seperated from Adjusting Screw
> (Drew P.)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 18 May 2011 10:38:44 -0700
> From: David Wise <David_Wise at Phoenix.com>
> Subject: Re: [R-390] R390 NON A IF deck mods in ER
> To: "ka9egw at britewerkz.com" <ka9egw at britewerkz.com>, Dan Osborne
> <wb5afy at wb5afy.net>, "R-390 at mailman.qth.net" <R-390 at mailman.qth.net>
> Message-ID:
> <FFF45F8A4E2B6F4CA4920B3B028CE73D317768DB at SCL-ExchMB.phoenix.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Somebody on the list (I'm too busy to search the archive) analyzed the situation and concluded that, provided you leave your oven heaters off (which you should do anyway), the R-390A power supply can easily handle the native 25.2V load of the R-390 IF deck. You only have to change some connector pinouts. Much easier than a 6.3V rewire.
>
> Dave Wise
>
> >-----Original Message-----
> >From: r-390-bounces at mailman.qth.net
> >[mailto:r-390-bounces at mailman.qth.net] On Behalf Of
> >ka9egw at britewerkz.com
> >Sent: Tuesday, May 17, 2011 6:07 PM
> >To: Dan Osborne; R-390 at mailman.qth.net
> >Subject: Re: [R-390] R390 NON A IF deck mods in ER
> >
> >Issue 139, Dec. '00
> >
> >73, Brian KA9EGW
> >
> >-----Original Message-----
> >From: r-390-bounces at mailman.qth.net
> >[mailto:r-390-bounces at mailman.qth.net]On Behalf Of Dan Osborne
> >Sent: Tuesday, May 17, 2011 2:35 PM
> >To: R-390 at mailman.qth.net
> >Subject: [R-390] R390 NON A IF deck mods in ER
> >
> >
> >Well - anyone remember which issue of ER had the article on the
> >filament string mods required to use
> >a NON-A IF deck in an A rcvr ??
> >
> >The Java code on the ER search page wont run for me...sigh...
> >
> >tnx
> >
> >Dan O
> >
> >_______________________
>
> ------------------------------
>
> Message: 2
> Date: Wed, 18 May 2011 17:44:36 -0700 (PDT)
> From: "Tom M." <courir26 at yahoo.com>
> Subject: Re: [R-390] R390 NON A IF deck mods in ER
> To: ka9egw at britewerkz.com, Dan Osborne <wb5afy at wb5afy.net>,
> R-390 at mailman.qth.net
> Message-ID: <321921.81951.qm at web36208.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> I wrote that article. My objective was to replicate the R-725 wiring. It can
> be done an alternate way as pointed out but this is how Motorola did it. 73 Tom
>
> Here is the conversion procedure. I use one of these in my 390A. I have not
> tested the alternate method.
>
> 73 Tom
>
> --------------------------------- cut here
> ------------------------------------------------
>
>
> Conversion of the R-390 IF Deck for Use in R-390A For Improved Audio,
> Or
> Make Your Own R-725
>
> Thomas F. Marcotte, N5OFF
>
> As many of the readers of Electric Radio know, the US Army created a modified
> R-390A version for direction finding known as the R-725/URR. I wrote about this
> modified radio in this publication a few years ago.
> The main difference between a R-725 and the R-390A is that the R-725 utilizes a
> custom built IF deck that is very similar in construction to the R-390 IF deck.
> It has tuned circuit selectivity instead of mechanical filters. The mechanical
> filters of the R-390A created distortion when that radio was employed for radio
> direction finding use. In an internal Collins engineering report published in
> 1952, Lou Couillard wrote of the improved R-390A, which at that time was called
> the R-390(XC-3), "Although the superior shape factor of the mechanical filter IF
> is desirable in most applications, consideration should also be given to an
> alternate tuned circuit design for use in special applications. The excellent
> shape factor of the mechanical filters precludes the possibility of linear phase
> shift across the passband. Where a linear phase characteristic is desired such
> as in direction finding equipment, a tuned circuit IF is necessary."
>
> Employment of the tuned circuit IF is exactly what was done in the R-725.
> Motorola was awarded a contract in 1956 (476-PH-56-91) to prototype the
> R-725. I know of a couple of these Motorola sets existing today.
>
> Packaging of modified sets for quantity DF use were handled by Arvin Industries
> and Servo Corporation of America. Approximately three hundred R-390A's were
> modified to the R-725 configuration. These sets are relatively tough to find
> today. New IF decks were manufactured by the modification companies (actually
> salvaging some of the components from the now junker R-390A IF decks) and
> installed in existing R-390A's. The new IF decks were named "SERIES 500 IF
> STRIP ASSY." They looked almost just like R-390 IF decks (see the comparison
> photos), except that the IF connectors were relocated to match the cables and
> connectors in the R-390A chassis. The circuits were designed to plug and play
> in the R-390A instead of the R-390. The decks are not interchangeable (until
> now that is, after performing the modification described herein).
>
> Notwithstanding DF capabilities, a side benefit of the SERIES 500 deck is that
> it provides a smoother sound than does the stock R-390A IF deck. Mechanical
> filters are said to "ring" and after a while can be fatiguing to the listener.
> The purpose of this article shall be to describe how one may "roll his own"
> SERIES 500 IF deck from a surplus R-390 IF deck. Please note that I don't
> advocate trashing of a good R-390 to do this mod. The IF deck I started with
> came from a Motorola junker. I would urge you to likewise find a junker R-390
> as a source of an IF deck for this project . Make sure that the deck is in
> working condition prior to beginning the modification.
> The R-390 IF deck was designed to operate with one 25V filament supply
> (unfortunately the 25V supply available in the R-390A is insufficient to power
> all of the filaments in the R-390 IF deck). The R-390A deck was designed to
> operate with a combination of 6.3V and 25V filament supplies. The task involved
> in this conversion is to rewire the R-390 filaments to comply with the voltages
> available in the R-390A and provided at the main IF deck connector, plug and
> play, without the addition of any new power transformers. Each of the twelve
> tubes in the R-390 IF deck must be addressed for full compliance with the
> voltages available from the R-390A. Refer to the schematic in Fig 1 as to the
> final filament wiring configuration. We will also drop the B+ a bit.
> Plug P112 of the R-390A shall be plugged-in to the R-390 IF deck at jack J517.
> There is much commonality here, except for the connections mentioned herein.
> In general, you will be converting 25V series connections into 6.3V (herein
> referred to as 6V) parallel connections for most tubes, and moving the
> connections of the BFO/PTO/ballast tube series to a different connection point
> in jack J517. The 6V filament supply shall be provided to the R-390 deck by pin
> 20 of P112 from the R-390A.
>
> General instructions: Refer to the schematic for the original R-390 as the
> "before" schematic, and Figure 1 as the "after" schematic for filaments. Use
> the best soldering technique you can in this limited access space. Don't
> insulate or bind any wires until instructed to do so. You will be utilizing
> some of the new 6V supply connections more than once. Make sure you can
> recognize your new wires. I used black wire for the 25V supply, red wire for
> the 6V supplies, and green wire for new grounds.
> The first task is to install a B+ dropping resistor to better match the 180V B+
> that the R-390 IF deck is expecting. To do this, locate inductor L503 under the
> IF deck. This will be found snapped into a holder right above pin 2 of J517.
> Disconnect one end of the coil, and install in series with it (the equivalent
> of) a 470 ohm 2 watt resistor. This will tame the B+.
> The first tube circuit we'll work on is the ballast tube circuit.
>
> V508 (5749) and RT512 (3TF7) These must be supplied by the R-390A 25V filament
> supply. To do this, sever the connecting wire at pin 8 of jack J517 (underneath
> the deck) to free this slot up (hint: save access to the connector end of the
> wire as you will use it to wire supply to V509). Then, sever the connection at
> pin 2 of RT512 and wire this pin to pin 8 of J517 of the R-390 deck with a long
> piece of new wire. The filament return connection remains unmodified. This
> modification will make the BFO/PTO/ballast tube series connections identical to
> the R-390A 25V filament supply connections. As mentioned above, this 25V supply
> is insufficient to supply the remainder of the tube filaments, thus the need to
> employ the 6V supply for this task.
>
> The following 6V tubes shall have filaments wired from the 6V R-390A supply.
> The filament pins of these tubes are pins 3 and 4. Don't sever any connections
> unless instructed to do so. The modification will use as much existing R-390 IF
> deck wiring as possible (and thus may seem a bit screwy to you until finished).
>
>
> V504 (6BJ6) 6V will come from its existing connection at pin 4. Ground will come
> in the next step.
>
> V503 (6BJ6) Wire pin 3 of V503 to pin 4 of V504 for 6V supply. Ground V503, pin
> 4.
> V502 (6BJ6) 6V supply will come from an existing connection at V503, pin 3.
> Ground V502, pin 3.
>
> V501 (6BJ6) Sever ground connection at V501, pin 3 and wire pin 3 to V502, pin
> 4.
>
> V505 (6AK6) 6V supply will come from existing connection at pin 4. Ground will
> come in the next step.
>
> V506 (6AK6) Ground pin 4 of V506. Wire pin 3 of V506 to pin 4 of V505 for 6V
> supply.
> V509 (6BJ6) Locate the free wire which was cut from underneath J517, pin 8, and
> connect it to the 6V filament supply at J517, pin 20.
>
>
> The following tubes are 12AU7's wired in various series schemes in the R-390.
> They must be rewired according to their 6V option for use in the R-390A. Note
> two of the connections require dropping resistors on the 6V source of V507 and
> V510 to obtain the desired 5.3V filament voltage.
>
> V511 Sever ground connection at pin 5. Connect pins 4 and 5 together for 6V
> supply, ground pin 9.
>
>
> V507 Sever connections at pins 4, 5 and 9, including the two resistors (one 120
> ohm and one 22 ohm). Wire 6V supply from your previous work at V505, through
> the deck opening for variable capacitor C525, to pins 4 and 5 through a 3.9 ohm,
> 1 watt resistor. Ground pin 9.
>
> V 510 Sever connections at pins 5 and 9. Ground will come from existing pin 4
> connection. Remove 120 ohm resistor between pins 4 and 9. Wire pin 5 to pin
> 4. Wire 6V supply from J517, pin 20 to V510 pin 9 through a 3.9 ohm, 1 watt
> resistor.
>
> There are no changes to any of the other connections in the R-390 deck.
> Prior to installing the modified R-390 deck in your R-390A, you must check your
> work.
>
> Perform continuity checks from J517, pin 8, with RT512, pin 2.
>
> Perform filament supply and ground continuity checks as follows. Note: There
> will be more than one ground connection at various tube sockets, but the
> filaments should have continuity exactly as shown.
>
> Filament supply is checked from J517, pin 20.
>
> V501, filament, pin 3; ground, pin 4.
> V502, filament, pin 4; ground, pin 3.
> V503, filament, pin 3; ground, pin 4.
> V504, filament, pin 4; ground, pin 3.
> V505, filament, pin 4; ground, pin 3.
> V506, filament, pin 3; ground, pin 4.
> V507, filament, pins 4 and 5; ground, pin 9.
> V509, filament, pin 4; ground, pin 3.
> V510, filament, pin 9; ground, pins 4 and 5.
> V511, filament, pins 4 and 5; ground, pin 9.
>
> Now insulate any bare connections, and use mini-tie wraps to secure the new
> wires to sturdy nearby points.
>
> To enable final installation of the deck in your R-390A, you'll need to make two
> adapter cables. These cables shall consist of jumpers (RG-59 is OK,
> approximately eight inches in length) with BNC's on each end. You'll also need
> two adapters of the type found on the back of the frame of the R-390A at the IF
> OUT jack (AMPHENOL 47200). This will provide crossover from MB connection
> (R-390A standard)to BNC (R-390 standard). Connect P-218 of the R-390A to J-526
> of the R-390 IF deck with one of the cables. Connect P-213 of the R-390A to
> J-525 of the R-390 IF deck with the other cable. It is a good idea to label
> these cables. See the photo for reference.
>
> Install the deck in your R-390A. You will notice that the screw holes are the
> same as for the R-390A IF deck, however the screws of the R-390 deck are of
> larger diameter. I did not change these screw as they are captive into the
> deck. The BFO, BANDWIDTH, and power connector of the deck will hold it in
> place, however I would not install it in a Jeep this way. Changing these screws
> is optional.
> When you turn on the power, make sure your dial lamps light up normally. If
> they don't, you have a filament supply problem so turn off the set immediately
> and troubleshoot.
>
> For great sound, instead of using the built in audio deck, I prefer to tap the
> audio from the diode load jumper at the back of the set. Through a 0.1 uF or
> larger capacitor, feed this signal into your line audio amp of choice, and enjoy
> the tuned circuit audio of the new R-725, errrr, R-390A with tuned circuit IF.
> You'll get the smooth sound of the R-390 and R-725, but have the parts
> availability and support common to the R-390A for the balance of the set. I've
> used my modified IF deck in two different R-390A frames, and it worked equally
> well in both. In my opinion, it makes the long term listening experience much
> more enjoyable.
>
> If you have any questions about the mod, please feel free to write.
>
> 73 DE N5OFF
> QRT
>
> Thomas Marcotte is a registered professional engineer working in Lafayette, LA.
>
>
> References:
>
> Cost Reduction Program for Radio Receiver, R-390/391( )/URR, L.W. Couillard,
> Collins Radio, 1952.
>
> TM 11-856/TO 31R1-2URR-154, RADIO RECEIVER R-390/URR, January, 1955.
>
> Servo Corporation of America drawings for R-725 series 500 IF deck, Order No.
> 36-039-N-5-00093(E), September, 1965.
>
> TM 11-5825-231-24, DIRECTION FINDER SETS AN/TRD-23, AN/TRD-23A AND DIRECTION
> FINDER SETS AN/TRD-15 AND AN TRD-15A, August, 1973.
>
> TM 11-5820-358-35, FIELD AND DEPOT MAINTENANCE MANUAL, RADIO RECEIVER
> R-390A/URR, May, 1980.
>
> Special thanks to Wally Chambers and George Rancourt.
>
>
>
>
>
>
>
>
>
> ----- Original Message ----
> From: "ka9egw at britewerkz.com" <ka9egw at britewerkz.com>
> To: Dan Osborne <wb5afy at wb5afy.net>; R-390 at mailman.qth.net
> Sent: Tue, May 17, 2011 8:07:28 PM
> Subject: Re: [R-390] R390 NON A IF deck mods in ER
>
> Issue 139, Dec. '00
>
> 73, Brian KA9EGW
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Dan Osborne
> Sent: Tuesday, May 17, 2011 2:35 PM
> To: R-390 at mailman.qth.net
> Subject: [R-390] R390 NON A IF deck mods in ER
>
>
> Well - anyone remember which issue of ER had the article on the
> filament string mods required to use
> a NON-A IF deck in an A rcvr ??
>
> The Java code on the ER search page wont run for me...sigh...
>
> tnx
>
> Dan O
>
> ______________________________________________________________
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>
> ------------------------------
>
> Message: 3
> Date: Wed, 18 May 2011 21:19:05 -0700 (PDT)
> From: "Drew P." <drewrailleur807 at yahoo.com>
> Subject: Re: [R-390] RF Module Adjustable Slug Seperated from
> Adjusting Screw
> To: r-390 at mailman.qth.net
> Message-ID: <224215.9286.qm at web38505.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> Paul wrote:
>
> <snipped>
>
> "This particular R390 appears to be a low mileage Collins original, still has its original green gear!. It had a short on the audio pre-amp plate circuit. To get it going, I swapped the audio module and the set started working. Needed a ballast tube (I'll replace with 12BA6's for PTO/BFO and short the ballast tube socket) and had 3 weak tubes also. Has anyone tried keeping the 6BA6 PTO/BFO tubes intact and used a diode to replace the ballast tube ?"
>
> The radio will work with just a diode to replace the ballast tube, but the voltage to the PTO and BFO tube heaters will be too high - about 9 volts RMS on each of the two heaters. If you place a 20 ohm resistor in series with the diode, then all will be copacetic in Heatersville.
>
> Drew
>
>
>
> ------------------------------
>
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> End of R-390 Digest, Vol 85, Issue 11
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