[R-390] R-390 Digest, Vol 152, Issue 5

Wed Nov 14 22:18:37 EST 2018

Hello all,Just a test.Rich wd2q
In a message dated 12/9/2016 5:01:46 PM Eastern Standard Time, r-390-request at mailman.qth.net writes:

 Send R-390 mailing list submissions to
    r-390 at mailman.qth.net

To subscribe or unsubscribe via the World Wide Web, visit
    http://mailman.qth.net/mailman/listinfo/r-390
or, via email, send a message with subject or body 'help' to
    r-390-request at mailman.qth.net

You can reach the person managing the list at
    r-390-owner at mailman.qth.net

When replying, please edit your Subject line so it is more specific
than "Re: Contents of R-390 digest..."

Today's Topics:

   1. Re: DIY R-725 (Tom M.)
   2. Easier R-725 conversion (Tom M.)
   3. R-725 schematic and other documents available (Tom M.)
   4. ARR15/R105 (Perry Sandeen)
   5. R725  conversion thoughts (Perry Sandeen)
   6. Re Filament Voltage (Perry Sandeen)

----------------------------------------------------------------------

Message: 1
Date: Fri, 9 Dec 2016 11:29:41 +0000 (UTC)
From: "Tom M." <courir26 at yahoo.com>
To: Ken Harpur <kenharpur at startmail.com>,     "r-390 at mailman.qth.net"
    <r-390 at mailman.qth.net>
Subject: Re: [R-390] DIY R-725
Message-ID: <644834024.340731.1481282981755 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Ken,
I originally though the new transformer in the R-725 was for the IF filaments, but the late Wally Chambers had the right answer; it was for the PTO only to provide hum bucking.
All the other filaments in the new IF deck come from the R-390A PS and the modification I wrote up is faithful to the SERIES 500 IF deck as built by Motorola, Arvin and Servo. 

73 Tom 

      From: Ken Harpur <kenharpur at startmail.com>
 To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net> 
 Sent: Friday, December 9, 2016 2:18 AM
 Subject: [R-390] DIY R-725

Hi everyone,

About a year ago I made my own R-725 by rewiring a 390 deck following Tom's guide. While daunting it is well worth the effort IMO. I paced myself and did it over a few nights, budgeting for rewiring two sockets per evening. This ensured I didn't become restless and impatient thereby eliminating the possibility of me making a mistake. 

The challenge for me was keeping the soldering iron away from other components and wiring! The results were better than expected...it seemed to transform the radio. The RF gain action was much better, carrier level meter deflection was more lively and signals seemed to jump out of the radio. The interesting thing is the 390A deck it replaced was 3/4 rebuilt and otherwise functioning normally so I put it down to loss in the mechanical filters. My ears aren?t the best anymore so I didn?t notice much of a difference in audio although a better quality speaker might yield more dramatic results. The main transformation for me was the overall performance of the radio?said receiver is currently packed away while I re-establish my ham shack after moving back to my hometown but I clearly remember tuning around 40 meters and signals were everywhere. Tuning around the local broadcast band and many stations would have the carrier meter almost at full deflection. Being curious, I swapped b
 ack the original 390A deck and despite both decks having the I.F Gain pot set up identically (150mV @ -7V at the diode load) the receiver went back to being relatively deaf by comparison.

Would I do it again? Yes and no?While my own experience was extremely positive, if I am ever lucky enough to acquire another 390 deck I wouldn?t re-wire the tube sockets again but I would install an additional 26v filament transformer similar to the real R-725. I am curious though?I wonder if the factory fitted 26v transformer is for the PTO and the series 500 deck gets it?s 26v from the power transformer, or does the additional 26v transformer supply both the I.F Deck and the PTO? Hum bucking supply for the PTO suggests the former.

Kind regards,
Ken 
ZL3AA

______________________________________________________________
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: 2
Date: Fri, 9 Dec 2016 11:49:44 +0000 (UTC)
From: "Tom M." <courir26 at yahoo.com>
To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
Subject: [R-390] Easier R-725 conversion
Message-ID: <1484643962.1050322.1481284184103 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Group,
Along the R-725 conversion journey one chap wrote me that if you keep the overs off, the R-390A PS has the power to run 24V filaments in the r-390 deck.
I have not tested this and it's not what was done in the R-725 but it sounds appealing as it's a lot less work.
OP, please chime in.
Thanks Tom

------------------------------

Message: 3
Date: Fri, 9 Dec 2016 11:55:30 +0000 (UTC)
From: "Tom M." <courir26 at yahoo.com>
To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
Subject: [R-390] R-725 schematic and other documents available
Message-ID: <850818552.1058693.1481284530374 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Group,? in my search of various files I found the SERIES 500 IF deck schematic and other interesting R-725 docs that I can email to interested parties as a zip of several PDFs.
Please write me here if you want a copy of this schematic and the other PDFs and I will email them to you.

73 Tom

------------------------------

Message: 4
Date: Fri, 9 Dec 2016 21:21:20 +0000 (UTC)
From: Perry Sandeen <sandeenpa at yahoo.com>
To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
Subject: [R-390] ARR15/R105
Message-ID: <1634491327.38701.1481318480230 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

Hi,?
Would the gentleman who wanted to buy it please contact me off list. ?It is packed and ready to ship.
Regards,
Perrier

------------------------------

Message: 5
Date: Fri, 9 Dec 2016 21:32:22 +0000 (UTC)
From: Perry Sandeen <sandeenpa at yahoo.com>
To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
Subject: [R-390] R725  conversion thoughts
Message-ID: <636606058.69192.1481319142660 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

List,

The 390 Non A IF uses series wired filaments with a voltage supply instead of a constant current type.

This may have been done for expediency without consideration of long tube life.

Yes, most filaments are almost the same resistance but not always.

The other major PITA is if you want to change one tube.......

Personally, I'd take the filament rewiring PITA so I could run the filaments at 6.0 V. per the RCA tube manual ?data. ?This will also allow you to mix/match different tube types for better performance.
Pick your poison?
Regards,
Perrier

------------------------------

Message: 6
Date: Fri, 9 Dec 2016 21:56:55 +0000 (UTC)
From: Perry Sandeen <sandeenpa at yahoo.com>
To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
Subject: [R-390] Re Filament Voltage
Message-ID: <1822753121.70279.1481320615673 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

? List,?
BTW, on the R390A Collins used a 6.1 filament voltage although ski's say 6.3 volts.
It's on the power transformer.
Regards,
Perrier

------------------------------

Subject: Digest Footer

_______________________________________________
R-390 mailing list
R-390 at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/r-390

------------------------------

End of R-390 Digest, Vol 152, Issue 5
*************************************