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  #1  
Old 10-10-2021, 09:15 PM
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RCA AM/FM 2-XF-931 "The Townley" PROJECT.

Since there is an official thread for radios, I might as well start it here.

I had run out of TVs to work on, and got this on Ebay for a fair price.
I have just now started to bring it back to life.

Info here.
https://www.radiomuseum.org/r/rca_rc1121a_2xf931.html

https://i.imgur.com/iuv79xM.jpg schematic.


As I started to restore it. It was clear that it was worked on before. Someone made a mess of it.
someone tacked in a Silicon rectifier in parallel to the selenium rectifier m1, C1a failed, but was NOT removed from the circuit, it was originally a 80uf 180v, they have in there now a 80uf 450v in parallel, R29 has been replaced with a 3 OHM 5 WATT resistor, meaning that B+ was way way too high.

This destroyed the audio output tube ( replaced ), electrolytic caps have now been replaced with new ones and the old ones cut out, selenium rectifier is out of the circuit, and for NOW the 3 ohm has been replaced with a 30 ohm until I can work out the value it needs.

Paper caps have been replaced, and am Starting to replace resistors, have not really found any bad, but most are 30% out of tolerance.

have tested it!
https://www.youtube.com/watch?v=vSzGC29wpLE
AM sort of works, poorly seems WAY off freq. but FM is dead quite.

gonna keep on replacing resistors and replace the FM only tubes, and see what happens.

this is my first vintage AM/FM radio.
go figure, i get one that someone messed up.
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Old 10-11-2021, 09:56 PM
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gonna take a while for the 3 tubes I ordered to show up with the USPS slow down. V 4/5/6

SOME of the resistors in there i can not reach w/o messing things up.

some resistors seem to be quite off R9 2.7 k checked at 3.6k, r10 checked a 7k r11 at 88k ( not replaced yet, but will this week)

I'm not sure if any of this is enough to kill FM on this.
I'm not even sure if some dweeb went and started tweaking things in here before I got it.
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Old 10-12-2021, 10:18 PM
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replaced a few more resistors / caps today, still no improvement in AM, FM is still dead quiet.

at this point, i have no idea if the OEM RCA 19x8 tube mixer oscillator is any good, or able to even run at FM freq, have no tube tester, so have a new one ordered to be safe. but it must be running at AM freq at least.

even if the RF amp was bad, I should be able to hear something on FM, and it DOES seem to work for AM, also, the ONE combo AM/FM if amp seems to be working to some degree, or I should not be getting any AM at all.

at this point however, I have no idea if someone has gone a turned coils on this thing or not.
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Old 10-15-2021, 10:55 PM
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OK, at this point I seem to know WHAT is happening, but not yet WHY it is happening.

Tonight I slapped together a isolation transformer out of an old Stancor P-6379, grabbed a crappy old O-scope and hooked it all up and looked at the local oscillator 19x8 plate (pin3) at L6, and could see in AM that it WAS oscillating, and changed as I changed station, but as soon as I changed to FM, it stopped DEAD.
Nothing at all.
The new 19x8 won't be here till next week, so I wont know if it is a bad tube or something else that is causing this.
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Old 10-15-2021, 11:33 PM
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Wouldn't the FM local oscilator be WAY out of the range of your "crappy old O-scope?"
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Old 10-16-2021, 01:13 AM
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Quote:
Originally Posted by old_tv_nut View Post
Wouldn't the FM local oscilator be WAY out of the range of your "crappy old O-scope?"

perhaps, but even with it's limit of 3 Hz -2MHz, i should be able to see something on the screen other than a flat line. :/

Now that I know that there is no risk hooking it to a scope, i could try to see way my Tektronix 7934 can make of it. 500 MHz
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Old 10-16-2021, 02:25 PM
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using the Tektronix 7934 pretty much showed me the same thing, NOTHING when i switched to FM mode.

video here
https://www.youtube.com/watch?v=v2Esh0rI8SY
started in AM , tuned up and down, then changed to FM, then set scope to what SHOULD be able to see it on the screen, then switched back and forth from AM/FM and phono.

it's just not working at FM frequency for some reason will have to see what a new tube does.

AND, just to prove that the scope CAN see that high, i grabbed my eico 324 rf signal generator and set it to 95 MHz, and fed it in.
https://i.imgur.com/5aVnrpy.jpg

in the meantime I may try feeding the output from the Eico into it to see what happens.
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Old 10-19-2021, 06:48 PM
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I'm pissed off at USPS again, they LOST my shipment of 3 tubes ( 2 12au6 & 1 19x8 ) between the PO and my mailbox, HOW THE HELL do they loose something within 6 miles from the station to here?

I would not be so critical if it was not the 4th time this year it's happened, the 2nd time with tubes, 1 time with a Vert blocking transformer, and once with a thermistor, ALL of which are rare parts.


USPS is going to hell
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  #9  
Old 10-19-2021, 07:14 PM
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Quote:
Originally Posted by Yamamaya42 View Post
I'm pissed off at USPS again, they LOST my shipment of 3 tubes ( 2 12au6 & 1 19x8 ) between the PO and my mailbox, HOW THE HELL do they loose something within 6 miles from the station to here?

I would not be so critical if it was not the 4th time this year it's happened, the 2nd time with tubes, 1 time with a Vert blocking transformer, and once with a thermistor, ALL of which are rare parts.


USPS is going to hell
The local State Farm office didn't get any PO box mail for over a month...Our agent was PISSED with the USPS. After repeated complaints they finally checked and figured out they were sorting it into the wrong PO box. Those envelopes contained thousands in checks (that could be washed and forged) and could have resulted in lapses of coverage that could ruin lives.

My ma ordered a box of Walkers shortbread cookies for the holidays to our home in Wisconsin.Tracking has it marked as delivered...IN FRICKEN NEW JERSEY!

I know they can't find employees and can't fire people, but some asses really need a good kicking. I think I'd institute a system where bad/repeated mistakes go on record and they know when staffing is easier they will be canned. If that doesn't work maybe prosecute the worst mistakes or make their BS haunt them in their job search.

Go Brandon!
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  #10  
Old 10-19-2021, 08:02 PM
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At this point, I'm still not sure why AM works and FM is silent, be it the oscillator not wanting to go to FM rates or the 2 FM IF amps.

And until I can get new tubes and be sure they are working, I can't go forward and perhaps work through the chance that the FM part may be way out of alignment and causing no audio.
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Old 10-20-2021, 06:30 PM
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It's official, USPS has lost the package..
NOT from the long distance from PHOENIX AZ to Texas, but the short FEW miles from to PO to the mailbox, the words " incompetence" and "ineptitude" come to mind.
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Old 10-21-2021, 02:05 AM
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Your lost packages incidents reminds me of how for the longest time my Medicaid, and Social Security paperwork was getting mailed to my landlords house rather than to my house/apartment, but in that case it wasn't the USPS's fault it was the state's fault because for some reason or another they had my landlord's listed as my primary guardian rather than my parents... Go Figure!

Also there was a point in time where I wasn't even getting any of my mail delivered to my house at all including important Medicaid paperwork that was supposed to be delivered to me so that I could get my Medicaid instated for another year (I'm on disability and what not which is why I have Medicaid) and supposedly the USPS's excuse for not delivering my mail was because "no one was emptying the mailbox on a daily basis" so they thought no one lived here anymore so they held all of my mail going back nearly a month at the post office. So when I explained to the post office that I was still living there and that I just forgot to get the mail for a while, they told the postal worker that delivered to my neighborhood to keep delivering my mail even if the mail box is full.

Let's Go Brandon!
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Old 10-23-2021, 02:22 PM
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here we go again the replacement set of tubes to replace the LAST ones that USPS lost last week was due to arrive today, and it is not here.

I'm doing my best not to go on a rant on what is at fault with USPS lately because that would go deeply into a political rant
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Old 10-23-2021, 11:08 PM
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USPS just keeps missing the mark...

after failing to deliver the package last weekend, an opening a search Monday, I get this from them on Wed.

"Our tracking and geo location shows your package was out for delivery to the mailbox on October 16, 2021 at 7:10 am. The carrier has searched the other mailboxes within the cluster box. Regrettably, it was not located. If you are still missing your package, I have provided a vendor letter attached to this email that you can send to the shipper explaining that the non-receipt of this package was not your fault. I apologize for any inconvenience this may have caused you."

blah blah
"An apology is no substitute for good service, but I want to offer one on behalf of the Postal Service."
yeah yeah blah blah they wash their hands if it, I now have to get a refund from the seller, and get replacements from some place else, which are also NOW LATE!!

But just when you think it's over with this screw up, 4 days later, after they sent the letter saying they lost it, and could not find it, and I had to ask the seller for a refund, it mysteriously show up in the mailbox a week late! WTF?

The only upside to this is, the tubes worked!
the local oscillator is now working in FM mode, and I can tune in FM stations!
https://imgur.com/ZrvMQ7Z

But i will most likely have to align the who thing.
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Old 10-23-2021, 11:25 PM
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Progress!
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