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Mon May 6, 2019, 06:32 PM

Epay "Score" - 1950 Motorola mini tube portable





Motorola 5P31A, 1950, 4 tube, roto-tenna.

It's 6:30 here.

Picking up one strong local station with birdie.

If God wanted it to pick up stations, it would have been born with transistors.

8 replies, 276 views

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Reply Epay "Score" - 1950 Motorola mini tube portable (Original post)
wonderwarthog May 2019 OP
Spitfire May 2019 #1
wonderwarthog May 2019 #2
Spitfire May 2019 #3
wonderwarthog May 2019 #8
oldenuff35 May 2019 #4
wonderwarthog May 2019 #7
_eek May 2019 #5
wonderwarthog May 2019 #6

Response to wonderwarthog (Original post)

Mon May 6, 2019, 08:48 PM

1. Neat.

With enough wires and connections you can eventually receive a lot of stations!
Continuous tuning from 29.6 Mhz to 960 Mhz AM/FM receiver that I worked on in the early design stages.
Switchable high side or low side injection to eliminate superhet interference...

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Response to Spitfire (Reply #1)

Mon May 6, 2019, 09:32 PM

2. Cool rig!



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Response to wonderwarthog (Reply #2)

Mon May 6, 2019, 09:49 PM

3. Yeah, it was a fun project.

I actually spent most of my career (in one way or another) on it.
While it was continuously tuneable across all frequencies, we software blocked the transmission of critical navigation, television, and other frequencies not required for airborne tactical use.
Here is the data sheet on the final radio:
https://www.cobham.com/media/1019239/cobham_rt-5000_datasheet.pdf

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Response to Spitfire (Reply #3)

Fri May 10, 2019, 11:16 PM

8. Thanks!


Awesome work!





(Holy Crap!)


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Response to wonderwarthog (Original post)

Tue May 7, 2019, 12:38 AM

4. and have made in japan/china on the back.

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Response to oldenuff35 (Reply #4)

Fri May 10, 2019, 11:12 PM

7. Not this set.


Made in USA, with military components.

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Response to wonderwarthog (Original post)

Fri May 10, 2019, 02:37 PM

5. Please tell me you brought that up with a variac.

Always best to avoid that wonderful smell of selenium.

I have a very similar RCA..Same year.

Looks like this one.





Was a huge pain to refurb, almost as bad as working on a T/O, so damned cramped... I did a Moto last year, the black block with the caps and resistors was a pain in the ass.

https://www.radiomuseum.org/r/motorola_5p31a5_p_31_ch_hs_599hs5.html here's some more info on yours.

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Response to _eek (Reply #5)

Fri May 10, 2019, 11:05 PM

6. Thanks!


Yep, got variac.

That is a gorgeous RCA, and yes, these Motos are a notorious bitch to work on. Two sided printed circuit board, tinkertoy module, etc.

I just posted a video on another one of these I got today, this one works beautifully.

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