Hallicrafters SX-71

[John Greenland]

Greetings all, and a belated Happy New Year.

I have just been given one of these radios in beautiful condition.

Has anyone worked on one and have some speclal observations.?

BTW it has not been powered up in years including now !

TTFN
John G.

[Ralph Spracklin]

Hey John

Happy New Year to you also.

NICE Radio, NICE Acquisition! Is this the White Faced Version from 1949, or is it the Black Faced later version? And did you get the correct Speaker with it?
And did you see this YiuTube Video
Hey John

NICE Radio, Nice Acquisition! Is your unit the early White Face 1949 Version or one of the later, Black Face Versions. Also did it come with the speaker? Have you seen this Video on YouTube?

Ralph

Ralph

• This reply was modified 2 years ago by Ralph Spracklin.

[John Greenland]

Hey Ralph,

It is the dark faced unit.
The speaker that was with it, is rather large and has the output transformer mounted on it.
I am not familiar with the unit itself and have only owned a couple of the low end Hallicrafters for hobby use.
It does seem to be well looked after.

[John Greenland]

Hi all,
Further to the above rcvr I was also given an RCA Avr-20-a aircraft rcvr.
Stock pic btw, mine is in better shape.
I believe the appropriate transmitter is also in the box.

Any one ever played with either one of these ?

The great internet says an external power supply which is not there — too bad.

• This reply was modified 1 year, 11 months ago by John Greenland.

Attachments:

1. 

   Rcvr-front-view.jpg
   

[Ralph Spracklin]

Evening John

Your radio is of course was built to operate on a 12 Volt acid cell battery. The earlier version of this unit was also built to operatae on a six volt battery. I have attached a link to “radioremembered” ,which shows the schematics and an article, whichdescribes how those vibrator type powrer supplys work. However this schematic is for a six volt version. So it would need to be modified to suit the deands of your radio. If I were faced with the problem I would find an old 12 volt automobile radio and cannabalize ii for all the parts I would need, and would build a Power Supply for it. As for the six volts required for the Heater filaments, I would place a six volt tap on to of the 12 battery. Fot the HV side you would need make certain that the donor set had a Power Transformre rhat could provide 250 Vo;ts at about 51-60 ma.

Now all you will need is an airctaft to put the radio in. (haha)

https://www.radioremembered.org/vpwrsup.htm

Ralph

• This reply was modified 1 year, 11 months ago by Ralph Spracklin.

[Ralph Spracklin]

Hey John

I just realized that the unit shown is not your unit. It could very well be that your unit, is a Six Volt Unit, which will of course require a Six Volt Power Supply??? If that is so you would need the guts of a Six Volt Battery Radio. I think that the Car Radio should be from 1954 or earlier model of North American Cars. Also the matching of the Power Transformer in the donor radio should match 250 Voltage as well as the ma otput.

Ralph

• This reply was modified 1 year, 11 months ago by Ralph Spracklin.

[John Greenland]

Ralph

Thanks for all the info. I do indeed have the 6 volt unit. I also have a couple of transformers around to build a supply with 6.3 volts for the heaters and 250 volts DC for the B+.

According to the deceptive info I have found the only difference between a 6 volt and a 12 volt versions is in the 12v version that put the heaters in 2 strings of 2 heaters each with a resistor for one of the strings to balance the current.

I am going to replace a couple of the old wax caps first and see if the unit works. Unfortunately the transmitter that was with the package was barbarized by someone who had no clue about what they wee doing and were trying to modify the unit. It seems their useless work resulted in a small fire and an end to their “project “.

Acid core solder does not work well either !

TTFN

[Ralph Spracklin]

John

That link to ” for radioremembered site” was not a good link, even though I just copied it and pasted it to my post. Ihave corrected it and tested it. Click on it again and you should be able to open up that site. And maybe you have aleady figured this out yourself. Maybe you will get lucky and find a Transmiter unit somewhere else.
If I can be of any further help, let me know.

Ralph

[Author]

Posts