[GreenKeys] A request- ST-5A 2206 demodulator unit schematic, literature, anything?

[Ralph Mowery]

What you seem to have is a st-5A .  The original st-5 was very basic.  Just enough to demodulate a rtty signal.  The A version added on a few things like autostart (which pulls in the relay to turn on the motor).

The st-5 came out first, then the st-6 and later some of the features of the st-6 were added.

 

The 2206 is an IC that generates audio tones.  Usually a pot to set the mark and another for the space.  Not sure where you would find the exact circuit for the one you have, but should be easy to find for a genetic 2206 circuit.

 

Look here for a little info on the st-5

 

http://www.rtty.com/development/tu/st-5/

 

The relay should be open when in auto and pull in when a signal similar to rtty is tuned in.  Maybe just the mark tone.   That is because many would leave just a receiver on, especially a VHF FM receiver and when the tone started the replay would pull in and turn on the motor and the printer would start up.  A few seconds after the mark tone stops the motor would then turn off.  

 

We had a local  group of about 15 people that monitored all the time.  All that was on was the receiver and a demodulator.  If anyone sent rtty on the frequency the jprinter would turn on and print out, then cut off at the end of the transmission.

 

73 de Ralph ku4pt

 

 

 

 

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Mark Hall
Sent: Saturday, March 28, 2020 7:02 AM
To: greenkeys at mailman.qth.net
Subject: [GreenKeys] A request- ST-5A 2206 demodulator unit schematic, literature, anything?

 

Hello everyone.

 

This is a demodulator I've been looking for information on, but not an obscure or home built one. It is either HAL/Mainline and very well-built, and from checking it in an open area with a fire extinguisher, no ceremonial smoke ascends. No burnt offering to the goddess Electra today!

 

With the "hood up", everything looks clean. When "Auto" is selected a meaty "KERCHUNK" ensues from the beefy GE relay- I did this with my hand on its case and it was SOLID. It felt like it barked out "ACHTUNG!" Besides the two stacked ST-5 cards, there is a smaller board right behind the meter on the bottom of the case that looks like it was a later add-on. The 2206 chip, 4N28 opto and a Teledyne 712-D TO-5 cased relay make me wonder about this...

 

I'd like to get it back up and running. It might not take much. Thank you in advance for any help!

 

73!

 

Mark

 

  

 

 

Here is a link to my iCloud photo album of the little beast: https://share.icloud.com/photos/0OiFrYILpWMxvH5q9l0BYE-7Q. It's one interesting little spud.

 

The boards? Right here, at the bottom of the page:

 

 

 

 

 

 

 

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