[GreenKeys] DT600 replacement op amps

[Ralph Mowery]

Other than using the 741 IC instead of the 709 for most of the circuit  and the loop, keyer and power supply , Is there any real difference in the dt-600 and st-6 ?

 

In the late 1970’s I did not have much money and built a st-6 on a single piece of perf board except the power supply .  I had some 741s so used them every where except the first one (limiter) . I do not recall what I used, but it was a high impedance IC.  I also redesigned the low pass filter as I ran out of parts.  A few years later I picked up the circuit boards and kit for the ST-6.  Running mine and the kit built st-6 into separate printers I could not tell any difference in the print quality under difficult conditions.  One thing I did have was a Heathkit frequency counter, so the filters were all tuned very close to the correct frequencies.

 

Ralph ku4pt

 

 

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Jim Pruitt
Sent: Thursday, July 09, 2020 1:34 AM
To: GreenKeys at mailman.qth.net
Subject: Re: [GreenKeys] DT600 replacement op amps

 

Gil the DT600 is here:
http://rtty.com/development/tu/dt-600/dt-600.htm
with schematic here:
http://rtty.com/development/tu/dt-600/dt-600.jpg

It was designed by K4OAH and some other Navy Mars members in the mid 70's.  The original article was in the February 1976) issue of Ham Radio Magazine.  The original article had a pc board layout.  That board was single sided and had provisions for a loop supply on it but the board still used the 22 pin .156" (or was it .196") spacing edge connector.  Data Technology Associates in Florida took that board and made it double sided and removed the look supply circuit.  I know that Garey had arguments with Irv Hoff over the design of the ST6 and this was Garey's answer to the ST6.

I have a Data Technologies version of the pc board.  I also have a built DT600 that has the original single sided pc board in it that I picked up at a hamfest last year.  I do not have a working teleprinter so the loss of a loop supply does not matter.  The DT600 was like the ST6 in that the input circuit uses the 709 while all other circuits use the 741.  They are dual inline 8 pin sockets that I have mounted although the 709 (TO package) is shown being hand wired into the dual inline footprint.

I just thought that with all the newer op amps that there might be a drop in replacement for at least the 741's.  I always thought the DT600 was a great converter.

Thank you.

Jim Pruitt
WA7DUY

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20200711/c20c7c17/attachment.html>