[GreenKeys] Connecting 28 ASR to a TU

[Jack]

Al,

 

I’ve been a RTTY/Teletype “nut” since the early-1960’s. Maybe I can

help.

First off, some RTTY converters were set up for “low tones” which are

1275 and 2295 HZ. ITTY uses 2125 and 2975. However, even if the tones

are not correct, you should see some type of movement on the

tuning meters.

You should check the TU output (loop) with a milliammeter to see if

you have 60 ma. of current. And, switching to DC voltage measurement,

look for something around 100 to 130 VDC. This would be with the

TU in “Standby” or “Local”. If you plug in the 28 and it runs “open”,

try reversing the connections. Some TTY’s still have their internal

polar relays connected.

Also check that the TU’s have the proper power supply voltages

present (usually plus and minus 12VDC, and the loop voltage). 

Those older units might have bad power supply capacitors

or open/shorted diodes.

If all else fails, I’d be happy to check out the TU’s for you if you

want to ship one or two of them to me (New York).

You are probably aware that there is very little “traditional” RTTY

on the Ham bands anymore. Most of what you hear is computer-

generated RTTY and the computers don’t send the CR/LF functions

for the end-of-line. This would not make your 28 happy.

ITTY is the best way to go to make sure you have everything 

working correctly.

I’d suggest you focus on getting the ST5000 to work first. It’s

a simpler unit and those ST6’s can be pesky.

 

73,

Jack K2TTY

 

 

 

 

 

 

From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of tokens at myranch.com
Sent: Wednesday, October 11, 2017 11:38 AM
To: greenkeys at mailman.qth.net
Subject: [GreenKeys] Connecting 28 ASR to a TU

 

I recently acquired a 28 ASR  and have it working locally. Problem is getting it to copy off the air. I obtained two TUs with hopes that they would be in working condition. One is a Hal ST-6 and the other is a Hal ST-5000. The ST-6 was kit built with modifications. It arrived with all the boards rattling in the box. When I opened the chassis every board was loose. The ST-5000 looks as if it is brand new. It arrived in its original box with all the original cables and connectors waiting to be made up. My assumption is that with either one of these TUs if I fed in a rtty signal I should see deflection on the meter. I have tried itty from the internet connecting to the line out of the computer and I have tried rtty off the air connecting to the line out of the receiver. In both cases I see no sign of meter movement with either TU. I know there is a signal being fed into the TUs as I can connect to a separate scope and see the deflections with the signal. At this point I don’t know if I have two dysfunctional TUs or whether I am trying to use them incorrectly.

 

Any help would be welcomed.

 

Thank you.

 

73,

Al W8KHP

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