[RTTY] Help!!!

[Tom Osborne]

OK all you guru's out there, I need help.

I'm setting up a '430 for 2nd radio here and have it hooked to an
Astron RS-20A power supply.  When I turn the radio on it
receives, but when I go to transmit, the radio starts to chatter
and the display goes away.  I tried it on the '840 and it won't
work on it either
I tried---

1.  Using the power cord on another Astron power supply and it
works ok, so it's not the cord.

2.  Put a voltmeter on the output of the power supply and the
voltage is constant at around 13 volts.

3.  Put a toroid on the power cord (thought it might be RF) and
that didn't help.

4.  Put a power cord that I knew was good on it and it still
didn't work.

Now I'm stumped and don't know what else to check.  Think it may
be a current problem?  If so, why does the voltage not change?? 
Any ideas?  73
Tom W7WHY