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Author Topic: TT delta 580  (Read 6428 times)

Posts: 9

« on: November 28, 2014, 08:49:23 PM »

I recently got a TT 580 Delta in a trade. The problem was it didnt have a power cable. I made a cable (using pins 1 and 4) to power the radio with an Astron power supply. The problem is the power knob will no longer power off the radio off/on. I tried to jumper pins 2 and 3, but that didnt work. Anyone have experience making this work? Also, the shut off protection feature doesnt work any longer. I have a TT power supply I use for my Omni that I have connected to the 580 and everything works as it should. I would like a way to get the power switch and shut off protection to work on the 580. ideas???


Posts: 18518

« Reply #1 on: November 28, 2014, 11:35:41 PM »

The switch on the front panel controls the power supply.
The Astron isn't set up to be switched from the rig.

Similarly the over current protection is built into the supply, not
the rig. With a non-TenTec supply you need to use a magnetic
circuit breaker for that function (and risk damaging the finals if
you don't. )

Posts: 18518

« Reply #2 on: November 29, 2014, 10:17:10 AM »

Let me clarify this a bit now that I have  real keyboard to type on...

In the Ten-Tec supplies one side of the power transformer primary is routed through a pair of
wires on the power cable and to the switch in the rig - the switch connects to nothing else
internal to the radio.  So with a Ten-Tec supply this puts the switch on the front panel in
series with the power switch on the supply itself, which is why the switch works.  This
requires 2 wires in the power cable that carry 120VAC for the switch.

The Astron supplies aren't wired that way, which is why the switch doesn't work.  You can't
just put the switch in line with the +12VDC from the supply because it isn't rated to carry
20A.  The best way to make the switch functional without modifying a conventional power
supply is to use it to control a 12V power relay - this way you still only have the two power
wires coming from the supply, with the relay connected somewhere in the wire itself.  This
is the approach that I used with my Argosy.

This also has the advantage of removing the 120VAC from the radio itself - not everyone
working in the internals of a 12V rig is going to be alert for AC power wiring.  Since the
switch is on the volume control (I think?) there are also reports of AC hum being picked
up into the audio from the AC wires to the switch.

The over-current protection circuit is built into the power supply, between the negative side
of the rectifier and the negative chassis ground.  While the ALC circuit in the rig will protect
the output transistors from excessive voltage, this is required to prevent damage due
to high current, as can happen when the load impedance is too low.  The rigs don't
have a standard SWR shutdown circuit like those from most other manufacturers, so this
protection is critical.  Ten-Tec used to sell fast magnetic circuit breakers to use with these
rigs in mobile operation, or with a non-Ten-Tec power supply, but now recommend purchase
directly from the manufacturer.  Some folks mount the breaker (which looks like a big
toggle switch) beside the rig and use it as the main ON/OFF switch, so it solves two
problems at once.

So you either need a magnetic circuit breaker of the proper current rating, or another
Ten-Tec power supply.  (Though the circuit is available in the manual for the 251 power
supply if you want to build it into a different circuit.)

Posts: 0

« Reply #3 on: November 30, 2014, 06:44:05 PM »

Excellent advice. I may purchase a magnetic breaker, and build the mobile/battery circuit also. It would be handy for a field day.
Now, has anyone cured the vfo drift problem yet? My 580 needs to get some serious use, and maintenance.
Audio quality is also an issue. It sounds plain "tinny". I will probably recap certain sections soon.

Posts: 18518

« Reply #4 on: December 01, 2014, 02:17:26 PM »

Quote from: KA8FHW

...It sounds plain "tinny". I will probably recap certain sections soon.

More likely to be the BFO adjustment relative to the center of the filter passband.  Does the pitch
of the background noise change when you switch sidebands?

My Argosy is the prior generation (and I also have the original Argonaut 505) and I haven't had
any problem with electrolytics yet. I don't have any plans to shotgun the capacitors until I see
at least a couple of them fail.

Posts: 365

« Reply #5 on: December 01, 2014, 05:07:01 PM »

Agree that it is most likely that the carrier point is out of adjustment. There are individual trimmer cap settings for LSB and USB. The shift in "pitch" of the background band noise when switching between LSB and USB is certainly a good clue to help confirm that. I've brought my 580 Delta's carrier point settings back into spec by ear. It is not that hard to do.

Being a PTO VFO, there will always be some drift, + or - 100 Hz is certainly well within the range of "normal" for that type of radio, especially for awhile after power on and as it warms up.
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