Nautel Ampfet 10kw

[HadYourPhil]

I have an early Nautel 10kw Ampfet (blue cabinet and modules) from 1985. I am in a situation where I may very well have to use it as a night transmitter. Trouble is, it takes almost 30 seconds to "warm up". This Nautel doesn't have an RF Kill circuit like the newer ones do... Has anyone found a way to have one of these older Nautels come up faster, or been able to modify one to have an RF Kill/Mute circuit?

[VelvetR]

I have an early Nautel 10kw Ampfet (blue cabinet and modules) from 1985. I am in a situation where I may very well have to use it as a night transmitter. Trouble is, it takes almost 30 seconds to "warm up". This Nautel doesn't have an RF Kill circuit like the newer ones do... Has anyone found a way to have one of these older Nautels come up faster, or been able to modify one to have an RF Kill/Mute circuit?

I had one for about 10 years, replaced it with an ND25 some 16 years ago.  I don't recall it having taken more than about 10-seconds to come up from a cold start and, even at that, I associated that minimal delay with the remote control system.  Only problem I occasionally had was that it wouldn't come up at all.  Sounds serious, but it really wasn't.  The early Ampfet PA modules used cheap flat-blade connectors which tended to oxidize.  Once I figured that out and cleaned all the connectors every six months or so the problem went away.  I have no concrete reason to suspect it but somehow it nags that you may have something similar.  Hey, it wouldn't cost anything to pull all the modules and clean up connectors.  Again, I don't know why, but it feels as though it might be at least part of the problem.

Curious:  Are you somewhere around Seattle?  If so, that Ampfet might even be the one I traded in!

[HadYourPhil]

About as far from Seattle as possible!

This Nautel was purchased new in 1985 for (then) WDCQ in Ft. Myers. The calls are now WINK, the power is 50kw days and 2.2kw nights. The XR50 doesn't do too well at 2.2k so I'd like to use the old Ampfet at 2.2k, which it has done and does do very well. I'll check the connectors. THe transmitter has spent its life in an air-conditioned building so it is pretty clean. All I had to do to get it back in top shape was replace an FET and set the power module voltages at 72v.

[OKCRadioGuy]

I know the 1988 model I used to be responsible for muted.  I think it was right on the terminal strip behind the meters.  Hopefully your unit is the same.  Maybe the three year difference or the 10 to 50 difference could have a variance.

[HadYourPhil]

No RF Mute on my model that I can find...

I cleaner the contacts on all 54 (!) modules. It seemed to help the power up time by a bit. Now more like 12-14 seconds.

[Kent T]

Clean every module contact, clean all those connectors. Both will make the Ampfet slower to come on. And do so at least yearly.

[Jeff Welton]

Sorry for the late response - been on the road and got behind in listserver traffic

This rig was shipped in Dec. 1985 - I'm pretty sure that vintage didn't have the PWM kill (identified as RF Inhibit) option. That was added, as I recall, somewhere in 1986/87. What you could do, though, is leave the transmitter enabled and TX ON, then break the interlock between TB1-7 and TB1-8 (on the interface panel, back of transmitter, waist high, to the left - you'll need to remove the fan panels, watch out for the connectors so you don't tear the wiring loose).

And a definite YES on cleaning the connectors annually - hit them with a drop of Cramolin Red (or DeOxit ProGold) and scrub them with a toothbrush. Do NOT use ScotchBrite or other abrasives - once you wear the silver-cadmium plating on them, you'll be cleaning them every 3-6 months.

Best,

Jeff

[VelvetR]

Jeff, pls check personal messages re a particular ND series.

I ran into a use for Cramolin not long ago and had a little trouble finding it within about 500 miles.  Hadn't used it since tending a relay-based GE master control switcher in about 1970 and had (mercifully) forgotten all about it and the way it smelled!

[bilco]

If it has multiple power levels, could you set one of them to zero, turn it on ahead of time at that level, then switch to the 2.2KW when needed?  That might come up in power immediately.
Bill

[HadYourPhil]

Bill, I'll investigate that possibility. Right now I have one power level at 10kw for emergency backup and the other at 2.2kw for night power. The interlock referenced above is what I use to turn the transmitter on and off as that's what the manual recommends.