[R-390] PTO Tenny Bolts and war strories

[JMILLER1706 at cfl.rr.com]

I had to make my own tool by filing away on a small allen wrench until it worked more or less, but it was still a hassle to use.  I seem to recall a post from someone last year I think that did identify the tool size and mfgr., but I can't remember for certain.  If you got a PTO with the slotted screws on the ring, you are lucky... some were made that way.  Anyway maybe search the posts last couple of years for the topic.

----- Original Message -----
From: Flowertime01 at wmconnect.com
Date: Tuesday, April 5, 2005 11:08 pm
Subject: Re: [R-390] PTO Tenny Bolts and war strories

> Seen a dozen examples of how to adjust the linearity ring, none 
> tell the 
> wrench size
> for that tiny screw that I've been able to find. Most likely I 
> missed that 
> part of the instructions.
> 
> Best 73
> 
> Tom NU4G
> 
> _______________________
> 
> Tom, this is another one of the do it your self tool making 
> adventures.A small slot in the end of a shaft. 
> 
> -------------------------
> Personally, I think that inserting any metallic object into the 
> innards of 
> the PTO may possibly upset the reactance of the circuit.  73,Glen 
> Galati, KA7BOJ
> 
> Glen, the PTO assembly has a transformer on it. The can has an 
> adjustable 
> slug like the one on the top of the Crystal Osc deck. Some of the 
> models have a 
> round "nut" on the shaft with two flats. You need a slotted tool 
> to fit the 
> flats, or you turn the shaft with a pair of pliers. A good home 
> made slotted tool 
> is better. So you are not really going into the PTO to do an 
> adjustment. 
> 
> Strange but some times running the PTO for maximum signal will not 
> give the 
> best signal to noise. Mostly some where in the alignment process, 
> you peaked 
> the PTO transformer for maximum signal through the receiver. 
> Usually some where 
> above 8 MHz so the first mixer was not in the signal path mix. Do 
> it this way 
> until you have a week or so and want to play with your receiver. 
> You can then 
> try varying the coil adjustments and checking the signal to noise. 
> Tweak and 
> measure and tweak and measure and find the real good settings.
> 
> -----------------------------------------------------
> I don't have any B+ on the output cables of any of the 390's I 
> currently have 
> on the bench.
> 
> Once upon a time in Nam I had an R390 on the bench. I though I had 
> an adapter 
> cube from an AN/URM 25 that had a cap inside it. It in fact had 
> been rewired 
> straight through as a barrel connector. I did not know this and it 
> was the 
> only reason I was not shot. Plugged that critter in between the 
> receiver and the 
> only frequency counter in the whole shop. Smoked the front end 
> resistors out 
> of the frequency counter. It was dead lined for almost 60 days 
> until the parts 
> come in. That shop had no counter and there were 200 plus 33's 
> that knew just 
> who it was that killed the important item of test equipment. We 
> ran the PTO 
> cabled up in circuit with a Tee and cap. We had no idea how the 
> load changed and 
> just did it that way. It was so much nicer to use the frequency 
> counter and 
> not count cycles on the oscilloscope display. Sorry I do not have 
> an R390 
> schematic to detail the exact reason the frequency counter will go 
> up in smoke if 
> not isolated. But I sure as hell barely lived through one 
> experience with an 
> R390 PTO that did smoke a frequency counter.
> 
> Roger. KC6TRU
> 
>    
> 
> 
> 
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