[R-390] PTO problem, part II

[Norman Ryan]

Tisha's mention of "stuck-on heaters" reminds me that it is a good idea to disconnect the heater wires permanently while one has the PTO open.  There have been instances where the PTO heater's thermostat gets stuck with disastrous results to the innards.

A special foray into the PTO isn't necessary just to disconnect the heater wires;  a simple fix is to remember to keep the Heaters On/Off switch located behind the receiver in the "Off" position.  At normal room temperatures the receiver is exceptionally stable after a thorough warm-up.

Check behind the receiver and see where the heater switch is set and try operating with it "Off" if it isn't already;  the difference likely will not be perceptible in most instances.

If you operate with the heaters off, change the main 3 amp fuse to a 2 amp fuse for maximum protection of the B+ circuits.

73 de Norman, KG4SWM




>________________________________
> From: Tisha Hayes <tisha.hayes at gmail.com>
>To: R390A <r-390 at mailman.qth.net> 
>Sent: Thursday, July 11, 2013 12:11 PM
>Subject: Re: [R-390] PTO problem, part II
> 
>
>Since it appears there is some sort of internal binding you may want to buy
>a spare PTO and put it in service. They are not unavailable; even on eBay
>you can get one for $30-$80. Then you will feel less hesitant about opening
>up the funky one you have to see what is binding.
>
>You can probably fix it but it is going to be a "learning experience" and
>may be like the wire reattachment saga on the mechanical filters a few
>weeks ago. If you could not get replacement parts (all of the spare PTO's
>in the world suddenly vanished) then you could go to heroic lengths after
>you taught yourself to be a machinist and metallurgist.
>
>If they had been "cooked" by stuck-on heaters or turned way past their end
>limits you can have a bent shaft, stipped parts or a melted plastic piece
>(if you saw the inside it would be immediately obvious)
>
>I would rather listen to the radio than to spend weeks working on one item
>where I have spares. The PTO would become a rainy day project but the
>problem would not keep me from having the receiver on the air.
>
>That is just my personal opinion, YMMV (your mileage may vary) but I am
>being a bit pragmatic about it.
>
>-- 
>Ms. Tisha Hayes/ AA4HA
>
>"Objective considerations of contemporary phenomena compel the conclusion
>that success or failure in competitive activities exhibits no tendency to
>be commensurate with innate capacity, but that a considerable element of
>the unpredictable must invariably be taken into account." -- George Orwell
>______________________________________________________________
>
>