[Boatanchors] more sp-600 questions

[James A. (Andy) Moorer]

----- Original Message ----- 

> 1: The various military manuals refer to a serial number for parts 
> identification as well as troubleshooting.
> The question is to which serial number does it refer. My radio has two 
> serial numbers. One is on the badge
> plate on the front panel which says it is a r-542/frr sn 390.Doing a 
> little detective work revealed that it
> really is a r 274c/frr.
> The plate on tuning unit assembly cover states that it is a jx-14 sn 7703.
> Which one do I use?

It depends on what you are doing with it. If you are using TM11-851, you 
will need to use the one on the badge plate on the front panel. That is the 
Signal Corps serial number. If you are using the Hammarlund manuals (Issue-1 
through Issue-7, plus a special one for the JX-17), then you will need to 
refer to the serial number on the tuning unit cover. If you are using the 
Air Force manuals, your guess is as good as mine.

> 2: T3 (if transformer, crystal filter) has a piece of masking tape on it 
> bearing the words 456 xtal (sic)
> installed. The rest of the sub assembly seems to be original. Does anyone 
> know why this xtal was changed
> from 455kc? I do assume that this (value) was done with a purpose in mind, 
> rather than that value was
> on sale at the local electronics store that day.

The units were never delivered with anything but a 455 kHz crystal there. If 
somebody stuck something else in there, it is probably because they didn't 
have a 455 kHz one. Also, don't believe anything that is written on a piece 
of masking tape in a receiver without checking it. I wouldn't be surprised 
if the crystal wasn't really 455 kHz.

James A. (Andy) Moorer
www.jamminpower.com