[R-390] School House bugs

[Craig Heaton]

Not so young any more, Roger. If the Amelco was 100%, I'd have nothing to
do! The only thing not original on this infested beast was a 12BY7 in place
of the current regulator tube RT510, the tube socket was rewired also. It
was clean (spot less) inside & out. Original tubes, all the BBOD's were
there, old electrolytic caps, front panel had no rack rash, no wear on the
knobs.  

 

Swapping modules from a 100% Motorola didn't cure the loud audio. Could be a
wire harness issue in the Amelco? But I've rung out the wiring dozens of
times. I think I have plenty of time here on the 3rd rock from the sun in
order to play radio some more....

 

Comparing the two; Motorola vs. Amelco, the Motorola wins hands down as to
better components & detail to assembly. As things stand today, both have the
same sensitivity and the Amelco is now stable. One thing to note: R104 &
R105 per the schematic are 2.5K pots in parallel. Measure across the ends of
either pot and one should see a resistance of 1.25K and somewhere in the Y2K
manual the 1.25K value pops up in support of ohms law. The Motorola measures
a tad above 1.5K which leads one to believe those pots are around 3K each.
No problem there considering 20% tolerance of the mil spec pots and my VOM's
don't have a fancy sticker traceable to NIST. I'll place money that Motorola
picked the 20% high side of 2.5K and built a better receiver. 

 

Craig,

 

From: Roger Ruszkowski [mailto:flowertime01 at wmconnect.com] 
Sent: Monday, July 21, 2014 10:53 AM
To: r-390 at mailman.qth.net; hamfish at efn.org
Subject: Re: [R-390] School House bugs

 

Craig,

 

A most unbelievable state for a receiver.

 

The theory always was, It was working fine yesterday.

Now it does not work.

There is one and only one thing wrong with it at this time.

Find the problem and fix it.

 

Things in the school house were in awesome good shape.

This is how it looks in the field and this I show we expect you to keep it
looking

young man do you under stand me?

 

Happy to hear you are getting the problems fixed and the receiver restored.

 

Roger.