SB-101 Crystal Nightmare!

[Dave Edwards]

Could it be the 'looseness' of your Rube Goldberg arrangement allows the 
xtal some movement...the ever so slight shaking of the holder in 
effect...'kickstarts' the quartz into vibrating????
I dunno, having had dozens and dozens of Heaths over the years it seems the 
goofy problems always show up.
I love them, but there is a reason why I sold my HW101 in 1973 and grabbed a 
TS520!
...Dave.
----- Original Message ----- 
From: "Pat Bunsold" <wa6mhz at COX.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Saturday, August 26, 2006 5:13 PM
Subject: SB-101 Crystal Nightmare!


I had Mike N6IEFs SB-101 almost working!  It received and transmitted great 
on all bands except the 28.0-28.5 segment.  Since that is the most important 
part of 10 meters, I really wanted it to play.  But for some reason, the 
36.895 Mc xtal wouldn't oscillate!  I played with the Het osc coil and 
watched the V19 output with no response.  The Crystal may have been bad!!! 
So I tore one out of a HW-101 in the pile and installed it.  STILL no 
output!!!  Measuring the correct voltage on the coil and seeing proper 
continuity through all the switches and wires, it was a hair tearer!  I 
removed the wire coming from the xtal switch and installed a HC-6 Xtal 
socket from V19 pin 7 to ground.    Plugging in the HW-101 xtal, it now 
worked!! That told me something was fishy about the rotary switch.  But it 
worked fine on all other bands.  I tried the original xtal and no response. 
Unsoldering it open, I found the quartz disk boke in half.  OK, that Xtal 
has had it!  I had read on here that someone openned the xtal and was able 
to mouse around with the disk and make it play again, but today was not  the 
day.  TOUGH to get those open!!  Anyway, I clipleaded the xtal to the socket 
and found with one end connected to the switch contact and the other 
connected to ground, the xtal would oscillate.  But soldering it into the 
board made it stop.  I experimented with different ground locations and 
tried buss wires to run grounds to that xtal pin, but it still wouldn't 
work!!  Something about that Crystal doesn't like being where it should.  I 
soldered on crystal leg to a ground pad on the PCB just below it (carrier 
Oscillator PCA) and ran a wire from the 2nd pin up to the switch.  NOW it 
worked!!! I have no idea why, as ground is ground, and my liberal use of 
additional grounding wires made no difference.  Also, the other 3 xtals in 
that range have no problem!!  What in the world??  I did notice that the 
coil is now very touchy for proper oscillation, while the norm is a very 
broad tuning slope.  But the xtal is oscillating on the proper freq and 10M 
now works, so I closed it up.  Obviously, the Mickey Mouse mounting method 
is not shock protected and very poor installation techniques, but it was the 
only way I could get it to work!  The best I can figure is that this xtal is 
very marginal and it is lucky it oscillates at all!  So I am looking for 
more 36.895 Mc xtals now, one to replace in the HW-101 and one for the 
SB-101.  Also need a 12.395 Mc xtal for 75 Meters also robbed at one time. 
I see these on Ebay now and then, but they command unreasonable and 
outrageous prices.  Anyone have a lead to these without having to order 
factory replacements?  And anyone have an explanation as to why this xtal 
would not oscillate in the PCB yet works  fine outboard??  These radios can 
be tough to fix!
73
Pat
--
Pat Bunsold WA6MHZ
San Diego Section Manager
Curator, Crest Radio Museum

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