FW: SB-101 Crystal Nightmare!

Sun Aug 27 21:53:39 EDT 2006

--...   ...--Dale - WC7S in Wy

From: daleputnam at hotmail.comTo: kd2e at comcast.netSubject: RE: SB-101 Crystal Nightmare!Date: Sun, 27 Aug 2006 19:52:29 -0600

I have experienced similar situations with the xtal controlled motorola equipment, when it was new, and when aged a while... like within the last few years. All I could ever come up with was that the extra or stray additional capacitance to the circuit was effective in making the circuit work, however more capacitance usually would make it more critical in some manner to adjust. Seen this in VHF, UHF, 50 mc stuff, and even some cb sets. Stands to logic that the Heathkit equipment would do it too. Simply put, the particular xtal in hand... has a personality conflict with the circuit in the bush.  There are various ways to look at the problem, but with it somewhat within the range of operation, it may be best to leave it alone, for the time being. Some of the circuits, have been completely rebuilt, replaced everything, one piece at a time to find the one in error. That didn't work. Never found the problem, found that with a different xtal, it would. New parts or not. Not necessarily a new xtal, just a different one. If a circuit was failing with two of the same xtals, I could usually find a part that had changed value, it may or may not be a part close, maybe one on the other side of the active osc element. Or maybe a combination of two or three parts changed a bit. One one way to the end of its tolerence, the other the other way.   Good Luck with it,--...   ...--Dale - WC7S in Wy

> Date: Sun, 27 Aug 2006 10:08:14 -0400> From: kd2e at COMCAST.NET > ----- 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> > -----------------------------------------------------------> Products bought, sold or traded here is the responsibility of the> parties involved.  This list and the City of Tempe are not responsible> for losses or misrepresentations of any kind.  Buyer beware!> > -----------------------------------------------------------> This list is a public service of the City of Tempe, Arizona> -----------------------------------------------------------> > Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH> To post - HEATH at LISTSERV.TEMPE.GOV> Archives - http://listserv.tempe.gov/archives/HEATH.html > > -----------------------------------------------------------> Products bought, sold or traded here is the responsibility of the> parties involved.  This list and the City of Tempe are not responsible> for losses or misrepresentations of any kind.  Buyer beware!> > -----------------------------------------------------------> This list is a public service of the City of Tempe, Arizona> -----------------------------------------------------------> > Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH> To post - HEATH at LISTSERV.TEMPE.GOV> Archives - http://listserv.tempe.gov/archives/HEATH.html

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