Re: {Collins} 651S-1 issue

the optical encoder in the 651S-1 seems to be identical to the one used with the 851S-1 which might be easier to find.

vy 73 Heinz DH2FA, KM5VT

Von meinem iPhone gesendet

> Am 29.10.2017 um 17:14 schrieb Michael Student via Collins <collins@xxxxxxxxxxxxx>:
> Bob, Take a look at the optical encoder. I’ve had mechanical issues relating to rotation direction and count. It’s a little mechanical marvel that predates off the shelf encoders and this may be your issue , the rest is up to you. 
> 73, Mike
> Sent from Mail for Windows 10
> From: Robert Nickels via Collins
> Sent: Saturday, October 28, 2017 7:04 PM
> To: Collins
> Subject: {Collins} 651S-1 issue
> My 651S-1 (S/N 2308, red LED display) has an odd tuning problem and I 
> thought I'd see if this might by chance sound familiar to anyone.    The 
> 10 Mhz, 1Mhz, 100Khz, and 10Khz tuning steps work as expected, but when 
> you tune in 100Hz steps using the main tuning dial, there is an odd jump 
> in frequency.   For example:
> Display       Actual
> 8000.0     8000.0
> 8000.1     8000.1
> 8000.2     8000.2
> 8000.3     8000.3
> 8000.4     8040.0
> 8000.5     8040.1
> 8000.6     8040.2
> 8000.7     8040.3
> 8000.8     8080.0
> 8000.9     8080.1
> As you continue to tune, the same sequence repeats - I've used 8 Mhz as 
> an example but the same jumps in frequency occur through the tuning 
> range.  Sensitivity and everything else seems normal, in fact you can 
> tune to any desired frequency if you do the math to correct for these 
> weird offsets.    There is clearly a pattern here but I haven't yet been 
> able to correlate what is going on to a particular circuit, other than 
> it seems that bits are being added.
> Since the display shows the correct frequency steps up and down as the 
> encoder changes, that indicates that the correct BCD data is being 
> presented to the synthesizer and suggests a problem somewhere in the 
> A10, A11, A12, or A13 boards.    I've done basic things like re-seating 
> the boards and checking for damaged components but everything looks 
> fine.   Since these boards are full of flat-pack ICs made by Motorola, 
> Raytheon, and Sylvania the chances of doing board-level repair are 
> somewhat daunting.
> So I wonder if there might be any sources for spare boards either to 
> borrow for substitution or to purchase?   Or, if I'm able to identify a 
> particular IC, is there any hope of obtaining something like a Sylvania 
> SM153 frequency divider IC?
> Thanks and 73,
> Bob W9RAN
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