[time-nuts] Z3816 Oscillator Saga

Chris syseng.greenfield at btconnect.com
Fri May 2 11:51:14 UTC 2014

On 05/01/14 08:51, Peter Schmelcher wrote:
> Chris,
> This hi res pic might help you. I modified my Z3816A to improve the
> performance. I changed the grounding and added a few extra capacitors.
> This pic is close to the start so very few changes.
> -Peter


Thanks very much for sending that. The damage is in fact to the underside
of the board, not the top side. I was using a solder sucker to remove the
solder around each oscillator pin, which was then free enough of solder
to use pliers to wiggle each lead side to side to free up. Unfortunately,
the pliers slipped and sheared off ~3 parts from the underside of the 
It's not clear if all the parts are resistors or caps, though one is a cap
for sure. It's too much to expect you to strip your board out just to send a
pic, but if you ever have to do that, a jpg would be appreciated. It's 
difficult to find info on these units, and haven't been able to find a 
It's not clear what all the pins of the header are for, though some may 
be to flash
the cpu with firmware. There may also be added factory commands for 
things like
replacing the oscillator, though one would expect that to be an auto 
within the firmware. The fact that the efc always returns to the most 
recent value
at power up and not do a sweep through the whole range might suggest 
this is not
the case.

Anyway, powered up the original 260-0558 oscillator on the bench today, with
a helipot of the efc input and get the following:

EFC	Frequency, MHz
0v	5.000 003 54
1v	5,000 002 59
2v	5.000 001 57
3v	5.000 000 55
4v	4.999 999 53
5v	4.999 998 51
6v	4.999 997 35

Voltage for exactly 5Mhz output = 3.5413v

So the oscillator looks good and the fact that the Z3816 doesn't lock 
with that in
place suggests that some of those damaged parts are needed :-(.

Have another of Ebay fluke seller's MTI 260-0664 ordered. The original 
is in the
Z3816 and don't want to take it out again until i'm sure that it's 
necessary. At
~$18 each, it good to have a spare and will characterise that on arrival 
to see what
the differences are between that and the 260-0558. Knowing my luck, 
probably find
the efc is the opposite sign, or negative, but time will tell.

Have posted this to the list as well, in case the info is useful...



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