Vintage Synth Repair

Hello all:


I've isolated a dead crystal in a ksp8 effects unit that drives the 44.1 kHz master clock.  It's a 22.5792 MHz part in a surface mount HC-49 package with part number A225J1T. I think it's 50 ppm accuracy, but I don't know what the load capacitor requirement is other than knowing the value of the caps on the board.


I'm trying to get one from the manufacturer but if that doesn't pan out, should any 22.5792 MHz unit work? Don't know much about crystals...


Thanks -


Scott in Ohio

A&MS should have it in the US.  It was in the part stock sent from YCNA to them. The part was also used in the K2600 If not, you can get from other sources.  Sometimes Kurz. engineer Hal Chamberlin would "tweaked" the clock circuit to eliminate clock harmonics to meet FCC guide lines by reducing the bandpass so that only the fundamental frequency. ie a clean sine wave came out; no overtones.


You should see a sine wave typically more than 4 Volts peak to peak out of the clock circuit to avoid any timing errors.


Are you sure you are not looking at the master MPU clock that has a frequency like 22.1 Kilo Hz?  That frequency is scaled up in the Megs.










On Tuesday, June 3, 2014 3:14 PM, "'65 Lotus' Lotus@... [vintagesynthrepair]" <vintagesynthrepair@yahoogroups.com> wrote:



>
>
> 
>
>Hello all:
> 
>I've isolated a dead crystal in a ksp8 effects unit
that drives the 44.1 kHz master clock.  It's a 22.5792 MHz part in a
surface mount HC-49 package with part number A225J1T. I think it's 50
ppm accuracy, but I don't know what the load capacitor requirement is other than
knowing the value of the caps on the board.
> 
>I'm trying to get one from the manufacturer but if
that doesn't pan out, should any 22.5792 MHz unit work? Don't know much
about crystals...

> 
>Thanks -
> 
>Scott in Ohio
>
>
>

Hi Scott,


A typical proccessor crystal will have 20 to 50pF of load capacitance. If there is a capacitor from each uP pin to ground, these are assumed to be in series to give the load capacitance value.  Any crystal that you can get will probably work. If you have a problem with it not starting, it may be the load caps. Let me know the required load on the new crystal, and I'll send some capacitors over (assuming you are OK with SMT soldering).
The 50ppm number is the "make accuracy" of the crystal in part per million, for our purposes 50ppm will be fine. From your comments it is a surface mount PCB, so probably no markings on the capacitors :o(.
Have a look at Digikey and Newark, to see if they do the frequency, I know they do lots in the HC49 smt package.


Best of luck


Cheers


Paul


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