SL1200 at 78rpm

Love it or hate it, it just won't stop
RussellS
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#16

Post by RussellS »

t-m

Is there nothing on the 'net that shows the schematic?

Thanks for the update. Hang in there...
I either do, or I don't. There is no 'try'.
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t-m
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#17

Post by t-m »

I really mean data sheet for the AN6680 :) ... but no I can't find one.

It could still be the crystals as the ones I have were very cheap. I've some different ones on order so will try them when they arrive.
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Dave Cawley
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#18

Post by Dave Cawley »

No guesswork is needed. It's a standard gate oscillator.

What was the specification of the crystal you used ?

Dave
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t-m
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#19

Post by t-m »

It was a 9.8304 Mhz HC49/4 crystal, can't find the load capacitance, but i'd think 20pF
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Dave Cawley
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#20

Post by Dave Cawley »

Give me a link to where you bought it from ?
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t-m
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#21

Post by t-m »

Like an idiot I bought them cheap from eBay and looking back at it there were no other specs given.

I'd expect they're like these though, but I can't guarantee the specs unfortunately.

http://uk.farnell.com/jsp/search/produc ... id=2063993
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Dave Cawley
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#22

Post by Dave Cawley »

The Farnell one should be just fine.

Dave
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t-m
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#23

Post by t-m »

Thanks! I'll give that a try in place of unknown random ones
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t-m
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#24

Post by t-m »

Just to update, I tried those crystals and one with a different load capacitance. In my SL1200mkII at least they unfortunately do not work.
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Dave Cawley
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#25

Post by Dave Cawley »

I think that's because it is series and not parallel resonant ?

Dave
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John Caswell
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#26 16 2/3 rpm

Post by John Caswell »

TD125????

John
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t-m
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#27

Post by t-m »

Dave Cawley wrote:I think that's because it is series and not parallel resonant ?

Dave
I think these should've be ok in parallel, I can only assume the Load Capacitance is wrong, although i've tried 20 and 30pF crystals.
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Dave Cawley
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#28

Post by Dave Cawley »

I'm not convinced. You often can't substitute crystals of different types. Maybe remove R222 ?

However it's a standard gate oscillator, what did you measure on the input and output ? DC and waveform ?

Regards

Dave
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t-m
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#29

Post by t-m »

I checked the sheet again, definitely the right type. I didn't try removing R222 but I tried halving its value but no difference. I measured it at pin 4 of the AN6680 and there was no waveform just stuck high (correct waveform with the original crystal).
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Dave Cawley
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#30

Post by Dave Cawley »

The data sheet didn't specify parallel resonance. The output should not be hard high regardless. I would re-visit this ?

Dave
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