ZX21: CERAMIC RESONATOR

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
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fordp2002
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ZX21: CERAMIC RESONATOR

Post by fordp2002 »

I am puzzled as to how the ceramic resonator is wired on the ZX81?

It seems to only show two terminals but the device has three terminals?
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Lardo Boffin
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Re: ZX21: CERAMIC RESONATOR

Post by Lardo Boffin »

The middle pins goes to ground by the looks of it:
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fordp2002
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Re: ZX21: CERAMIC RESONATOR

Post by fordp2002 »

Lardo Boffin wrote: Thu Nov 26, 2020 3:26 pm The middle pins goes to ground by the looks of it:
Thanks.

The bottom is OK to trace but the top is hard due to the silk screen and my dodgy eyes!
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Re: ZX21: CERAMIC RESONATOR

Post by Lardo Boffin »

From the top from a photo I took of a zeddy I desoldered and rebuilt:

BB306DA0-EAAC-4ED8-86D6-EF663BF5C5D7.jpeg

Hopefully I counted the ULA pins numbers correctly.

Pretty sure looking at it the top pin is not connected. It looks like it in the photo but I think that is just a scratch.
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ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
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Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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1024MAK
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Re: ZX21: CERAMIC RESONATOR

Post by 1024MAK »

fordp2002 wrote: Thu Nov 26, 2020 11:06 am I am puzzled as to how the ceramic resonator is wired on the ZX81?

It seems to only show two terminals but the device has three terminals?
The middle (centre) pin is connected to 0V/GND, one of the outer pins connects to C6, the other outer pin is not connected to anything.

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fordp2002
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Re: ZX21: CERAMIC RESONATOR

Post by fordp2002 »

Thanks for your help. That's what I thought but it still looks wrong to me!

Is there a known part code for the resonator? I think that will be the hardest to source new (after the ULA but we know they do not sinclair ULAs).
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Re: ZX21: CERAMIC RESONATOR

Post by Lardo Boffin »

Good luck with the resonators. When I rebuilt a zeddy from scratch (viewtopic.php?p=27533#p27533) I had endless fun with them.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
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TS 1500 & 2000
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Spectrum 48ks plus a DIVMMC future and SPECTRA
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1024MAK
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Re: ZX21: CERAMIC RESONATOR

Post by 1024MAK »

They are actually normally used as part of a filter circuit in, for example, analogue televisions. Hence are rather hard to find these days.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
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fordp2002
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Re: ZX21: CERAMIC RESONATOR

Post by fordp2002 »

FordP (Simon Ellwood)
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Re: ZX21: CERAMIC RESONATOR

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