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Old 9th Sep 2023, 6:04 pm   #1
__i4cy__
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Default AY-5-1202A clock IC (continued)

3½ years on and this 70s clock kit is finally working again.

I couldn’t find a single AY-5-1202A new or old. Donberg no longer stocks this part. After coming across a newer GI datasheet revealed there is also a AY-5-1200A part, not mentioned in the original datasheet. Although rare, this part still can be found, and is a drop in replacement for the AY-5-1202A, except that the display colon will not blink every second.

After fitting the new AY-5-1200A chip the clock instantly burst into life, confirming my original suspicion that the old chip had failed.

I have also added a MOV, Zener and decoupling capacitor for mains spike suppression purposes – hopefully preventing this IC meeting its sibling in silicon heaven.
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Old 9th Sep 2023, 7:36 pm   #2
turretslug
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Default Re: AY-5-1202A clock IC (continued)

It's lovely when something works out like that isn't it! I'm something of a VFD fan, lovely crisp, clear characters, not to mention one of the last outposts of thermionics.

For longer than I care to remember, I've had a Pioneer DT-510 VFD component timer as the bedside clock, about 15 years ago it developed a peculiar fault where ISTR it skipped odd minutes beyond the 50th minute of the hour, I reasoned that only the main IC was clever enough to do this (not much else in the circuit!) and ordered a new MN6076 from eBay China for about a tenner delivered, accepting that I might just get a plastic blank devoid of silicon.... Nope, all was fine and dandy and it functions nicely to this day. Likewise, it got an MOV after a supplementary 100mA fuse (several ohms) before the mains transformer, there was a bypassed fuse holder inside already- maybe only certain markets? I did fit a dimmer control to the VFD grid, as standard it was fiercely bright, not helpful to either sleep or display longevity.
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Old 9th Sep 2023, 7:46 pm   #3
Lloyd 1985
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Default Re: AY-5-1202A clock IC (continued)

Very nice!

I rescued the VFD clock from one of our old ovens many years ago, kept it in the workshop displaying the time, sadly it got dropped and it broke the evacuation pip off the back of the display, I was quite upset about that! I did buy some VFD’s from Maplin before they closed down, but they were smaller than the original display, they did work though! I’d love to get a replacement display for it, but many searches later and one still hasn’t turned up.

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Lloyd
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Old 9th Sep 2023, 9:27 pm   #4
60 oldjohn
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Default Re: AY-5-1202A clock IC (continued)

I made the Easy Build Digital clock in the September 1975 PW using the AY5-1224. This was for a LED display. I wonder if there are any similarities in the chip? BTW its still in use and as good as ever.

John.
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Old 9th Sep 2023, 9:45 pm   #5
__i4cy__
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Default Re: AY-5-1202A clock IC (continued)

I forgot to mention that the original post (now closed) is at...
https://www.vintage-radio.net/forum/...d.php?t=163497

Also the clock kit advert from WW May 1976 that I got for Christmas later that year as a kid...
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