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Old 25th May 2023, 12:44 am   #21
SiriusHardware
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Default Re: Embedded micro's start up procedure.

The 'idle' state of I2C bus lines (SDA and SCL) is high, so both lines being high would not in and of itself cause a problem.

I think your main issue is the lack of clock oscillator oscillation, we might as well wait and see if the replacement crystal / resonator sorts it out and take it from there.
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Old 12th Jun 2023, 10:46 pm   #22
samjmann
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Default Re: Embedded micro's start up procedure.

Quick update.

Fitting the 6mhz xtal has made no difference. The only slightly wrong voltage is pin 18. This is a mains detect input. The cct description says that if this is missing the micro 'sleeps'...

There is a full wave rectified dc from two two diodes on a double secondary winding on the mains tx. It's then clamped to 5v. The voltage quoted on the manual is 4.7v. I'm getting 3.8v. This just might... be a problem. There is no smoothing on this feed.

Will report back soon!

Thanks again for all the help. SJM.
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Old 20th Jun 2023, 8:48 pm   #23
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Default Re: Embedded micro's start up procedure.

Just to close the thread...

After fitting the resonator, the oscillator still failed to start.
There was one voltage that was slightly low, pin 18 at 3.8v. The diagram quoted 4.7v.

I was then lucky enough to have another identical product to compare with. The pin 18 voltage of the micro was just the same on this unit as well.

All I can conclude is that it must be the micro as on the reference unit the xtal runs all the time the mains is present. I checked the reset also on both, there was no difference.

And of course the part is no longer available from Panasonic as you might expect.

Thanks again to all that replied and gave up their time on research of the part etc.

Regards, SJM.
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Old 20th Jun 2023, 9:42 pm   #24
kalee20
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Default Re: Embedded micro's start up procedure.

Can you tack in an external oscillator to drive the microcontroller's clock pin? Saves dumping a decent tape deck.

Or is it just not worth the trouble!
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Old 20th Jun 2023, 11:24 pm   #25
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Default Re: Embedded micro's start up procedure.

I'm not going to those lengths. This deck has Dolby C and auto bias calibration as well. So it was worth a good try. The thing was both decks are mechanically in good order, both R/P heads showing little wear. Keep looking on ebay or similar for a donor.
SJM.
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