Anyone good with Timer/Control Logic?

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Hello all,

I have here a DAT deck from 87, which can fully play/record via multi-bit converters but with one minor hick-up, a timer.
Hopefully with some advice and reference to the datasheet below it can be suppressed?

CXP5058 pdf, CXP5058 description, CXP5058 datasheets, CXP5058 view ::: ALLDATASHEET :::

Short Version:
Essentially this timer prevents it to work continuously in record-pause mode, which is the only mode it can record/play - without tape.
Timer puts the main control IC into STOP mode, (from rec-pause mode) so I have to re-press REC to get the ADDA functions again, every ten minutes.

Long Version:
DAT decks have two intermediate stages to record, the first is record-pause mode (standby), once pause is released it enters record-play mode (write).

When record-pause mode is activated, the head begins to spin beside the tape thats already loaded (DAT uses a rotary drum).
In this mode for long enough, the tape would disintegrate (EDIT: Or so I thought) therefor SONY added a timer to STOP spin after 10mins.
Its a fully functional ADDA via SPDIF in this mode otherwise.

A brief eureka moment with a dummy tape, initially a work-around the inevitable tape length problem by informing logic 'tape present', was shortly countered when this timer made itself apparent. :smash:

Anyway, with a tape loaded, dummy or normal, this timer cut's out every 10min.
Releasing pause to enter write mode isn't an option; missing tape in the dummy messes with the servo's.
Normal tape can be used but operation limited to 120mins.

Full schematics are available, but the timer and modes are contained inside this IC (datasheet above).
The rec-pause/play buttons link directly to this IC and so is the best shot... (albeit a long one).

Any Ideas?
 
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Instead of feeding an S/PDIF signal to it, can you feed I2S? If YES, why not go straight between 7220 and 1541 with I2S? This section of the recorder should always stay on (it may be affected by the 10min timer, via muting circuit, but that can be fixed quite easily). This solution would give you the best possible sound as well; furthermore, you can disconnect all other sections - including the drum with heads, further reducing negative impact of these unneeded sections on sound quality.

Fooling the logic is quite cumbersome; it can be done though, but would provide inferior results sound-wise, to what I suggested above.


Nick
 
Thanks for the advice. I considered alternative i2s interface but the level meter would be redundant then, the main reason to keep it, mainly for demonstration/education purposes.

the tape floats on a cushion of air and does not touch the drum. The timer is there to protect the mechanism from failure.

So the spinning is to produce air? that is rather neat! But then how does the timer relate and/or prevents damage if it's designed to spin for hours in normal operation in Write record-play mode anyway? In record-pause mode only the drum is active so what does the timer prevent if it's not 'headwear'?

If it's not possible to bypass I'd sell it though it's a retro bit of gear, over-engineered in all aspects, multi-bit conversion back to front, muse caps heavyweight mechanism, copper chassis, lot's of adjustment pots etc. Would be sad to see it go...

FYI: The dummy tape was as easy as prying two 'plastic mirrors' 2mm small, situated just under the lip of the DAT tape. If you look carefully, there's on one on each side, poke them with a pointed device, to pop them out. Their purpose is too reflect light emitted from inside the drawer compartment back into a sensor, also in the compartment. When I cut the tape to 'extend' recording time the 2mm mirrors aren't blocked so inform logic 'tape not present', which disallows the next stage (record pause).
 
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Besides the 555 timer, would coupling the SPDIF signal to the REC button be feasible?

For instance, when I play signal from PC (or USB to i2S as already suggested), I could use part of this signal to re-trigger the REC button on. Because SPDIF flickers, is there some sort of component that can be used to converter the flickering to simulate me pressing REC?

Another incentive to do it this way is to work-around another problem which is I also have to re-press REC for sample rate changes.
 
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