My first digidash fix. (FIGJAM!)

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IZU069
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My first digidash fix. (FIGJAM!)

Post by IZU069 » Mon Aug 05, 2013 11:20 pm

Not only my first digidash fix, but also one of my first thread starts (in any forum LOL).


In short, I was contacted by a new owner with a flashing digidash. He had done his research and concluded it was a dry solder joint (and not gunk under the PSU board etc).

He brought over the disassembled digidash and I agreed with his evaluation. I said how usually I'd expect to see swollen or blown electrolytic caps and that diode were also prone to failure in old electronics, but all looked fine apart from a lifted plastic surround on one of the electrolytic caps.
But upon resoldering the few sus joints I saw that the lifted plastic was in fact a blown cap, so he left it with me. He also left an IMO an unnecessary and certainly excessive number of orange Australian currency notes. (With another 450 such notes I'd be out of debt.)

I replaced all electrolytic caps (10 of) with quality low ESR types of either higher voltage rating or size (uF) or both (so that they filled the same footprint/diameter) except for the 3 smaller 50V 4.7uF which were replaced by the same but "low leakage" types. All caps were 105°C rated as were the originals.

I also found a diode with one end missing and determined it was a 15V Zener. I replaced it and an adjacent diode with new 15V Zeners. (Maybe these should have been 16V Zeners, but they are for over-voltage protection and whether 15V or 16V probably is not critical. However I'll determine the correct size before my next repair.)


A phone call about an hour ago gave the very pleasing "it works" news.
It's been taken for a test drive and the full dash is working properly. YAY!


This was a straightforward fix except for track damage on the diode's damaged end, and the need to properly desolder the old components to leave nice clean holes for easy insertion of the new parts. But we both marveled over the cleanliness of his PCBs, and the beautiful design of the digidash.
But spurred by this repair, I may open up to others seeking digidash repairs.


FYI...
During this repair I removed the PSU PCB from a previously repaired (butchered) digidash donated by RodeoBob (THANKS Bob!). I also removed all its vacuum-fluorescent displays for a look at the components underneath and was surprised to find a 54 pin SMD chip (Yazaki 6616) - I didn't think they existed back then, but originally I was thinking it was the same as the original 1980 digidash but they would have been for the G200W etc and different to the 1986 turbo 4ZC1-t etc.

I also determined that like other visible chips in the digidash there is no web data for many of them.
But also that my digidash stage 2 proposal would require an entirely new display PCB. (Stage 2 was a complete replacement of "intelligent guts" with a uPC. Stage 3 was then an enhancement of the stage 2 "standard OEM" programming to provide other info and alarms and probably interfacing to PCs etc for user configs or modifications.)

I still reckon a complete PSU replacement (stage 1) should be possible though I have yet to determine the voltages and currents required.

Whether Stage x ever happens depends on demand. Enough basic repairs or PSU faults may realise Stage 1, but also spur or fund Stage 2 etc. I see Stage 2 etc as a love job due to the dozens or hundreds of hours involved (and then PCB production etc), and since I no longer have the need to get my Piazza(s) on the road... (Ego & pride go to other sacrificial projects.)


So, how many want (how many) digidashes repaired?

And hypothetically, if stage 2 was to be realised, should I consider including other peripheral circuits (like the OD computer and similar controls (pod controls, cruise control, anti-theft), maybe climate control, wiper control, or others? Harnesses could be made to interface to existing wiring. Some control might be better left to other replacements (probably using cheap PICAXE devices).
I'd expect the EMS to be separate - namely a Delco upgrade if that were desired. (Though my own EMS with distributorless electronic ignition was once on my drawing board - until the Delco came along, and I told other so-called experts that those things they said could not be done had been in production since 1990 (LOL).)


PS - I expect the new owner to soon join IsuzuPiazza.
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Post by eyecon » Tue Aug 06, 2013 7:45 am

Good stuff izu069. Although I now a 2 or 3 spare digidashes the original one in my car misbehaves intermittently. If/when I get it repaired I'll send it to you.

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Post by IZU069 » Tue Aug 06, 2013 8:57 am

The intermittents are likely to be due to what I covered - like bad caps if flashing, or the odd dry joint for other sub-display losses. They should be easy. PSU transformer or other breakdown intermittents may be more complex, but its transistors should be replaceable, and some transformers could be obtained from real-dead digidashes - but hence my desire for a modern SMPS shipped replacement.

It's faults like the dead voltmeter mine had (my other Piazza has an analog dash) that are probably impossible to fix if it's the main chip - unless the display is removed and chip replaced with another from a dead dash. But knowing that such components will dry up, hence my stage 2 proposal.


But nice knowing you have those spares.
When ready, I may ask for all to send their dead or faulty ones. I can then determine the main cause of failure.
If merely the caps and misc minor issues, I can arrange a bulk buy and fix for a relatively cheap repair.
If PSU faults are common, the PSU replacement will be worthwhile. The "standard repair" might then be a PSU "with less caps" replacement (since PSU replacement is probably a preventative failure measure).
I'll worry about stage 2 when that seems justifiable and I inherit lots of round tuits.


BTW - the parts for the repair I described cost $8.22, but that excludes petrol, silastic and conformal coating spray that I used on both PCBs (trackside only) to harden against moisture & corrosion etc, and of course labour. Oh - and solder and soldering power (LOL). Any good solderer with good desoldering abilities could do the repair. But bad solderers (and unsuitable soldering irons) will make a mess that will take lots of work to repair.


But I'm rapt. I finally realised some old round tuits and a good digidash is on the road with that Piazza remaining OEM - and many would argue a better looking dash than having analog counterparts.

Thanks for the support and feedback eyecon.
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Post by eyecon » Tue Aug 06, 2013 1:49 pm

You da man. IMO its the digidashes that strengthen the Piazzas character, and over time, appeal.

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Post by Ghost » Tue Aug 06, 2013 4:03 pm

Always wanted a DigiDash in mine, but I think if I were to get one now I would make one from scratch, and it would be a digital mechanical hybrid.
Just need to get around to learning some basic programming to control an ARM board and decide what I can actually display on it.
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Post by IZU069 » Wed Aug 07, 2013 10:46 am

These days using a screen is probably the simplest implementation, as well as being infinitely configurable (though only in 2 dimensions LOL). Maybe a few GPS touchscreens etc...
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Post by eyecon » Wed Aug 07, 2013 2:28 pm

Even better an ipad mini or similar sized touchscreen tablet.

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Post by IZU069 » Wed Aug 07, 2013 2:36 pm

Yeah - I thought about including that but considered it implicit (ie, forgot to include and didn't bother to edit).
It's more of a physical size issue as well as overall looks.
But plenty of screen gauges etc have been done though usually as centre consoles. mp3car.com comes to mind.
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Post by eyecon » Wed Aug 07, 2013 6:49 pm

Also have a look at the Toyota LFA. everything on the dash is fancy digital graphic representations of speedo, tacho etc. As soon as I saw it reminded me of a fancy ipad mini screen.

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Post by Ghost » Wed Aug 07, 2013 6:53 pm

Wonder how well a 7" tablet screen will squeeze between the speedo and rev counter.
I should go and measure the one out of my wreck.
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