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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 28th Mar 2023, 11:03 pm   #1
Sparky67
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Default NEC Storage Device FZ0H4732

Hi all,

Does anyone recognise the NEC FZ0H4732 used as a storage device to back up memory from the 1980s, and can explain what it actually is please?

Difficult to tell, FZOH4732 is also a possibility.

Thanks

Martin
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Old 28th Mar 2023, 11:30 pm   #2
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Default Re: NEC Storage Device FZ0H4732

What's it look like?

I found an NEC "thingie" that turned out to be a bubble memory cartridge.

There's a photo of one on that twitter thing.

I won't link to it in case it violate one or more of the inscrutable rules.
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Old 29th Mar 2023, 8:52 am   #3
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Default Re: NEC Storage Device FZ0H4732

I have only spotted it on a cct so far, havenít opened up the unit to see what is there. Google didnít find a link to the ref number, hence the question.

It appears to supply a back-up voltage if the normal powered rail fails. Just concerned there could be a NiCd device in there which, after 30 years, might decide to leakÖ I will get the screwdrivers out this evening.

Martin
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Old 29th Mar 2023, 3:31 pm   #4
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Default Re: NEC Storage Device FZ0H4732

Can you post the section of the cct? It might help to identify it.
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Old 29th Mar 2023, 8:00 pm   #5
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Default Re: NEC Storage Device FZ0H4732

Here is that section of the processor and memory board...
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Old 29th Mar 2023, 8:33 pm   #6
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Default Re: NEC Storage Device FZ0H4732

Looks like a NiCd, I see a trickle charge resistor & isolating diodes... and 30 years ago preceeds a supercap which you'd see in a modern equivalent, although more likely a DS1210 or similar with a lithium cell.
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Old 29th Mar 2023, 8:39 pm   #7
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Default Re: NEC Storage Device FZ0H4732

Looks like its going to be a super cap or rechargable battery, just to provide back up power to the memory. Better check the physical condition as they are infamous for leaking nasty chemicals and destroying circuit boards.
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Old 29th Mar 2023, 8:46 pm   #8
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Default Re: NEC Storage Device FZ0H4732

Most likely FZOH473Z
Supercap 0.047uF 5V
Brief details page 90 of this pdf:-
http://bitsavers.trailing-edge.com/c...tion_Guide.pdf
Advert:-
https://worldradiohistory.com/hd2/ID...-Page-0038.pdf
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Old 29th Mar 2023, 10:03 pm   #9
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Default Re: NEC Storage Device FZ0H4732

Thanks George. Well spotted! The parts list is less legible than the circuit, so apologies for the incorrect reference. That's put my mind at rest regarding potential leakage.
Think it's 0.047F rather than uF though...!
Cheers,
Martin
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Old 29th Mar 2023, 10:20 pm   #10
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Default Re: NEC Storage Device FZ0H4732

Oops - habit strikes again...
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Old 30th Mar 2023, 12:49 am   #11
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Default Re: NEC Storage Device FZ0H4732

Quote:
That's put my mind at rest regarding potential leakage.
Actually supercaps are also equally notorious for leaking and causing damage, as I think Mark1960 meant to infer. One well known example is the supercap in original Xboxes, which leaks either electrolyte or corrosive gas and can cause a lot of damage.

PCB mounted Nicads are also well known for silently destroying their hosts, two examples are the Acorn Archimedes and Amiga 500 with added 0.5MB memory module, in which there is a realtime clock with a battery...

I have a Z80 microprocessor PCB which was in excellent condition and working order when I put it away for a few years, when I got it out again all of the IC pins within 2cm-3cm of the onboard Nicad memory backup battery were an evil looking green colour and when I tried to blow off the residue from the top side of the PCB, all of the screen printed legends in that region just drifted away like confetti.

If I find a PCB mounted supercap or Nicad or NiMH battery in anything now, I remove it from the PCB and wire flying leads to the pads originally occupied by the Supercap or battery, and mount the replacement supercap or battery well offboard in a sealed container.
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Old 30th Mar 2023, 1:03 am   #12
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Default Re: NEC Storage Device FZ0H4732

Hopefully then Supercapacitors won't leak, as they claim they don't in that advert from 1985 (so it seems these have been around for > 30yrs - I first used one around 23yrs ago, debating whether to use a rechargeable lithium coin cell, and recall Maplin selling 1F ones quite a few years before that in the 90's).

Although I'm not sure how long Supercapacitors actually last - A Panasonic HDD recorder I had seemed to have these, but it's now lucky to get >1hr backup of Time without mains-power. And we found some Ultracapacitors (Much lower ESR, than the typically 100R of Supercaps, for providing surge-currents, had quite a short shelf-life - Possibly due to a manufacturing / design fault).

Maybe a Ramtron (Now Infineon) FRAM is a better solution for just RAM backup, with no battery or limited-storage capacitor, providing 10's of years memory backup and often available for less than potted-up NVRAM's with internal battery.
However, if you need to run an RTC as well, then still need a backup voltage supply to run it.
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Old 30th Mar 2023, 9:10 am   #13
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Default Re: NEC Storage Device FZ0H4732

Quote:
Hopefully then Supercapacitors won't leak
Not my experience, unfortunately.
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Old 30th Mar 2023, 10:39 am   #14
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Default Re: NEC Storage Device FZ0H4732

Quote:
Originally Posted by SiriusHardware View Post
Quote:
That's put my mind at rest regarding potential leakage.
If I find a PCB mounted supercap or Nicad or NiMH battery in anything now, I remove it from the PCB and wire flying leads to the pads originally occupied by the Supercap or battery, and mount the replacement supercap or battery well offboard in a sealed container.
I did that with a Compaq Portable III.

Sadly my sealed container wasn't up to much & it ended up toast.

Ho hum.
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Old 30th Mar 2023, 11:39 pm   #15
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Default Re: NEC Storage Device FZ0H4732

Quote:
Originally Posted by SiriusHardware View Post
Quote:
Hopefully then Supercapacitors won't leak
Not my experience, unfortunately.
Well I suppose they are just Electrolytics (even if 'Double Layer'), which have apparently been known to leak and cause PCB damage - especially early SMD ones, that virtually all failed in around a year, when they first started using these in camcorders etc.
But I seem to have been luckily with Electrolytics, never finding one that has leaked and damaged a PCB - Although I've seen a few that have exploded their contents inside equipment (mainly due to someone reversing the 12V supply!)
And many in SMPSU's that have bulged a lot around the vent, after they've got rather too warm due to ESR going high over time. So always try and use at least 105degC rated types, with as long a lifetime at that as possible / fit higher-voltage ones with more margin / bend away from heat-sources, within the space available.

Whilst I've not seen the white powder that comes out of some NiCad batteries damage battery contents, it does (or venting gas?) rather attack PCB tracks, turning copper blank and causing solder-resist to flake off (probably occurs first, exposing the copper). And can be difficult to get solder to stick to the remains of the copper, to try and restore the tracks.
I've not seen NiMH PCB-Mount backup batteries used enough, to see if these are any worse. Although I've jet to see AA ones leaks (Only AA NiCads I saw leak white powder, was after they'd been directly-soldered to ends, without using proper spot-welded tagging, so may have damaged their safety-vent.

On Acorn BBC Master computers, it seems they forgot to put a diode on the main board to stop main supply trying to charge the original Lithium battery mounted next to keyboard, causing them to explode! So they replaced this with an external 3xAA alkaline battery pack, plus put a diode and safety resistor fitted in-line. And this was mounted on a bracket far enough away, for any leaking cells (as most Alkalines these days eventually do) to not cause famage / recommended taking it to a dealer every year! to have the battery pack changed (no doubt at rather a lot of expense...). So most just fitted a standard AA battery holder (hopefully retaining the inline diode lead).
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Old 31st Mar 2023, 11:05 am   #16
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Default Re: NEC Storage Device FZ0H4732

Regarding backup batteries my particular favourite is the PC clock chip with a built in lithium cell.

I eventually discovered that one might carefully remove the epoxy over the cell & replace it.
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