Cheap Meter required for NJM9210F chip to repair Digimess?

[Chris56000]

Hi!

I bought a cheapie Digimess DMM200:-

http://uk.farnell.com/digimess/dm200/multimeter-dig-bench-4000-count/dp/1076811 

as "sold as seen" and unfortunately I found a problem with the DMM chip, a Japan Radio NJM9210FC, which appears to be jumping at random between ranges and several LCD segments gone!

Can anyone point me in the direction of cheaper models of DMM/clamp meters that use a '9210FC DMM chip please?

I got a set of circuit-diagrams for the Digimess from the seller and I've got the chip datasheet saved and there's good IR desoldering-tackle at work I can use, so it's just a matter of another chip!

Suggestions, anyone, please?

PS!

Is there another type of DMM chip likely to be compatible with the LCD used with the '9210 or would I have to get a new LCD panel to match another DMM chip design - I believe these things are multiplex-drive!

Chris Williams

[CJay]

Tektronix DM254?

Thought not...

However if you mean NJU9210F


https://www.aliexpress.com/item/Single-chip-digital-multimeter-IC-NJU9210FC-NJU9210/32474123033.html

Oh and those Digimess schematics wouldbe nice to see as well

[Chris56000]

Hi!

My apologies - it IS NJU9210FC I should have said!

I'll post the two pages of circuit I got when I can find them!

Chris Williams

PS!

Ali Express says this device is no longer available! - is there known to be a pin-compatible equivalent?

[CJay]

Yeah, I spotted that after I'd posted.

Might be worth making these guys an offer?

https://www.ebay.com/itm/NJU9210FC1C-00-QFP-3-3-4-DIGIT-SINGLE-CHIP-/361893332683?epid=1232813840&hash=item54428606cb:g:KL4AAOxyUrZS8OMi

[Chris56000]

Hi,

I have seen this:-

https://www.ebay.com/itm/NJU9210FC1C-00-QFP-3-3-4-DIGIT-SINGLE-CHIP-/361893332683?epid=1232813840&hash=item54428606cb:g:KL4AAOxyUrZS8OMi

but considering the very low price of some 3³₄ - digit Chinese DMM's it's a bit on the pricey side for just the chip on it's own - surely Cryustek, etc., have done one the same or second-sourced the '9210 they seem to copy everything else, failing that there must be a cheap dmm I can scavenge for one?

Chris Williams

[retiredcaps]

NJU9210FC is cheaper on aliexpress.  Starts at $24 USD + free shipping.

[Chris56000]

Hi!

I had another look on Ali Express - I don't know why the previous link turned up "no longer available" - I did find one for $24.00 (£18.37 approx sterling!) which is much more reasonable, so I've ordered one!

I'll post the tear-down and repair along with the schematics when the chip arrives, but before I attempt to fit another IC I'll service the PCB and all the voltage-regulators, smoothing capacitors, control/switching transistors, etc., etc., first!

Another project hopefully rescued from the dead - DM200s are £135 - £139.99 on Farnell or SJ Electronics!

Pic on the front of the manual:-

http://www.digimessinstruments.co.uk/manuals/english/mdm200engandger.pdf

Chris Williams

[Chris56000]

PS!

This meter uses those Chinese staple fare, 8050s and 8550s as switching and control transistors – would locally–obtained BC182L/BC212L series devices do for servicing purposes?

Chris Williams

[CJay]

The 8050 and 8550 aren't expensive or hard to get, BC182/212 are a fifth the Ic, maybe BC327/337 might be better alternatives...