Cheap Meter required for NJM9210F chip to repair Digimess? - Page 1
Forum section: electronics / testgear

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 24, 2017, 05:37:20 pm
content: Hi!I bought a cheapie Digimess DMM200:-http://uk.farnell.com/digimess/dm200/multimeter-dig-bench-4000-count/dp/1076811as "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

author: CJay
author_rank: Super Contributor
timestamp: October 24, 2017, 06:13:15 pm
content: Tektronix DM254?Thought not...However if you mean NJU9210Fhttps://www.aliexpress.com/item/Single-chip-digital-multimeter-IC-NJU9210FC-NJU9210/32474123033.htmlOh and those Digimess schematics wouldbe nice to see as well

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 24, 2017, 06:17:13 pm
content: 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 WilliamsPS!Ali Express says this device is no longer available! - is there known to be a pin-compatible equivalent?

author: CJay
author_rank: Super Contributor
timestamp: October 24, 2017, 06:32:01 pm
content: 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

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 24, 2017, 07:29:00 pm
content: 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:KL4AAOxyUrZS8OMibut 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

author: retiredcaps
author_rank: Super Contributor
timestamp: October 24, 2017, 07:56:02 pm
content: NJU9210FC is cheaper on aliexpress. Starts at $24 USD + free shipping.

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 24, 2017, 08:58:53 pm
content: 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.pdfChris Williams

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 26, 2017, 01:05:35 am
content: 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

author: CJay
author_rank: Super Contributor
timestamp: October 26, 2017, 06:21:38 am
content: 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...