Re: Craftsman 82357 DMM bad resistance measurement
I ordered some 2sc4081 yesterday but it's good to know that there's lots of options. I figured they were pretty generic, but one transistor certainly isn't the same as every transistor obviously. Thanks for the further feedback!
bkenobi
Member
Last Activity: 01-17-2023, 01:36 PM
Joined: 12-01-2022
Location: Seattle, WA
-
Re: Craftsman 82357 DMM bad resistance measurement
I found a vendor on Aliexpress that only has a lot of 50 and reasonable shipping but will have to wait a while for it. The DMM works as is so not a problem. I won't get it from these guys though....Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
Doesn't look like the MMBT3904 is on that list. That compatibility list looks like it's pretty common transistor but curious if it has a "standard" part number that would reference all typical of that type. I tried looking on Mouser and digikey thinking I could get them from the US quicker. But I quickly found that I didn't know what specs I should even be searching for. I can put the new part on, but I'm lost on how to sucessfully find a compatible replacement. I'll use the list in that compatibility list to try again...Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
I have a few extra transistors from a project that are the same size. I'm curious if these would be acceptable replacements? I can order the ones in the link but it appears I have to order 100 and wait a month so if I could use what i have, that would be nice.
[url]https://www.digikey.com/en/products/detail/micro-commercial-co/MMBT3904-TP/717395[/url]
[url]https://cdn.badcaps-static.com/pdfs/cd39dfa7d757b3592b10b8eb29eb7d54.pdf[/url]
I don't know how to read the datasheet to confirm compatibility...Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
I got a few minutes to test the DMM this afternoon. Although the display is still missing some segments, it's better after adding dielectric grease and a few layers of electrical tape on the back side of the board where the screen contacts the pads. I can confirm that with the SMD components removed, I now see the correct resistance reading.
Assuming I can get the display segments back with improved shimming, does BR25 offer enough info to help source new modules? It seemed like Mouser has a lot of modules in SOT-23...Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
This is the post I found that said the board required shimming after inspection. It happens to be the location where the software has been archived so a dual benefit in posting! I will investigate this next time I get to it. I don't know if it's a shimming issue or a bad contact to the grounding plane on the back of the case. If bad ground, I imagine a little dielectric grease on the spring/contact location might resolve.
[url]http://greyghost.mooo.com/82357/[/url]Re: Craftsman 82357 DMM bad resistance...Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
I pulled the transistors. I tried to get a picture of the markings but couldn't get the lighting right with either my phone's camera or my SLR. After pulling, I was able to get one on each that seem to indicate BR25. A quick search suggests it could be a shottky diode?
I reassembled the DMM but the contacts on the display seem touchy so some segments weren't working. I don't think it has anything to do with the transistors though as I removed and reassembled and the unit and it was a bit better (more segments). I...Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
Thanks for the suggestion. I'll take a look and see if they look like I can remove them. Can these be tested prior to removal or do they need to be isolated to properly diagnose their function. Assuming these are the bad components, where would you recommend sourcing replacements? I've used Mouser and Digikey in the past but seems like 1 or 2 transistors might be too small an order for them to consider.Leave a comment:
-
Re: Craftsman 82357 DMM bad resistance measurement
Nobody has been inside the unit because I've owned it since day 1 and I've not worked on it. I think a fuse blew once (not sure of circumstances) so I recall having to open it around 10-12 years ago to replace the large ceramic fuse (socketted so I wouldn't consider that "working" on it). Otherwise, nothing has been worked on. I used my air rework and some solder flux to clean the ugliness up but I imagine sufficient heat to reflow that solder could have been enough to damage the chip.
The attached pictures...Leave a comment:
-
Craftsman 82357 DMM bad resistance measurement
I have a Craftsman DMM model 82357 that I bought in the late '90s or early 2000's. I believe it's equivalent to one of the WENS 20TRMS units. I like the unit but recently I noticed the resistance values are incorrect. My best guess as to why is last year the probe touched a ground plane while doing a continuity test with the board powered. The GFI receptacle kicked off so I assumed no damage to anything. I generally look at continuity rather than absolute resistance so perhaps something else caused the issue.
In any case, I opened the case and overall I don't see anything clearly... -
Re: New Members - please post your introductions here
Posting to get full access. New here but have been on many forums over the years.Leave a comment:
No activity results to display
Leave a comment: