Triplett 4800 DMM checkout and restoration - Page 1
Forum section: electronics / testgear

author: xrunner
author_rank: Super Contributor
timestamp: April 02, 2015, 04:25:31 pm
content: Just got this in. A used Triplett Model 4800 bench DMM. It's kinda cool. There's another short thread on it here but I'm going to post more pics and show anything I find out in the process of checking it out.

author: xrunner
author_rank: Super Contributor
timestamp: April 03, 2015, 10:49:15 pm
content: Well I've been busy with this. Turns out the LCD had a problem, prolly due to age. It had bubbles in the back and it just didn't look good. It appeared the polarizer film and other materials in the back were pulling away. So I did something I've never attempted before - I rebuilt the polarizer stack.I got the materials from an old LCD monitor. Fortunately it had the right materials that worked with this LCD. I just took the sheets out and cut them to size. I had to strip the back polarizer but it came off OK. I tested the polarizer first to make sure the orientation would work, and it did. I then just made up my own sequence of materials. Pure white, diffuser, polarizer, and a clear sheet. I tried a bunch of combos since I had the opportunity and found the one that looked best.When I got it all together and put it together I was very pleased. It actually looks better than the parts of the original that weren't coming off. Now I can get back to testing the thing.

author: timofonic
author_rank: Frequent Contributor
timestamp: April 04, 2015, 05:55:59 am
content: Hello.Great fixing! Does it have backlighting too?What precision does these guys have? I did read about old Keithley having tons of decimals (x.xxxxxxxxxxxxxxxxxxxxxx), not sure if used the correct word.Do they do autorange?

author: xrunner
author_rank: Super Contributor
timestamp: April 04, 2015, 12:37:54 pm
content: Quote from: Circuiteromalaguito on April 04, 2015, 05:55:59 amNo.QuoteOh yes.QuoteThe basic DC accuracy is +/- 0.04% +/- 2LSDThe complete operator manual is here with all the specs -http://www.triplett.com/wp-content/uploads/2012/11/84-477.pdfIt can measure frequency, temp., peak hold, can monitor and alert when a signal is outside a range, and it has a DIN connector at the back that can output an analog voltage that follows an input and can control an external relay.Only problem is I can't locate the cal procedure. I have a 10V reference on my breadboard and the DC is only off by + 0.004 V as it stands, and a 10k precision resistor (0.1% tolerance) measures ... exactly 10k, but I'd like to get the service manual. Might have to write Triplett and beg for it because the thing has 17 pots and trimmers in it and none of them indicate a clue about what they adjust and it ain't in the manual.If you want to play with one here is some more from the same Ebay seller I got mine from -http://www.ebay.com/itm/761-MC1-Triplett-True-RMS-Digital-Multimeter-4800-Power-Tested-Lot-9-/281651892240?pt=LH_DefaultDomain_0&hash=item4193c2d010

author: xrunner
author_rank: Super Contributor
timestamp: April 05, 2015, 12:44:45 pm
content: Just gettin it cleaned up as usual. Seems to be working OK so far.Oh, and make that 20 pots and trimmers - I found three more.