FLUKE 8024A Repair - Page 1
Forum section: electronics / repair

author: ronsr333
author_rank: Newbie
timestamp: March 08, 2014, 08:21:52 pm
content: Need Advice! Picked up a Fluke 8024A (No display). Installed a new 9VDC battery, checked connections from the battery through the On/Off switch to U8. Full battery voltage is present at Vdd/Vss at U8. Need suggestions as to where to go next. Check electrolytics, take display apart and clean?? Clean and reseat U8?Any help?

author: retiredcaps
author_rank: Super Contributor
timestamp: March 09, 2014, 05:47:43 am
content: On my Fluke 8020A, I get about 2.65VAC on the lcd at 50Hz. On my Fluke 75 II, I get about 1.55VAC on the lcd at 64Hz.I'm not sure what it is on the 8024A, but see if there is any ACV and the frequency?I would also take apart the lcd assembly and clean it with IPA.

author: ronsr333
author_rank: Newbie
timestamp: March 09, 2014, 02:11:20 pm
content: Thanks for reply. Taking today off (Sunday). Will do on Monday and let you know how I make out.

author: ronsr333
author_rank: Newbie
timestamp: March 10, 2014, 06:46:42 pm
content: retiredcaps: What pins on the LCD did you make the AC measurements??

author: retiredcaps
author_rank: Super Contributor
timestamp: March 11, 2014, 04:46:39 am
content: Quote from: ronsr333 on March 10, 2014, 06:46:42 pmOn the 8024A, it might be different. A rare chance for me to "justify" a dual display meter. My black probe is connected to the 9V battery negative terminal.

author: ronsr333
author_rank: Newbie
timestamp: March 11, 2014, 10:34:15 pm
content: retiredcaps: I am measuring 2.98 vac on the same pin as you show. I think the 8020 & 8024 both use the same intersil chip. Can't find my frequency counter to measure the frequency. Will provide frequency when I find it. I think that having a good reading here means that the U8 chip is probably working and that the problem is either a bad connection on U8 or in the flexible connector to the LCD. Will try to take apart the LCD assembly and reseat U8 and clean all contacts. I assume IPA is a good cleaner here.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 11, 2014, 10:43:31 pm
content: Quote from: ronsr333 on March 11, 2014, 10:34:15 pmYes, use IPA. Let it dry thoroughly before reassembly.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 18, 2014, 10:39:14 pm
content: Since Fluke and Intersil co-developed the 7106, the datasheet for the 7106 shows a test pin (pin 37).In the Intersil 7106 datasheet, there is a way to do a "lamp test". I'm assuming this will work for U8? If it does, it at least confirms the lcd itself is okay.I haven't done this myself so I don't know if it is a valid test or not.edit: Found a nice website that shows how to test.http://www.petervis.com/meters/ICL7106%20and%20ICL7107%20Digital%20Meter/ICL7107%20LED%20Display%20Settings.html

author: ronsr333
author_rank: Newbie
timestamp: March 21, 2014, 08:10:50 pm
content: While apart, I have measured the resistance of the conductivity of the elastomer ("zebra") connector. I am getting a pretty high resistance 2K on most of the conductors. Is this normal??Ron

author: SeanB
author_rank: Super Contributor
timestamp: March 22, 2014, 05:48:13 am
content: Normal, as the LCD is mostly a capacitor. The backplane is a low frequency, typically between 20 to 100Hz depending on the design.

author: ronsr333
author_rank: Newbie
timestamp: March 30, 2014, 02:32:59 pm
content: Thanks Sean B. Awaiting a new ICL7106 A/D Converter; purchased on ebay. I intend to boil the Zebra connector (as suggested in another post) and try again to see if anything works. Be back after.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 30, 2014, 04:46:18 pm
content: The history of the 7106 and how Fluke and Intersil are involved is detailed below.https://www.eevblog.com/forum/testgear/old-fluke-multimeters/https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg319838/#msg319838Thus, the 7106 is not an exact drop in replacement for the Fluke IC.