4 x 7 Segment LCD Replacement - Page 1
Forum section: electronics / projects

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 16, 2012, 10:50:27 am
content: I have an LCD which isn't displaying some segments and some are dull. For example in the pic below the display should be reading 1675https://www.dropbox.com/s/t0b1e1ykmq5lx2d/2012-05-16%2010.39.29.jpgIs this likely to be the LCD module or something external?I took it apart and the LCD module looks likethis one. (datasheet) Under the module is a philips PCF2112P which according to the datasheet is a 32 segment LCD driver.I'm hoping this is a fairly standard part? Does anyone know where i might get one or if the one above would work (i.e. it has the same pin mappings as one without the colon)Any help appreciated

author: free_electron
author_rank: Super Contributor
timestamp: May 16, 2012, 11:02:24 am
content: Looks like a standard lcd for usage with an icl7106...

author: markus_b
author_rank: Regular Contributor
timestamp: May 16, 2012, 11:27:54 am
content: Did you check out the contacts between the LDC and the controller ?Often there is a sort of rubbery contact strip squeezed between the PCB with the controller and the LCD. These can deteriorate with age and no longer make contact. If you press down on the LCD, do the missing segments suddenly appear ?

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 16, 2012, 11:33:41 am
content: Thanks for the replies.The LCD is mounted into a 1 inch(ish) standoff header. I was going to take it out but it feels very tight in there and i didn't want to break it. Although if its not working anyway...

author: markus_b
author_rank: Regular Contributor
timestamp: May 16, 2012, 11:50:17 am
content: Be careful, if it is just the contacts then you can try to fix it at low cost. If you break the LCD it may be difficult (and expensive) to find a replacement.Does the header link the LCD to the PCB ?What material is it made of ?You may also have fissures on the PCB, solder joints, glass. It looks like the device is used in a rough environment.

author: T4P
author_rank: Super Contributor
timestamp: May 16, 2012, 12:15:47 pm
content: It's definitely a ICL7106'd screenI had one of my prototypes screen display many segments poorly because the icl7106 had a dry jointBut this looks like a multi point problem so i suspect either the LCD actually failing or the contacts going hopeless and i can suspect the 7106 at the same time.If it actually uses a 7106..

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 16, 2012, 02:36:20 pm
content: Given the philips PCF2112P under it i would think its not a 7106! Its all through-hole so i might touchup the joints before trying to remove it from the header

author: T4P
author_rank: Super Contributor
timestamp: May 16, 2012, 02:58:12 pm
content: Quote from: Chet T16 on May 16, 2012, 02:36:20 pmOk . I'm wrong then. but still the same stuff applies, i used the same THLCD screen that he linked on my prototype

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 16, 2012, 03:08:52 pm
content: I'll check it out. As it happens i'm having LCD issues with my power supply that uses a few 7106'sRegarding the environment, its a main dealer car diagnostic tool so lived its life in a workshop. I thinks its ~18 years old assuming it was never replaced

author: free_electron
author_rank: Super Contributor
timestamp: May 16, 2012, 03:32:27 pm
content: you can perfectly drive an icl7106 compatible lcd using a pcf2112 . nothing special about that.a passive lcd is a passive lcd. nothing difficult.

author: sorin
author_rank: Frequent Contributor
timestamp: May 16, 2012, 07:11:03 pm
content: http://www.futurlec.com/LCDDisp.shtml(+$5 shipping)http://www.ebay.com/itm/180725935280but , I dont thing that the problem is the lcd.

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 16, 2012, 10:18:11 pm
content: I had another look and poking about that the screen doesn't make any difference. Well, poking it from behind makes all the segments light up.I've ordered a new screen along with another order for bits so i'll try that but i'll redo the solder joints while i wait for thatHeres a pic of how its mounted

author: markus_b
author_rank: Regular Contributor
timestamp: May 16, 2012, 10:59:24 pm
content: It looks like it is mounted in a raised socket. Did you try to remove it , clean the contacts and plug it back in.You can also measure the signal on the missing segments and compare with good segments. You'll need a scope for this, though.

author: Chet T16
author_rank: Frequent Contributor
timestamp: May 18, 2012, 09:25:17 am
content: I got the LCD out and cleaned up the contacts but its still exactly the same. It was quite tight and those screens are very fragile!

author: Chet T16
author_rank: Frequent Contributor
timestamp: June 02, 2012, 03:42:57 pm
content: I forgot to post this, thanks for the replies everyone, a generic one was identical