EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: Serracin on October 16, 2018, 02:51:37 pm

Title: WaveTek DM27 meter issue
Post by: Serracin on October 16, 2018, 02:51:37 pm
This meter is showing erratic measurements.
If I remember right, there is a chip that needs to be changed
Any ideas please?
Title: Re: WaveTek DM27 meter issue
Post by: coromonadalix on October 16, 2018, 09:37:18 pm
service manual :

https://elektrotanya.com/wavetek_dm-23xt_25xt_27xt_info_sch.pdf/download.html (https://elektrotanya.com/wavetek_dm-23xt_25xt_27xt_info_sch.pdf/download.html)
or
http://www.xn--80alh0b.xn--p1ai/DOWNLOAD/dm27.pdf (http://www.xn--80alh0b.xn--p1ai/DOWNLOAD/dm27.pdf)


The main chip is an icl 7106  and doesn't cost a fortune,  Datasheet : https://www.intersil.com/content/dam/Intersil/documents/icl7/icl7106-07-07s.pdf (https://www.intersil.com/content/dam/Intersil/documents/icl7/icl7106-07-07s.pdf)

You have a couple of TLO62  op amps,  and u70  is an 3ra024 ic, i think its an proprietary ic ???  seen old un-answered threads for searching this same ic ???
Title: Re: WaveTek DM27 meter issue
Post by: lowimpedance on October 16, 2018, 11:26:29 pm
This meter is showing erratic measurements.
If I remember right, there is a chip that needs to be changed
Any ideas please?
  Just a thought if its kind of functioning, perhaps a very good clean is a simple enough exercise. From the outer casing, input terminals to the PCB itself.
Check for any bad/cracked joints etc. and the switch selector traces are in good condition first before thoughts of chip replacement.
Contamination around the ADC of the 7106 will manifest as unstable drifting measurements.
Note, without pictures I have no idea how clean or otherwise your unit is!.
 If cleaning does not help then a good think as to whether this meter is worth further effort or its time to treat yourself to a new DMM. depending on how many you already own of course  :P.