Half an Instrument Panel is better than none

[Aztec62]

Bob, saw this and thought I'd chime in. The 88/89 cluster seems to have an issue where the idiot lights (Telltale's in GM speak) stop functioning but the bulbs are not bad. I have at least five like this sitting here presently myself. There appears to be an issue with the lamp driver circuitry within the IPC that I've not nailed down yet. Transistor switches are used internally to drive the lamps from logic signals from the cluster CPU. I hope to eventually have a fix for this.

 

The cluster with the missing clock/odometer display is also an internal failure of the cluster. It is unlikely to be a power supply issue as the other portion of the display is working still (there are two separate VFD panels that comprise the digital portion of the display but these share a common power supply circuit internally) so it is either the display glass itself (though this is unlikely) or the serial to parallel shift register driver IC's for that half have failed resulting in no display output.

 

I've not looked recently to see if anyplace is still servicing the 88/89 clusters. The 90/91 type is still repaired by a few Delco authorized shops, but these are getting thin as well. If you are not inclined to repair the bad ones you have now, I may be interested in picking them up as cores. I have had some success repairing these myself, depending on the type of failure and whether the needed parts can be sourced.

 

Kevin Dierkes

 

Kevin,

do you have a schematic for the IPC or any other info?

I know a bit about electronics because it is part of my daily work.

And I have a dead IPC in my Reatta ("00 Error").

 

I would like to try a repair myself.

 

Henning

[kdirk]

Unfortunately, there is no publicly available schematic for either version of the IPC - or most other Reatta modules for that matter. GM has managed to keep these very closely guarded and presumably they exist only for the use of authorized service providers. I have figured out a few things on my own without the aid of service data but many components (transistors and IC's notably) are scrubbed and relabeled with Delco house numbers further complicating the sourcing and replacement of failed parts.

 

The failed Telltale's on the 88/89 cluster is an interesting case. Most of these lamps are controlled by logic switching which is in turn driven by serial data received and processed by the CPU in the cluster. So, a failure anyplace in the circuit between the CPU and the lamp drivers will knock out the malfunction indicators. I've not really torn into this yet, as I have far too many things going already, but intend to tackle it eventually. I don't imagine it is that complicated compared to some cluster malfunctions I've encountered.

 

Of course, if someone else figures it out first and posts a solution, that would be great.

 

Kevin

[DAVES89]

I took electronics as a high school freshman in 1971. I'll do it...lol