Can you ID this mysterious broken wire inside my digital cluster?

[hardwareguy]

While refurbishing the digital cluster, I found a wire that appears to have broken off but I can't find where It might go. I presume it links the microprocessor board to the display board but I can't find a little tuft of wire or other wire remnants to give me a hint as to where it should be soldered to.

The wire originates on the microprocessor board from a pad labeled "check" as shown in the pic.

[Z_Karma]

Luckily i have a digi display under my bench here at work that needs a bunch of corrosion scrubbed off.

That wire dead ends in that adjacent harness. Likely a test or calibration point after the final assembly.

digidash.jpg

[hardwareguy]

Excellent! Thanks for the help!

I bet it's a waveform test point in that case.

My cluster is on the bench for a recap and joint touchup. It has Matsushita capacitors and Matsushita caps made from the late 70s through late 80s have a fairly predictable failure mode where in the rubber lead seals leak causing green or gray corrosion at the leads. It's annoying, but at least one doesn't need an ESR meter to tell they're bad.

Fun fact: These same caps are used in Technics, Panasonic, National and RAMSA (all Matsushita brands) gear from the same time period and cause all sorts of problems that are easy to fix with just a change of caps and a little corrosion cleanup.

I'll be using TDK X7R multilayer ceramic caps for everything 3.3µF and smaller and Panasonic TA 125°C caps for the larger electrolytics.

[Z_Karma]

Excellent background information!

The OEM cassette players and amplifiers manufactured by Hitachi and Clarion often suffer the same cap failure. Not a concern with most owners that ong ago ditched the cassette players.

Nissan used Clarion as a manufacturer for the 84AE headunits that had the bodysonic setup, but Hitachi for the cosmetically identical non-bodysonic stereos. They then used Clarion for the later EQ headunits.

I've got the printed service manuals for the two Clarion models, but haven't serviced any that I've collected (i'm not a electronics tech, more mechanical tech that knows how to use a DMM and which end of the soldering iron is the hurty bit).

[hardwareguy]

These Panasonic/Matsushita caps found their way into tons and tons of equipment made by countless manufacturers. They lasted a good while, often more than 20 years but sadly weren't as long lasting as other famous Japanese brands like Nichicon, Nippon ChemiCon and Elna which sometimes went 40 years before failing.

Newer Panasonic caps do not suffer the same failure mode and appear to be extremely durable. I use them extensively in repairs and new things I come up with. The FC is a good all-round type that offers ESR that's low enough to use in most switching power supplies and long life at higher temps. For underhood circuits or powertrain controls, go for the Panasonic TA or another lower ESR 125°C or higher cap for extra durability. (Nissan used an ancestor of the Panasonic TA in one spot in the ECU and in the TCU. I suggest duplicating this choice because the modules will crash if these caps go bad.)