Did a little searching and didn't come up with anything, so figured I'd ask.

The cluster lights (speedo/tach) on my '88 R100RT are inop. The backlighting, that is. The turn signals, neutral light, etc, all work properly.

My only other (brief) airhead experience is a 1975 R90/6. If I recall back in my dim memory, there was a flexible printed circuit board of some kind inside the cluster that tended to go bad. Was wondering, before I start tearing into things I know little about, if the RT of my vintage uses the same "guts" inside the gauge cluster as the old /6 did. Either way, advice and or link to any DIY or tech tips anyone knows of regarding how to troubleshoot and or repair the gauge backlighting would be appreciated.

Sorry if this is probably a noob question but I didn't turn up much on Google either. Thanks for any guidance.