Have taken speedo out of instrument cluster and taken circuit board off the back of the back using the procedure of lifting the pointer needle over the 0 stop, letting it come to it’s natural rest spot, marking it on masking tape and pulling the needle off. I unsoldered the two leads to the interval microswitch and removed the board. Everything worked out just as it was described in the FAQs. I’ve confirmed that the capacitors are almost certainly the problem as I can see some corrosion around the IC pins and the solder joints. Generally the board and speedo is in very good condition. The ODO gears all look like they’re OK - no teeth stripped or binding so I’m not going to do anything with the ODO. The speedo is very delicate and the slightest slip could destroy it. The capacitors have been shipped from Mouser so all I have to do now is wait until they arrive. I put the instrument cluster back in the car without the speedo. All the exterior lights work so I can still drive it, but nothing on the dash does, no gas gauge, clock, temp gauge or instrument lights. I guess things are wired in series with the speedo connectors, which makes it seem unlikely that I’ll be able to test the speedo gauge by itself outside of the cluster.