I discovered that the surgical spirit I bought from Tesco pharmacy was not pure ethanol and also had oils added to it . I didn’t use it and went ahead with the cleaning using the iso-propanol.

Taking the board out was straight forward and I didn’t need any instructions for that part.

I followed the cleaning instructions and removed quit a lot of yellow / brown residue from the back of the board using three cotton buds. The fourth bud had no obvious dirt on it so I moved to the front of the board. I suggest adding a magnifying glass to the tools list. At least for my old eyes, I needed magnification to be able to see the component labels clearly. On my board, the crystal was labelled Y901 rather than Y921. At first I thought the super capacitor had leaked; there was some white material underneath it. On closer inspection I think this may be heatsink compound distributing heat to a small copper pad under the body of the capacitor. I used a small brush with quite stiff bristles (I think it was intended to be a stencil brush for small detail work). I found it easier than using cotton buds where strands of cotton would snag on the solder joints. The stiff bristles easily got between the pins of the chip etc without causing damage. After applying the cleaning fluid, blotting the brush on tissue dries the brush so that it can then be used to remove excess fluid from the board. I repeated that process 3 times as well. I took a few pictures of the front & back of the board and close ups the timing circuit components. It wasn’t easy to get the lighting right but they might be useful to orient others to the correct area for cleaning.

Finally getting to the point. Did it work? Well, given the intermittent behaviour I’ve seen it’s a bit early to say for sure BUT I have not seen a blank clock display since I put it all back together (3 hours ago) and I have recorded from standby for the first time in 6 or 8 weeks. So I’m almost ready to say it’s fixed. I have scheduled a few recording events for tomorrow as a more comprehensive test and will report back…. but I am very optimistic.

Thanks for all your help! It is amazing to me to find such a helpful forum with posts from real experts – for a device that ceased production years ago. How are you at diagnosing Land Rover transmission faults?

MS_Boffin

All the recordings worked ok and i have only seen correct clock behaviour since cleaning so I think its fixed!!

Considering the help I got here, no problem at all to post the pics. I need to make some lower quality images first. Anyone know the file size limit for uploads?

MS_Boffin

If you mean the silver cylinder, that is the crystal and the white substance is probably silicone adhesive to hold it down to the pcb. The super cap is the large black device in the top left hand corner.

I’m not sure I can be demoted. Is there a category below “new member”?

Sorry if I confused anyone but hopefully the pictures will help with future clock problems.

Now I’m going to watch the F1 race I recorded earlier today

MS_Boffin

Hi I have cleaned two now and just bought one from flea bay. I have found the back of the board is very tacky, one I cleaned did not work until I cleaned the rear off the board and just I believe the white stuff is part of the build covered by IPC