75 280Z Clock Repair?

[HusseinHolland]

Found a thread on a 77 280 that showed rebuilding a Quartz clock, and referenced rebuild instructions (for the earlier type like mine?) without any link

EDIT - found this thread linked searching on another forum - says 70-78Z, however I can only assume they never took apart a 75 version as it looks zero like the pics of the motorized version he shows (later in the thread) & describes repairing

Before anyone mentions it, I'm not paying ZClocks $351 for a rebuild.

circuit diagram posted on other forum - don't know if its accurate

Has anyone found a common failure / repair point for this? I con't see anything blatant with the mechanism or the circuit board, but it doesn't work when I apply test voltage by way of a 9V battery

Edited August 30, 2023 by HusseinHolland

[Captain Obvious]

I've been inside that clock version in the past (surprised?   ). Not an expert, but might be able to help.

What's yours doing or not doing? Completely stone dead?

[HusseinHolland]

2 hours ago, Captain Obvious said:

I've been inside that clock version in the past (surprised?   ). Not an expert, but might be able to help.

What's yours doing or not doing? Completely stone dead?

Yes - stone dead. I seem to have continuity across the circuit, but perhaps that's not the key. The mechanical aspect seems tobe all intact, no binding, etc. the shaft with magnetic(?) weight/wheels spins freely & will oscillate if manually activated. I'd really like to fix it rather than gut & install more modern internals(did that with the Fiat X1/9). Appreciate any input Captain O!

Edited August 30, 2023 by HusseinHolland

[Dave WM]

most likely the 10uf or .22uf cap, Easy fix as long as you dont smoke the TINY wires of the coil when messing about with it. That was what it took to get mine going. 

 

Edited August 30, 2023 by Dave WM

[HusseinHolland]

5 hours ago, Dave WM said:

most likely the 10uf or .22uf cap, Easy fix as long as you dont smoke the TINY wires of the coil when messing about with it. That was what it took to get mine going. 

Thank you - so, did you just replace all the capacitors, or start with a particular one? No idea how one would circuit test a capacitor, if it's possible?

Edited August 31, 2023 by HusseinHolland

[Captain Obvious]

Well we could work into this in a couple of ways. First option would be to start by shotgun replacing the electrolytic caps (as DaveWM mentioned) and see what happens. Electrolytic caps are known to not last forever. They contain chemicals inside that eventually dry out, or leak out, or sometimes they fail short. In any event, they're a known source of long term issues and may or may not be what's causing the problem with your clock. So I'm certainly not poo-pooing the shotgun approach in this case, it's a valid approach.

If that shotgun approach isn't doing it for you, we can get into some specific measurements you can take that might help narrow down the problem.

And speaking of which.......

10 hours ago, HusseinHolland said:

Yes - stone dead. I seem to have continuity across the circuit, but perhaps that's not the key.

When you say you have continuity across the circuit, where are you taking that measurement? If you're taking that measurement across the blue and black wires, then there's a problem. You should not be seeing significant "continuity" across those two wires. So talk some more about that.

[HusseinHolland]

10 hours ago, Captain Obvious said:

Well we could work into this in a couple of ways. First option would be to start by shotgun replacing the electrolytic caps (as DaveWM mentioned) and see what happens. Electrolytic caps are known to not last forever. They contain chemicals inside that eventually dry out, or leak out, or sometimes they fail short. In any event, they're a known source of long term issues and may or may not be what's causing the problem with your clock. So I'm certainly not poo-pooing the shotgun approach in this case, it's a valid approach.

If that shotgun approach isn't doing it for you, we can get into some specific measurements you can take that might help narrow down the problem.

And speaking of which.......

When you say you have continuity across the circuit, where are you taking that measurement? If you're taking that measurement across the blue and black wires, then there's a problem. You should not be seeing significant "continuity" across those two wires. So talk some more about that.

Yes - across the I/O board connections - when I connected a 9V battery to test it, I register 9V across the circuit with my multimeter. Another electronics guy said the caps dry out & fail. His suggestion is to first replace the 3 caps on the circuit board. What did you do?

EDIT - when I saw your post, I only registered the 2nd half, after your quote. So, yes, I'll do the caps first & go from there.

Edited August 31, 2023 by HusseinHolland

[Captain Obvious]

48 minutes ago, HusseinHolland said:

I'll do the caps first & go from there.

Sounds like a plan. Root problem might not be one of the caps, but it's certainly a good place to start without really digging into it.

If that doesn't take care of it, we can go from there.

[Dave WM]

one thing you can take note of is when 9v applied to the power input of the clock does the balance wheel move at all, even just a bit, if so its prob good as far as the wire. Like CO said there is plenty of more that can be checked after the capacitor replacement, but 90% of the time its going to be that on 50 year old caps. As I mentioned in the video, the hardest part is the delicacy of the board traces and wire from the coil. Just be super quick and use a proper solder iron for any work. Even then you may lift a trace.

[HusseinHolland]

1 hour ago, Dave WM said:

one thing you can take note of is when 9v applied to the power input of the clock does the balance wheel move at all, even just a bit, if so its prob good as far as the wire. Like CO said there is plenty of more that can be checked after the capacitor replacement, but 90% of the time its going to be that on 50 year old caps. As I mentioned in the video, the hardest part is the delicacy of the board traces and wire from the coil. Just be super quick and use a proper solder iron for any work. Even then you may lift a trace.

No, no movement at all.

Thanks for the vid - I have wicking braid & a fine tip soldering iron I haven't used for many years - I used to solder chip pads into 90's Volvo ECU's in order run programable chips, but that was many years ago, and I have had to wear prescription glasses since 2012. I have to dig out my light table/magnifier so I can be careful with the coil winding, so thanks for the caution there.

[Dave WM]

hmm, nothing at all. If you wanted to do a bit of diag before desoldering you could check the output from the zener with a VDC reading. IIRC my wheel would bump a tiny bit with power applied to the clock. 

Edited August 31, 2023 by Dave WM

[HusseinHolland]

So, I went through my stash of components & found I have a Tantalum .22uf cap, so I may as well use it instead of a plain aluminum cap

also dug out my work station so I can hopefully see wtf I am doing

also have some zener diodes, so I can replace that also if need be

Edited September 1, 2023 by HusseinHolland