The clock is ticking!

[Brian in VA]

After a lot of Pelican thread searches, I've got my clock working finally!



The hole in the dash



The inner bits. The capacitors were rotted, one fell apart in my fingers during removal of the innards.



Bad parts coming out



New caps going in. BTW, they can be replaced with 100 mf 35 W caps, not just 16 W. The shack didn't know this, but google did.




Finished clock.

Happily ticking away. Thanks to everyone who has posted on this before. The interior seems so much better now for some reason, though the second hand still won't work (I kid.)

[Mitch Leland]

Brian,

You're my hero if you can make that "Cracker Jack" clock work... BTW: that's not a second hand, it's a "time marker" for lack of a better description. Maybe someone else can better describe its function.

[DRACO A5OG]

Start Fun Time Marker?

BTW, Can you give the specs of those capacitors? Think of fixing my extra clock.

[Fishrule]

Brian,

I'm with Draco: can I get more info on those capacitors? Radio Shack has two that seem to match your specifications:

model number: 272-1016

and model number: 272-1028

Which is the correct one?

[Brian in VA]

Thanks guys and I was joking about the "second hand."

Fishrule, use 272-1028, the 100 microfarad 35 Volt caps (W above is a typo)

Im out of town right now, but when I get back I'll write up some steps and tricks.

Brian

[Fishrule]

Brian,

Thanks for the quick response. I look forward to the steps and tricks.

-Kyle

[dtxscott]

Yeah, they were naive using a 16V cap.

One bad regulator incident and the clock would likely be fried.

Great writeup!

[Brian in VA]

OK, back home now with a real keyboard.

So, the first and most difficult part is removing the black clock face ring. I had to search for a very small, thin screwdriver to use. Push it in behind and twist, working around face and eventually it'll let go if you pull on it at the same time. Look at this for a better description of this part: Pelican Technical Article: VDO Clock Repair

The back of my clock was different than he described though. Anyway, take off the face and store the screws securely (mine disappeared and after searching the garage floor for 30 mins I found them right where they were supposed to be, hiding in plain sight.)

Next, unscrew the two screws on the back that hold the clock bits inside. Now a single wire sticking up through the back of the unit is left holding it in. Unsolder while pulling down and the parts will come out.

I sprayed some electronic cleaner on everything too. 1 of the capacitors was obviously damaged. On the back side, unsolder all 4 pts for the two capacitors. Replace with two 100µF 35V Radial-lead Electrolytic Capacitors. They are marked +/- and both go with the neg pole to the outside of the board (which is marked neg also). Trim the wires after soldering in. Resolder the center back wire and replace screws etc. I found replacing the face ring pretty hard too but eventually it popped back into place with some cursing. Miraculously it is still ticking away.

Hope this helps. Also, for VDO Quartz clocks only.

Brian

[drola]

thanks to this thread i got my clock working. total cost was $3.19.
one less thing on the "i gotta fix that" list.
thanks again!

[Brian in VA]

Strong work Drola, mine's still going too

Brian

[mnewport]

Yeah, they were naive using a 16V cap.

It's not the voltage value that's the issue. A typical rule of thumb for any design engineer would be to use a capacitor with a voltage rating at least 25-30% higher than the system calls for. Add to this the fact that a 16V cap can withstand overvoltage conditions for a period of time without sustaining damage (I'd be surprised if we would ever see 25-30 volts DC with huge amounts of ripple current anywhere in these cars no matter what conditions exist). The problem is the dielectric material. Large capacitance values (in this case 100uf) require a dielectric substance that will provide a high amount of capacitance in a small amount of space. The only type of capacitor that will provide this is an electrolytic capacitor. If we tried to use film, the capacitor would be prohibitively huge and expensive. While the upside of an electrolytic is large, cheap capacitive properties in a small space, the downside of is that the dielectric material dries up over time, and the capacitor simply fails, as is the case in these clocks.

For awhile I suspected that certain weird CIS problems may be caused by drifting or failed capacitors in the control box. Since most of the caps in the control box are film, I suspect the likelihood of that being the issue is lower than if the caps used were electrolytic. Some day I'll reverse engineer the circuit just for kicks.

[Nick Triesch]

Wow, you are lucky! My clock in my 85 only works on a road trip. Keeps perfect time. But then when I get home, Clock only works for a few hours after the car is shut off. Very strange. Nick

[Canada Kev]

Well, if that aint the perfect excuse for going on a road trip...

[gopher]

Thanks for the great advice on fixing a VDO analog quartz clock in this discussion.

I replaced the two capacitors in mine using Radio Shack 272-1028 parts, and now it works great!

The hardest part was opening the clock by prying open the flange around the front. I wish someone had a great MacGyver tip for that!

Thanks again for the guidance. I would never have thought to fix my stalled clock by replacing capacitors.