VDO Clock Crystal Info?

1982911SCTarga · 07:06 PM

Does anyone have the specs or source for the crystal in a VDO clock for an SC?

Thanks!

Brian

1982911SCTarga · 08:07 AM

I think I've got my clock diagnosed down to a bad capacitor. The capacitor is a Frako 100/16. There are two of these in the VDO clock. When I supply 12v to the clock, one capacitor is doing its job and the other does not.

Off to Radio Shack for a new 100 microfarad capacitor.

There's some interesting information here about Mercedes clock repair, which uses the Frako capacitors as well. Mercedes clock repair

1982911SCTarga · 12-10-2005, 07:09 PM

Sometimes I amaze myself. One trip to Radio Shack for a $1.29 100 microfarad electrolytic capacitor, a bit of soldering and my clock is happily ticking away. Too cool!

911FL · 12-10-2005, 07:52 PM

Excellent! How did you open the clock up to work on it? I'd like to see if I can get mine ticking again as well.

1982911SCTarga · 12-11-2005, 04:20 AM

Just like the speedometer, you open up the clock by prying around the bezel that holds the glass on the front.

Once that is done, remove the two screws in the back of the clock housing. Then, you need to unsolder the negative (ground) connection from the back of the housing. Now you can slide all the clock components forward and out of the housing.

You should be able to check the gear train by carefully turning the motor and observing the gears moving and eventually the minute hand moving. If your gear train is OK, you've likely got something wrong in the clock's electronic circuit.

911FL · 12-11-2005, 07:20 AM

Thanks, I'm going to make this a fun project. I've got nothing to lose since the clock doesn't work anyway.

MOMO3.2 · 12-11-2005, 09:05 AM

I know I am going to jinx myself by posting this but, my 87 Carrera's clock keeps time as well as my Swiss Army watch. It has not lost any time over the past three years!

Mike

1982911SCTarga · 11:02 AM

That's the spirit, Dan. My perspective was the same: I was out nothing if my repair efforts failed. I was simply going to re-install the clock. I can't see spending beau-coups bucks on something like our 911 clocks. Save the big dough for really cool stuff.

A couple other observations: I checked the two capacitors with my analog multimeter. The capacitors have polarity (there are positive and negative terminals). You should see the ground (negative) side indicated on your circuit board. This polarity is important, too, if you need to replace one or both capacitors.

I checked the old capacitors by first applying 12v to the clock using a spare car battery. Then, using the positive and negative probes of my multimeter, I checked for the presence of voltage in each one. One would show voltage and the other one wouldn't.

Be careful removing the clock bezel (or any of your other instrument bezels). Work slowly prying carefully with a screwdriver and it will eventually come off.

The clock is really a charming item -- very analog and old school.

Brian

911FL · 12-11-2005, 05:34 PM

Thanks for the encouragement. I have always been an analog guy. Owned several digital watches over the years but could never tell the time on those newfangled things. I bought my Carrera with the clock non-functional and it has drove me crazy since day one.

It's funny by the way that I have had the pleasure of meeting other NoVa pelicans lately. Even more ironic is that's where I'm from. My wife and I have a condo in Annandale, but I have been working here in Florida for the past two years trying to finish my Ph.D. Don't miss the weather. Small world is all I can say...

911FL · 12-11-2005, 08:10 PM

One question. The clock is on the bench and I'm ready to open it. When you say to pry off the bezel, how did you get it started? There is no room to insert a screwdriver on mine and this is a part I really don't want to screw up. Do you need to bend the metal up to release it, or is it just pressed on by friction. If I get past this point I feel the rest will be straight forward. Thanks,

Early_S_Man · 12-11-2005, 08:27 PM

Dan,

Here is an article that may help ... from the Pelican Tech Articles page:

http://www.pelicanparts.com/techarticles/Mult_gauge_repair/mult_gauge_repair.htm

1982911SCTarga · 12-12-2005, 03:16 AM

Dan, the black clock bezel has a lip that is pressed just slightly around the clock housing. I used a couple of different screwdrivers of varying blade widths to pry the bezel lip up by leveraging the screwdriver between the clock housing and the lip.

Work slowly all the around the clock housing over and over. It's like opening a can, although much more slower. The photos in the referenced articles in this thread are helpful.

Good luck!

Brian

911FL · 12-12-2005, 07:34 AM

Thanks for all the help Brian. I was able to remove the bezel last night and this is what I found. At first I thought it was sloppy manufacturing but a quick voltage test (.700 mv for the one on the left and .125 for the one on the right), followed by a gentle prodding with my finger at this cap is toast. Off to Radio Shack I go today during lunch to pick up two of these. I'm thinking that I might as well replace them both at this age, since time will be working on the left one as well. I really hope this works. I'll keep you posted.

1982911SCTarga · 08:11 AM

Dan,

On the new electrolytic capacitors from Radio Shack, the side with the black stripe is the negative (ground) side.

Hope you get your clock up and running. It's a badge of distinction to say your clock works.

With a working clock on my SC, I have a new excuse now to go into my garage. Whenever, I come back in the house, my wife asks me what time it is.

Brian

Bill in OKC · 12-12-2005, 08:35 AM

I just got my clock working last week too. My 84 clock would tick if I held it just right or bumped the voltage up - it turned out the coil had a few burned windings. A second '89 clock advertised as working on ebay... didn't tick at all but the coil looked good - so I swapped the circuit boards and now the resulting Frankenstein clock ticks and keeps perfect time.

1982911SCTarga · 12-12-2005, 11:04 AM

Bill, wow, your repair skills are impressive. I checked the coil on my clock for continuity. Had it not been OK, I doubt I would have gone further down the road to R&R'ing the thing. Removing and replacing the circuit board or the coil is not a job for the faint-hearted. There's lot of potential for little gears to go everywhere.

Brian

Bill in OKC · 12:48 PM

There are 4 points holding the circuit board on (both coil posts, the ground post and a power post close to the +spade connector) and since the board has traces on one side only it comes off relatively easy. The mechanicals/gears stay firmly in place along with the coil - luckily enough. I tried to find some documentation on the IC that was on the board but I gave up. Interestingly the circuit boards had changed sometime between 84 and 89 (different IC & only 1 cap on the '89) but they are interchangeable. My 'burned' coil still had continuity - but I'm guessing a few of the windings were being bypassed.

johncarlos2003 · 01:24 PM

my clock keeps perfect time but the second hand doesn't move- i don't really care that much and am happy to have it work in general but if anyone has an idea on the second hand only id love to hear it- thanks!

len911 · 12-12-2005, 12:59 PM

Quote:

Originally posted by johncarlos2003
my clock keeps perfect time but the second hand doesn't move- i don't really care that much and am happy to have it work in general but if anyone has an idea on the second hand only id love to hear it- thanks!

If you are referring to the "white" hand, it is not the seconds hand, but just a marker... Lou

1982911SCTarga · 12-12-2005, 01:21 PM

Bill,

Doesn't the coil serve as an electromagnet to power the armature? The way I was figuring it as I studied mine is that the circuit powers up the capacitors, which then fire based on the frequency of the clock crystal, thus energizing the motor to drive the geartrain forward a certain amount.

Another question, what exactly is the practical application of the white marker needle? Would you use that feature in rallying?

Funny how we obsess about the slightest things with our P-cars and take such great pride in our mechanical victories.

Brian