75 280Z Clock Repair?

[Captain Obvious]

1 hour ago, HusseinHolland said:

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

Cool. With your stash, you're already well on your way!  

So is that tantalum cap polarized? I don't see a polarity marking on it, but the tantalum caps I've worked with were. And if it is polarized, make sure you get the polarization correct. Tantalum caps really don't like to see reverse polarity, especially at temperature.  I'm wondering (thinking?) that might be a ceramic cap and not tantalum.

And who doesn't have a bag of 5.1V Zeners laying around?   

[dutchzcarguy]

6 hours ago, Captain Obvious said:

And who doesn't have a bag of 5.1V Zeners laying around?   

I don't! 😉

I wouldn't use the (old?) tantalum caps where the orig. one is a electrolitic.. just get yourself some new c's that are new.. if you gonna use old caps to replace very old one's... that's work for nothing.. you can get the 3 (i counted) caps for a few dollar!  Most times these capacitors are the culprit.

Watch the plus and minus, put them in correct!

[HusseinHolland]

13 hours ago, Captain Obvious said:

Cool. With your stash, you're already well on your way!  

So is that tantalum cap polarized? I don't see a polarity marking on it, but the tantalum caps I've worked with were. And if it is polarized, make sure you get the polarization correct. Tantalum caps really don't like to see reverse polarity, especially at temperature.  I'm wondering (thinking?) that might be a ceramic cap and not tantalum.

And who doesn't have a bag of 5.1V Zeners laying around?   

I have to assume it's a ceramic cap, no polarized marking. I used the Aluminum electrolytic caps, to be safe.

With it all back together , the winding energizes momentarily. I checked the spindle centering (because I dislodged it during disassembly ) and that the coil winding is pretty much centered in the spool. I assume it doesn't need 12v to trigger it, since it runs off 5v....

Zener shows approx 5v output, so I don't think that is bad...

Edited September 1, 2023 by HusseinHolland

[zclocks]

Ok, I couldn’t take it any longer without making a couple of comments.

You can break out the test gear and spend most of the day looking for the bad part or just replace the caps and transistor.

To start if you apply 12 vdc to the assembled clock and the balance wheel  moves the coil is good. The wheel may move ever so slightly so look closely.  If it doesn’t then the coil is bad and you need to find another board.

 De-soldering /soldering is the biggest problem because you can cook the insulation on the coil wire. Once that happens you destroy the coil.  No joke you need to be uber careful soldering the 10uF cap next to the coil. Guess which cap usually goes bad? These are electrolytic caps and you need to replace all with the exact values. No subs.

You can also have a bad transistor (C828) so why not replace it. Almost any general NPN low noise amplifier transistor will work. The zener diode rarely goes bad unless you’ve applied something like 24vdc to the board. I’ve seen it happen.

 These 4 parts cost around $5 and will last years longer that the originals.

Last, but not least I don’t charge $351 to repair this board, that’s a completely refurbished clock converted to a Quartz unit. I do have this repaired  280z circuit board for $60.

 Good luck and let me know if you need help.

Ron

[Captain Obvious]

9 hours ago, HusseinHolland said:

Zener shows approx 5v output, so I don't think that is bad...

Actually the way you measured the zener voltage, you are almost spot on. You are at 4.94 V across the zener.

So it won't start by itself, but what does it do if you give it a push start? Will it stay running, or does it come back to a stop? And if it does come to a stop (which I assume it will), does it stop in about the same amount of time as if there's no power applied at all?

In other words.... Does it take longer to come to a stop when you give it a push with the power applied, or does it stop in the same amount of time whether there is power applied or not?

Nice photography. But I'm thinking we shouldn't be surprised.   

[HusseinHolland]

4 hours ago, zclocks said:

Ok, I couldn’t take it any longer without making a couple of comments.

You can break out the test gear and spend most of the day looking for the bad part or just replace the caps and transistor.

To start if you apply 12 vdc to the assembled clock and the balance wheel  moves the coil is good. The wheel may move ever so slightly so look closely.  If it doesn’t then the coil is bad and you need to find another board.

 De-soldering /soldering is the biggest problem because you can cook the insulation on the coil wire. Once that happens you destroy the coil.  No joke you need to be uber careful soldering the 10uF cap next to the coil. Guess which cap usually goes bad? These are electrolytic caps and you need to replace all with the exact values. No subs.

You can also have a bad transistor (C828) so why not replace it. Almost any general NPN low noise amplifier transistor will work. The zener diode rarely goes bad unless you’ve applied something like 24vdc to the board. I’ve seen it happen.

 These 4 parts cost around $5 and will last years longer that the originals.

Last, but not least I don’t charge $351 to repair this board, that’s a completely refurbished clock converted to a Quartz unit. I do have this repaired  280z circuit board for $60.

 Good luck and let me know if you need help.

Ron

 

Hello Ron

Thank you for the advice. I've done the 3 caps, and after that I got a twitch from the balance wheel. so I will see if I have an NPN transistor to try.  I missed refurb boards on your site, so if this doesn't work, I will be hitting you up for a board. I want to keep this clock if possible. 

[HusseinHolland]

1 hour ago, Captain Obvious said:

Actually the way you measured the zener voltage, you are almost spot on. You are at 4.94 V across the zener.

So it won't start by itself, but what does it do if you give it a push start? Will it stay running, or does it come back to a stop? And if it does come to a stop (which I assume it will), does it stop in about the same amount of time as if there's no power applied at all?

In other words.... Does it take longer to come to a stop when you give it a push with the power applied, or does it stop in the same amount of time whether there is power applied or not?

Nice photography. But I'm thinking we shouldn't be surprised.   

It doesn't stay running. If I push start the wheel it doesn't continue to run if powered, I don't think there is any difference in spin duration  powered or unpowered. 

[zclocks]

Check the trans  configuration as I've posted here. You can modify anything, but the NTE 199 is a direct fit.

BTW I also have a 75 280z

Ron

 

[zclocks]

One more item. Check the coil resistance . You should have 200ohms on each coil.

 

[HusseinHolland]

20 hours ago, zclocks said:

Check the trans  configuration as I've posted here. You can modify anything, but the NTE 199 is a direct fit.

BTW I also have a 75 280z

Ron

 

 

Ah - so I assume I need to alter the post to board configuration (swap  b & c?), since I bought 2N3904 transistors. 

My 75 is CA market - so if you need any of the 75 smog-specific components I may be able to help 🙂

I'll check the coil values also.

 

[AK260]

Check the trans  configuration as I've posted here. You can modify anything, but the NTE 199 is a direct fit.
BTW I also have a 75 280z
Ron
 

Ron - you’re a super good man! I love the fact that you are helping someone doing it for themselves even though you make money from repairing these. Few of you in the world fella, well done!

[HusseinHolland]

So, I replaced the transistor this morning - BUT - I got myself kerfuddled on leg orientation; between looking at the circuit board, transistor orientation, and the schematic from Ron I neglected to note the schematic says "view from underneath".

As a result, I have the pin orientation al wrong

What it needs to be

Edited September 4, 2023 by HusseinHolland
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