Dialog 11 NPC and capacitors are still an issue

[Martin P]

As a non-electronic person that does not have a cell phone or a Facebook thingy I am not naturally in contact with things like capacitors.
I learned about those playing with Deckel NC machine and somehow assumed that this was an old issue limited to early 80ies electronics.
There are some that look like bakelite, so I learned to be weary.
Then I saw some videos on Youtube on fixing 5 year old flatscreens from the trashbin by replacing 20 cent capacitors. So apparently not just an issue of antiquity.
As I am working on a secret Dialog 11 project I encountered the dreaded dead NPC card. I did notice that there is one large capacitor installed.
After replacing this the problem was gone!
Just to verify I then spent 16€ on a chinese tester (on top of the 20 cent capacitor) that arrived today and I measured 373 nano Farad instead of 220 micro Farad. Not that I know what this means, besides its probably out of range.

I also got hold of a defective TFT for my D4, which was originally sold by FPS in 2014. They said its too old to fix, but would gladly sell me a new one.

So I gave it to a more electronic friend of mine and he replace some micro capacitors. Now its working again.

Lessons learned:
Laymen can get positive results poking around looking for the obvious.
Chinese stuff can be super(c)heap and still do the job (I hate to say it).



Other NPC hint:
When in the 65000 parameter block it says **,*****,** or similar for a SW bloc, the SW was not read.
In my case it was the piggy back card that holds the SPS (PLC). I am still not sure if it was the EPROMs or the EPROM holder though.
Investigation ongoing.

 

[ballen]

Hi Martin,

I agree with what you have written

I've built and repaired a lot of electronics over the years. For example, three Heidenhain DROs. All three of these had power supply problems. In one case I replaced a 3-pin voltage regulator and electrolytic capacitors. In the other two, only the capacitors were bad. There is no question that in solid-state electronics from the past fifty years, electrolytic and tantalum capacitors are the most likely elements to fail. An inexpensive ESR tester is very helpful for identifying those, although the capacitors are so inexpensive that it makes sense to change them all, even if they are not bad (yet).

Of course if there is anything mechanical (switches, potentiometers, motors, moving-coil meters, ...) that is even more likely to fail than the capacitors. But it's usually also pretty obvious what is wrong.

Cheers,
Bruce