ESR meter and ....the fairy tales of the cap-kits...

[level42]

I think you guys will like this video I made yesterday:

http://youtu.be/vQB7te6SunY


[EDIT] PLEASE NOTE: the small spots On the display that I mention in the video were only on the plexi protection above the actual display. Mike has upgraded these since so this shouldn't be a problem anymore. I have simply removed the plexi and it looks perfect, just have to be careful not to stick anything into the hole that could damage the display.

[Etienne MacGyver]

LOL @ WE ARE IN THE BASEMENT ! 

[Superully]

LOL @ WE ARE IN THE BASEMENT ! 

"well, actually, we are in my kitchen" i almost peed my pants!!!

anyway, thx for that great video, seems like this "machine" would be a nice thing to have

[level42]

 

Yup !

One thing I forgot to mention: Once you've got one of these: DISCHARGE THE CAPS FIRST !! Use a small resistor to do that (shorting them is not something caps like very much....)

[Etienne MacGyver]

You should mention that in the videodiscription maybe..

not all people that see that video are reading this post aswell 

[level42]

Yeah, already thought about that...

[Belike]

Very useful video, thanks a lot André!
A short video would be also great from the discharging method.

[kroustibat]

Thanks andre, i can got to sleep with something new learned

[Q*ris]

"Sometimes electronics is easy" 
Thanks Dre!

[level42]

Hey guys....

A little more info....

I found the cap that I measured being bad looked a bit weird for a normal electrolytic (aluminum) cap. So I checked the schematics of Ms.Pac and found out that they indicate a Tantalum cap at C5 and C10.

When I hear Tantalum I immediately think of these kind of caps:


BUT...the one's I measured wrong didn't look like those at all. Using the power of Google I quickly found out that there are also "wet" Tantalum caps, that look much more like regular electrolytic caps:

Compare, wet tantalum:


and (old fashioned) aluminum electrolytic cap:


Since these kind of old fashioned "regular" electrolytic caps (GOD I would love everyone used the term Elco for it, like we do in Holland....) were all around the Ms.Pac board I didn't notice the difference...

HOWEVER, the ESR meter can still measure these just as well and so....they _are_ bad.

So I checked for some replacements and almost got a heart-attack:
http://nl.rs-online.com/web/c/?searchTerm=wet+tantalum&sort-by=default&sort-order=default&view-type=Grid

Note that these prices are EACH. I guess we're running out of Tantalum ? Should I sell mine to get the Tantalum out of them ?

My _real_ question is....what are the differences between a wet-tantalum (yes, this word sounds dirty) and a regular aluminum elco ?

[level42]

Mmmm, again Mr. Google seems to know the answer:
(You may jump to the conclusion right away if you want, last page of course)
http://ecadigitallibrary.com/pdf/CARTSASIA05/CARTSAsia0527_lpr.pdf

So....I should be OK using a regular cap....(elco)

[Etienne MacGyver]

Sjeez, that prices does not make us happy 

[Vnera]

Man those prices are crazy!! If i remember correctly i still have a few of those  Once bought the all the electronic components of a monitor repairman when i was 8 years old

[level42]

....which means they might not be that good anymore.... elco's ("caps") tend to stay in better health when used regularly then on a shelf.

On the other hand....the story is not over....

I checked the schematics where cap C5 and C10 are used.

C5 is used across the input of the voltage regulator for the +5V. Instead of a more common 7805, a 78G is used, which can be regulated (contrary to a 7805 which is fixed output). However, the cap seems to perform the basic input filtering of the regulator. Usually you see something like 0,33 uF regular caps there. On data sheets for 7805 they are even indicated to be not necessary if the filter caps behind the rectifiers are physically close to the regulator....
SOooooo, IMHO it is VERY uncritical which type of cap is used here and I have no clue why they chose a wet tantalum ??
I'm sure I'll be fine with a regular elco with the same value there.
(I wonder what effect the high ESR would have had in this application...)

Now for C10:
That one is used in the reset circuit as far as I can see. Doesn't seem to critical either ? Any ideas, Robin, Andreas ?
I think it looks like it's safe enough to use a 10uF regular aluminum cap for both ?

[Belike]

Received my early Xmas gift today.


Before you ask why did I bought this model, some answers:
-I like it's shape much more than the russian one
-From 1945 to 1989 there were only russian products were available in Hungary, I bought more than enough from them for my whole life.
-It has the auto discharge function

After a few tests it seems like a great product, the only disadvantage is that the crocs are too big for accessing smaller caps, André's equipment have sharp pins, I guess it's easier to handle it in these cases.
Anyway, I have a masterplan to fix this, simply attach some pins to the crocs.
I tried to make a video, but my camera didn't focus to the equipment, I will have to borrow a better one if you are curious it's live action.
Btw. that 10% capacity difference in this pic is acceptable, or it has to be replaced?
I guess the serial resistance is ok in this case.