CF82E30 cards with different capacitors

[oyanliz]

Hi all,

I have two never recapped CF82E30 cards with factory caps. When I started recapping them, I have realized that one of the card is fully loaded by 2.2uF 50V capacitors and the other it has only four 2.2uF 50V capacitors, the rest of caps are 10uF 35V, as showed in the schematics. All the components of the cards, as resistors, relays, diodes... look the same on both.

Is this because there is not difference between wich of these caps can be used on these cards? Or is it something else I´m missing with this?

I am going to replace all the caps by 10uF 50V Panasonic caps, but I would like to share the issue just in case.

Thanks to all in advance.

Best regards.

Oihan

[amillar]

Very strange, but you should definitely make them all 10uF!!! (Just improves the low frequency response a bit.) I do very vaguely remember that 2.2uF caps were heavily used in early desks for space saving, then changed to 10uFs as capacitor technology improved. But as you say the mixture (on two cards of the same age) is odd.

Cheers,

Andy

[oyanliz]

Thanks for answering Andy.

I taked the photo to the "card 7" after changed the 10uF 50V caps and the photo of the "card 8" is before any change of any cap. Initially, both cards look the same, with all original yellow caps and I was going to change all of them until realize about the issue. As both caps are the same sizing, is it possible to get confused someone in factory when the cards were built?

I ask this because if I find any similar issue, I will continue recapping without get on doubts.

Anyway, is not a big issue so...

Best regards.

Oihan

[amillar]

As both caps are the same sizing, is it possible to get confused someone in factory when the cards were built?

Not very likely, although not impossible. In 1984 the 611 cards were automatically tested for correct component values, but the 651 cards weren't (because not so many were made). All the 651 cards, and the finished 651, were tested by a chap called Keith - brilliant darts player! - and that was all he did, for years and years; you can see the "KD" on the test sticker. So although someone could have built them wrong I would have thought it was unlikely that Keith wouldn't have noticed as he would have spotted that it looked strange.
But the factory in Brandon (where the PCBs were assembled) did make mistakes - I started at SSL three months after these cards were made, and my first job (for a couple of weeks) was automatically testing 611 cards, and certainly this was one of the mistakes that did happen.
Cheers,
Andy

[oyanliz]

Thank you so much for the info Andy!!

Very best regards!!

Oihan