Centre Section Cards

[MarconeMusic]

Hi All

Just going over my Centre Section to get a definitive Cap list. I've seen the cap list by Marc Mozart and its a little different from what I see in mine, so i made my own.

In doing so, i've looked at the Centre section and wondered about it a little.

I have been told it was upgraded to "G" as it was an E at purchase.

I've found, in boxes, what I was told are the E cards that were upgraded.

Im not anything other than curious about the whole situation.

Does anyone know about this 'upgrade' procedure? Would all cards be changed to do this or only certain ones?
Ones ive found are the 22 Card, 25 Card, 27 Card and 28 Cards

I'll attach photos of the cards that i found in the boxes and the cards that are in the Centre currently.

In the pics, The cards that are photographed alone are the ones from the Centre section at the moment, The ones with two in the pic are from the box of parts.

Thanks!

M

[MarconeMusic]

Plus the whole Centre section pic:

[marcmozart]

I think the service manual has the history of changes. On some cards, they went from polar caps to bipolar caps, lots of little improvements were made. That said, my summing and monitor cards are the very last G+ edition, probably with the most changes from E-series cards.

[amillar]

Hi,

We didn't upgrade any of the centre section cards for the G series, there were only two changes we made IIRC to the 651:

• It was painted grey
• The Monitor Level pot had an extra '11' added  - so that you could turn it up to 11. (Yes really, we made a Spinal Tap joke - the really funny thing was that hardly any customers believed that we'd done it as a joke, they thought we must have changed the circuitry. In fact on both E and G 651s the control actually goes to 10 1/2)

We were going to upgrade it, but when we started looking at it we just couldn't work out where to start, and there wasn't enough money in the budget to fund a complete redesign.

The much later G+ upgrade sadly I don't know anything about, sorry.

Cheers,

Andy

[amillar]

P.S. sort of vaguely in answer to the original question a bit: for electrolytic caps in the audio path of the 4k/6k it really doesn't matter too much what value you use for most of them, as long as you don't go lower in value or volt rating of what was in there originally. Mostly we just fitted the physically largest caps we could at the time - even so, the low frequency roll off across the desk was pretty bad (compared to the 9k for example). So whilst going 10x bigger might cause strange noises at power up (even stranger than you get already), going up to double or 4x in value (now that caps are much smaller) is unlikely to do any harm and might do some good.

Just never ever change the values of any of the ceramic caps, or change them from ceramic to anything else. At least as long as you've got 5534s fitted. 5534s are a complete pig to stop oscillating.

Cheers, Andy

[MarconeMusic]

Very interesting information!

You guys are awesome for the amount of knowledge

Making my cap order tomorrow, I like to have enough caps for any piece of gear i buy, that way im sorted and can rebuild when i have time. Just waiting on word from Roger the SSL tech around here, We're gonna chat tomorrow and make a plan. Unsure about Panasonic or Nichion or Elna, but thats for another discussion.

These Spare cards... any worth in keeping them? or put em up for sale...? ...

[amillar]

Unsure about Panasonic or Nichion or Elna, but thats for another discussion.

I'll be interested to read that discussion - I'd love to be able to say that at the time we carefully listened to and selected the best sounding manufacturer for polarised caps, but we didn't! Although we did sometimes ban manufacturers if we got reports back from the field that they sounded bad (but I really can't remember now who we banned.) Bipolar caps we did listen to, even now I've got a collection in my spares box left over from the listening tests, but of course the manufacturers have probably changed their processes many times since then so just because a particular manufacturer's cap sounded good (or rather, didn't sound bad) in 1990 doesn't mean much now. I particularly liked the red plastic housed ones that were the first bipolars we used, can't remember where we used them (13 card?), and oddly can't see any in my spares box so don't know whose they were.

If anyone's ever wondered why we didn't use tantalum capacitors for decoupling - they are MUCH better for decoupling than electrolytics and have much longer life - it's because Colin had used them in the A (and B?) series and had unfortunate incidents where they burst into flames. (They were pretty new in the late '70s.) By the late '80s we really should have started using them, but he was dead set against them. After leaving SSL I went into designing very long lived, high reliability, safety-critical systems and tantalum caps worked just fine!

Cheers, Andy

[waltzingbear]

do you mean the deep red/maroon ERO ones? with the yellow bottoms?

the problem with those is that if exposed to too much heat build up they fail fairly easily. Studer used those in the A820MCH and if the full complement of dolby cards was in the machine the heat buildup over time caused them to crack and fail.

Cheers
Alan

[MarconeMusic]

Apparently my centre section is different than Marc Mozarts list and different from Roger Ginsleys list, which is different from Marc Mozarts list as well..

So, i have something weird and will be picking the caps based on whats in there..

I think were gonna get Panasonics, Roger recommended them as the ones to get.

[Spanzor]

What kind of luck has anyone had who's modded/upgraded their monitor section?

[marcmozart]

Apparently my centre section is different than Marc Mozarts list and different from Roger Ginsleys list, which is different from Marc Mozarts list as well..

So, i have something weird and will be picking the caps based on whats in there..

I think were gonna get Panasonics, Roger recommended them as the ones to get.

Yep my center sections cards are dated 2000-something, probably the very latest edition ever made and a lot different from earlier cards.