Author Topic: Center section 82E24 card issue  (Read 328 times)

skipburrows

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Center section 82E24 card issue
« on: March 13, 2021, 03:07:12 AM »
Good Day all,
Long time reader of this great forum first post.. thanks for any help in advance.
I am servicing a late G plus manufactured in late 2004. It been cared for very well and has developed a center section issue.

Itís definitely on the 82E24 card as I had a loner and confirmed the following issue.
Any external monitor has no meters and signal is distorted on the control room main output. Also the afl output is also distorted. The funny thing is when I press the mono button the distortion totally cleans up. Also when the meter follows is pressed ie  desk output/ external/ follow selection the distortion changes  and gets worse on the later two. Unfortunately The school who owns the console canít find the 24 card extender set. So I am working somewhat blind here.. Iíve swapped all gate and amp chips and no change so I suspect itís a j112 or perhaps a bc212. Iíve used a good meter on diode check and ohms and for the life of me canít find a fault. I know itís a real challenge without an extender but with all the brain power here Iím hoping for some suggestions  that might clue me in.Thanks so much for your suggestion.
Cheers
Skip Burrows

WiktorTRS

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Re: Center section 82E24 card issue
« Reply #1 on: March 14, 2021, 10:42:16 PM »
Hi,
Are there ceramic capacitors soldered at the bottom (solder) side of PCB? Isolation tubes on their legs act as resistors when getting old. They can even cause a short circuit. Remove them and replace with new ones. You can measure them with DMR. They are acting as  potentiometer.
I had the issue in my desk but mine is from 1986... so they were conducting as wire.
Good luck!

horizonsound

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Re: Center section 82E24 card issue
« Reply #2 on: March 14, 2021, 10:51:09 PM »
Yes, they corrode and crack, leaving the exposed leg of the resistors which can short out on the traces.

See below.

Anthony


jimlfixit

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SSL rubber sleeving durability problem
« Reply #3 on: March 15, 2021, 02:09:06 AM »
Yup, unfortunately the rubber sleeving used back then is not so durable these days.
The card shown is from 1980 so that is 40 years old. SSL mainly used Hellermann sleeves and I do as well these days but, a packet I have here shows a shelf life date as these items break down over time, especially when any form of heat could be involved.
The ones shown on the resistors in the picture are probably TH10 versions which means thin wall and 1mm internal core diameter. Other versions used by SSL were even thinner but the main one used for the bigger twin screen Brandrex cables was an H20 x 20 (2mm internal diameter x 20mm in length). Neve and other 'old school' console manufacturers also used rubber sleeves so, expect them to corrode and breakdown over some 40 years or so as well.
Hope this helps and regards from Jim (trying to reconstruct my website from scratch at the moment ... argh).

skipburrows

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Re: Center section 82E24 card issue
« Reply #4 on: March 16, 2021, 06:47:43 PM »
Hey guys thanks... I actually have a late 24 card here that has the new rubber sleeves. So itís still, well like soft rubber. So Iím still back to a j112 or a bc212. (All diodes test fine)Just a bit confused at what could be the common link that is the failure as described in my earlier post. Itís a really tough one without en extender board. I might just have to be (as my dad would say) a bottle changer and start replacing the j123ís and 212ís. So any other ideas before that fiasco would be fantastic!! You guys are great...

Cheers

Chris Simon

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Re: Center section 82E24 card issue
« Reply #5 on: March 16, 2021, 07:17:42 PM »
You'll probably want to do junction tests on all the BC212's before shotgunning them out. Start with the External To Meters function. Does the switch light up when you press it? If it does, then BC212 "TR15" is O.K. If it doesn't, suspect the transistor. It's not uncommon for the BC212s to develop base-emitter shorts.

skipburrows

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Re: Center section 82E24 card issue
« Reply #6 on: March 16, 2021, 07:32:22 PM »
Hey thanks Chris,
Yeah all the logic lights function and switch logic works. Iíve done  the usual in circuit test on every 212 and j112,s all measure perfect and measure when compared to my loaner card! I can normally see the 212 fault as Iíve had that junction short or open a ton of times. This one is really kicking my butt. The signal has no meter and control room out is crap and also the afl is junk. However when I press mono the signal cleans up on the control room out but the meters are still down. The extra weirdness is when I press the meter function switches desk out/follow cr/ external the distortion changes... so weird. Any help before being a ďbottle changerĒ would be great!!!
Cheers to all!

DaveCox

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Re: Center section 82E24 card issue
« Reply #7 on: April 06, 2021, 03:43:56 AM »
Hey Skip, I have an extender card for the 82E24 I could possibly loan you assuming you are still trying to resolve your issue. Where are you located?

Dave

skipburrows

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Re: Center section 82E24 card issue
« Reply #8 on: April 06, 2021, 02:47:39 PM »
Hey Skip, I have an extender card for the 82E24 I could possibly loan you assuming you are still trying to resolve your issue. Where are you located?

Dave
Hey thanks a ton Dave. I managed to get the female 65 way extender off eBay. I have t been able to go back to the school yet as I am going to move the entire studio from a temporary studio I put together and move it again!!! To a permanent facility. This is because the school did a brother in law deal and hired a bunch of idiots that had never build a studio before... what could possibly go wrong!! Anyway I will have a chance in a few weeks and will report back.. really appreciate your offer. Might need to borrow a 55 way female extender at some point...

Cheers

DaveCox

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Re: Center section 82E24 card issue
« Reply #9 on: April 06, 2021, 11:05:30 PM »
No probs, have a quick look at your extender card as I found out the hard way that the extender cards are specific to each master section card. The keyways are in different positions. There will be a sticker on it detailing which card it's for.

jimlfixit

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651 centre card extender info
« Reply #10 on: April 09, 2021, 11:22:56 PM »
Yes, as I remember it from my days at SSL 1980-87, SSL sold extender card sets for the 651 and the channel modules.

1   The channel module extender card comprised of two PCB's, one of which plugged into the actual channel on the console busscards with a big PCB and then it extended out via 3 x 50 way ribbons to a smaller PCB which the channel module plugged into, in order to test it outside of the console frame. I believe that Recycled Audio, here in the UK has its own version of this for sale.

2   The 651 extender set was not sold a lot back in the early years due to the price but, as someone states on here, they were a mix of different extender cards which had (from memory) 55 and 65 way connectors. The idea was that you could raise (or take out) the 651 centre section within the console, plug in the right extender card and work on the card which had the problem.

Both 55 and 65 (if I am correct on this) cards within the 651 had different keyway gaps. The cards in the 651 had the blue (T&B??? ... Thomas and Betts??? or maybe I am wrong and they were Amphenol or something else) PCB upright connectors with a gap at different places where a metal keyway (block?) was fitted so you couldn't plug a card into the wrong place, if this makes sense?

Not many clients ordered the 651 extender set as it was quite expensive due to the different connector types and the keyways involved but, it shouldn't be hard for someone, these days to do their own version I guess (with help from others on this forum!).

Regards from Jim Lassen in the UK and hope you are all well and busy considering all this Covid stuff affecting our industry BIG TIME?