BBC Maida Vale studio 3 4040E

[StarF666]

Things are going well at the moment. We finished the patch bay and will soon start with the new studio wiring. Still need some EDACs and Jim seems busy. The problem with the monitor outs solved itsself (like a lot of problems lately). This time playing around with the monitor cuts suddenly made the outputs come alive one after another. I think all those logic circuits and relays just need some juice again. And I will at some point replace capacitors on the logic boards. But for now all switches and logic dependend functions just work.
We also fired up the Atomic plasma brick and the plasma mainboard. We've got at least one working plasma meter  But I have to check the grounds one more time as I get a weird noise on all audio paths once the plasma mainboard gets power. Luckily I found a grouding scheme in the docs. BTW: What is the "common" way to set levels with plasmas? I can switch them from group to tape but there doesn't seem any way to monitor the inputs. Maybe I should RTFM.
Lastly we fired up the computer. We don't really plan to use it but who knows. Might be fun to use it with our two MCIs 2".
So while we will start to get the studio ready for the SSL I will start to check the audio paths. I got my oscilloscope and a true RMS multimeter ready. Any hint on a good free or shareware software spectrum analyzer/measurement software?
That's all for today.

Greetings,
Martin

[Artur D'Assumpção]

Looking very clean!

Use the computer! It rocks, once you start messing with the SSL mixing system you'll understand why it was a success!

Btw, the new "SSLMixed" computer will support your keyboard!

Cheers,

Artur

[StarF666]

Great to hear about the keyboard support. As I said, we might keep the computer to use it with our tape recorders.

[xmax]

Noise with the Atomic brick? You must have a problem elsewhere. We have plenty out there with
zero issues including Kilmister on this forum. Remember the HV for plasma is referenced to the logic
rail which is referenced to the audio rail, so I imagine if anything in the new power wiring is
a little off, noise havoc could happen. The build is looking great!
I'm sure we can get to the bottom of it. N

[StarF666]

Thanks Norman. I'm sure it ain't a problem with the power brick. It's probably something with the power wiring or maybe something on the plasma motherboard.
Didn't have time to investigate this further. We had a very odd problem and I don't know if anybody is aware of it but on older Es the switch cards for dynamics and EQ are a little different. When cleaning the channels, my partner simply removed all switch cards and the switch caps and then randomly reassembled them. I had a burning input amplifier a week ago but did not find anything, guessed a failing op amp. Then the other day another burning input amplifier.  I had put in a few channels and realized that some were not working. After some checking I found the 2A fuses on the failing channel mainboards where gone (at least one per channel). We traced it down to the switch cards. In certain positions they shortened +20V to ground. My partner was very embarrassed. Maybe I should make a thread somewhere to warn other users?
We checked all channels and put in most of them. Still have problems with some but it starts to look like a 4k.
Norman, I know your video for the alignment procedure (math ist math). I'm a little confused anyway. What should the voltages read on the center section? I guess 18.5V vor +/- rails. And where should I measure the logic voltage (and this is the one I really don't know where to set).
Once I'll be back on the plasmas, your help is very welcome.

Greetings,
Martin

[xmax]

18v or 18.5v on the audio rails (your call it really makes no difference, but some swear by 18.5) Then 6.5v,
Between the +18v audio and the 11v (sometime called 13v, welcome to ssl land!) logic rail. Cheers! N

[StarF666]

Thank you. I will stay at 18V for now. I have to switch parts of the desk on and off as long as we are working on it and with 18V voltage can swing a little. Might go for 18.5V once it's in its final parking position.
The monitor outs are still not working properly. They put out a very quiet signal altthough it doesn't sound distorted or anything. I'll take care of this next. Then I'll go over the power cabling once more to get the plasmas working.
Sill looking for some audio measurement software to check some signals. I now have some test speakers at the main outs and it doesn't sound like it's missing something. But I know the capacitors on the input modules (and probably the other channel modules) are a bit below spec. The center section looks like it has been recapped at some point. All values are to spec and it has different capacitors all over the place.
We also installed the faders. Some VCAs seem to have some noise, but only one seems to be really bad. We'll need some new VCA cards anyway.
Oh and I tried Total Recall... it's awesome!

Stay tuned
Martin

[waltzingbear]

If your metal work is in good shape, the module should lock into the up position and you don't need a piece of plywood to keep the module up. Probably just pull up a little more.

Cheers
Alan

[StarF666]

Thank you Allan. Unfortunately, the mechanism is worn out and does not lock up reliably. We tried to fix it but it's not really secure. That's why the plywood.

[StarF666]

Just a short update. Spend another day finding the problem with the monitor outs. Somebody replaced R78 (the 10 ohms "fuse" resistor) on the logic card (82E24) with a 1,5k resistor) wich dropped negative supply to almost 0V. Don't know how anything on that board could have worked. Got the mini LS output working now. Main monitor outs and switching the monitor matrix to "quad" still doesn't work (it switches but no sound at any monitor out). Will start over bughunting on the 24 and 22 cards now. But it's nice to listen to the SSL sound while working on it. 

[Artur D'Assumpção]

Hi,


I don't know if you're already doing this but I though it would be nice just to put it out there:

I will suggest you to bug hunt using a technique taught by my buddy Norman and which proved to be very effective in these cases. Use a guitar amp and a guitar cable, place the - on the console frame (for ground) and probe with the + side. You can find by just "hearing" where the sound eventually stops! - CAUTION: put very low volume on the guitar amp!

You can use this to probe the backplane of the 651 and then in the faulty card.

I hope it helps!

Cheers,

Artur

[xmax]

Or a scope or any audio analyzer, a amp works in a pinch, a cap and resistor in line is also a good idea. N

[StarF666]

Thanks for the advice. I have a scope here which I use for these things. I have another problem which distracts me from the monitor outs. I keep burning R15 on the channel input cards and I just can't find what's faulty. It happens after I switch the console on but not every time. Mostly after the desk was out for several days but sometimes just for the night. It's always the current limiting resistor in the negative line and sometimes it also kills the 2A fuse on the channel motherboard. It only happens on startup. I'm currently checking the 82E21 card in the center section. When I switch on the SSL it's both in mix and record status simultaneously and I usually switch it to one status and flip them a bit to make sure mix and record bus are in a defined state. Dunno if the two things are connected and I really can't get down to why the input cards keep burning. it's mostly just one card failing on startup. And somedays the desk just works fine. It drives me nuts.

[DigitalMetal]

Hi,

Im new to the forum today (found it while doing some of my own personal research) I've previously been on the prodigy pro/group diy forums for years.

I saw the title of this thread and had to come and have a look, I'm actually an Engineer at Maida Vale looking after the studio's and although I've only been there for about 6 months I've been in other parts of the BBC for 7 years one of the main reasons I moved to MV was to get my teeth into the SSL's before they are all gone and deal with music recording studios rather than the Radio and TV studios i used to look after.
Right now we have two 9000J's and although i was not around in the days of your 4K we might still have some info knocking around if there's anything specific you need i can find out.
I know for certain one of my colleagues who used to look after your desk so i can direct any questions to him on your behalf anyway great to see what you have done so far and good luck with the project!

Neil

[marcmozart]

Welcome Neil!

I'm actually an Engineer at Maida Vale looking after the studio's
Neil