ADR Express Limiter

[bugbrand]

Hi,

I have a not-so-happy (cosmetically, at least) one of these headed my way, so have been looking around for any service docs - but.. drawing a blank.

If someone could help me out, I'd be mighty appreciative!
(even better, upload to the Tech Docs section?)

Thanks! Tom

 

[RuudNL]

GroupDIY member Mutterd has more information, you could send him a PM.

https://www.gearslutz.com/board/geekslutz-forum/934836-adr-express-limiter-manual.html

(By the way: I suppose this is the same Mutterd...)

 

[mutterd]

yup - thats me - I have (and love) one of these and have some docs I can share if they will help  - ADR is notoriously complicated to calibrate but its worth the work for sure…

PM me here and we'll work something out…

Timothy

 

[bugbrand]

Ok! Super! Will message now - thanks!
Yeah, heard the setup was complex.. Well, first things first - get the box, repair some bits & check it even works roughly to spec!

 

[bugbrand]

So.. it arrived.

How many compressors do you know with memory backup batteries? You know, the sort that have great tendency to leak.. with leakages causing PCB trace disintegration..
Yep, there's an onboard battery here! And on mine (+ the area around) it does not look healthy.
Haven't delved in at all yet, but thought I'd share this - useful knowledge/gotcha for anyone considering picking one up.

 

[mjrippe]

Sorry to revive a zombie thread, but I have one of these beasts and it is confounding me!

It was sitting for many years and on first power-up looked promising.  Then it shut down.  Turned out the battery had leaked and took out the 15v regulator.  Ok, remove battery, clean PCB, replace regulator, turn it on - it works!  On one side :-(

Start tracing signal on CH1 and find a leaky cap, replace that and it works!  Except turning the release time past 12 o'clock or engaging the RMS setting causes gain reduction with no signal present :-(

Replace caps in sidechain section, now it is behaving better.  RMS and relase time act normal.  Let's calibrate this thing and get it back to work.

So I get to the FET bias (see doc below) and with -30dBm in and the FET law and Bias pots both full CCW (anti-clockwise) I get -32dBm out.  Adjusting the FET law pot only LOWERS the output.  Same on both channels. 

Everything is set as it should be - unbalanced in and out, clipper off, pre-emphasis off, etc.  Can't figure what I'm missing or if there is a typo in the docs!  Any help would be much appreciated!

 

[MagnetoSound]

Hey, mjrippe ...

I am not in a position to help you (yet) but the weird thing is I bought one of these today, and have been having fun with it this evening and it has suddenly f'd up!

I would be very grateful for a copy if you have the docs ...?

Maybe we could troubleshoot together - mine has got stuck in full GR position, meter pinned to the left and very low output. It was fine earlier today ...

It also has the leaky battery and the board around it looks suspect (although the 7815 is fine).

 

[mjrippe]

Hi Magneto,

Check the caps in the sidechain section (4x 22uf).  Really a full set of electrolytics would be smart, but I don't have them all on hand so I've been replacing them as I find bad ones.

Full manual with schematics and calibration is available for a short time here:
https://www.dropbox.com/s/1ixk1ooz86uyipf/ADR%20Express%20Limiter.pdf?dl=0

Let me know how you get on!

Mike

 

[guy_4]

Hello Mike,

Would you also have in your files the ADR  F600 Broadcast full manual, with schematics and calibration ? 
I am looking for one since bit of time... :'(

Best,
Guy

 

[mjrippe]

Would you also have in your files the ADR  F600 Broadcast full manual, with schematics and calibration ? 
I am looking for one since bit of time... :'(

Added to the Tech Docs section:
https://groupdiy.com/index.php?topic=56151.msg874315#msg874315

 

[MagnetoSound]

Hey Mike,

Well that's pretty damn cool! Thanks so much.  ;D

I will attend to the side chain caps forthwith, and of course report back.

Cheers,

Dan

 

[MagnetoSound]

So it's not the caps.

The GR meter is pinned. COMP and LIMIT leds are stuck on. GR is actual, and output is low. None of the pots or  logic switches have any effect (though all are working) ...

This looks to me like a DC biasing problem somewhere in the sidechain or detection circuitry.

I will continue to trace around and see what I can suss. The manual has little to no troubleshooting help, and I don't really know what voltages I should be expecting. Any help/pointers gratefully received.

 

[mjrippe]

You can check the transistors in circuit with a multimeter, just make sure the two channels measure the same.  I did pull FET4 and it was OK too.  If you need DC voltage measurements I can tell you what mine reads, though I don't know if it is 100% correct!

Anyone have any insight on my calibration questions a few posts back?

 

[MagnetoSound]

The stuck LEDs were due to the LM747 that drives them having locked up. It was also leaking positive bias onto the voltage follower control line. After I pulled that the lights went out and the GR improved somewhat.

I've since traced and replaced several of the BJTs in the voltage follower that were blown, close to the control line. I now have full output and pretty normal gain reduction but I have the same fault that if I turn up the release time or turn RMS on, the GR goes up, even with no signal. I have ordered some more 22uf 021s and will replace those when they arrive, but I can't fathom out what else it might be. Both FETs in the VF circuit seem ok.

I am also replacing any suspect logic chips but so far they have all been ok.

I'd try and help with your calibration if I could Mike, but I haven't yet been near the varilossers and don't really want to until the VF is working as it should.


EDIT:  I suppose it may be that the 747 is needed in circuit to balance the control line with it's non-inverting input (as long as it is working properly, that is). I shall see when the replacement comes.

 

[MagnetoSound]

Anyone have any insight on my calibration questions a few posts back?

I am thinking perhaps we should compare quiescent control voltages. If you can only reduce gain with the FET trimmers, might it suggest that your control line is biased slightly into cutoff?

It is late here now, I'll do it in the morning.

 

[MagnetoSound]

[Deleted my last post as I had two transistors in backwards when I took my measurements. I will get back in a few days when my replacement parts are in ]

 

[rjb5191]

[Deleted my last post as I had two transistors in backwards when I took my measurements. I will get back in a few days when my replacement parts are in ]

Any updates on this?  I have as sick express limiter as weill.

 

[frenkonio]

Hi guys, I'm in the process of rebuilding partially a leaked Ex-press Limiter too. All ok with new components, had to change all leds on the frontpanel too and rebuild the buttons (took all buttons off, cleaned inside, etc.).
But... I have no sound on channel 2 and a very very weak signal on channel 1 that is almost crackling. I have replaced lots of the 22uF caps, measured a bunch with my trusty ESR (from Peak) meter but at this moment I haven't solved anything. Any help will be appreciated!

 

[mutterd]

you were able to revive the dead pushbutton switches on the front panel?

those are tuff to deal with, how did you do it?

this boxes are awesome when working.

T.

 

[frenkonio]

you were able to revive the dead pushbutton switches on the front panel?

those are tuff to deal with, how did you do it?

this boxes are awesome when working.

T.

Yes! I was able to change all leds of the frontpanel as lots were messy and with low lights on. Pushbutton are working perfectly, I simply lift the red buttons out with the same tools you find for mobile phones (small triangular piece of plastic), cleaned the oxided parts internally, donate a new form to the internal small sheet of metal that pops up the button and voilà, they work like new.
I solved the issue on one channel, there was a missing trace from one side to another of the pcb that the leakage corroded. Also solved a very bad crackling pot with Deoxit. Now I got one channel working ok, the other one is simply no sound (or, to say better, it's almost audible but there' also a sort of fixed pink noise with very low volume when you crank up the output pot. The input pot doesn't make anything when you move it). I found the schematics, trying to understand where to point on now.