IRS Beta/Gamma Servo Control Unit

dobbhill

Vinyl Addict
I'm looking for a calibration procedure. I want to make sure that my servo system is doing its job..It sounds good, but I believe the left side is just "not quite rite."
I could just shut up and listen, but these psychiatric conditions.....

I'd appreciate anyone's personal experiences under the hood of the SCU that one might share with me.

Happy Listening!
D
 
i don't think anyone knows, frankly. there is a schematic for the Beta/Gamma unit in the Beta technical sheet PDF, but that's it. one thing you could do is measure the voltage at certain positions in the right channel (such as near any adjustment pots), and then adjust the left channel pots to match.
 
I was looking for the "easy" way. I guess I'll have to drag out the signal generator and start investigating....
D
 
i think there was talk once (somewhere) of trying to get ahold of the company that built these -- i don't think Infinity designed them. i'm not sure whatever came of that. heck, i could have even imagined it!
 
Firstly,adjust your controls on the front of the SC to:-
HP Filter - 15
LP Filter - 164
Bass Contour - 0
Low Freq Phase - 0
Low Freq Level - 0
Open Loop Gain switch on the back of the SC unit is set to where you normally have it with the amps you use.
Inject a 50Hz frequency tone via a signal generator into the input jacks of the SC one channel at a time.
Measure the frequency you have coming out via the output jacks one channel at a time.
If there is a difference,you then have to adjust either the left or right channel offset and either the left or right channel level or gain until you have the same freq coming out as injected.
In your case Dave the left channel needs the adjustment.
If both channels are completely different in output to what was injected then both channels need adjustment.
I have tried to include a pic of where the pots are located and which is which but am having trouble doing so.
Since nobody has the exact correct bias adjustment for this unit,as a reference point,this is what I would do:-
Pick the channel that sounds correct (when playing music and remember which it is) and then follow the above proceedure and make adjustments to the opposing channel to suit or match the correct sounding one.
On another "bass" note,
I have not completely "cracked the nut" so to speak of the SC as the accelerometer has been,due to ventures in life that are more important at present.
I got so far and stopped,but guarantee the next time I pick up on it I will see it through.
Hope this helps all. :thmbsp:
 
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yet another point

Thanks for that info MrLegit :thmbsp:

I found this on EBAY plus other pics, someone selling a control woofer for
Infinity Delta Gamma and others it says...
MORE PICS HERE
The control woofers in my IRS Beta's do not have this little board attached :scratch2: sure does look like a woofer from those speakers.
Beauty ring is part of the casting as is mine, so is it the year they were made and this is a mod or are they for other Infinities ? Just a thought.

delta-gamma.jpg
 
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Thanks for that info MrLegit :thmbsp:

I found this on EBAY plus other pics, someone selling a control woofer for
Infinity Delta Gamma and others it says...
MORE PICS HERE
The control woofers in my IRS Beta's do not have this little board attached :scratch2: sure does look like a woofer from those speakers.
Beauty ring is part of the casting as is mine, so is it the year they were made and this is a mod or are they for other Infinities ? Just a thought.

delta-gamma.jpg

John,
One woofer in each column will have the board. Usually 2nd from the top woofer. You have to have the board, as that is where the servo wiring attaches. Then that board attaches to the accelerometer under the dustcap.

You had your woofers out, you had to disconnect the extra wire from one of the speakers, yes?
 
No board on mine only 3 terminals to hook up the internal cable in the cabinet ...

JM
 
OK, interesting. I kind of stand corrected. I just looked at my Beta control woofers and they too are just the strip with resistor like SicMans.

HOWEVER...My Gamma control woofers had the little board. I know, I had to unsolder the leads when I sent them to Bill Watkins. I prolly have pics around, as I took a few shots to verify lead placement when putting things back together. My Gammas were bone stock purchased from a friend that had them since new.

So at some point, they changed designs and moved the circuitry either closer or further from the accelerometer. This is kind of how Infinity rolled back in the day. Many design changes that went undocumented. Which one is newer is anyones guess!
 
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MrLegit: Thanks so much! You are always so generous to share the info you have. I need to swap channels first to ensure that it is the SCU and not the speaker/accelerometer. Then I'll bust into that SCU and take pictures and measurements....we shall see.

NumbDiver: I apologize. I should never speak in absolutes...I should have stated that I had never come across a IRS B/G control woofer with anything more complex than a resistor/terminal board.

JM: Yes. Like that.

All: Please share pictures/data/experience about this vintage of servo system. We are all on our own when it comes to the servos, and keeping them running as designed. I was working on a database a while back, but got distracted by bigger things. I'll try to finish it and publish it soon...

Dave
 
I had my controller open the other day because my large amp was giving me problems and forgot to take pics. I'll see what I can do about pics of mine. Also it would be good to get any part #'s off the board or REV #'s stamped on the pc boards too. Date codes on parts may give a clue unless they bought mass quanity when the speakers and servos started to be released.
Carry on men !!! and ladies if you're interested too.
 
Yes, I have the day off.....from work, that is...

So, I swapped sides on my servo/woofer setup:
I connected the left side amp and speaker through the right channel on the servo and my "problem" (the howl from too much gain) followed the amp/speaker. Next, I'll isolate the amp channel to determine if it's the amp channel (doubt it: Crest Audio FA901) or the servo control woofer.
Ain't this stuff fun?!?

D
 
The control drivers that have the mounting strip (not PCB) with the 3.9K resistor soldered across the two outside terminals (once soldered in place and in circuit it becomes a 1000ohm resistor) are the first generation control drivers.
The control drivers with the PCB's attached to the frame of the driver are a later version in the production run or from the spare parts divisions within Infinity.
 
bump on an old thread :) you are all Lucky I have Delta's but really wonder how the addition of the servo makes things sound :) maybe one day I will walk into a good will and find a servo sitting there no one understands what it is and its just been waiting for me!
lol
 
Nick I own both the Gammas and Betas. As far as the servo control the difference is night and day with the deltas. I would suggest if you could acquire a servo unit and a 2nd amp you will be amazed.
 
There in lies the rub lol if i could find an accurate schematic and proper parts list i think i would get my nephew to build one from scratch, figure out the PCB and have a short run made but .. none of that exists or so it seems, lol the schematic is out there I believe but not a really legible copy, in an ideal world i would find a broken one and rebuild it from scratch. Cause these are somewhat unobtainium amplifiers i have in spades, and the few that do come up, pelople want more for the crossover than deltas seem to even sell for by them selves LOL
 
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