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Refurbishing Acoustat 2123 interface, have ?'s
Refurbishing Acoustat 2123 interface, have ?'s
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Old 22nd August 2014, 12:23 AM   #11
AcoustatAnswerMan is offline AcoustatAnswerMan  United States
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Quote:
Originally Posted by Atom666 View Post
Andy
Just to make sure I understand this the correct transformer wiring should be
Spectra 3300 = RED
Spectra 2200 = Orange
Thanks
Andrew
Note 4 on the drawing is CORRECT - it's the labels on the schematic that are backwards. The RED tap is for two-panel speakers, and the ORANGE tap is for three-panel systems. Sorry for the confusion.
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Old 22nd August 2014, 09:31 PM   #12
bolserst is offline bolserst  United States
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Quote:
Originally Posted by AcoustatAnswerMan View Post
Note 4 on the drawing is CORRECT - it's the labels on the schematic that are backwards. The RED tap is for two-panel speakers, and the ORANGE tap is for three-panel systems. Sorry for the confusion.
Corrected(I think) drawing attached...please confirm.
The Spectra sector wiring and bass equalization notes may prove helpful for the OP as well.
Attached Files
File Type: pdf Acoustat_MK-2123_Spectra2200-3300_corrected.pdf (196.8 KB, 78 views)
File Type: pdf Acoustat_Spectra_Sectors_Bass_EQ.pdf (212.4 KB, 43 views)
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Old 23rd August 2014, 12:45 PM   #13
AcoustatAnswerMan is offline AcoustatAnswerMan  United States
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Quote:
Originally Posted by bolserst View Post
Corrected(I think) drawing attached...please confirm.
The Spectra sector wiring and bass equalization notes may prove helpful for the OP as well.
The attached schematic is now correct. Thanks.

I had a odd dream last night wherein an Acoustat owner sent me a check for $400 in appreciation of helping him with a question about his speakers. Okay...who needs my mailing address?
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Old 20th September 2014, 09:59 PM   #14
Chamberman is offline Chamberman  United States
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I have finally received all of the parts and began working on going through these Acoustat boxes. I included some pictures of the first box I completed. All caps were replaced, new binding posts, higher capacity 1 ohm Vishay resistors, and new switches. If anyone wants to replace the switches in these interface boxes, they are still available. Honeywell produces an identical drop-in switch (Part #12TS115-3), Mouser carries them at a cost of about $13 ea. The new switches are rated for a higher capacity, the old ones were 15A/125VAC/.75hp, the new ones are rated for 20A/125VAC/1.5hp.

The 100uF/100v NP electrolytic in the crossover had leaked electrolyte out of the lower side of it. It turns out the 47uF in the network was only rated for 50V. I was wondering why it was so much smaller than the 100uf, but the voltage rating was facing downwards so I couldn't see it. I'm sure that one was run well beyond its rated voltage capacity at some point in the past.

The binding posts are a bit of a pain because of the fact Acoustat designed the backside of the posts to be the support for the main x-over board. This greatly limits your options for replacement unless you would like to completely redesign the support scheme. We decided to go with these posts that are of a similar design as the originals, but with better quality gold plated brass parts and a larger cable capacity.
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File Type: jpg 20140920_145727.jpg (708.9 KB, 137 views)
File Type: jpg 20140920_143607.jpg (675.5 KB, 133 views)
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Old 23rd September 2014, 12:03 AM   #15
Chamberman is offline Chamberman  United States
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Okay guys I have a few questions for the Acoustat experts.

I am setting up the bias on these 2123 boxes and they are both a good bit low. I have the ultrasonic boards mounted in the chassis as the instructions state to do. These have the 15VAC adapters. I am checking them with both a 1000X probe and simultaneously with a second meter hooked up directly to the red taps. The lower voltage reading on the second meter with the 1000X probe disconnected maxes out on the first box at 68VDC and the second at 65VDC. Once I connect the 1000X probe to the 5KV tap the supply loads down to about 55VDC at the red tap and I measure about 3kv on the 5kv tap with the 1000X. So even accounting for the loaded tap I only have maybe 3600V without the 1000X probe connected. This seems extremely low compared to the 4300V I need.

Reading through the info on Andy's site I see that too high of a voltage can be an issue and a change to a lower voltage zener on the ultrasonic PCB is needed to correct that issue. Is it possible the opposite is true here? Do I need to switch that zener out for a modestly higher voltage? At this point I do not know which voltage zener is in there. I would have to drop the pcb out to determine that.

The good news is of course they are both off by approximately the same value so there should be no component failure involved.
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Old 23rd September 2014, 01:08 AM   #16
Chamberman is offline Chamberman  United States
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The bias board in these boxes differs from the schematic. There is no zener, a jumper is installed in its place and likewise no 470 ohm limiting resistor. I am assuming the zener and resistor were removed to allow for higher operating voltage as now the full DC rail is able to reach the base of the regulation transistor. I modified the schematic as previously supplied to account for the boards installed in these boxes. I also measured the voltage at a few points in the circuit and put those measurements into the schematic. The voltage measurements seem as expected. I am however surprised that I can get that high of a voltage out of the reg transistor, I expected at least a 1 - 2V loss.

BTW Michael told me that this low bias voltage was an issue before the upgrades, so whatever the issue is it started before the work that was just completed.
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File Type: jpg Mk2123_Intfc.jpg (44.2 KB, 121 views)
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Last edited by Chamberman; 23rd September 2014 at 01:11 AM.
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Old 23rd September 2014, 02:18 AM   #17
Chamberman is offline Chamberman  United States
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I think that I am slowly piecing this puzzle together.

I found this article on audio haven about upgrading the US board. Due to the fact this board has the 4.7uF capacitor, .001uF film cap and no HV feedback wire attached it looks like this is one of the very early boards. The date codes of the electrolytics I replaced were '87 & '88. So it appears that what I need to do is to convert this older rev board to match the newer rev schematic that is posted here in this thread. I'm surprised that all of the holes and component silk screening is there to make it the newer 1991 rev, but none of those components are present. What's up with that?

In addition, While measuring I left my meter checking voltage on pin 3 of the IC and decided to check the 5KV tap with the 1000X probe and the HV had climbed to 3.7KV with just the loading of the meter on that IC circuit. When I pull the probe off of pin 3 of the IC the HV drops back to 3KV, so the circuit appears capable of operating as intended.

I included a picture of the board I'm measuring.
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File Type: jpg Ult_Son_PCB.jpg (673.4 KB, 114 views)
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Last edited by Chamberman; 23rd September 2014 at 02:21 AM.
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Old 23rd September 2014, 08:36 AM   #18
tyu is offline tyu  United States
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Yea...i saw that The board was diff....maybe Andy can say.... send him a e-mail....i have never seen that board...
Driving the panel Transf with that low bias is not good!
3k is low....
But where is the 500m...? the end of it is were to put the probe? ......... is the 500m on a nother board?
i run my panels... more like 4.7-5k.........youll get 3-4db more output with the high bias
thanks for the pic

Last edited by tyu; 23rd September 2014 at 08:58 AM.
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Old 23rd September 2014, 10:48 AM   #19
Chamberman is offline Chamberman  United States
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Quote:
Originally Posted by tyu View Post
But where is the 500m...? the end of it is were to put the probe? ......... is the 500m on a nother board?
Yes, the multiplier and 500M resistor are on a second larger board.
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Old 23rd September 2014, 12:40 PM   #20
Chamberman is offline Chamberman  United States
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Originally Posted by tyu View Post
But where is the 500m...? the end of it is were to put the probe? ......... is the 500m on a nother board?
Here is a picture of the two boards.
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File Type: jpg Acous_Upg.jpg (635.3 KB, 107 views)
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