Thanks for giving me peace of mind. I do have cut out pieces that are covered in felt, and fit into those 4 hex windows. I do place them at night for privacy.
LF transformers disconnected, amp still shutting down
I tested this last weekend by disconnecting the LF transformers in both speakers. I noticed that there is a convenient jumper, which I disconnected, wrapped in a tiny bit of clear non-sticky plastic to keep it clean, then overwrapped in electrical tape and secured to the 1 ohm resistor (which wouldn't be carrying any current, now that the transformer is disconnected.
In two separate tests on successive days I got shutdowns with two sources, the second being a source I have used for years without issues before May this year.
The shutdowns both occurred after about 90 minutes of operation, playing at a very normal level (not blasting). I used the digital readout of my preamp to set the level identical to what I normally use.
Strangely, I did not find the speaker output level to be very much lower than what I am used to. I have always been crossing over at 100 Hz, so the Acoustats only play 100 Hz and above. There might have been somewhat less output in the midbass and lower midrange, but the highs sounded pretty normal. Combined with my subwoofer, it was quite pleasant.
I tested the HF transformer a few months ago by disconnecting it at the power resistor (which required unsoldering, and re-soldering when the test was finished). So I have now tested one speaker by disconnecting both the HF transformer in one test, and the LF transformer in another test, and either way, with only that one speaker attached to my amplifier (and the other input to the amplifier shorted), still gotten shutdowns.
At this point, the only thing left in the speaker to test would be the power resistor. If the big polypropylene capacitor which I added to it (replacing the old electrolytic) happened to short out, this would still not present a direct short to the amplifier. So I don't see how any capacitor failure could explain the problem. On the other hand, if the 16 ohm resistor has a fault, even if that fault were merely a momentary open, this could cause a reverse voltage flyback when connectivity returns, tricking the amplifier into shutting down.
That is now, as it was before, a low probability guess. However, as I've already eliminated the big obvious things, low probability guesses are all I have left.
Of course there is also the amplifier itself. I'm thinking of trying an altogether different set of speakers next weekend. However, the amplifier was just sent to and returned from the factory, and it had no issues driving the Acoustats for many years.
I tested this last weekend by disconnecting the LF transformers in both speakers. I noticed that there is a convenient jumper, which I disconnected, wrapped in a tiny bit of clear non-sticky plastic to keep it clean, then overwrapped in electrical tape and secured to the 1 ohm resistor (which wouldn't be carrying any current, now that the transformer is disconnected.
In two separate tests on successive days I got shutdowns with two sources, the second being a source I have used for years without issues before May this year.
The shutdowns both occurred after about 90 minutes of operation, playing at a very normal level (not blasting). I used the digital readout of my preamp to set the level identical to what I normally use.
Strangely, I did not find the speaker output level to be very much lower than what I am used to. I have always been crossing over at 100 Hz, so the Acoustats only play 100 Hz and above. There might have been somewhat less output in the midbass and lower midrange, but the highs sounded pretty normal. Combined with my subwoofer, it was quite pleasant.
I tested the HF transformer a few months ago by disconnecting it at the power resistor (which required unsoldering, and re-soldering when the test was finished). So I have now tested one speaker by disconnecting both the HF transformer in one test, and the LF transformer in another test, and either way, with only that one speaker attached to my amplifier (and the other input to the amplifier shorted), still gotten shutdowns.
At this point, the only thing left in the speaker to test would be the power resistor. If the big polypropylene capacitor which I added to it (replacing the old electrolytic) happened to short out, this would still not present a direct short to the amplifier. So I don't see how any capacitor failure could explain the problem. On the other hand, if the 16 ohm resistor has a fault, even if that fault were merely a momentary open, this could cause a reverse voltage flyback when connectivity returns, tricking the amplifier into shutting down.
That is now, as it was before, a low probability guess. However, as I've already eliminated the big obvious things, low probability guesses are all I have left.
Of course there is also the amplifier itself. I'm thinking of trying an altogether different set of speakers next weekend. However, the amplifier was just sent to and returned from the factory, and it had no issues driving the Acoustats for many years.
Concern about the 16 ohm resistor
What is the power rating of the 16 ohm resistors in the Medallion C version?
In the speaker that has me most concerned (I have solidly verified that this one speaker by itself can cause amp shutdowns, in many different tests), I noticed something bad when I was cleaning it. The exposed wire that you clamp the slider onto is somewhat damaged underneath the clamp. There is a thin groove that starts on one side of the wire, and goes through the wire to the other side, not straight across, but over the course of about 3/8 inch. In other words, a gap. I squeezed the visible wire to narrow the gap, but short of trying to solder it back together (which I suspect would be very risky....the ceramic itself could crack) I'm not sure what I could do to fix it. I clamped over the identical location hoping that the clamp itself might help assure continuity. The impedances measured constant with my DVM however.
I think this issue may have occurred many years ago when I was first setting up the speakers, I may have over-tightened the clamp.
One thing I do not know is how deep inside the ceramic the wire goes. If most of the wire is actually exposed, the problem I see could be bad. And furthermore, if there is only a small remaining contiguous piece of wire, that piece could get "burned out" more easily.
What is the power rating of the 16 ohm resistors in the Medallion C version?
In the speaker that has me most concerned (I have solidly verified that this one speaker by itself can cause amp shutdowns, in many different tests), I noticed something bad when I was cleaning it. The exposed wire that you clamp the slider onto is somewhat damaged underneath the clamp. There is a thin groove that starts on one side of the wire, and goes through the wire to the other side, not straight across, but over the course of about 3/8 inch. In other words, a gap. I squeezed the visible wire to narrow the gap, but short of trying to solder it back together (which I suspect would be very risky....the ceramic itself could crack) I'm not sure what I could do to fix it. I clamped over the identical location hoping that the clamp itself might help assure continuity. The impedances measured constant with my DVM however.
I think this issue may have occurred many years ago when I was first setting up the speakers, I may have over-tightened the clamp.
One thing I do not know is how deep inside the ceramic the wire goes. If most of the wire is actually exposed, the problem I see could be bad. And furthermore, if there is only a small remaining contiguous piece of wire, that piece could get "burned out" more easily.
Need to replace the female mini plug on board
I have a pair of spectra 6600's with one that needs a new female on board mini plug adapter as it is not functioning..led does not light up though replaced. Does anyone know where I might be able to get one that fits the ultra sonic repair board or have one from any of the spectra series that had the exterior power supply.If anyone has a mini female adapter it would be appreciated.
Would an alternative be directly soldering the leads from the external adapter to the board, if so there are 3 solder points on the board and which wires from the adapter would need to be attached to the solder points?
I have a pair of spectra 6600's with one that needs a new female on board mini plug adapter as it is not functioning..led does not light up though replaced. Does anyone know where I might be able to get one that fits the ultra sonic repair board or have one from any of the spectra series that had the exterior power supply.If anyone has a mini female adapter it would be appreciated.
Would an alternative be directly soldering the leads from the external adapter to the board, if so there are 3 solder points on the board and which wires from the adapter would need to be attached to the solder points?
Thanks. Foolproof, no. After taking the upper panel off, it became obvious why. The vertical part of the woofer box (the part the ES panel attaches to) is visibly tilted and is not loose or defective. Also pretty easy to tell it was never touched after manufacture.
Not clear how that panel was registered (if at all) to the box, but clearly it was easily possible to misalign it in assembly. Looks to me like no alignment/registration features at all. Apparently QC was off that day also
On the other speaker the panel is almost perfectly vertical.
Thanks for the disassembly directions. Yes I need to change the socks.
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I don't think you can repair the resistor if it has a broken wire. The wires are solidly encased in the ceramic. Far easier to replace it. The resistor is rated 50 watts. You can use a non-inductive model if it makes you happier, but I don't think it matters at audio frequencies. The easiest course would be to replace it with two resistors, whose combined value is 16 ohms.
Thanks. Foolproof, no. After taking the upper panel off, it became obvious why. The vertical part of the woofer box (the part the ES panel attaches to) is visibly tilted and is not loose or defective. Also pretty easy to tell it was never touched after manufacture.
Not clear how that panel was registered (if at all) to the box, but clearly it was easily possible to misalign it in assembly. Looks to me like no alignment/registration features at all. Apparently QC was off that day also
On the other speaker the panel is almost perfectly vertical.
Thanks for the disassembly directions. Yes I need to change the socks.
Sorry to hear you got a bum speaker box. The panels and boxes weren't mated at the factory, so it would be difficult to detect that problem with the box. Not making excuses. Too bad the original owner didn't complain of the problem, as getting it replaced would have been easy then. Do you think you can remedy the problem?
Finding an exact replacement for the power jack may be difficult, as each jack manufacturer tends to have unique mechanical dimensions and solder pad locations. I designed the board layout (note the ajs initials on the board) and spec'd the components over 20 years ago, so I don't remember who manufactured the jack. It's probably out of production anyway.
Your idea of soldering the wall transformer wires directly to the board is fine. The output of the wall transformer is AC, so polarity doesn't matter. I don't have a board to look at, so I can't give you exact instructions on which solder pads to connect the wires to. You may find that one of the pads isn't connected to anything else in the circuit. If that's the case, solder the wires to the other two. Or, you may find that two of the pads are connected together on the board, in which case you'd solder one wire to the connected pair, and the other wire to the third pad. Hope that helps.
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AcoustatAnswerMan, I started a new thread that I'm hopeful you'll have time to look at. Thank you in advance if it's something you can help me with!
Acoustatanswerman et al -- what interfaces do I have here?
Acoustatanswerman et al -- what interfaces do I have here?
Actually I only noticed it after I had removed the panels. It's very easy to notice on the box alone. Originally I had assumed the "legs" of the panels were not perfectly in plane with the panels, which is hard to measure or observe.
Yes, for anyone else having this issue, it's easy to remedy. Each panel is fastened to the box with 4 bolts, 1 upper and 1 lower on each leg. To tilt it, simply insert shims of the appropriate thickness (eg fender washers) between the legs and the box. To tilt the panel forward, insert the shims at the upper bolts, to tilt it back insert at the lower bolts.
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I just posted this information on another thread, but I wanted to also post it here in my thread.
I recommend these replacement parts for the bias multiplier. Both can be purchased from www.mouser.com. You'll need ten of each to service one pair of speakers.
Vishay GP02-40 diode, 250 mA, 4000 volts
Mouser p/n 625-GP02-40-E3
Vishay 564R30TSD33 capacitor, 3300 pF, 3000 volts
Mouser p/n 75-564R30TSD33
Be sure the interface circuitry is completely discharged before work. This can be done by either waiting several hours after being unplugged, or you can use an insulated test lead to short the red pin plug to ground.
The capacitors are not polarity sensitive and can be inserted either way.
The diodes ARE polarity sensitive. Be sure to document the orientation of the original diodes by noting which end is marked (usually with a paint dot). These marks will correspond to the banded end of the new diodes.
Be sure all solder connections are good, and in particular watch for any stray whiskers of solder that might be bridging parts of the circuit.
If you lack the skills or confidence to do the work, any good electronics technician should be able to do the work if you supply the parts.
I recommend these replacement parts for the bias multiplier. Both can be purchased from www.mouser.com. You'll need ten of each to service one pair of speakers.
Vishay GP02-40 diode, 250 mA, 4000 volts
Mouser p/n 625-GP02-40-E3
Vishay 564R30TSD33 capacitor, 3300 pF, 3000 volts
Mouser p/n 75-564R30TSD33
Be sure the interface circuitry is completely discharged before work. This can be done by either waiting several hours after being unplugged, or you can use an insulated test lead to short the red pin plug to ground.
The capacitors are not polarity sensitive and can be inserted either way.
The diodes ARE polarity sensitive. Be sure to document the orientation of the original diodes by noting which end is marked (usually with a paint dot). These marks will correspond to the banded end of the new diodes.
Be sure all solder connections are good, and in particular watch for any stray whiskers of solder that might be bridging parts of the circuit.
If you lack the skills or confidence to do the work, any good electronics technician should be able to do the work if you supply the parts.
The original wall transformers were rated at 12 VAC, and if your speaker was originally supplied with 12-volt transformers, you should continue to use them.
Later speakers were designed for a 15 VAC transformer, and should be used with same.
I don't consider any performance difference between the two.
Thank you. The power supply (if I read the diagram correctly) consists of a rectifier/filter followed by an adjustable voltage regulator and that feeds an oscillator that gets rectified by the voltage multiplier to arrive at the 5kV that feeds the panels. Is the high voltage critical as to accuracy, and is there a specific voltage spec to adjust for at the output of the regulator?
You are correct on the operation of Acoustat's "Ultrasonic Bias Power Supply (UBPS)". This supply was introduced mainly to service world-wide markets, where the only safety-agency approvals required were for the wall transformer itself, and not for the speaker. Added advantages are that the bias supply is regulated, and therefore immune to mains voltage variations, and that it is adjustable, greatly reducing unit-to-unit variations. The exact value of the high voltage bias is not critical, but I'll make some comments. Acoustat's design criteria is that the bias voltage is nominally 5 kV, which is a good compromise between efficiency and performance in a wide variety of climates (high and low humidity, altitude, etc.).
The most important thing is that the bias voltage is the same for each speaker in a pair, thus ensuring proper channel-to-channel balance. Thanks to the adjustability of UBPS, this is easy to obtain.
For hybrid speakers like the Spectra 11 and 1100, bias voltage is perhaps a little more critical, as it does affect the efficiency of the ESL portion, but not the woofer section. Therefore, the bias voltage can be used (within limits) to control the relative volume between woofer and ESL.
Measuring the bias voltage is a little tricky, and due to the high output impedance of the supply, virtually any measuring method will tend to give a lower reading than the actual voltage. But as long as both speakers give the same "incorrect" reading, then you know you have the bias voltage matched between speakers.
I have a written procedure explaining different ways to measure the bias. It's probably been posted somewhere before in this thread, but when I have a chance, I will post it here again.
P.S. You must measure the final high voltage output: measuring the output of the low voltage regulator won't work, due to variations in the circuitry that follows it.
The most important thing is that the bias voltage is the same for each speaker in a pair, thus ensuring proper channel-to-channel balance. Thanks to the adjustability of UBPS, this is easy to obtain.
For hybrid speakers like the Spectra 11 and 1100, bias voltage is perhaps a little more critical, as it does affect the efficiency of the ESL portion, but not the woofer section. Therefore, the bias voltage can be used (within limits) to control the relative volume between woofer and ESL.
Measuring the bias voltage is a little tricky, and due to the high output impedance of the supply, virtually any measuring method will tend to give a lower reading than the actual voltage. But as long as both speakers give the same "incorrect" reading, then you know you have the bias voltage matched between speakers.
I have a written procedure explaining different ways to measure the bias. It's probably been posted somewhere before in this thread, but when I have a chance, I will post it here again.
P.S. You must measure the final high voltage output: measuring the output of the low voltage regulator won't work, due to variations in the circuitry that follows it.
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My bad. I failed to consider the variability after the regulator. Thanks.
ULTRASONIC BIAS POWER SUPPLY - ADJUSTMENT
Measurement and adjustment of the high voltage biaspower supply is vital to the proper operation of the speaker. If an imbalance in playing volume is noted, or any modifications or repairs have been made, the bias power supply should be measured and adjusted if required. Two methods of measurement are provided.
Measurement and adjustment of the high voltage biaspower supply is vital to the proper operation of the speaker. If an imbalance in playing volume is noted, or any modifications or repairs have been made, the bias power supply should be measured and adjusted if required. Two methods of measurement are provided.
- This procedure requires specialized equipment and electronic skills. DO NOT attempt this procedure if you are unfamiliar with safe operating practices around high voltage (+5000-volts DC).
- Do not be concerned about the exact voltage measurements. Due to variable loading effects of different meters, it is impossible to accurately measure the output of the supply. What is important is that both speakers are adjusted to read the samevoltage using the same meter.
- This procedure requires that the interface be disconnected from both the speaker and amplifier. Do not plug in the wall transformer until told to do so.
- Location '5KV' is the point (used for method #1 only) for measurement of the 5000 volt powersupply. Location '5KV' is the circuit pad next to the "+5 KV" label located at the center of the large printed circuit board.
METHOD #2 (Alternate) Using a 10 megohm input impedance digital voltmeter, connect the ground (black) lead of the meter to chassis ground (at the solder lug attaching the white wire to the chassis). Apply power via the appropriate wall transformer, and allow the system to stabilize for several minutes. Connect the hot (red) lead of the meter to the red pin-plug terminal (where the panel connections are normally made). DO NOT CONNECT THIS TYPE OF METER TO LOCATION ‘5KV’. Adjust the trimmer potentiometer on the PC board until the probe reads approximately 75 volts DC. This reading will correspond to an actual 5000 volts, but the measurement is greatly reduced due to the voltage divider effect of the power supply and voltmeter.
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Charles,
I thought I would mention my experience with an Eagle 2 driving Acoustat Model 3 (non medallion and no C mod). After a while the amp would shut down. I put the amp on the test bench and could find nothing wrong with it, checked both speakers, same, working perfectly. I put it down to the type of load the Acoustats present to the amp. It's not the first solid state amp to shutdown with them either. They tend to get very hot before shutting down.
On several other conventional speakers, the Eagle 2 performs fine with no issues.
I did have an FPB300 here for a while but never got to try it with the Acoustats, so not much help there. I use various different 100W tube amps and don't have any issues at all driving the M3's to loud levels. Sonically, the tube amps wipe the floor of any solid state amps I've ever tried with the M3's, though I think Acoustats own amps did a reasonable job from memory back in the day. A Moscode 300 I have sitting around works fine too and is happy enough even driven hard for long periods.
Probably not much help to you, but there you have it.
acoustats
hi Andy:
i'm glad to see you joined this forum and appreciate your expertise and participation!
i just bought a vintage pair of 1+1s and besides needing new grill cloths, i was wondering if they needed the caps replaced or any other upgrades? they have the hafler mk-121C interfaces with medallion transformers
i'm an EE so i can do all the work myself; just need access to the parts
also, i got zapped once working on some spectras - how long will the caps hold a charge or do they need to be discharged when going into the interfaces?
i like the straightforward design philosophy in the acoustat product line, and can tell they were hand built; simplicity and direct is usually the best approach; i do not care for the 2 wire AC cords on the interfaces and i'm surprized the metal covers are not grounded for safety
thank you
Jack Zack
hi Andy:
i'm glad to see you joined this forum and appreciate your expertise and participation!
i just bought a vintage pair of 1+1s and besides needing new grill cloths, i was wondering if they needed the caps replaced or any other upgrades? they have the hafler mk-121C interfaces with medallion transformers
i'm an EE so i can do all the work myself; just need access to the parts
also, i got zapped once working on some spectras - how long will the caps hold a charge or do they need to be discharged when going into the interfaces?
i like the straightforward design philosophy in the acoustat product line, and can tell they were hand built; simplicity and direct is usually the best approach; i do not care for the 2 wire AC cords on the interfaces and i'm surprized the metal covers are not grounded for safety
thank you
Jack Zack