Sheldon thank you again. One moment I pondered about the idea that a small piece of tape could solve my problem fast and easy. But no, I think it would an unwise move now that I've come so far and having the panels spread out for me. So I will replace the membrane and why not doing it myself after all it's DIY here. At first I will try to get the necessary parts nearby in Holland, mylar, coating and glue. As for the tensioning of the mylar. As a newb particularly the method with tape and a spring balance seems promising to me. If I can't get parts locally I will contact ER audio in Australia.
Can someone please explain to me the different protection circuits the quad 2905 would have. I see two different effect. One is the speaker distorts but doesn’t shutdown and my amp protection doesn’t kick and shut it down (quad artera). The second is no sound and the amp shuts down. Are these two different causes? Is one a spark and the other too much power going to the speaker?
Thanks
Thanks
There are two different clamping mechanisms in any of the modern quads (63's and newer; inside they are the same). There is an overdriving clamp circuit that was originally more sophisticated with a soft clipping and then a hard clipping, but that was replaced in the later 63's (about SN30000) and newer with a set of stacked diode bridges with zeners across them. This new circuit clamps at ~7000v. In theory that is before the panels arc.
The second circuit, which is effectively identical in every modern quad, is a RF receiver that triggers a triac that shorts the input of the speaker (because screw your amp) if the circuit senses an arc. This one is triggered by bad panels and typically sounds like the speaker got quieter and is distorted.
The clipping circuit would only be active on very loud peaks. But the arc clamp can happen anytime if you have a bad panel. I can imagine that if the amp is playing a quiet passage and the clamp fires, it may not trigger the amp's shutdown circuit. But if the passage is over some current sensing threshold, then it shuts down.
Sheldon
quadesl.com
The second circuit, which is effectively identical in every modern quad, is a RF receiver that triggers a triac that shorts the input of the speaker (because screw your amp) if the circuit senses an arc. This one is triggered by bad panels and typically sounds like the speaker got quieter and is distorted.
The clipping circuit would only be active on very loud peaks. But the arc clamp can happen anytime if you have a bad panel. I can imagine that if the amp is playing a quiet passage and the clamp fires, it may not trigger the amp's shutdown circuit. But if the passage is over some current sensing threshold, then it shuts down.
Sheldon
quadesl.com
Obviously it's hard to diagnose without seeing the speaker, but my money is on a bad panel. The clamp circuit is really simple (and assuming the power supply filter cap is good), there's not much to go wrong. Because it's doing the clamping, people naturally gravitate to thinking something is going wrong there. It's a classic case of shooting the messenger.
Sheldon
sorry, I’m a little slow on the uptake.
Two,circuits, clipping and clamping.
Clipping due to overdriving
Clamping due to sparking
Clamping causes distortion
Clipping causes the speaker to shutdown??? Could it also trip my amp off? Can a spark cause the speaker to shutdown?
Some background:
1) It does clip on loud but not too loud music
2) I’ve heard clamping on these speakers due to sparks and fixed the issues with failed panels. They’ve all in tip top shape now and I no longer get clamping from sparks.
Two,circuits, clipping and clamping.
Clipping due to overdriving
Clamping due to sparking
Clamping causes distortion
Clipping causes the speaker to shutdown??? Could it also trip my amp off? Can a spark cause the speaker to shutdown?
Some background:
1) It does clip on loud but not too loud music
2) I’ve heard clamping on these speakers due to sparks and fixed the issues with failed panels. They’ve all in tip top shape now and I no longer get clamping from sparks.
Not really no, but I listen quite loudly. Always have. It’s definitely the clipping. I’ve heard the speaker when it clamps due to a spark and it distorts but doesn’t shutdown the amp. This only happens during big loud music. In your experience is it possible for something to fail that could cause the clipping circuit to kick in too early? Is this where that 25v capacitor comes in?
There could be a problem with the zener strings or rectifier diodes in the clamp circuit, such that one of the bridge rectifiers is essentially shorted out. That would make the limiter run at 2/3 of the normal level. I've not seen that behavior before personally, but anything is possible.
The service manual is on my website, if you look at the schematic, you can see the three stacked rectifier bridges with zeners in them: http://quadesl.com/modernRefs/ESL2905.pdf
Sheldon
The service manual is on my website, if you look at the schematic, you can see the three stacked rectifier bridges with zeners in them: http://quadesl.com/modernRefs/ESL2905.pdf
Sheldon
Recall that the 2905 service manual has some errors in the schematic.
Corrections posted here: Parts for the Quad ESL 63
When the zener string clipper activates, it effectively shorts the secondary of each of the transformers so the amplifier is being asked to drive 2.5ohm below 100Hz, dropping to around 1 ohm above 1kHz. While this is 1 ohm higher than when the SCR spark detector activates, it is still pretty brutal. The early ESL-63 clippers that operated on the primary side of the transformer were much gentler on the amplifier...dropping the impedance to 5 ohm below 100Hz and 3.5 ohm above 1kHz. Most amplifiers would handle that just fine. Makes we wonder if the newer zener clippers were intentionally made to drop the impedance lower to encourage people to NOT overdrive their speakers.
Corrections posted here: Parts for the Quad ESL 63
When the zener string clipper activates, it effectively shorts the secondary of each of the transformers so the amplifier is being asked to drive 2.5ohm below 100Hz, dropping to around 1 ohm above 1kHz. While this is 1 ohm higher than when the SCR spark detector activates, it is still pretty brutal. The early ESL-63 clippers that operated on the primary side of the transformer were much gentler on the amplifier...dropping the impedance to 5 ohm below 100Hz and 3.5 ohm above 1kHz. Most amplifiers would handle that just fine. Makes we wonder if the newer zener clippers were intentionally made to drop the impedance lower to encourage people to NOT overdrive their speakers.
This is perplexing to me. Let me give the history
I received the speakers in a state where they couldn’t even be powered due to terrible noise
I found 2 totally destroyed membranes and two in kind of bad shape. Two per speaker.
All other membranes were inspected and were in good shape
All 4 bad membranes were rebuilt and put in one speaker.
That speaker continued to distort and clamp.
I switched the main board with the good speaker.
Bad speaker continued to clamp
I switched all panels with the good speaker so that the rebuilt ones were in the good speaker.
Much improved but it continues to clamp/clip at higher (not too high) volumes.
The good speaker never clamps or clips.
I see two different behaviours:
1) High pitched female voices at higher volume cause the speaker to suddenly distort (clamping)
2). Higher volume but big dynamics music causes the speaker to shutdown and my amp to trip
My conclusion.
It’s not the membranes or an issue with the main board
I put the bad membranes
I received the speakers in a state where they couldn’t even be powered due to terrible noise
I found 2 totally destroyed membranes and two in kind of bad shape. Two per speaker.
All other membranes were inspected and were in good shape
All 4 bad membranes were rebuilt and put in one speaker.
That speaker continued to distort and clamp.
I switched the main board with the good speaker.
Bad speaker continued to clamp
I switched all panels with the good speaker so that the rebuilt ones were in the good speaker.
Much improved but it continues to clamp/clip at higher (not too high) volumes.
The good speaker never clamps or clips.
I see two different behaviours:
1) High pitched female voices at higher volume cause the speaker to suddenly distort (clamping)
2). Higher volume but big dynamics music causes the speaker to shutdown and my amp to trip
My conclusion.
It’s not the membranes or an issue with the main board
I put the bad membranes
If I am understanding the swapping of components described in Post #71 properly, the problem didn't follow the panels or the board. Only the transformers and delay line boards stayed consistent with the problem speaker? Is that correct? Rather than lifting the 330 ohm resistor, you could also monitor the clamp driver voltage with a multi-meter as shown in Post #47
@ stokessd, have you ever experienced arcing in Quad transformers or delay lines? I have had issues with transformers arcing internally on other ESLs. This distorts the sound by itself, but could also possibly trigger the TRIAC clamp.
@ stokessd, have you ever experienced arcing in Quad transformers or delay lines? I have had issues with transformers arcing internally on other ESLs. This distorts the sound by itself, but could also possibly trigger the TRIAC clamp.
I've had individual delay line coils go bad. They can actually intermittently connect and make a similar clamping action. The wire in those coils is super thin, and will burn out near one of the connections to the terminals in the plastic bobbin holder. The wire never fails in the coil due to the reasonable thermal conduction to the neighboring wire, but the burn is always where a the wire is surrounded by wax and doesn't have any heat sink to speak of. Apparently the wax even with the phase change taken into account isn't as good a heat sink as the rest of the copper in the coil.
I have microscope pics of the delay line faults and fixes if anybody cares.
I haven't seen an input transformer fail in a quad yet.
I've never seen the resistors or the caps in the delay lines go bad either.
Sheldon
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