QUAD 2805 low volume one side

Yes, the wax does melts with desoldering.
Just be very precise when soldering parts back on. It might look like the soldering is good, but parts "hangs" in the wax and there is no or bad electric connection.
Use paraffin to protect again. You can dip of brush on.
 
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Thanks both. What exactly is the purpose of the wax? And is it paraffin wax? As in candles? I have some beeswax, but does it need to be non-organic?
I bought the QUADs to get away from building or modifying; if I had only known... :(
They are the only main speakers I have ever bought, as opposed to making them, and are more trouble than any of my builds.
 
Bees wax corrodes the copper. Or at least it discolors it, so I'm not sure that the copper is not affected. Don't see any coloration when paraffin is used, so I prefer that.
The wax is for arc prevention even over time when dust comes in.
You can also use a spray can of isolation material.
 
Thanks Jos. I had forgotten how much they dislike dust! I have beeswax and paraffin wax candles, so melting a little of either is easy enough.
The 8 diodes have arrived, although the step in the FR makes me suspect there is something else amiss. But I will replace them as soon as I can figure out a way to keep the kitten out of my hair. Literally, sometimes!
Annoyingly someone has just replied to my for sale ad; I will have put him off for a week or two, without scaring him off. Living down in the bottom left hand corner of England, I don't get many bites.
 
Having at last managed to remove the pcb, I checked all 8 diodes in situ. All check out at 1.14 ohms on my multimeter diode tester. Annoying, so they are not the problem. While I was at it I checked all the others, and they all check as OK. So do the caps (apart from the two electrolytics; i will need to lift a leg of them).
So the problem is elsewhere. Considering that the upper frequencies, above about 1kHz, seem to be the depressed region, I'm thinking I will need to remove the grilles and disconnect the audio input to each middle panel and measure the audio output. The one that makes no difference will be the one receiving only a partial signal and will be the faulty one. Either the panel or the connection to it, or the delay lines feeding the higher frequencies.
Have I understood that correctly? Is there a simpler check I can perform before I go that far? Can I check the delay boards first? The speakers have to stay in the living room, and need protecting from kitten claws at all times. And he is very quick to get into stuff!
BTW, the FR responses in post #15 are at different levels; the lower frequencies are probably fairly equal, it's the higher frequencies which are depressed on the blue trace.
 
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If you place your microphone close to each ring element and compare left/right, you may be able figure out which one is misbehaving. If it works, it should be quicker, easier, and safer than disconnecting the individual elements. To get the most discrimination, you'll need to be very close though (like near the panel's grid structure, so the dust cover/grille probably needs to be off if it's just one part of the ring array that's depressed).
 
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you can measure the wires going up to the panel rings down at the delay lines. The resistance from ring to ring should be about 5K give or take, working outward. But the outer three wires will measure about 350k between them. I've seen the delay line inductors go bad and that resistance number will be way higher.

Sheldon
 
Six months on, and I am finally getting back to this. Life got in the way, as it does. The cat is bigger and even more of a nuisance, so I can't leave the speakers unprotected with him around.
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I have resoldered the PSU board, so I am back to where I started, with them all wrapped up again.
Sheldon; checking the resistance on the delay lines, do I measure from the output of the inductor to the same point on the next line? And can that be reached without removing either the front or rear grille? I have to lock the cat out each time I unwrap a speaker, so I am trying to minimise the time it takes.
 
6 db seems a lot for a bad coil. I was wondering about your clamp circuit in the bases. Can you apply a signal tot he input of each speaker and measure the output of the input board tot he panels and delay lines? Put in a fractional volt signal into each speaker because the voltage is increased significantly and you want to stay within the range of your DMM. Verifying the electronics in the base can be done with feline accompaniment.

BTW, I'm still chuckling about the crazy eyes on that cat.

Sheldon
 
Hi folks, just to note I have taken on this project from ABD, the OP for this thread. They are arriving tomorrow. I believe the OP in discussion with a number of interested parties strongly believe now that there is a bad coil. I have sourced a set of delay line boards from an ESL63 to potentially scavenge a replacement coil but is there any advice on how I go about identifying which coil has gone open circuit? Measure across the legs of the coils?
 
you can measure the wires going up to the panel rings down at the delay lines. The resistance from ring to ring should be about 5K give or take, working outward. But the outer three wires will measure about 350k between them. I've seen the delay line inductors go bad and that resistance number will be way higher.

Sheldon
I have checked resistance as you suggested and the coils appear to be fine measuring about 5.4-5.6k between each and about 350-360k between the outer three points. So it doesn’t appear to be the delay lines. I am going to reflow all the solder joins at the panels next.