For anyone following my original post and who may appreciate the steps in trouble shooting your CLS speakers without knowing too much about ELS speakers, here's where I've landed.
I found a schematic online and there's a simple writing on the top that says "Approx 280 volts at X former pins 5 and 8". Probing pin 8 on the transformer required me to remove (lift up) the circuit board, but when plugged in, I only read 107VAC between pins 5 and 8 on this transformer. There is the start of my problems. I'm going to replace this transformer and keep going.
I noticed the power resistors R1 and R2, 27K ohm/15K ohm look burned up on the board. I want to see what I should measure across those. They definitely got hot, but not sure they are bad yet. That's next.
I'm also looking to measure V+. Any ideas of what V+ should measure and the best place to measure it?
Finally, I want to probe the output to the panel with a high voltage probe. I'm not sure what exact measurement, but I understand it should be about 3800V. If all works in the electronics, these all should check out.
Doug
The approximately 280 volts is at the secondary of the power transformer where it feeds the voltage multiplier stack, correct?
First question: do both speakers exhibit the same problem? A bit of a coincidence, no?
Second question: Does the CLS 1 have circuitry that senses the presence of an input signal and turns on the bias? There might be an LED inside that lights when the bias is energized. Does it light?
The bias voltage isn't zero when not energized, it's at a "standby" value that's supposed to minimize dust collection when not listening. That 107 volts you measured might be the standby value.
The schematic I've seen, which doesn't seem to correspond exactly to my CLS II, throttles back the bias voltage with a voltage divider, with one leg shorted with a triac. If memory serves me, it is such that the bias is in standby when the triac is turned *on*. In either case, you probably need to be feeding the speaker a signal to get valid measurements. Be careful, because you will then have a second source of high voltage in the box which, unlike the bias supply with very low current capacity, could be lethal.
As far as what the bias voltage should measure, the theoretical value is 280 volts times the number of sections in the multiplier stack times 1.4 (square root of 2, the "crest factor"). But due to the aforementioned low current capacity/high impedance of the bias supply, even with a high impedance high voltage probe, you may not get that.
When I used to work on CRT monitors, I was pretty confident that the voltage I measured with a Fluke high voltage probe and a Fluke multimeter it was designed to work with was correct. But there, the current capacity was enough to knock me on my ass, even kill me.
A standard safety precaution is to work with one hand, with the other kept out of the way or in your pocket. It would behoove you to observe that. That means when you do something like measure the voltage between pins 2 and 5 of the bias step-up, you really should use something like a "grabber" clip or alligator clip. While the bias voltage itself is about the same as the annoying shock you get from walking on a carpet in winter and touching a doorknob, there is plenty inside that box to mess you up, including the 280 volts from that transformer and, with music playing to actually activate the bias supply, the music signal itself.
