SpeakerTalk

[speakerguru]

[audiolabtower]

Hi, there was no test position on the Mk1 (at least not on serial 3XXX). They must have had a way of testing the Mk 2 SStop without having to put 300W into a brand new speaker maybe?

My first traces had the input cap going to the contact on its own but I could not then see how the rest was connected. It must be the pole in that case. I shall try again with that assumption, thanks.

[speakerguru]

Sorry I can't help with the tracing but although I try to only work part time these days, I do have a lot of work on, atm.

[Innercity126]

Hi,

Sorry to be so ignorant, but regarding the LED circuit, where do the actual wires from the circuit board connect to on the crossover?

When I purchased my 105.1's this circuit was not connected, and the previous owner had modded the crossover to use with an active, outboard, crossover.

I have since put all the crossovers back to factory, but I just don't know where the LED circuit board wires connect to. I surmised that the actual LED simply connects to the LED i/p’s on the crossover, but I’m clueless about the circuit board wires.

Please, correct me if I am wrong, and thank you for any assistance you can provide.

William

[audiolabtower]

It should be obvious from the photos, the yellow and brown on topside board go to the led, the input wires are on the opposite edge (marked I/P), white and black go to amplifier output, i.e. the circuit is in parallel with the crossover.

[Innercity126]

[audiolabtower]

Ah, I see, so you have no led driver pcb? Well it is not necessary - if you want to see the led and check listening position you could temporarily connect a 1.5V battery in series with a 100-200 ohm resistor to light the led - but don't leave out the resistor

p.s. I've just looked at my original notes and at the top of the mid/treble pcb where on one side the tweeter wires are connected, next to them is where the led circuit input was connected, black to negative (common track to tweeter negative and black 4mm terminal), and next to it white to positive (track which goes down to red 4mm terminal).

[proffski]

[audiolabtower]

Ooops! shows how many years since I've done electronics, thought it was a normal 0.6V Try a PP3 with 700 ohms or so?

[proffski]

[audiolabtower]

I also just remembered the last time I actually tried it - it was with a CR2032, which is of course 3V, that's why it worked!

[audiolabtower]

Well curiosity got the better of me - the only way to check the tracks under the "Yel" label was to take the board out of the 105 again. My assumptions about the tracks were wrong, because my assumption about a single pole switch was wrong. Checking contacts with a meter showed a quite different setup, which is what I should have done in the first place rather than thinking you could work it out from some photos.

The switch is 2 pole, one pole is for the 5k1 resistor feeding the led trigger circuit from the resistor ladder setting the trigger voltage. The other pole always connects the input cap to the rectifier and power supply circuit, except in the "Off" position, where the whole circuit is open circuit and cannot affect anything coming out of the amplifier (as it should be). The listening position has the pull down ladder removed to trigger the led from much less rectified voltage.

Here is the correct circuit

[speakerguru]

Yes that all makes a lot more sense. Well done. Good job!

[audiolabtower]

Thanks for the help. The only thing I couldn't see was anything on the diodes. I guess that a standard 1N901 is not safe for 200W output swings so maybe they are 200V diodes to be safe?

[Thierry]