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Old 26th June 2013, 06:17 AM   #5061
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Originally Posted by scm View Post
Steve
Hi SCM, I just had a look at my records and as I thought, your unit was from a Stephan Tremblay from Canada. And it is at least third hand now as he bought it second hand and was heavily modded by the owner/s that were ham fisted with a soldering iron.
I did replace all the quad matched LED/LDR's which were potted and soldered into 2 x 8 pin DIL sockets which also had to be replaced and then it had to be recalibrated at a labour and parts cost of $120.

This was the email I got back from the Stephan after I repaired it.

"Hi George,
It arrived safely yesterday. I just want to thank you for helping me with the Lightspeed. It now sound so much better. The sound is fast & clear with tons of details. The soundstage is huge and the balance is well centered! The music is just flowing...What a difference!!!
I am very happy that I can enjoy it properly. This is a awesome product and I can listen to 12 or 1 o'clock with plenty of gain.
My setup: Macmini > cEntrance DAC (25 ohms) > Lightspeed > Yamamoto A-08s (200K input impedance) > Klipschorns
Best, Stephan (from Canada)"

Two weeks later, he was having problems again.

" Hi George, Greetings from Canada. Sorry to ask for your help again but since yesterday I am only hearing a little bit of music throught my LS. Almost no vocal and no power whatsoever! I have always triple checked every connection with the RCA in/out wiring to make sure I was not doing anything wrong."

I had the feeling that maybe there might be some big dc offset from the source or back from the poweramp that was cooking the led/lrd packs. As I have said above first change the 100kohm dual log pot I suspect this now.

Cheers George
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Old 26th June 2013, 06:23 PM   #5062
scm is offline scm  United States
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Well George you are absolutely correct.
I just received it, now I do I go about getting the cover off do I work from the front, the back or do both end plates have to come off ? I want to post pictures of the insides with your approval of course.

Steve
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Old 26th June 2013, 09:32 PM   #5063
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Originally Posted by scm View Post
Well George you are absolutely correct.
I just received it, now I do I go about getting the cover off do I work from the front, the back or do both end plates have to come off ? I want to post pictures of the insides with your approval of course.

Steve
You have P/M re dismantling procedure.
This is the pot you'll need to buy. Please do not turn any of the calibration pots inside this unit has been calibrated to the new quad set of led/ldr's, hopefully they are still OK.
http://au.mouser.com/ProductDetail/A...p8VJhNJL8jA%3d

PS: Break of the little lock tab on the new volume control, as it will not sit flat if you don't.

Cheers George
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Last edited by georgehifi; 26th June 2013 at 09:42 PM.
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Old 26th June 2013, 10:58 PM   #5064
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Can you imagine how much better his sound would be if he used a Lightspeed Attenuator for each control!

Feeling cheeky, had my double shot of caffine this morning
Cheers George
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Old 27th June 2013, 02:44 PM   #5065
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Bits of solder spatter here and there...one component in the middle of the board looks like two out of four wire connections are blown/melted apart.

Not too encouraging at this point
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Old 27th June 2013, 06:22 PM   #5066
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Quote:
Originally Posted by scm View Post
Bits of solder spatter here and there...one component in the middle of the board looks like two out of four wire connections are blown/melted apart.

Not too encouraging at this point
Post a picture? Begs the question how much power was applied.
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Old 27th June 2013, 09:50 PM   #5067
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Quote:
Originally Posted by scm View Post
Bits of solder spatter here and there...one component in the middle of the board looks like two out of four wire connections are blown/melted apart.

Not too encouraging at this point
I have asked scm not to post pictures of this unit as it was heavily f****d with, as is now not representative of how a Lightspeed Attenuator looks, and I would not like a picture of this circling around on Goggle images.

The spatter is remnants of all the mods this has gone through don't worry about that, the little blue trim pot is for calibration don't touch that, and the 4 loops of wire are for calibration also and dictate which channel needs calibration to the other, two are open circuit and two are closed don't touch these either.
The front panel 100kohm dual log pot is what you first need to change as this is the maybe the culprit and the easiest thing to do, I just hope the 4 matched led/ldr's are ok if not then your seller (steven) had a serious problem with his system that has done damage to them again.

Cheers George
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Last edited by georgehifi; 27th June 2013 at 10:00 PM.
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Old 27th June 2013, 10:19 PM   #5068
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Thanks George. So at each corner of the blue trim pot only 2 out of the 4 wires loop back into the board then ( being closed) ?
Just to clarify, 2 of those wires located on opposite corners of the trim pot are by the looks of them burned through (being open)..if that`s by design then ok I`ll move on to the dual log pot.

Any chance the log pot may be found at Radio Shack ?

Thanks
Steve
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Old 27th June 2013, 11:31 PM   #5069
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Originally Posted by scm View Post
Thanks George. So at each corner of the blue trim pot only 2 out of the 4 wires loop back into the board then ( being closed) ?
Just to clarify, 2 of those wires located on opposite corners of the trim pot are by the looks of them burned through (being open)..if that`s by design then ok I`ll move on to the dual log pot.

Any chance the log pot may be found at Radio Shack ?

Thanks
Steve
That's correct by design, only two diagonal of the 4 links are connected for calibration purposes, to the untrained they may appear burned, but that is solder that's seen.
As for the pot the only good one I've seen from the US that has the correct pot shaft and diameter is the Mouser I've linked to in the above post. The voltage to the pot should be 5vdc measured from the negative side of the power supply.

Cheers George
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Last edited by georgehifi; 27th June 2013 at 11:35 PM.
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Old 28th June 2013, 02:36 AM   #5070
scm is offline scm  United States
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George..putting the fitment issue aside, are there any advantages to be had by going with an upper end pot like an Alps ?
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