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KSS-272A Substitution of laser diode
KSS-272A Substitution of laser diode
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Old 10th June 2021, 01:51 PM   #41
Salar is offline Salar  Germany
diyAudio Member
Join Date: Feb 2006
Location: Germany
Saw that you also spent quite some time with this topic :-)
Yes, but as I wrote in this thread

KSS-190A with new laser diode. Applicable for the KSS-151A too.

diyaudio-member anatech more or less deceived me and still sits on a Sony-CDP-102, a BU-1 Transport and ten Sharp LT022MC laser-diodes I gave to him
-in December 2017!
Without manolomos and you, nothing would have happened!
And there are other good people in this forum: Rockeater donated a CDM-1
and shipped it from Australia to Germany.
But I was very much consumed with a documentary movie from January 2020 until now, world-premiere is on Saturday @Berlinale, when a distributor is found, I'll be back in the diyaudiogame for some time. But all BU-1 based players I have are working, so I do not want to risk killing a working one - and prices - even for broken ones, rocketed up!
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Old 10th June 2021, 09:15 PM   #42
ManoloMos is offline ManoloMos  Spain
diyAudio Member
Join Date: Dec 2019
Location: Canary Islands
Hello. ĄDios mio! (Ohh my god!) is what I thought when I saw the picture. The work of the hardware is flawless.
I've though to buy some Technics or Onkyo with some Nec laser pickups, but I've doing other things. Not all in life are CD players.

Well, but I've seen that you uses the cd player laser pickup circuit for to see the waves. I'd don't do this. I'd do an independent amplifier circuit, DC coupled. You can do a circuit that can be useful for other laser pickups.
With a separate laser pickup amplifier, you can amplifier the laser signal with DC component. And if there is DC component, you can rest or compensate it for to carry the out to zero volts. This is necesary for to visualize it at the oscilloscope.

Another advantage of a amplifier circuit, is to separate the laser pickup with a flex cable, so, you get a more compfortable way of to manipulate the laser pickup.

I see two kinds of laser pickups:

-. With only photodiodes. For example KSS-151a. The amplifier must be a IV amplifier.
-. With amplifier and circuits, for example like KSS-272a. A simple voltage amplifier.

Asam ask for a procedure, a sequence of adjustment.
-. Laser power at minimun.
-. Signals connected to the oscilloscope, and carried to zero volts.
-. Connect Low Frecuency Generator with DC Offset to Focus coils.
-. Try to find something at first at the E-F photodiodes.
-. When appears something, adjust photodiode place until the moment A/C=B/D diodes.
It's not easy, because the right point depends of DC-focus voltage.

I've seen on internet these Technics SOAD70A . Photodiode array looks to be attached with screws, that's good, but the position is not compfortable. You can put a plastic strip on the photodiode array with soft glue for to ease the adjustment like I've done. If you do it, you get more precision at your move.

Best regards.
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Old 11th June 2021, 11:14 AM   #43
ASAMS is offline ASAMS
diyAudio Member
Join Date: Nov 2020
Thanks for your response!
I am actually not using the signals from the servo PCB, there are 4 simple I/V converters on the rear side of the servo PCB (as said, all inspired by your work .. don't want to say I copied all your ideas :-) ).
I am using the servo PDB only for the reference voltage for the I/V amplifier (power by single 5V) and the driver for the focus lens. Here I added a signal (from my USB scope) that I can change in offset (lens position) and amplitude.

I have installed an original pickup (not 'touched' earlier) and have adjusted the 'mirror' (which was a DVD before, but it's now a real mirror glued on the DVD). That is my reference (see 2nd picture).

Now the problem really seems to be to get all signals in the center of the diodes, which is an adjsutment in the ”m range. I need to improve the setup.
Anyway, I see that the signals in one direction changes differently than in the other. Not sure if this is now an adjsutment done by the cylinder lens. Need to try, but as said .. everything is so delicate to touch and to adjust.

To be continued :-)

@Salar: good luck on Saturday, used to live in Berlin for almost 11 years.
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