I need to take a close look at the laser block assembly. Pin 6 is labeled as ground but it is tied to -5v on the servo board. I am assuming this is just a typo, but if the laser is running on +5 and -5V it would explain the over heating! the trimmers were locked in place (before "I" messed with them) so I don't think that this is from anyone messing with them. so it's really puzzling. I will try and get a picture if i can zoom in close enough.
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Same goes for me.
I think I would do a quick of the rails with the old laser still fitted. Maybe look for any drys on regs anywhere.
I think I would do a quick of the rails with the old laser still fitted. Maybe look for any drys on regs anywhere.
OK well some success tonight and some problems. 1- I replaced the laser and it fired right up, read the disc and appears to play. But the unit has other problems as it will not come out of mute and the volume control doesn't work but I will get to those issues later.
What I did discover is that the servo board does have -5v on Pin6 and ground on Pin 1 just like the schematic shows and that the laser block is connected as show where Pin 6 should be ground and Pin 1 should be VC which I am guessing is -5V. I did not get to pin out the chukei board and see if it does a swap but I am guessing not!
I know that in other VRDS transports they used the KSS-151A laser. I can't find a pin out of the 151 and I wonder if they made a mistake and assumed both were pinned the same???
So the question now is should I just leave it as is and hope the new laser last's awhile or should I tear it apart and change it the way it should be??
Zc
What I did discover is that the servo board does have -5v on Pin6 and ground on Pin 1 just like the schematic shows and that the laser block is connected as show where Pin 6 should be ground and Pin 1 should be VC which I am guessing is -5V. I did not get to pin out the chukei board and see if it does a swap but I am guessing not!
I know that in other VRDS transports they used the KSS-151A laser. I can't find a pin out of the 151 and I wonder if they made a mistake and assumed both were pinned the same???
So the question now is should I just leave it as is and hope the new laser last's awhile or should I tear it apart and change it the way it should be??
Zc
The KSS240 is being "floated" between the rails, so that it "thinks" it's running +10VDC. There is no need for the laser's ld/pd circuit to be "real grounded", so it's perfectly fine running this way.
The damage makes me think that the laser diode catastrophically shorted, frying the transistor that supplies it. This can theoretically happen years after a laser diode has been static zapped, but I never really thought it possible in practice until now.
The damage makes me think that the laser diode catastrophically shorted, frying the transistor that supplies it. This can theoretically happen years after a laser diode has been static zapped, but I never really thought it possible in practice until now.
I wish I could find a data sheet for the M52104FP IC. in all the other schematics I have seen thus far that use the KSS-240A laser, they have Pin 6 grounded and Pin1 tied to -5V and is running from +5V. Running from +10v may be fine but that still leaves the issue of Pin 1 tied to ground and not -5V.
I will leave it as is, but it is something to think about. I need to get the other issues sorted out and that may be a much bigger issue.
I will leave it as is, but it is something to think about. I need to get the other issues sorted out and that may be a much bigger issue.
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Missed that the pin1 connector through to the main board is also a ground line, which I verified on the full manual schematic. Just checked the Denon DCD-1290 manual, and verified that the VC is not a supply line, but is rather a mid-point voltage bias pin, so using it or not depends on the servo chipset.
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But even that schematic you posted correctly shows Pin 1 as VC and Pin 6 as ground! and I do see in your schematic that the Pin 1 line goes to a VC test point. where as the VRDS-T1 (and hence Wadia 21) is not shown or as verified, connected that way! I really think this is a Teac factory mistake!
I doubt there's a factory error tbh.
In your diagram it doesn't actually say that pin 1 on P701 goes to Pin 1 on the KSS. It implies as much but doesn't quite go as far as showing that.
In your diagram it doesn't actually say that pin 1 on P701 goes to Pin 1 on the KSS. It implies as much but doesn't quite go as far as showing that.
I pinned it out, I took the dead laser apart and with a multimeter checked that Pin 1 really is connected as show and that Pins 5&6 are also as shown and the PCB's are labeled as to which is Pin 1 etc. So YES It is connected as shown!
But what I did find on a sony schematic for a cd player that also used the KSS-240A is that VCC is shown as +5, Gnd is gnd but VC is shown as +2.6v or almost have of VCC so maybe VC is not -5 but a half supply reference?? and if the T! is running off +/-10V Gnd would be half reference! But still every schematic i can find shows these lasers and pretty much all the KSS series to be running from +5v. without a datasheet it's hard to know but it's interesting.
But what I did find on a sony schematic for a cd player that also used the KSS-240A is that VCC is shown as +5, Gnd is gnd but VC is shown as +2.6v or almost have of VCC so maybe VC is not -5 but a half supply reference?? and if the T! is running off +/-10V Gnd would be half reference! But still every schematic i can find shows these lasers and pretty much all the KSS series to be running from +5v. without a datasheet it's hard to know but it's interesting.
You mean with 10 volts across the pickup. Very strange I agree but I think you have to take it as correct.
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