Hi Salar,
RV105 is indeed the drop out detector adjustment. The laser power adjustment is on the head itself, so no worries there. On the original OMS-5/7 the laser power adjustment is right on the board.
I always fine tune the E-F Balance with a drop out disc, one with sharp dropouts. You look at the eye pattern at 0.5mS / div and look at the drop out and recovery. You can see the envelope modulated by the tracking servo waveform. You adjust slightly to optimize the recovery. This will agree with the normal method but it's a finer adjustment. You will need to filter the trigger and adjust the trigger point to get a stable pattern. Your waveform should be no higher than 2 div.
-Chris
RV105 is indeed the drop out detector adjustment. The laser power adjustment is on the head itself, so no worries there. On the original OMS-5/7 the laser power adjustment is right on the board.
I always fine tune the E-F Balance with a drop out disc, one with sharp dropouts. You look at the eye pattern at 0.5mS / div and look at the drop out and recovery. You can see the envelope modulated by the tracking servo waveform. You adjust slightly to optimize the recovery. This will agree with the normal method but it's a finer adjustment. You will need to filter the trigger and adjust the trigger point to get a stable pattern. Your waveform should be no higher than 2 div.
-Chris
Big trouble, simple reason:
The slide ring which fixes the CD got stuck sometimes. So the CD could slightly vibrate, which caused the dropouts.
Made a new adjustment, with the ground screw/point of the Main P.C.B Board as reference.
Where needed, I adjusted the sometimes noisy ground on the scope, that it was symmetrically above and under the center horizontal line of the scope.
So everything is finished now. Sometimes, when the laser has to travel to the last track, the cd will stop, rest some seconds and than spin backwards. Maybe this is caused by the slightly bigger diameter of the pulley of the feed motor? (wrapped heatshringing rubber around it)
But a self made test CD (200hz sine together with 20050hz sine), which had audible clicks now runs perfect...
All the best, Salar
The slide ring which fixes the CD got stuck sometimes. So the CD could slightly vibrate, which caused the dropouts.
Made a new adjustment, with the ground screw/point of the Main P.C.B Board as reference.
Where needed, I adjusted the sometimes noisy ground on the scope, that it was symmetrically above and under the center horizontal line of the scope.
So everything is finished now. Sometimes, when the laser has to travel to the last track, the cd will stop, rest some seconds and than spin backwards. Maybe this is caused by the slightly bigger diameter of the pulley of the feed motor? (wrapped heatshringing rubber around it)
But a self made test CD (200hz sine together with 20050hz sine), which had audible clicks now runs perfect...
All the best, Salar
Hi Salar,
Sounds like your E-F Balance might be out a little. The feed motor pulley diameter increase may cause it to go too far forward on search. Possibly it may be too sensitive in normal play too, but less likely. It normally runs off the average DC component of the tracking servo and is therefore running on need. If your tracking error signal goes negative a lot, the diameter needs to be reduced or the proper belt installed.
See if you can get a drop out disc and check the eye pattern recovery as I detailed above.
-Chris
Sounds like your E-F Balance might be out a little. The feed motor pulley diameter increase may cause it to go too far forward on search. Possibly it may be too sensitive in normal play too, but less likely. It normally runs off the average DC component of the tracking servo and is therefore running on need. If your tracking error signal goes negative a lot, the diameter needs to be reduced or the proper belt installed.
See if you can get a drop out disc and check the eye pattern recovery as I detailed above.
-Chris
Hi Chris,
right, a plus of 0,3mm in diameter on the pulley, caused by the rubber, made the laser travel too far... removed it, cleaned the belt, now it works. I tried the eyepattern with a prepared disc (one black stipe, 1mm with) but could not interprete the signals. Turning E-F balance did not seem to change the signal of the eye pattern.
I measured the ohm value of the varable resistor of the defective OMS-7EII I bought ten years ago and aligned E-F according to it. As far as I know, nobody tried to repair the OMS-7EII when it went defective - I later found out, that a power transitor was blown. So all variable resistors should be in their original positions.
The E_F Balance is now around "eight o´ clock", taking the single ground pin as a 6.
More on the less noisier side.
The unit now runs perfect, hope I won´t have to open it the next ten years.
(My DYI cabinet makes this very complicated)
BTW, flat belts in a lenght of 5,4mm are not available any more, at least in Germany. Somebody told me, that the big chinese suppliers (about three of them, ten years ago, malaysia was the main supplier) do not manufacture this size any more.
Have a nice week and thanks a lot,
Salar
right, a plus of 0,3mm in diameter on the pulley, caused by the rubber, made the laser travel too far... removed it, cleaned the belt, now it works. I tried the eyepattern with a prepared disc (one black stipe, 1mm with) but could not interprete the signals. Turning E-F balance did not seem to change the signal of the eye pattern.
I measured the ohm value of the varable resistor of the defective OMS-7EII I bought ten years ago and aligned E-F according to it. As far as I know, nobody tried to repair the OMS-7EII when it went defective - I later found out, that a power transitor was blown. So all variable resistors should be in their original positions.
The E_F Balance is now around "eight o´ clock", taking the single ground pin as a 6.
More on the less noisier side.
The unit now runs perfect, hope I won´t have to open it the next ten years.
(My DYI cabinet makes this very complicated)
BTW, flat belts in a lenght of 5,4mm are not available any more, at least in Germany. Somebody told me, that the big chinese suppliers (about three of them, ten years ago, malaysia was the main supplier) do not manufacture this size any more.
Have a nice week and thanks a lot,
Salar
Hi Salar,
The adjusting point for E-F balance is dependant on the laser head. The method (equal waveform above and below zero on your scope) is close. The method I described is even closer.
At any rate, if your machine reads a disc quickly it must be in the ball park. Close enough then!
-Chris
The adjusting point for E-F balance is dependant on the laser head. The method (equal waveform above and below zero on your scope) is close. The method I described is even closer.
At any rate, if your machine reads a disc quickly it must be in the ball park. Close enough then!
-Chris
Now it's not that hard.Hi Chris,
well, touching RV104, E_F Balance with a screw, makes the laser jump on a dropout disc. I also do not see the recovery.
So i went back to aligning it according to the service manual.
But aligning the unit according to the service manual gives a more blurred eye-pattern. But he symmetry looks o.k.
To get a clearer pattern on the scope, i have to raise the amplitude first (RV101 Focus) then turning E-F makes the signal clearer.
But doing so makes the dc level of TP focus in stop way off the dc level, when the player runs. The service manual states, that the DC level of focus should not change in play and stop.
Also E-F is off the regular alignement stated in the service manual.
To make things short:
Has the eye pattern to be as sharp as possible?
All the best, Salar
well, touching RV104, E_F Balance with a screw, makes the laser jump on a dropout disc. I also do not see the recovery.
So i went back to aligning it according to the service manual.
But aligning the unit according to the service manual gives a more blurred eye-pattern. But he symmetry looks o.k.
To get a clearer pattern on the scope, i have to raise the amplitude first (RV101 Focus) then turning E-F makes the signal clearer.
But doing so makes the dc level of TP focus in stop way off the dc level, when the player runs. The service manual states, that the DC level of focus should not change in play and stop.
Also E-F is off the regular alignement stated in the service manual.
To make things short:
Has the eye pattern to be as sharp as possible?
All the best, Salar
Hi Salar,
The service manual instructions are valid for a brand new head. The suspension sags over time. Make you eye pattern the clearest. The E-F Balance adjustment should agree with the clearest eye pattern. It do it that way to get a machine running that someone else has messed with, then I fine tune it. One your E-F Balance is set, the eye pattern ought to be clear.
Do whatever makes the CD player work the best. I'll have to pay attention with the next one I get in. When something isn't working right, other things need to be compensated for. Also, check teh turntable hieght. Sometimes they get lowered over time. That will throw off your focus bias adjustment for sure.
-Chris
The service manual instructions are valid for a brand new head. The suspension sags over time. Make you eye pattern the clearest. The E-F Balance adjustment should agree with the clearest eye pattern. It do it that way to get a machine running that someone else has messed with, then I fine tune it. One your E-F Balance is set, the eye pattern ought to be clear.
Do whatever makes the CD player work the best. I'll have to pay attention with the next one I get in. When something isn't working right, other things need to be compensated for. Also, check teh turntable hieght. Sometimes they get lowered over time. That will throw off your focus bias adjustment for sure.
-Chris
Hi there,
Yesterday I've bought a Nakamichi OMS-5A at a carboot sale for 1 euro. Guess that's quite a bargain, although the thing's a bit scratched. But hey.... Can't have it all.
I actually suspected the thing to be dead but when I plugged it in it actually would start reading and playing CD's.
However, it doesn't want to play all CD's and unless their absolutely clean, scratchless and what not, it'll just throw out the CD after a couple of minutes spinning the thing.
I suspect that the thing's a bit off in calibration or the laser is weak..... And now I'm looking for the service manual. Seen them on eBay but I'm a bit reluctant towards eBay (don't know why.....). Next to that, I'm living in the Netherlands so don't know how that's comming along.
Also, I'd like to build a s/p diff coaxial out on the thing since I've got a realy nice DAC which I'd love to use on this Nak. So if anybody has some clues that they like to share.... Be welcome ((-:
But first things first.... The CD pickup.... Gotto clean the thing first... See where that's going (-:.... I'll let you know of my progress! (-:
Greetings,
Andreas
Yesterday I've bought a Nakamichi OMS-5A at a carboot sale for 1 euro. Guess that's quite a bargain, although the thing's a bit scratched. But hey.... Can't have it all.
I actually suspected the thing to be dead but when I plugged it in it actually would start reading and playing CD's.
However, it doesn't want to play all CD's and unless their absolutely clean, scratchless and what not, it'll just throw out the CD after a couple of minutes spinning the thing.
I suspect that the thing's a bit off in calibration or the laser is weak..... And now I'm looking for the service manual. Seen them on eBay but I'm a bit reluctant towards eBay (don't know why.....). Next to that, I'm living in the Netherlands so don't know how that's comming along.
Also, I'd like to build a s/p diff coaxial out on the thing since I've got a realy nice DAC which I'd love to use on this Nak. So if anybody has some clues that they like to share.... Be welcome ((-:
But first things first.... The CD pickup.... Gotto clean the thing first... See where that's going (-:.... I'll let you know of my progress! (-:
Greetings,
Andreas
When it is a OMS-5EII, take a look here.
http://www.diyaudio.com/forums/showthread.php?threadid=88616&highlight=
If not,maybe 5A and 5EII share the same PCM Decoder, CX23035...
All the best, Salar
http://www.diyaudio.com/forums/showthread.php?threadid=88616&highlight=
If not,maybe 5A and 5EII share the same PCM Decoder, CX23035...
All the best, Salar
Maybe this thread also helps a bit, the OMS-5, as well as the OMS-7 are Philips - based. (TDA1540 DAC)
http://www.diyaudio.com/forums/showthread.php?threadid=80425
http://www.diyaudio.com/forums/showthread.php?threadid=80425
Hi there,
Just installed my Nak on my improved tube-amp (replaced power capacitors). First I did not notice it but it seems like it has a lot of unrepairable read-errors. Strange 'ticks' in the music. Anyone got an idea what that might mean??
By the way.... The DAC is not exactly what you need to know when you want to install spdiff on a cd-rom player. I read it's the digital processing chips that you need to know. I'm still a bit reluctant to open the thing completely (I've been known to have some bolts and nuts left at the end of opening up this kind of gear) so I wondered if anyone knows which chips are inside......
Thanks many!
Andreas
Just installed my Nak on my improved tube-amp (replaced power capacitors). First I did not notice it but it seems like it has a lot of unrepairable read-errors. Strange 'ticks' in the music. Anyone got an idea what that might mean??
By the way.... The DAC is not exactly what you need to know when you want to install spdiff on a cd-rom player. I read it's the digital processing chips that you need to know. I'm still a bit reluctant to open the thing completely (I've been known to have some bolts and nuts left at the end of opening up this kind of gear) so I wondered if anyone knows which chips are inside......
Thanks many!
Andreas
Having once managed to get the CS8402A to work with the SAA7000, I have to seriously question whether it is worth the effort. Whilst all the spdif flags did what they were supposed to and there were no clicks and pops, the resulting sound was so unrelentingly bad, I had to conclude something must be wrong somewhere. Either that or the SAA7000 is not good without the SAA7030 and TDA1540.
Hi Andreas,
The signal processing occurs on the small board underneath. The components are mounted towards the bottom of the servo PCB. The black metal box on the rear panel contains the audio filter section.
Hi rfbw,
You could always allow the servo section to work and feed the eye pattern into another chip set. That should sound pretty good. Just rip one out of a CD player that has a cheap transport, but a good D/A.
-Chris
The signal processing occurs on the small board underneath. The components are mounted towards the bottom of the servo PCB. The black metal box on the rear panel contains the audio filter section.
Hi rfbw,
If the mech. is not set up properly you will get increased digital errors. The modified Nak OMS-5/7 has a wonderful servo section and a very stable eye pattern, low noise too. Being this is a Philips design, there is a coil that sometimes needs to be adjusted for the VCO. Misadjustment will cause exactly what you are describing, or even sound mutes and breakups.
You could always allow the servo section to work and feed the eye pattern into another chip set. That should sound pretty good. Just rip one out of a CD player that has a cheap transport, but a good D/A.
-Chris
My post was not so much about the Nakamachi, more the feasability of adding SPDIF to players based on the 14 bit Philips chipset. In this case it was another 14 bit machine, the CD104 and I had two at the time one, in pristine condition, used as a reference. I also used a dac with selectable inputs so I could switch between the modified CD104 and a Sony DVD player. The SPDIF modified '104 was absolutely dire.
Hi rfbw,
Also, that chipset was selectable between 14 and 16 bit. It's possible it wasn't jumpered correctly as well. That would make a mess out of things for sure.
-Chris
I understand. I was trying to point out other factors that could affect your result. I belive that there were at least two, possibly three chips that needed to remain connected.
Also, that chipset was selectable between 14 and 16 bit. It's possible it wasn't jumpered correctly as well. That would make a mess out of things for sure.
-Chris
anatech said:
I'd like to think I'm reasonably competent in these matters and that I have a fair grasp of the in's and out's of the SAA70x0 series devices, so when I say everything was as it should be I mean just that. But that is not to say you won't succeed where I have crashed and burned, so, by all means, on James, and don't spare the horses.
Hi rfbrw,
I have an OMS-7 that I'd like to improve the audio path in. As a transport, it shows very high potential.
-Chris
I know you are. Please don't think I was questioning your experience. It's just that we all sometimes miss the odd small thing and I was hoping to spark something in your memory.
I have an OMS-7 that I'd like to improve the audio path in. As a transport, it shows very high potential.
-Chris