Hi All,
did quick search across the threads, but nothing helpful so far.
Got T-Drive (MK1) older revision with CDM9/65 which can not read TOC from CD. After loading it spinning the disc OK and then start reading the TOC but without any result - it goes endless process without any outcome either erroneous or successful. LD is faulty hands down? Or it is possible to go for some checks before I throw a hundred bucks at ebay replacement.
I did figure that laser assembly goes for standard route after loading - its trying to focus and beaming
video is here: CDM-9 of Micromega T-Drive - YouTube
I can also see there's no pot adjusting LD current... Thoughts?
did quick search across the threads, but nothing helpful so far.
Got T-Drive (MK1) older revision with CDM9/65 which can not read TOC from CD. After loading it spinning the disc OK and then start reading the TOC but without any result - it goes endless process without any outcome either erroneous or successful. LD is faulty hands down? Or it is possible to go for some checks before I throw a hundred bucks at ebay replacement.
I did figure that laser assembly goes for standard route after loading - its trying to focus and beaming
video is here: CDM-9 of Micromega T-Drive - YouTube
I can also see there's no pot adjusting LD current... Thoughts?
You could try contacting Micromega asking for a circuit diagram... that's a very old model, you may get lucky/they may send it to you.
I think the adjustment trim pots are located underneath the transport... have a look.
Also, check the ribbon cables/connections between the mechanism and the PCB.
EDIT: ok, so the CDM9 is a full-blown player, it even spits the analog out 🙂
Check the IC7001, pin 3. That is your HF point at which you must see the eye-pattern (with the CD loaded). The schematics is quite straight forward, the service manual is available at ElektroTanya. IC7201 is a microprocessor which also has few very useful test-points, for easy fault finding.
I think the adjustment trim pots are located underneath the transport... have a look.
Also, check the ribbon cables/connections between the mechanism and the PCB.
EDIT: ok, so the CDM9 is a full-blown player, it even spits the analog out 🙂
Check the IC7001, pin 3. That is your HF point at which you must see the eye-pattern (with the CD loaded). The schematics is quite straight forward, the service manual is available at ElektroTanya. IC7201 is a microprocessor which also has few very useful test-points, for easy fault finding.
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If anyone still reading:
while digging deeper into the thing: checked laser diode and photodiodes, ALL OK, however can't get clear eye pattern, its blurred with my tek 3052 scope. Checked TT motor drive BJTs, one was half-shorten, replaced both and get NO DISK error. Startup procedure seems fine, got laser light, focusing, 2x try to focus and then no disk. Service menu is working (step 1 focusing, step 2 reading and spiining and step 3 hi-speed rotation). Got RF-in and RF out. Machine is using tda8808, tda8809 and saa7310 chipset.
Question: how the whole system checks if the disk is present? Which flag/leg shall be high/low? Some IC shall reporting to CPU that startup procedure is fine and the disk is present. Which one does and how?
Sorry for noob questions, this is my start into the digital audio.
while digging deeper into the thing: checked laser diode and photodiodes, ALL OK, however can't get clear eye pattern, its blurred with my tek 3052 scope. Checked TT motor drive BJTs, one was half-shorten, replaced both and get NO DISK error. Startup procedure seems fine, got laser light, focusing, 2x try to focus and then no disk. Service menu is working (step 1 focusing, step 2 reading and spiining and step 3 hi-speed rotation). Got RF-in and RF out. Machine is using tda8808, tda8809 and saa7310 chipset.
Question: how the whole system checks if the disk is present? Which flag/leg shall be high/low? Some IC shall reporting to CPU that startup procedure is fine and the disk is present. Which one does and how?
Sorry for noob questions, this is my start into the digital audio.
🙂 Generally speaking you need to look for the Fok or Focus OK signal. What happens is that the laser performs the Focus Search routine (initial lens bobbing) and it looks for a point of focus on the stationery disc (it's easier focusing on still disc than a spinning one). Once that is detected OK and the lens held at that point the Fok signal tells the servo to spin the disc up to the approx correct speed where the focus servo now attempts to get a focus lock on the moving disc. When that happens the tracking servo also kicks in and the data off the disc is then phase locked to the internal crystal oscillator by the platter speed adjusting to suit.
I wouldn't like to say where you might find the Fok on the Micromega... it will be a case of looking at data sheets for that chip set 🙁
I wouldn't like to say where you might find the Fok on the Micromega... it will be a case of looking at data sheets for that chip set 🙁
Thanks, Mooly.
I am using Marantz cd-72 servo schematic as it is very similar to what we have with Micromega T-Drive. Apparently there are FE flag (focus error), but unfortunately there's nothing about its behaviour, i.e. it should be high/low, certain voltage or so. Attaching pics, would appreciate any thoughts.
I am using Marantz cd-72 servo schematic as it is very similar to what we have with Micromega T-Drive. Apparently there are FE flag (focus error), but unfortunately there's nothing about its behaviour, i.e. it should be high/low, certain voltage or so. Attaching pics, would appreciate any thoughts.
There are no real clues I can see. It all looks to be done within the chip 🙁
If the the disc does actually spin up then it does suggest focus has been found. If the amplitude of the RF is basically OK (1.2v peak/peak) but just blurred then it is possible there is a problem with the tracking servo and that is why it will not lock.
It is not easy...
If the the disc does actually spin up then it does suggest focus has been found. If the amplitude of the RF is basically OK (1.2v peak/peak) but just blurred then it is possible there is a problem with the tracking servo and that is why it will not lock.
It is not easy...
Now it spinning only by means of service menu. Apparently, working for any philips cdm system, pressing stop+play+power on brings so-called service program. It can SEPARATELY runs focus drive, low-speed spinning + disc read (irrelevant to the focusing - just imperatively), hi-speed spinning w/o read. I suppose this is for servicemen able to check all motors and drives separaetly. So in my case - I can see focusing lens bobbing, spinning and reading the disc, high-speed spinning while the thing is in service mode. BUT in regular mode it just makes two attempts to focus and then NO DISK error.