I am looking for step-by-step instructions, with photos, to show how to set the CDM-2/10 laser diode voltage to 50mV for correct focusing of the TOC on a CD. I have the Philips C.D.M.-2 service manual, but it is not specific on which resistor on the control board (CB) must be used. I have seen comments here that it is located in the bottom right corner of the CB. I believe this to be R3131.
I remember searching the web and finding a site where this information was contained, but have since lost that history on my browser. I have read Laserology by Lamizator.eu, and while very informative, it is not specific enough for me. Yes, it shows the pots and what they are used for, but not the resistor location on the underside of the CB.
I have also read CDM2 Revision by Bakura, and while informative, not what I am looking for. The closest I have found is the CDM 4/19 to CDM2/10 laser swap blog on audiokarma.org - and while getting close to what I need, it is still short of what I once saw on the web.
Any pointers or URLs are most welcome.
Thanks
I remember searching the web and finding a site where this information was contained, but have since lost that history on my browser. I have read Laserology by Lamizator.eu, and while very informative, it is not specific enough for me. Yes, it shows the pots and what they are used for, but not the resistor location on the underside of the CB.
I have also read CDM2 Revision by Bakura, and while informative, not what I am looking for. The closest I have found is the CDM 4/19 to CDM2/10 laser swap blog on audiokarma.org - and while getting close to what I need, it is still short of what I once saw on the web.
Any pointers or URLs are most welcome.
Thanks
Yes, this will work. It is not the one I saw previously since it had two wires connected to R3102 and hooked up to a volt meter showing 53mV. Nevertheless, this provides the necessary resistor number and location for the tuning.
Thanks a bunch.
Off to the lab...
Thanks a bunch.
Off to the lab...
Actually, this does specify that you solder a jumper wire long enough that you are able to flip the transport right side up to either side of that resistor and measure the voltage on them, yellow lines at the resistor in the picture on page 5 indicate the locations to install the jumpers.
For Philips models with the floating loader, the mech can be very easily flipped up on its nose and secured in a slot moulded into the base for the purpose. Nothing else needs to be removed or disconnected. It can be run and adjusted in that position, in which case it is wise to remove the drive belt in case you accidentally hit "eject".
I have never found the laser test voltage to be out of range, luckily. Old presets can be difficult to adjust without becoming unreliable.
It's worth checking the voltages supplied to the mech. The CD650 supplies unregulated DC at voltages way out of spec for the servo board, and a transistor gets very hot as a result. Rather than adding regulators to the servo board, I inserted pre-regulators ahead of the main +5V -6V supplies. This method has the advantage of dissipating heat to the main heatsink rather than under the mech. Seems to work well.
I have never found the laser test voltage to be out of range, luckily. Old presets can be difficult to adjust without becoming unreliable.
It's worth checking the voltages supplied to the mech. The CD650 supplies unregulated DC at voltages way out of spec for the servo board, and a transistor gets very hot as a result. Rather than adding regulators to the servo board, I inserted pre-regulators ahead of the main +5V -6V supplies. This method has the advantage of dissipating heat to the main heatsink rather than under the mech. Seems to work well.
I have tried to adjust my CD555 compo system, but it seems I can't get more than 32mV to the laser even if the potentiometer is turned all the way. I just went through the service positions and the mech could only get the focal point when the voltage was maxed. And that didn't work every time either. In the service position 2 it seems the rpm is maxed. In the manual of CD-371 it says that "If the HF signal is not well coded or no disc is present, the turntable will start rotating at maximum speed".
So, what could cause the low voltage? ATM, the player wont recognize CDs.
So, what could cause the low voltage? ATM, the player wont recognize CDs.
It's pretty darn certain you have caps going bad. Specifically the European-made electrolytic caps in the servo area. To make any of these old Philips units reliable, the best thing is to simply go through and replace any lytic caps that aren't already Nichicon with Nichicon.
Thank you! I'd be fine with testing them with an LCR meter, to try to find an offender (and wonder whether an in-circuit test for ESR would be sufficient, since my soldering skills are suspect at best). But what board(s) would contain the potential culprits given my issue? Just the servo board?