Repair onkyo cd player manual#
This requires a laser current of 54.8mA, which is only 25% above the original factory current.Įvidently that original factory setting of 218uW was lower than what Onkyo specifies in the service manual (>250uW).Īt this time the RF-level (eye-pattern) is slightly >3V P-P. Other data I obtained for the TAOHS-series of optical pickups suggests 300-400uW for the target light output.īased on this I decided to increase the laser current in small increments while monitoring both laser current & the light output.įor now I am using 275uW of light output. It states >250uW of laser light is required to initialize a disc. Here is an interesting bit of information from the Onkyo service manual: I concluded the laser diode was probably OK, but because of long-term drift and aging the APC circuit was out of adjustment.
So, both light output & laser current were lower than the original factory setting. My first measurement of the pickup showed only 150uW of light output. This sticker on the side of this TAOHS-DG2 gives the original factory values for laser current ( 42.9mA) and the corresponding light output level ( 218uW). In that case the only practical repair is to replace the entire optical pickup. If a laser gets weak or fails from old age then the measured current will be much higher than the mA value given on the factory label. Optical pickup manufacturers often labeled the initial laser mA & uW. A 5% increase in current can double the brightness.Īnd because the APC circuit maintains a specified light output level (uW), the laser current itself will vary with time & temperature. Laser current is directly proportional to the voltage drop across the resistor.įor a typical laser current of 50mA there will be 0.75V (750mV) across the 15 ohm resistor.
Repair onkyo cd player Pc#
This PC board contains the APC circuit (automatic power control), the adjustment trimpot, and a 15 ohm resistor for measuring laser current. So follow along with what I'm doing but don't try it yourself! It is far too easy to permanently destroy the laser diode by altering the trimpot setting. This procedure is best left to experienced CD player technicians. It's critically important to monitor the laser current while making any attempt to adjust the trimpot.Īlso the light output must be monitored with a laser light meter such as my Leader LPM-8000. I’d like to get this Onkyo DX-120 into a condition where it will play most of my discs. Some sections of it look very well-made and precise, but some other parts in it look really crude to my eye. It sometimes seems “sticky.” I’ll have more on this after I post photos of the carriage assembly. However I don’t think the carriage is moving smoothly enough. The service manual shows 3V P-P and that’s what I’m getting. I am able to get a decent looking RF signal eye pattern.
The service manual describes a “skew adjustment screw” and states “adjust it for best eye pattern.” Adjusting this revealed that the adjustment must be all the way at one end to get the best eye pattern. These same discs plays without interruption in other machines.
However it won’t play through the damaged areas of “less-than-perfect” discs that have scratches. I raised the light output in tiny increments until I reached about 275mW.Īt this point it displays the TOC information rapidly and will play a CD which is in perfect condition. Another post on diyAudio suggested 300mW for this particular optical pickup (TAOHS series). The machine performs a focus search but fails to detect the presence of a disc. I recently dug it out of my storage unit. What intrigues me about this unit is the TAOHS laser pickup (made by Olympus?) and the use of several Yamaha IC chips for servo control, data decoding & recovery, & DAC. New project: Onkyo DX-120 CD player from 1986.