Delta 70.2 cd player help needed

[Gonethesame]

hi,

got a problem with a Arcam Delta 70.2 cd, everything worked well, and now when i power it on, turntable spins continously with tray motor spinnin to close the tray while 3s , the turtable stay spinning with error disk!

i checked the tray switchs , they works well , it seems that the Mab8441 doesn't reset, i checked pin 21 "reset" doesn't go "high" as http://www.acousticpsychos.com/Files...-170-cd-sm.pdf

service manual place the reset of this control IC..

is there any transistor who powers this reset?

really need help, if you have an idea? thx

[poynton]

There are known faults with early Philips CDM4 based players, usually the caps need replacing.

See Extending Philips CDM4 Life??


Andy

.

[amc184]

The reset input on a MAB8441 is an active high input, rather than the far more common active low type. It should go high briefly at start up, and then remain low during normal operation.

In my experience two things can cause uncontrolled spinning of the turntable motor:
- A loss of clock, where the master clock that provides timing for the CD player isn't running.
- A failure of the turntable drive circuit.

Your player has a brushless type spindle motor, so it's less likely to be the motor driver. A few questions for you:

- What test equipment do you have to trouble shoot the problem?
- What modifications have you done to the player?

[Mooly]

Just re-reading your first post... have you checked ALL the supplies and rails as spinning motors is a classic symptom of a missing rail. Measure them at their destinations (IC's etc) as well as the PSU as Philips based players often use small safety resistors hat can burn out or go high.

[Gonethesame]

hi,

thx for replying, about changes i made, i changed all chimics caps on digital and cdm4 servo board , after this all was working well, till laster!

i'had checked all regulator 78xx and 79xx , all is fine, droping 11v to 5v , at start up, reset doesn't get 5v even shortly, i changed the mab chip, i got spares of a old delta 70.3, its the same , i think as mooly said it could be a rail delaying or nullifying the reset!

[Mooly]

The circuit shows pin 17 of the MAB8441 as being the reset pin. That should be normally low and is pulled high to reset on power up via C17

Is the 5 volts correct on pin 28
Is pin 22 receiving the expected inputs from the drawer mechanism.

Maybe try and troubleshoot the constantly spinning disc motor as a way of working back to the fault.

[Gonethesame]

hi Mooly,

pin 17 doesn't receive a clear 5v at start up, can only read over 2v,

C17 has 5v

pin 28 has 5v

pin 22 receive 0v

i've changed the whole cdm4 with a working one, plus servo card, its the same; motor spinning and the pick up indexing , screen shows error!

[Mooly]

You would only see the 5 volts on pin 17 for an instant as cap C17 charges rapidly. Pin 17 should (I would imagine anyway) read 0 volts normally.

Pin 22... you would have to examine the leaf/microswitches to determine if that is correct. Can't determine from the circuit whether that is correct or not. If in doubt just force the level by unplugging the switches.

99% of the time faults like this usually have a simple cause.

[amc184]

You haven't answered my question about what test gear you have. If you have an oscilloscope I suggest you check that the SAA7210 is getting a valid clock signal (at pin 19). After that I would be checking the MSC output (pin 17), the PWM output that drives the motor, and the circuitry that follows.

Checking the power supply rails to every IC is standard practice for any malfunctioning piece of electronics, you should have done this before anything else.

[Gonethesame]

Thx alot,

Mooly, i'll test that, yersterday i powered up without plugging the digital board "mab8441", i plugged it after and the cd player worked nicely, curious , right away i tried the same trick, it went back on his spining sickness!


@amc, i got a multimeter , no osciloscope here..

my sens tells if its lika timing problem!
thx