Revox B225 skip tracks

[bogdyy]

hello
i have a problem with my B-225 cd player: it jumps tracks . It reads perfect , original discs , or CD-R , CD-R (audio) if they are not heavily scratched it doesn have any problems to start play ,to skip track etc...BUT on play after 1 minute or less will make problems reading , it will jump track sometimes just 1 ,2 seconds in advance,or some times 5 or even 10 songs at the time..i ve made some measurements from R63 on servo 2 board :when it plays normally the voltage reads 520 mVand for 20 30 seconds it will stay around that value , and after that the voltage gradually rises to 580mV (the rise is done in 5 to 10 seconds) and then will jump track , and the voltage drop to original value of 520mv and the cycle will repeat. the same thing is done with various discs ..with CDR for audio the original voltage is 440mV and will rise till 500 mV and then will jump ...ive replaced the capacitors from optical unit ,the crical ones from the power supply, but no luck..the optical pick up is dead ? or i am missing something...
any tips will be much appreciated
Best regards
Bogdan

[rene (NL)]

AW: Revox B225 skip tracks

Hello,

First I would change ALL elcos for new ones from a good brand (Panasonic FC have a good reputation) to be sure that every part of the system gets a clean DC voltage and current without noise and hum. Also check the flat cable for broken wires and make sure that all the pin contacts are clean since these can corrode and cause several malfunctions. The laser is not broken in my opinion since it can read discs. The service manual says that the laser current should be set to 500mV ±10% with the service disc but a clean and unscratched regular one will do either I guess. This adjustment should be done at ± 23 degrees Celsius room temperature.

Good luck with your B225! René

[bogdyy]

Re: AW: Revox B225 skip tracks

Hello,

First I would change ALL elcos for new ones from a good brand (Panasonic FC have a good reputation) to be sure that every part of the system gets a clean DC voltage and current without noise and hum. Also check the flat cable for broken wires and make sure that all the pin contacts are clean since these can corrode and cause several malfunctions. The laser is not broken in my opinion since it can read discs. The service manual says that the laser current should be set to 500mV �10% with the service disc but a clean and unscratched regular one will do either I guess. This adjustment should be done at � 23 degrees Celsius room temperature.

Good luck with your B225! Ren�

hello rene
many thanks for your replay , but i dont think its an elco problem ,i ve test all of the capacitors , and all reads fine , 90% of the cases they read better then the new ones ..i ve clean all of the contacts , checked the flexible cable , resolder every conector...adjust the laser current in 10 diferent positions from 450mv to 550mV ..the same result..i am guesing its an electronic part , other then the elcos..maybe an Ic or something..i want to repair the cd but i dont have all of the test equipament required ,
I just want to use another fan experience who encountered a similar problem..
to remove any trace of doubt, I will change all electrolytic capacitors Monday morning with panasonic FC and will communicate the results

[eckibear]

AW: Revox B225 skip tracks

This behavior could be caused by a sticky or loosened pickup swing bearing. The radial servo loop does allow some deviation until tracking is lost, then increases servo drive current rapidly. At this point the sticky bearing may brake loose and this process starts all over again. Check whether the lever moves free but without bearing play. Maybe the bearing is either worn out, adjusted too stiff or too loose. The latter will give reason for non-tolerable hysteresis within the servo control loop, similar/same effects will shop up.

[bogdyy]

Re: AW: Revox B225 skip tracks

This behavior could be caused by a sticky or loosened pickup swing bearing. The radial servo loop does allow some deviation until tracking is lost, then increases servo drive current rapidly. At this point the sticky bearing may brake loose and this process starts all over again. Check whether the lever moves free but without bearing play. Maybe the bearing is either worn out, adjusted too stiff or too loose. The latter will give reason for non-tolerable hysteresis within the servo control loop, similar/same effects will shop up.

hello
many thanks for your replay, could you be more specific? ive removed the pick up mecanism , and test what you say , the swing arm moves freely , and i dont think i have bearing play but i am not 100% positive , could you tell how can i test the bearing to be sure?
regards
bogdan

[eckibear]

AW: Revox B225 skip tracks

Throughout this work protect the laser diode from electrostatic. Make shure to discharge and work on a non-static table/chair(!).

The rotor arm should be moving without play. To check you may carefully push back and forth in radial and axial direction. Also push for tilt. You may put the unit on to of a cardboard box (shoe box) that will amplify the sound of the bearing.

After re-assembling, observe/make sure the flex cable does not touch the rotor arm.

There is a chance that the spindle motor has bearing play as well. However, that should manifest all time and not every few 10 seconds. So don't move any parts there for the time being.

Unless you have already, there is a service manual for the Philips CDM1 and CDM1-MKII as well available for free in the internet. This will give direction for correct adjustments if required.

[MilanMilosevic]

Re: Revox B225 skip tracks

Hello Bogdan,

I know it sound silly, but you haven't mentioned it... have you cleaned the laser lens?
Beyond that, I would immediately go to the section 4.2.7 of the Service manual and measure the DC component of focus signal. Whether your B225 is fitted with CDM0 or CDM1 transport, in many cases the spindle bearing needs height readjustment because the spindle drills a hole into it.
In addition, check if the following operational amplifier is running hot: Servo 2 PCB, IC2 (TL071).

Good luck!

[bogdyy]

Re: AW: Revox B225 skip tracks

hello

there is nothing wrong there, there is no play at the bearing , there is no strange mechanical movement..everything appears to move like they should..

[bogdyy]

Re: Revox B225 skip tracks

Hello Bogdan,

I know it sound silly, but you haven't mentioned it... have you cleaned the laser lens?
Beyond that, I would immediately go to the section 4.2.7 of the Service manual and measure the DC component of focus signal. Whether your B225 is fitted with CDM0 or CDM1 transport, in many cases the spindle bearing needs height readjustment because the spindle drills a hole into it.
In addition, check if the following operational amplifier is running hot: Servo 2 PCB, IC2 (TL071).

Good luck!

hello Milan
the lens is clean , and i do as you say , but no luck , i f i readjust the spindle height , i just "kill" the play or it behaves as before ..the voltage from section 4.2.7 apears to be good, does not exceed the 140mV barrier (it does that only if i will lower the spindle bearing too much..).. and the Ic2 does not heat..

[bogdyy]

Re: AW: Revox B225 skip tracks

Throughout this work protect the laser diode from electrostatic. Make shure to discharge and work on a non-static table/chair(!).

The rotor arm should be moving without play. To check you may carefully push back and forth in radial and axial direction. Also push for tilt. You may put the unit on to of a cardboard box (shoe box) that will amplify the sound of the bearing.

After re-assembling, observe/make sure the flex cable does not touch the rotor arm.

There is a chance that the spindle motor has bearing play as well. However, that should manifest all time and not every few 10 seconds. So don't move any parts there for the time being.
Unless you have already, there is a service manual for the Philips CDM1 and CDM1-MKII as well available for free in the internet. This will give direction for correct adjustments if required.

i found this link

http://www.nanocamp.de/?spurfuehrung

and follow the steps , but no luck , i used some sillicone oil to lubricate the bearing from the optical pickup but no luck , nothing changed..i will follow these steps too, since the bearing has a hole like the one on that photo

http://www.nanocamp.de/?hall_motor

but i really think i will have to start to do some electronics testing...

[MilanMilosevic]

Re: AW: Revox B225 skip tracks

i found this link

http://www.nanocamp.de/?spurfuehrung

and follow the steps , but no luck , i used some sillicone oil to lubricate the bearing from the optical pickup but no luck , nothing changed..i will follow these steps too, since the bearing has a hole like the one on that photo

http://www.nanocamp.de/?hall_motor

but i really think i will have to start to do some electronics testing...

Your tests have confirmed that the spindle bearing and height as well as mechanics are OK and therefore I wouldn't tamper with the transport anymore. The remaining to things to check are laser and electronics. There is a chance that the prism in the laser got partially opaque giving reading and tracking problems, and the only way to check it is to find a working CD transport and fit it and see if you get the same problem. For electronics, I believe you will need more sophisticated equipment and go through the entire checking and measurement procedure described in the service manual.

[eckibear]

AW: Revox B225 skip tracks

I've done some further studies on the servo 2 schematics and the radial servo system.

1) One thing to keep in mind is the IR receiver IC1, TBA2800. Odd as it seems this part (including photodiode) may do a lot of "funny" things to the machine. In fact, I just recently had given advice to another forum member to check or disable this part. His B225 showed all sort of strange behavior and he already did a lot of checks to no avail. Once the TBA2800 was removed everything was nice again! Maybe in your case the receiver generates signals requesting skips from the controller. See this thread: http://revoxforum.de/forum/showthrea...light=receiver

2) Likewise or related, you may be just another victim of the infamous "energy-saving lightbulb". These mid-frequency powered lamps are well known to emit "code" confusing many of the older IR remote receivers. Make sure no such bastard lamp is anywhere near. Better kill it or plug it into one of our EU commission members b...

3) If all of that doesn't help, you'll have to run further checks on servo 2 board. From what you initially described, i.e. sawtooth-like ramping voltage at R63 and consistent recovery of the peak voltage, I would infer that the laser is still fine. At point R63 you see the current signals of all photodiodes added. It should be about 600mV averaged, however tolerances are high and signal strength depends on CD material quality anyway. In your case it is somewhat less in operation and actually ramps upwards until drop-outs or skips occur.

In order to verify what really goes possibly wrong in this loop you would first need to watch signals RadErr1 and RadErr2, best simultaneously and on a scope. Please tell us whether you have a scope available.

4) In fact there aren't many Elkos on this board which may cause problems. Most caps are foil type, so no worries there. The only critical Elko could be C26, 47uF/16V at integrator IC10b (top of scheme). In my opinion it should be rather bipolar than polarized as shown in the service manual. In any case I would renew it if suspicious.

[bogdyy]

Re: AW: Revox B225 skip tracks

I've done some further studies on the servo 2 schematics and the radial servo system.

1) One thing to keep in mind is the IR receiver IC1, TBA2800. Odd as it seems this part (including photodiode) may do a lot of "funny" things to the machine. In fact, I just recently had given advice to another forum member to check or disable this part. His B225 showed all sort of strange behavior and he already did a lot of checks to no avail. Once the TBA2800 was removed everything was nice again! Maybe in your case the receiver generates signals requesting skips from the controller. See this thread: http://revoxforum.de/forum/showthrea...light=receiver

2) Likewise or related, you may be just another victim of the infamous "energy-saving lightbulb". These mid-frequency powered lamps are well known to emit "code" confusing many of the older IR remote receivers. Make sure no such bastard lamp is anywhere near. Better kill it or plug it into one of our EU commission members b...

3) If all of that doesn't help, you'll have to run further checks on servo 2 board. From what you initially described, i.e. sawtooth-like ramping voltage at R63 and consistent recovery of the peak voltage, I would infer that the laser is still fine. At point R63 you see the current signals of all photodiodes added. It should be about 600mV averaged, however tolerances are high and signal strength depends on CD material quality anyway. In your case it is somewhat less in operation and actually ramps upwards until drop-outs or skips occur.

In order to verify what really goes possibly wrong in this loop you would first need to watch signals RadErr1 and RadErr2, best simultaneously and on a scope. Please tell us whether you have a scope available.

4) In fact there aren't many Elkos on this board which may cause problems. Most caps are foil type, so no worries there. The only critical Elko could be C26, 47uF/16V at integrator IC10b (top of scheme). In my opinion it should be rather bipolar than polarized as shown in the service manual. In any case I would renew it if suspicious.

hello
I disassembled the entire unit , again, to clean every conector with alcohol , and to resolder them also , to remove any trace of stupidity in my "quest"..i ve removed the TBA2800 , and checked C26 (i dont have a better one , i have panasonic Fc , Elna , And nichicon .. but the original one is 47,2 Uf , V loss 0,4% , ESR 0.34 Ohm..). i will try to assembly the unit today to test it and if there is no change with the TBA removed ,tomorow i wil try to find a dual trace Scope to see those signals , and get back to you with the result ..;untill then what i expect to see there?


I really appreciate your effort to help me

regards
Bogdan

[bogdyy]

Re: AW: Revox B225 skip tracks

nothing changed with tba2800 removed .i ve done some measurements (not with a scope but with a dc voltmeter , tomorow i will see the real signals..)..i have these values..when it starts to play ERR1 is -0,910V and gradualy rises to -0,835V then skip then the voltage drops down to -0,890 V ..and ERR2 is -1,010 V and drops to -1,230V skip to -1,060V...etc..these measurements are made at the begining of the cd .

[steerpike]

AW: Revox B225 skip tracks

You don't need to remove the TDA2800 IR preamp; linking together pins 4-5 and linking 2-1 on the serial socket disables it. (same procedure to disable IR receiver on ANY B2xx series product)