I've owned my Pioneer DVL 909 for some 25 years and only use it very occasionally to save it from possible wear & tear because I simply love this marvellous piece of electro-mechanical machinery. Since a couple of days my mood is a bit down because all of a sudden my unit developed a fault. Switched it on and no preparation sound from the inside as usual. Silence. Pressed the button to open the tray..... nothing happened.
Symptom(s): Switching on the unit with main switch, the display shows "STOP", whilst the blue led light is flashing. The "stop" text disappears after a while and the blue led flashing led also goes out. If I press the DVD or LD "Open" button the display says "OPEN" and disappears after some time. Other than that nothing happens.
When I use the remote to switch into standby , it says "OFF" in the display, with with blue flashing led both momentarily, and after a minute or so the red led near the on/off switch shows.
I've taken the main and rear cover off and have carefully inspected what was possible from every view point. Everything looks like new. The rear LD reader is parked in its rear position and the small DVD reader unit is near the spindle.
Removed the tray and checked all the voltages. They are O.K. The +14V shows 13,9 but suppose that should be not serious. Belts are O.K.
This phenomenon has been described several times on different forums.
There is one thing that I found a bit odd. If the main power switch is "on" my fingers feel an light but definite electrical sensation when touching the chassis. Measured this against earth of AC outlet, and it shows 105 V AC.
Is there anybody who can advise as to the cause of the sudden failure of the player plus repair ideas, please? Thanks ever so much,
Rob.

With the unit unplugged, remove the top and look at the lower pickup to see the worm wheel location that moves the laser assembly. Now you need to put your hand on the upper laser assembly in the turn mechanism, turn the worm wheel to move it out and then turn it to move it back in. Then toggle the two on the base of the mechanical assembly toward the spindle motor (they move sideways) and then try again. Just checking to see if the switches have lost contact.

The front DVD/CD unit is in it's parked position.
The LD reader head at the rear can be turned from it's parking position into some travel towards the turning around.
At the back of this LD mechanism I find a 3 contact switch. It's a mother contact (the middle tab) that makes either with the above or with the lower tap. In parked position the middle ( mother) contact makes with the upper and breaks with the lower. (Shows 10K on Multimeter). Turn the reader a bit into direction of inversion, the lower two make contact and the upper is disconnected from middle ( then also shows some 10K). This switch seems to work properly.

This sounds like a serious hazard to me. The earth in the AC outlet will be the same earth a person will experience if they touch something round the house and I think there is a potential for harm here.

First of all, I made a mistake above when I said DVD and CD, which is wrong: CD/Laser is one carriage and the other is the red laser for DVD.
I've found behavior that could mean faulty switch contacts and/or faulty DC carbon brush motor of the DVD carriage.
The fact that the DVD comes to life again when you give the worm wheel just a little turn suggests a defective DC drive motor. These are by the way obtainable under nr. RF-130CH on aliexpress and cost around $1.00
Since I also had a situation where the DVD carriage had overshot it's forward motion and had ridden up and over the mechanical stop on the bottom plate, suggests a contact failure of 1 or 2 of the small white protruding switch levers on the bottom plate. When this overshoot occurs one hears a motor running noise with a bit of r-r-r-r-r-r on top which is caused by the carriage that has ridden up on the RH side, has lost almost all contact with the tracking and has got itself securely locked between the upper plate and the end stop. I've attached some pictures of that locked in overshoot situation. Sorry the text is in Dutch, but it has all been described here and the picture makes it clear.
The two problems with this player could possibly be related. Comments very welcome!!!!
As soon as I find a definitive diagnosis with proven cure I'll report about it extensively.

O.K. Here's what happened and how it was solved: Somehow the DVD carriage had missed the front switch ( which will remain a mystery why) and had jammed up against the barrier stopat the front as described earlier.
Placing the carriage back re-generated some function but the teeth of the first cam that's driven by the worm wheel was damaged. Under a strong magnifier with a Stanley knife blade that I somewhat heated I was able to "re-model" the teeth to an acceptable level. Takes a lot of patience. Then it worked but not reliably. I discovered that the DC motor now and the stopped and just hummed. Removed it from the carriage after extracting the carriage from the mechanism. Result with the Lab power supply (6V) of the bench: The motor had failed! It measured 12 Ohms in all positions which is good but still it would'nt start on its own and vibrated when running. Found another motor in a slightly older Pioneer LD player and used that one as a replacement. Result: Everything runs beautifully again especially since I also used the better cam from the defective donor unit. It's like new again.

In the end it all became much clearer:
After extensive exploration the problem is solved and I'll try and give a description of what has been found etc.
The fault that paralysed the unit was the overshoot in forward direction of the DVD laser carriage. It went all the way forward and rid up against the mechanical end stop whilst practically losing contact between the carriage drive cam and the track. With some effort the carriage was placed back on it's track and moved to halfway back. Switching the unit on again resulted in an awakening but after a few trials the same thing happened again.
Clearly the end switches were disregarded. To do the above ánd to get acces to these switches one must remove the upper part of the loading mechanism (the part fastened by 4 black screws) and some attachments. Then the 2 switches (white nylon) become visible through two holes in the bottom of the chassis. Since getting to the switches would require much more disassembly it's good to notice that they are connected with a flat cable to the CLDM assy, see service manual p.17 LMSB assy Switch S 104 & 105 that connect to the lower horizontal CLDM board CN 102.
If you want to check the (normally open) switches, you can check this with your Ohm meter on the flat cable end at CN102. However, the manual has made a mistake that is essential to be aware of. The flat cable is a 10 contact one.
CN101 on page 40 (that shows the board LMSB assy with the switches) shows 12 contacts (!!!!). This is a mistake copied from an earlier model. CN101 is a 10 contact connector. What's even more complicating things is that they have turned the connector 180 degrees around. This alters the numbering. So what is drawn as 10 is actually 1 and 1 is actually 10! (11&12 do not exist). Then 6 is earth switches to be measured against 7 & 8 (contact switches). If the switches show resistance when pressed in gently one could try and give them a short squirt with a mild contact cleaner via the pressed in button(s). A good clean of the flat cable where you do the measuring is also recommended.
When all this is done it's a good time to look at the condition of the gears of the carriage. If the gear that engages with the worm wheel of the motor is damaged, you might use a warm Stanley knife and try and "remold" it under a magnifier. Many have been saved that way and it's a good thing to do carefully because these gears are no longer available. In my case I was succesful in the remodeling. A further complication was that I found the DC motor had lost 1 of it's 3 windings and was a write-off. I ordered a identical looking and numbered one from Aliexpress only to find that the number is a "case-family" nr. and did not relate to voltage.... It was much too fast, which was a diappointment. Luckily a friend had a earlier LD Pioneer parts unit that held the same motor!
So in the end I was able to replace the remodeled cam ánd the defective motor and all is perfect now.
Finally it became clear to me that it's a good thing to open up your 909 or 919 after some 25 years and take the gears of both carriages and clean them and give them just a little soft synthetic grease. This greatly helps reduce wear and stickiness that will eventually give you a lot of trouble. The aforementioned squirt of non-agressive contact cleaner with a thin tube or bent injection needle into the end switches might also be a good preventive measure.
Hope this gives some support to people with the same symptoms. If you progress with care and use a few pages from the service manual ánd take a few pictures before taking things apart, nothing will go wrong. Good luck!