ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I have recently gotten a Beocord 6500 (type 4936). Unfortunately, the drawer does not respond to pushing the open/close contact button on the left of the front panel.
Putting power on works, alle lights on the front panel light up. When pushing the drawer button, there is no movement, and also I do not hear any parts moving/trying to move.
I am not familiair (yet) with the mechanical system behind this. So I am looking for tips, pictures or videos that help me solve this issue.Anyone who can help?
There were four plastic transit locks in the bottom case of the machine originally,but I imagine that they have been removed?
The drawer mechanism is driven by a motor and belt.The motor may have seized,although it's unusual,but the belt may have broken or stretched?
The drawer runs on rubber rollers which may have become distorted it the machine has been out of use for some time.This may prevent the drawer from moving,but you should hear the loading motor running.
You will need to dismantle the machine and lift the main pcb to investigate further.
Another possibility,is that the front sensor switch is not making proper contact,if the machine has not been reassembled correctly at some stage?
If the drawer functions when you have removed the top case,this would be worth investigating.
Nick
Thanks Nick for your response and suggestions!
Here's my response:
Four plastic transit locks: They have come with the deck and are parked in the four slots at the back. I am quite sure that the former owner has once transported the deck without using these transportation locks. I could also see that from the front panel, as it was not aligned straigth and the 5 pins (at the bottom of the front panel) were not aligned in the frame holes. I did manage in the meantime to get that all alligned and back in position.
Drawer mechanism: I have just succeeded in dismantling the casing, cassette operation panel and front panel. After that I have taken out the 6 red plastic locks to be able to move the main PCB up. And have access to the bottom of the drawer including the drawer motor and wheel.
Drawer motor & belt: I haven't seen yet that the drawer is driven by a motor and belt. I am not sure if there is a belt in this system. So far it seems, the motor drives the big black wheel directly. (See picture )
My questions now:
As Nick mentions, the big gearwheel is driven by a large belt.
You cab take out the complete gear by removing just 1 screw. The motor and the gearwheel can then be inspected.
If the belt is intact and in place,you can drive the mechanism from an external supply,but disconnect the motor from the main pcb so as not to damage the drive circuit.
If you connect a meter to the pcb connections for the motor,you should be able to read the drive voltage when you press the drawer "open"switch zone
Thanks Nick!I have taken the whole motor+belt+gearwheel and disconnected it from the PCB. This also enabled me to check the belt. It is intact and the tension is good.
As this is the safe way to put some power to the motor, I did with a 9 volt battery. After connection, it immediately started spinning. When changing the polarity, I could also see that the motor started spinning in the reverse direction. So motor and belt are both fine and working.
Somehow, the motor is not getting power when the drawer eject is being pushed. My next step is to check if the contact of the drawer release button is making proper contact. I checked how to pieces of the front panel are attached to each other. I haven't yet found a way to get clear access to the touch button on the left for drawer eject. So if you have an advise, let me know.
Can you switch the machine on and off via the stand-by button on the front of the machine?
You can get to the back of pcb 4(the front display pcb)by removing the three recessed Philips head screw's in the top of the moulding,then dropping the assembly forward.
Investigate the soldering at connector P7 on that pcb.
Yes, the stand-by button on the front panel is properly working.
If I push the eject button, then I can hear a click and feel a kind of physical switch. But again, I am not sure if it works properly.
Check the soldering on P7(pcb4)anyway.
Otherwise check around IC12 on the main pcb.This is the driver chip for the drawer motor.
You should see some activity at pins 6&7 when you "click" the drawer button.
Thnx Solderon!
I checked the soldering on PCB 4. It is in good shape making good contact between the button pins and the PCB trails.
Concerning IC 12, which chip is that on the main PCB?
(I have attached an overview picture of the PCB)
Correction. I just found IC 12. It's the one in 'portrait' in the bottom right corner.
I found there are two IC 12's. One on the large (upper) PCB, and one on the smaller PCB that's located underneath the large one.
Someone advised me to tip all soldering points of IC12. So I did with both IC 12's I found. This did not solve the drawer not opening issue.
Also I should add that besides the front panel control for opening/closing the drawer, also the controls for Play?FF/Rew do not work.
Any suggestions?
Ah,that's significant!!!
Those functions all share the same data route from the keyboard to the processor.
Check the soldering on the connector P13 on the main pcb.
Thanks solderon29!
I checked connector P13 (connecting the cassette control panel to PCB 4), but also connector P7 (connecting the front panel to PCB 4). Both connector's soldering looks good. (See picture of PCB4 bottom)
Besides, I also measured all wires in both flat cables, just to make sure there are no broken wires in the flat cables. I measured from connector point allhe way to the soldering point on the PCB. All wires in both flat cables are fine.
Would you have another suggestion?
Are you sure the OPEN contact is activated correctly - does it click?If it clicks, is any DC-voltage present across the drawer motor terminals (should be present for a few seconds after pressing OPEN)?
Martin
Are you able to "get technical"?Do you have a logic probe or oscilloscope?It's most significant that the data for all the functions (inc "open") you mentioned is not getting through to the processor?
You may have a faulty processor,but it's unusual.
You should see activity via a 'scope or logic probe on pins 21,22,23,and 24 when you operate the keyboard.(pin 21 being the crucial route for the functions you mention that don't work of course)
Are you able to connect the deck to a compatible Beomaster just to see if you can operate the play,forward and stop functions by remote control?
Thanks solderon29! I have a technician that can help me with an oscilloscope. My understanding is also that something seems wrong the processor handling. I do not have a remote control to check this. But maybe my friend has. I will check.
Checks on pins 21, 22, 23, 24: I will check this together with my friend and his oscilloscope. On which IC (and on which PCB) should I check this?
Sorry,yes but you will need a compatible Beomaster eg Beomaster 5500/6500,to operate with remote control,as the commands come via there.
Another easy check is with a multimeter to check the continuity of the data route.
With the Beocord unpowered,and the meter in a low range resistance mode,put one probe on pin 32 of IC9(one of the two processor ic's on main pcb)and the other probe on pin 21 of the same ic.When you click the "open" button,the meter should read about 1k ohm when the button is clicked,and infinity when released, if the data route is continuous.If this doesn't happen,you will need to trace the circuit to find the break.
Otherwise,checking with a 'scope should reveal what's going on(or not?) at pin's 21,22,23 and 24 of IC9.
The open contact is ok. The switch does mechanically click, and using amultimeter I could see it works.
The drawer motor terminals do not get any voltage after clicking the open switch. (I checked the working of the motor earlier, it does run when seperately putting power to it's terminals.
Indeed,but have you established that the data route for that function is continuous,as suggested above?
The fact that you can't operate play,wind and rewind either,suggest's that the data route for those functions and "open", is missing,or perhaps the processor ic is faulty?
Hi solderon29, in the meantime I have been able to do the measuring you suggested. With an oscilloscope and multimeter.
Again we started from the touch button on the fornt panel. Again, this one works. Looking at the flow of the signals for opertion functions (open/close drawer, and Play, FF/Rew, Stop), all starts at PCB 4, which is connected with 2 flat cables to PCB 2. The drawer motor is also connected to PCB 2.
We checked several IC's and transistors in the data route. And couldn't find a signal where it was expected. Then we noticed that one resistor on PCB 2 is burned (I added a picture of the location of this resistor). It is R55 (on the topside of the PCB it is labelled R55, on the bottom side it is labelled R65. I assume it should be R55, as R55 is listed in the spare parts list of the service manual and R65 isn't).
So maybe this is the cause. I have ordered a new one. Then I will put it into place, reconnect everything and test the system. Nevertheless, I also wonder what the cause has been for this resistor to burn down. Maybe the cause is still there, and could happen again.
Let me know if you have any ideas.
I think the resistor is in fact R65(22ohm)and it's a current limiter for the capstan motor,which suggests that you may have another problem too?It could explain why there is no play and rewind though,and would point towards a faulty capstan motor?
What might be happening,is that if the tape mechanism is jammed by perished drive belt's or lack of lubrication,the capstan motor is drawing excess current and triggering the machines protection system,so preventing any other functions?
Is the mechanism free to turn?Are the belts ok?
And make sure to fit a flame-proof type resistor again.Not just any resistor.
Dear Nick, thanks so much for your feedback, this is really helpful !
Glad you have such a sharp eye and attention, the resistor indeed is the R65. I misread it at first hand.
Concerning the motors/capstan/belt: I have taken the mechanism out of the machine and tested the both motors with a 9 volt batterij. They do both turn freely. And so do the belt, the both capstans, and also the driving for the FF/Rew. The belt is probably old a bit loose, so I will exchange that one. But at the moment it does make the flywheels turn.
I appreciate your feedback, as I am also wondering what caused the resistor to burn. I prefer not to have that happen again of course. Next step will be to replace the R65 resistor for a new 22 ohm one.
Forum member Martin suggested to use a flame resistor. Do you know how many watts it should be?
Hi Martin, thanks for your remark.
Can you send me a link of such a flame resistor of 22 ohm as an example?
And how many watts should it be? (1/4, 1/2 or .. watt)
1/4WIt's always a good handrule to never change ratings for safety components.
Oddly,there is no reference to this resistor in the parts list at all.I've looked in other manuals for machines that employ the same protection system,but they don't list it either.
As Martin suggests,it looks to be a 1/4 watt device,but I would imagine that it should be a "fusible"type resistor,ie intended to fail under load rather than "flameproof".
If the original was in fact o/c it would explain why the safety circuit is preventing the upc from operating the system,but the mystery remains over why the resistor burnt?
Well Nick & Martin, I have tried to find a metaloxide/flame proof resistor at 22 ohm and 1/4 watt. Very difficult to find unfortunately.
Is it an option to use a metal film resistor istead? Or else?
A bit expensive:
https://www.ebay.co.uk/itm/NTE-Electronics-QW622-RESISTOR-METAL-FILM-FLAMEPROOF-1-4W-22-OHM-AXIAL-LEAD/233149139127?hash=item3648c588b7:g:AiMAAOSwQKdcdxkS
And here:
https://www.cablesandconnectors.com/12200-12.HTM
Hi Martin,
So if I get it right, metal film is also 'flame proof'?That would make it a lot easier, as metal film is easier to find. The metal oxide resistors are very hard to get (a few pieces).
Hi KolfMAKER,
I have exactely the same problem, did you find a solution?
Thanks
Hi Alvar,
I have not yet finalized my repair. If you read through my full post and reactions, you can see what I have checked and done.
Current status is that I have to replace the burned resistor and check if that solves the issue. I will upload an update as soon as I have done that.
Best, KolfMAKER
Thank you very much KolfMAKER
Eager to know if we can find a solution for our problema.
All the best
Hi solderon29,
I have the same problem as Nick for the same beocord model. Ican detect any voltaje change in the drawer motor terminals when I switch on the open/close button, can you help me how to follow my investigation?.
My panel is also not working, the funny thing is that it was working before I dismantelled the BC to remove a piece of magnetic tape so this sounds to me as a broken connection or similar.
Any help will be very appreciated these days of confinament!
Thank you very much
KolfMAKER: Hi Martin, So if I get it right, metal film is also 'flame proof'?That would make it a lot easier, as metal film is easier to find. The metal oxide resistors are very hard to get (a few pieces).
No.Metal film resistors can also produce a flame when they burn.Use proper safety components where needed.
A little reading here (1/3 down this page);
https://passive-components.eu/resistors-non-wirewound-resistors-metal-film-foil-and-metal-oxide/
If you doubt the functioning of the front panel controls, I can recommend following.
Between the front panel and the print board in the player, is a flat cable. Use a multimeter and check each wire of the flat cable if it transfers a sgnal. You can do that afger disconnecting the flat cable at both ends. Or by measuring at the connection points in the print board at both sides.
Also check if the soldering of all connection points in the print board is still god enough. If not, heat it up with a soldering iron and maybe add a bit fresh solder.
Good luck!