[sonavor]

I have always had success and like this glue.  I have used it now for over ten years and have never had a problem with it.

[sonavor]

Hi Jacques,

I found some more pictures where I took a Beocord 8002 motor assembly apart and photographed it next to the Beocord 9000.

I attached the photos in this post. I also included a photo of the assembly back together.
In the photo with the two different motor assemblies, the BC8002 is on the left and the BC9000 on the right.

Regarding the trimmer resistor, I need to check on what its value is again.  I may have to open the ones I reassembled and measure them.  The motor PCB and components is not in the Beocord service manual.  I was thinking of adapting a surface mount trimmer as a replacement but while that would probably work, it could be a pain to implement it. Especially because it is meant to be adjusted from outside the metal case, through the access hole.  Then I realized that the adjustment hole for the trimmer and the PCB is right against the bottom of the metal cover.  I think it would be easier to run three leads out the back of the round PCB, where the trimmer mounts, and attach a nice Bourns trimmer outside the case.  It would be much easier to adjust and there is room where it won’t interfere with the cabinet.  The length of the wires would only be 10 to 12 mm as the PCB is right on the other side of the case.

That is as far I got with it as I got busy with some Beogram and Beomaster restoration projects.  These Beocord motors were a little side project to investigate the possibility of restoring them.  The restored motor did run good but I discovered that I still need to mess with some of the PCB components to dial in the speed as I couldn’t dial in the speed I needed with just the trimmer.

However, I did prove to myself that the motor bearings could be re-infused by Rudy successfully and that reassembly and use in a Beocord would be possible.  There are just a few things I need to go back and tweak.  Maybe sometime this year 🙂
Right now my restoration backlog is just to big to even consider any Beocord projects.

-John

[sonavor]

As I understand it, the motor assemblies for the different Beocord models (BC8000, BC8002, BC8004, BC6000 & BC6002) have a different motor assembly than the BC9000.

BC9000:
12M1 8400112 Motor — Pulley 12101 2722027

BC8000 through BC8004 (including BC6000, BC6002):
12M1 8400101 Motor — Pulley 12101 2722027

However, I believe that the actual DC motor for the Beocord 8000-9000 (the DC motor inside the assembly) is the same.  It is very similar to the Beogram 4002/4004 DC platter motor and I had Rudy re-infuse the oil in the bearings of a Beocord 9000 motor.

Martin Olsen would know for sure so maybe he will add something to this thread.

The Beocord DC motor is not easy to get to as it is inside a metal, outer shell that must be cut open.
I have attached some photos of the Beocord 9000 DC motor disassembled.

Compare the actual motor that is shown in the disassembled photo to this Beogram 4002 DC platter motor that Rudy restored for me. You can see how much alike they are.

The biggest difference is the motor assembly.  The Beocord 8000-9000 motor assemblies contain the DC motor, the metal shell and a circular circuit board.  The circuit board has a small trimmer resistor for adjusting the motor speed.  In my case, this Beocord 9000 motor had a failed speed adjustment trimmer.  The motor was also noisy before the bearings were re-infused with oil.

I had to cut open the metal outer shell to open the motor assembly and in order to reassemble it later I drilled two small holes and tapped them for two M2 screws.

It makes sense that these Beocord motors will eventually start making some noise just like Beogram 4002/4004 platter motors do with age…until someone re-infuses the bearings with oil.

-sonavor

[sonavor]

Option 2, running the motor by continually trying to keep it wet doesn’t sound like a good idea to me.

I have come across a couple of Beocord 8000-9000 motors that were squeaking pretty bad. The bearings were the source of the problem.
As I said, I believe the motors are quite similar to a Beogram 4002/4004 DC platter motor which we know need refreshed bearings after forty years.  I use a Dremel tool with a small cutting wheel to remove the rivets of the outer case/shell.  Once you get to the motor, the disassembly and restoration of the bearings should be the same as on the Beogram 4002/4004 DC platter motor.

-sonavor

[sonavor]

I re-read your original post. I was thinking motor bearings as I read it but I see that you are talking about the bearings on the capstan bearing.

I haven’t done anything with those parts other than treating them with some synthetic oil.
However, I think it would probably be better to re-infuse those bearings…and probably the two sintered bearings in the clutch assembly.

If you decide to go that route I would be interested in hearing your results.

-sonavor

[sonavor]

Hi,

The sintered oil bearings on the BG8000 – BG9000 DC motors are much like the Beogram 4002/4004 DC platter motors and do require restoring.  There is a big difference in the disassembly and reassembly however.  Not to mention the testing.

The Beocord motors are housed inside a metal housing that also includes a small, round circuit board.  The trimmer resistor for adjusting the Beocord motor speed is on that board.
If the trimmer resistor needs replacing I haven’t found a suitable replacement yet as it has to be a really low profile device.
Removing the metal, outer shell can also be a chore as it is fit together with rivets.  So those must be carefully cut out.  I reassemble them by tapping holes and using screws to fit the housing back on.

The Beogram 4002/4004 DC motors are pretty easy to test after restoring the motor bearings and reinstalling the platter motor.  You can run the platter motor for however long you want to test it with and use something like the Beolover RPM sensor connected to a computer.  The Beolover RPM sensor device will update the speed measurement every 10 seconds.

With the Beocord 8000-9000 motors you would have to rig up some testing device to perform a similar level of testing on the restored motor.  Of course you can do a short test with a 3KHz test cassette and measure the tape play with a WOW/Flutter/Speed tester to verify you get an accurate 3KHz output but the test cassettes are usually only a few minutes long.
That is better than nothing but I would prefer a longer motor test in the case of a rebuilt motor.

-sonavor

[sonavor]

Hi,

That is the correct operation of the 45 switch.
The press of the 33 when the Beogram is not playing a record is to aid when cleaning a record.  It essentially overrides the “off” state and activates the platter motor…but only in 33.
The 45 switch does not engage that function and only switches when the Beogram is on and either playing a record or searching for a record.

-sonavor

[sonavor]

That is great news.  I’m glad you got it back working again.  The Beogram 8002 is a great turntable to listen to.  I use mine all the time.

-sonavor

[sonavor]

Just the center wire of the shielded wire from PCB 2 connects to the single, terminal post on PCB 1.

Your other problem with the position detection not working sounds like either the position sensors are not working or not reaching the microcomputer board on PCB 2.

This post has some oscilloscope photos I captured of those signals for reference.
Occasionally a sensor device fails but I always suspect the wire connections first on these turntables.

[sonavor]

Be careful with the keypad.  I run into a lot of those where people have broken off the plastic tabs that hold the front plate with the keys tight against the keypad board.

The keypad boards haven’t been a problem area very often either.
The LDR devices can sometimes fail and the lamp can burn out but they aren’t usually a problem.

Check the press-to-fit, small ribbon connector that goes from the keypad assembly to PCB 1.
That is another problem area like the press-to-fit connector for PCB 1 to PCB 2.
…But start with tracing the Beogram 8002 power supply voltages first.

[sonavor]

Adjusting the forward/reverse LDR sensor sensitivity (for 620 mV) wouldn’t zap the microprocessor.  It is more likely that a cable/wire came loose or some other board trace cracked.  Those LDR adjustment screws can be a pain.

When a Beogram 800x project gets to this type of situation it is best to focus on the power supplies again.

Verify that you have the supply voltages from the transformer to the PCB 1 destinations.  Check the voltages on the three largest PCB 1 capacitors for the respective pre-regulator voltages (+24 VDC, -24 VDC and +13 VDC … or close to those).
From there, assuming those voltages are good, check the output of the +5 VDC regulator and the +15 VDC regulator.
If you have +5 VDC on PCB 1 then  it is a good guess that it is not making it to PCB 2 (where the microcomputer IC is).
The twenty pin ribbon connector between PCB 1 and PCB 2 can often be a problem.  Especially if the pins in the PCB press-to-fit connector do not mate well.

I happen to be finishing up a Beogram 8002 restoration now.  You can take a look here.  The posts are in reverse order (most recent first).  The power check post is here.
That Beogram 8002 had a few of its own moments when connector pin issues were preventing proper operation after the electrical restoration work.  That is typical of a Beogram 800x turntable though.

I would expect your Beogram 8002 to be okay…once you find the failed connection.

-sonavor

[sonavor]

Hi Alf,

I still suspect a connection somewhere if the Beogram 8000 was previously working…rather than a bad microcomputer IC.

John

[sonavor]

I thought you had a standby indication on the display.

Okay, if you don’t have a standby dot do you have the wire connected from the uC (PCB 2) metal box over to the single connection terminal on the small add-on board?
If your Beogram 8000 has that add-on board (“Control for uC”) then it needs that added connection wire.  If that wire is not connected then you won’t have a standby dot and the Beogram will not turn on.

John

[sonavor]

Hi Alf,

Your measurements at P2-8, 9 and 10 show why you don’t have +15 V.  The base (P2-10) isn’t turning on 0TR1 so +15 V is not enabled.

Your measurements at P6-4 and 1TR21 base don’t look right seeing how there is no change really between Stby and Play.  1TR21 is always on so +15 V is always off.

When the Beogram 800x is in Stby the uC is turning 1TR21 off via the control signal from 1IC1-38.  When the uC turns power on the control line goes low enough to turn 1TR21 off and allows +15 VDC to be enabled (via 1TR20, 1TR19 and 1TR18).

The source of your problems it appears is that the primary control, 1TR21, is always “OFF”.

Perhaps the Power On/Off signal from the uC isn’t able to reach the base of 1TR21.
Check the P6 connections.  That big connector can be a problem sometimes.  You might have to also check inside the uC (PCB 2) box for the integrity of P6-4 to the 1IC1-38 pin.

John

[sonavor]

Just to clarify the problem…

Can you measure –

P2-8 to ground
P2-9 to ground
P2-10 to ground

– measure them twice, once at standby and once when pressing Play

Also do two measurements (Stby and Play) at –

1TR21 base to ground
1TR21 collector to ground
1TR21 emitter is connected to ground so other than verifying that connectivity, no measurement there.

John

[sonavor]

Your +-25 V off of your bridge rectifier is good.  That is what you should see at those nodes.

How about continuity from 0TR1 collector all the way to  1C28 (instead of 0TR1 to P2-9 and P2-9 to 1C28) ?

Have you connected up a scope and monitored what is happening at P6-4 (the on/off control signal) or right at 1TR21 base?

John

[sonavor]

I would focus on the fact that you were able to get it working, briefly, by wiggling P2.
You won’t always be able to see a broken trace.  Check continuity between the related P2 wires/traces for where they came from and where they are going to.

In other words, see that the output of 0TR1 reaches P2-9 on the board.
On the board side check continuity from P2-9 to 1D25, 1C28 and other +15 V destinations.
Also check continuity around 1TR21 (wiring/traces to and from 1TR21).
Check that the grounds are good but it seems like the problem involves P2-9.

John

[sonavor]

Hi Alf,

P2-2 should be close to +5 V, which you say you have.
P2-9 should be close to +15 V

1TR21 controls power on/off from the uC.  Check the voltages around 1TR21 and if they are not good then check for broken traces.

That PCB 1 board is very susceptible to breaks in the traces.  Especially at the bend in the board.  Every Beogram 8000/8002 PCB 1 board I have seen is bent (curved) from the way it mounts on the frame.  More than once I have had to jumper traces around the bend because of breaks in the trace.

This was a Beogram you had previously restored to working condition, right?

-John

[sonavor]

Hi Alf,

You are on the right track in checking the power supply voltages.  Follow those voltages to where they stop.  Is the +5 VDC reaching PCB 2 ?  What is the output voltages of the regulators for +5 V, +15 V and -15 V ?

Check the PCB 1 connector pins where +5 V and +15 V connect from the chassis.

-John

[sonavor]

Oh, that’s fantastic.  We’re always glad to hear that it provided some help.

-sonavor

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