Hi Jerry

Congratulations on getting such an excellent sound system.  You won’t regret it.  However, it does take some time and effort to get all of the pieces back to their best condition. 

I note that you are a gold member and must have downloaded the service manuals from the site.  These should help you immensely.

Regarding the lack of sound from the BC8002, in light of the fact that you have neither channel nor PPM readings, I would first have a look at the record/playback relay located straight after the tape head.  If this is sticking or faulty, it might be the source of your problem.  Signal path tracing on these machines isn’t difficult as long as you have some suitable equipment.  If there is no signal going onto board 2 at Plug 9, pins 1and 2 then the problem is on the preamp circuit side and it could be a relay or head problem.  You could also have a look for possible grounding issues and faulty solder joints while you are at it.

The tape lid should be fairly easy to sort out.  There should be a 1 to 2 mm gap between all of the top panels and if there isn’t, one of the panels has not been set properly.  Taking the panels off isn’t too difficult but you need to take care with all of the plastic pins because at this stage of their life, they break very easily.  The removal sequence is clearly outlined in the manual and if you have any further difficulties, don’t hesitate to ask.

Regards

Geoff

Hi Geoff,

Thanks for your help!  I'm not sure where to pick up signal ground to test voltage on pins 1 and 2 of connector 9 on board 2, I just don't have much experience with such.  What should I see in the way of signal voltage once I do find a good signal ground?  I did pop the top off the relay and sprayed cleaner in there.  I cannot observe any movement of the relay when switching the tape to play or stop so that could easily be part or all of the issue.  Is there anything special one needs to do to check the output of the tape head?  What should I see on which pins measuring signal output from the head to the connector right next to the relay?  Would you think it better to try to find a good board 3 and sway it out, try to do the component swaps on this one or look for a properly functioning 8002, 8004 or 9000?

Regards,

Jerry

Hi Jerry

I am not sure what you have in the way of useful testing equipment but at the very least, you are going to need to have access to a good multimeter.  You really need a scope for the best examination of the signal path but I assume that you haven’t got one.  If you have a multimeter, I would first carry out the following checks.

The signal from the heads pass to board 3 via plug 8.  Plug 8 has 11 terminals assigned as follows:

P8.1     Erase signal

P8.3     Erase ground

P8.4     Right signal record

P8.5     Right signal playback

P8.6     Right sheath ground

P8.7     Left signal record

P8.8     Left signal playback

P8.9     Left sheath ground

P8.10/11          Empty

In my case the normal record signal cables are white and the playback signal cables are pink.  The relay simply grounds either end of the head connection to configure a record or playback line.

With the set switched off and disconnected from the mains:

Remove the white plug with the head signals, P8

Measure the resistance across pink and white wires on each channel at the head.

You are looking for a resistance indication of ±260ohm. 

Now measure the resistance across the pink and white wires at the plug to check that the wiring is OK.  This should also give you a resistance of ±260ohm.

Put back the plug P8

Connect one end of resistance meter to the ground, I use the black wire next to the head.

Measure the resistance at the pink and white terminals on the head

White should be grounded giving a very low resistance

Pink will be show ±260 ohms, ie ready for recording.

These readings should confirm that the playback signal path is not being obstructed at the relay.

The signal path then goes through the relay to R102/202, the dark red resistors (56ohm) either side of the relay.

Probe both ends of these resistors and it should indicate ±260 and  ±320 ohm.

These checks should confirm that you have a good tape head operation and the playback signal should be getting past the relay.  If that is the case then you will need to look further down the signal path for your problem.

Disconnect the multimeter and operate the tape recorder with the case open in service mode.

To check the action of the relay

Switch the unit on and put in an empty tape

Press REC OPEN

Press RECORD

Press STOP

Repeat RECORD, then STOP

Watch to see if the relay is moving

Press Record and the copper contacts come up, press STOP and the contacts go down

That should keep you going for a while, did you manage to sort out the problem with the tape lid?

Good luck

Regards

Geoff

If not already solved, check R2 and D13 on PCB3.

This solved similar problem for my BC8002.

Hi Geoff,  Thanks for the detailed recommendations.  I was able to follow them and could determine that the head appears to exhibit the correct resistance both at the head itself and at the connector.  The probes at ends of the two dark red resistors showed much lower resistance values than shown in your note.  Probably means the relay is bad.  When attempting to check the operation of the relay as indicated I found that the tape mechanism would no longer work for whatever reason.  Now the head and pinch roller mechanism is properly pulled forward by both solenoids but the motor no longer starts/turns and the mechanism does not latch in position.  On play it clicks forward, stays there for a few seconds and then clicks back.  Neither fast forward or fast reverse work now either.  Neither REC  OPEN or REC buttons appear to do anything.  I must have done something to screw it up as that all did work when I began.  Ugh!  I did some more probing but could not find the cause and don't know where/how the motor is activated.  I assume there is a micro switch somewhere activated when the mechanism is drawn forward.  Any suggestions for this now very obvious amateur?  Thanks.

Jerry

Hi 

Hi Jerry

Sounds as if you are having fun with this one!!  Not sure what you have done to the tape deck but you could note the following:

The motor starts as soon as the set is connected to the mains and the display lights come on.  It only switches off when you switch back to standby.  Therefore as long as there is power and the set is switched on, the tape deck motor should run all the time.

None of the tape transport functions will work without the motor.  However, the solenoids will actuate but will kick out as soon as it realises that nothing is moving.

Check to see if the motor is turning and the belt is moving.  You may have inadvertently slipped the belt off when you refitted the deck.  Also put a voltmeter across the two terminals on the top of the motor, you should get 13 or 14 volts showing that the power supply is OK.

See if this helps get the motor running again.

Regards

Geoff