Have you tried using a remote control, might give you an idea if it’s the key pad or ic chip.

Keith.

Keith no I don't have a remote for this unit, I seem to recall using Peters remote for his BM8000 on this machine and I think it worked fine, however I cant be sure.....non the less I have started to take a look inside, always a bit exciting.....starting by removing the dial drive cord and tape, im a bit nervous about breaking the tape

PCB6 looks favourite as a staring point so with reference to the diagram below (click it to view as it saved too big) I have found I'm getting the correct voltages for each of the volume select pushbuttons (1 to 15v) when each is depressed measuring at the cathode of 6D8. when doing this I can balance the drive motor 5M1 back to null by moving the volume potentiometers when depressing buttons 0 to 30 only, above 30 the motor drives and can be stopped by rotating the volume potentiometers but cannot be balanced i.e. rotating the pot beyond the point at which the motor stops turning does not reverse the motor as it does onoperation of buttons 0 to 30.....I think the positive here is that I'm getting the correct voltages out of 6IC6 when pressing each preset button.

Next I have checked the voltages I'm getting at the cathode of 6D5 when I select RESET and move the slider from 0 to 60 and I measure the correct voltages 1 to 15 respective to the 0 to 60 volume levels.....interestingly I can also only bring the drive motor back to null at preset levels 0 to 30 using this control method......when using the manual raise and lower volume switches everything is fine. I need to look harder...…...

Looking at the manual, 1-5 6pcb shows the volume chip ic6 which shows pins 5,6 and that run the top end. Just wondering if the has gone faulty.

The volume control board is known to develop lots of cracked solder joints, particularly where connectors are soldered in, and the trimmers oxidize.

Martin

Keith

Looking at the circuit diagram I can see that the top end comes from those pins too, thing is when I measure the voltage at the cathode of 6D8 for the steps 0 to 60 I do get the prescribed readings 1 to 15v, this suggests to me that the signals to 6 IC6 are good. When I run the manual volume control up and down the motor drives up and down correctly too, this suggests  6 IC5 is functioning ok too......I have tested the diodes 6D4, 6D5 and 6D8 and all are good....I have also removed and tested all the trimmer on PCB6, the problem is the same when trying to adjust the preset volume also, at the same point.....I think I need to check the slave volume potentiometer as it is commom to both volume control methods.....it should be noted that the actual volume of the unit goes up and down with the manual volume control buttons, it looks like the 5R6 pot has three variable resistors, one for the volume of each channel and one for the slave volume which is common to both step volume and preset volume functions...so three in total, anyone known these to fall over in the past?

Craig

Ok.....spent an afternoon going over the function of 6 IC6 and using the truth table below confirmed the IC is working exactly as it should...all inputs and outputs respond to the functions identified, so a little progress

Martin

Thanks for that I will go over all the soldered joints and reflow them, I have replaced all the trimmers and removed them yesterday to check them out too. Going by what I have proved with the 6 IC6 functions all checking out from the control panel pushbuttons I think the CPU is good. Looking at  6 IC5 I can see it has been replaced in the past, whats bothering me is that everything works fine at volume steps 0 to 30 then it goes to rat@hit.....

Craig