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  • Re: BG8000 fuse issues

    Hi ALF, Ok, last time you indicated that it was positive 3.2V, if it is negative then it's less than the 0.7V maximum that the diode is supposed to control. Since you are holding a stable 33.33 rpm you can assume the AC integrating opamp is doing it's job. Before you tackle the 45 rpm issue I'd look at the carrier sensor. Are you getting a square wave output at 1IC1 pin 8 and 1IC2 pin 14 per the section 1-5? Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Fri, Jul 14 2017
  • Re: BG8000 fuse issues

    Hi ALF, For the 3.2V you measure at the gate of TR26 are you measuring AC or DC? Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Thu, Jul 13 2017
  • Re: BG8000 fuse issues

    Hi ALF, In your post it is not clear whether you have solved the high speed platter issue. You only indicate that the output of IC1 is a square wave. Can you confirm that the TT now holds 33.33 rpm? If it does have stable speed then did the replacement of IC1 or IC3 fix that issue ie. did you replace them one at a time and measure the outcome? If you have stable speed then there is no need to check PC7 at the moment. The PC7 board was added to help solve a platter speed issue - see the bottom of
    Posted to BeoGram (Forum) by Lonnie on Thu, Jul 13 2017
  • Re: BG8000 fuse issues

    Hi ALF, Based on your CMOS readings of 1SD = Low, 1CD = Low, 1D = High you are getting a correct response of 1Q = High . Can you remove the input voltage, maybe by removing 1R50 or P4(7) and confirming if the output goes low. Does your BG8000 have the additional board PC7 which controls the uC chip? From jpeg P1010309 it looks like it does. If CMOS 4013 is working correctly this board might be the next thing to check. Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Tue, Jul 11 2017
  • Re: BG8000 fuse issues

    Hi ALF, The voltage should be measured from pin 7 of the integrator not pin 2. Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Mon, Jul 10 2017
  • Re: BG8000 fuse issues

    Hi ALF, To investigate the speed issue have you read the Beogram 8000 Technical Product Information pdf section 1-9 through 1-11? You can measure the voltage at the gate of 1TR26 to see if pin 2 of the integrator is correctly indicating a positive voltage since your RPM is too high. You can also check if 1D36 is working correctly to keep the positive voltage at no more than 0.7V. You can then work upstream or downstream from there. Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Sun, Jul 9 2017
  • Re: BG8000 fuse issues

    Hi ALF, I'd leave 0TR1 for the moment, it won't switch on until you sort the power supply to the CPU. There should be 5V at the output of 0IC1 and D20 the zener diode should hold it below 6.2V. Given that you measured 7.12V on the base of TR17 and there should be a 0.7V drop across D15 that would mean 6.4V on the output of 0IC1. There also seems to be too much voltage drop in R75 so I'd pull TR17 and measure it. I'd also check D15. Regards Lonnie (Melbourne)
    Posted to BeoGram (Forum) by Lonnie on Sun, May 7 2017
  • Re: BG8000 fuse issues

    Hi ALF, I think I may have been leading you up the proverbial garden path, the +15V coming out of 0TR1 is controlled by the POWER ON/OFF section of the circuit. This is controlled by the CPU and given that you don't have 5V at the CPU to turn the ON/OFF section on you also have no +15V. 0TR1 is a voltage regulator that provides the stable +15V. TR18 helps control the base of 0TR1. Google discrete voltage regulators for plenty of data and descriptions. Back to the issue with 5V can you test the
    Posted to BeoGram (Forum) by Lonnie on Sat, May 6 2017
  • Re: BG8000 fuse issues

    Hi ALF, It's not surprising that the fuse still blows, you have made any changes to address the issue. You have two issues that need to be resolved, the missing 15V and the blowing fuse. Lets stick with the 15V first. Can you measure the voltage at the emitter of TR18 / R79 and the voltage at the junction of R77 & R78? Regards Lonnie
    Posted to BeoGram (Forum) by Lonnie on Fri, May 5 2017
  • Re: BG8000 fuse issues

    Hi ALF, The +15V measurement at C28 should be independent of the 5V power supply so I think you need to work out why you are only getting -0.6V. A couple of basic things to check: Make sure you measure the positive end of the cap. Make sure connector P2 is properly inserted. Confirm that there is no shorts between the pins of P2 since this has been re-flowed. Confirm you have ~zero resistance between the following: the poitive end of C27 and the emiter of 0TR1, the junction between R77 and R78 and
    Posted to BeoGram (Forum) by Lonnie on Fri, May 5 2017
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