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  • Re: Beogram 6500 fuse constantly blowing

    Kim, I am humbly honored by your kind words. Thank you. The truth is that ALL the members are a part of the success of this forum.
    Posted to The Workbench (Forum) by Menahem Yachad on Sun, Apr 18 2021
  • Re: Beogram 6500 fuse constantly blowing

    Looking at this problem as you describe it, this would be my procedure - cheap and quick enough to do, without getting into in-depth troubleshooting.. 1. On the PSU PCB, Replace the 4 Si rectifier bridge diodes, with a 1.5A unit - perhaps the 1N5393 or similar. 2. Replace the 12V regulator with a L78S12CV - more robust 2 Amps Connect a 60W incandescent bulb across the fuse terminals - saves fuses. If the problem still happens, then disconnect the output of the 12V Regulator from the circuits down
    Posted to The Workbench (Forum) by Menahem Yachad on Sun, Apr 4 2021
  • Re: Beogram 400x projects

    Absolutely OUTSTANDING. The talents exhibited by this forum's members are truly impressive.
    Posted to BeoGram (Forum) by Menahem Yachad on Fri, Mar 19 2021
  • Re: BeoLab 9 Overhaul

    Yes, I would very much like to believe that it is so simple - just replace the 33079. Experience has taught me otherwise. So, I had already used Freeze Spray, and that caused no change at all. In the old days (before SMD), it would have been very simple - just desolder the legs of the parts around here, and in 20 minutes, the defective part is identified. But here, I've had to cut the PCB traces from Pin 14, which go to the surrounding parts, and I have not been able to cut every trace, simply
    Posted to The Workbench (Forum) by Menahem Yachad on Sun, Mar 14 2021
  • Re: BeoLab 9 Overhaul

    Scoped all the inputs and outputs of the MC33078 Dual and MC33079 Quad OpAmps. Without a scope, this troubleshooting would be absolutely impossible. What I was looking for is exactly this: OpAmp input Clean, OpAmp output Distorted. Found this exactly on IC204 MC33079 - Pins 12 and 13 Input - Clean, Pin 14 Output - Distorted. This is now the area of interest, as shown on the photo. This IC is under the metal shield on PCB1 (Crossover). Either the OpAmp itself is defective, or the surrounding components
    Posted to The Workbench (Forum) by Menahem Yachad on Thu, Mar 11 2021
  • Re: BeoLab 9 Overhaul

    Checked the Inputs and outputs of the STK amp. Pin 11 on the STK403-130 is the input - shows the crackling, so I'll be reverse engineering the circuit backwards from the preamp to the STK to find the culprit. The schematics would be helpful here....
    Posted to The Workbench (Forum) by Menahem Yachad on Wed, Mar 10 2021
  • Re: BeoLab 9 Overhaul

    PCB1, also described as the Crossover PCB, is the faulty PCB. Next step is to isolate the faulty components.
    Posted to The Workbench (Forum) by Menahem Yachad on Wed, Mar 3 2021
  • Re: Beogram 4000c - Recreated Limited Edition

    [quote user="Beozip"] They have hidden a limited secret. Do you find them? [/quote] Before I opened the link, I thought to myself - Maybe the secret is a vintage radio there. And then I open the link, and so - there is a beautiful collection of vintage items - the best part of the store!
    Posted to General Discussion & Questions (Forum) by Menahem Yachad on Mon, Mar 1 2021
  • Re: BeoLab 9 Overhaul

    [quote user="Beobuddy"]Crackling noises are never caused by degraded electrolytic capacitors. From all the defective BL9's I've had, none of them had issues caused by these. [/quote] All the electrolytic capacitors have already been replaced. That's the first order of work - to replace ALL confirmed defective parts. The crackling is the ONLY problem remaining, therefore you are correct that the capacitors are NOT the cause of the crackling. The crackling comes from the tweeter
    Posted to The Workbench (Forum) by Menahem Yachad on Thu, Feb 25 2021
  • Re: BeoLab 9 Overhaul

    [quote user="Beobuddy"]You do not know this[/quote] On the contrary! Checking ESR in-circuit is a perfectly reliable method of determining whether the capacitor is functional or not (except in a tank circuit). For capacitance, you are correct. Capacitance MUST be checked out-of-circuit. However, after ESR has confirmed a bad cap, the capacitance is of academic value only. Can you expand on the actual causes of crackling problems in your past experience with BL9's?
    Posted to The Workbench (Forum) by Menahem Yachad on Thu, Feb 25 2021
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