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  • Re: Beomaster 1900-2 T2903 dead after recap

    Looks ok to me, EXCEPT: 14ohms on TP15? That seems too low. That's over one amp once you bring the unit out of standby and the BD136 (TR31) can only take 1.5A I think there's something wrong and worth investigating. Disconnect PCB7 so that you get rid of the low ohm light bulbs in parallel (IL1/2/3) and measure again.
    Posted to The Workbench (Forum) by manfy on Sat, Dec 5 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    Well, yeah. But I still don't like it. I crunched some numbers: The manual claims your unit has an idle consumption of 25W. At 240V that makes some 100mA in the mains line. The power amp will probably need 200mA idle current at 31VDC, which translates into 20+ mA in the mains line. So that leaves 80mA for the 15V transformer; roughly 1.2A at 15VDC. You're measuring 14 ohms of pure ohmic resistance in normal state; that means >1A. In the circuit diagram I see no immediate justification
    Posted to The Workbench (Forum) by manfy on Sat, Dec 5 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    [quote user="Andreas"] I see, of course i wouldnt want anything to blow. I would like to tell you a big thank you for going through this with me step by step. If possible i would like to send you a good austrian wine for your effort :) [/quote] Well, I'd have no problems with that -- but let's get the Beomaster running first. [quote user="Andreas"] I am thinking if there could maybe be a blown fuseable resistor around TP15. [/quote] A fusible resistor? In the 1970s? In
    Posted to The Workbench (Forum) by manfy on Sat, Dec 5 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    Minor correction: It seems that the BM1900 has a mechanical on/off switch, so of course, 15.7V on TP16 will only be available after switching on and not after plugging in, as I had claimed earlier. To get you jump-started with your troubleshooting: - Measure the resistance between TP16 and GND. You'll probably measure a small value or a solid short circuit. This would explain the blown fuses F1. - find the source of that short circuit and fix it. Since you changed the electrolytic capacitors
    Posted to The Workbench (Forum) by manfy on Fri, Dec 4 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    [quote user="Dillen"] Is TR27 no longer insulated from the heat sink? [/quote] Probably not. Good catch! Since he had to remove the transistor from the heat sink to take out the board, Andreas probably forgot to add the mica sheet when he put things back together. Or the mica sheet is damaged.
    Posted to The Workbench (Forum) by manfy on Fri, Dec 4 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    [quote user="Andreas"] So just to be clear the zener diodes 2D51 and 2D52 are blown because i read voltage both ways on the multimeter in diode mode ? I should change these first right ? [/quote] No!! Do NOT start changing parts without having figured out first what the root cause for this damage was! My impression is that you're fishing right now and you're eager to get the Beomaster running as soon as possible. It's exactly that eagerness that can lead you on a path of destruction
    Posted to The Workbench (Forum) by manfy on Thu, Dec 3 2020
  • Re: humming/buzzing transformer Beomaster 1200

    [quote user="Aad Jansse"] I got a pair of hearing aid devices the other day, which gives me access to the higher frequencies in surrounding sounds. It is only too bad that these things also amplifies the nasty sound that the BM1200's transformer produces. It was not a disturbing thing before. Apart from taking away these devices from my ears (I appreciate the improved sound reproduction through the speakers very much) what could be done to eliminate this humming?. [/quote] I'm slightly
    Posted to The Workbench (Forum) by manfy on Thu, Dec 3 2020
  • Re: Beomaster 1900-2 T2903 dead after recap

    [quote user="Andreas"] TR28= E 20,3v C 0v B 20,7v D5 goes through both ways but i guess thats alright [/quote] Not really! 2D51 is a 9.1V zener, 2D52 a 5.6V zener. Both diodes are important for the proper function of the 15V regulating circuit TR27/28/29. TP16 should measure 15.7V as soon as the unit is plugged in switched on with the main on/off switch -- provided the regulator circuitry is working and properly adjusted with R151. You said earlier that 2F1 blew several times. I'd be
    Posted to The Workbench (Forum) by manfy on Thu, Dec 3 2020
  • Re: Beomaster 1000 2317 - Main Switch Screen

    Hi Christian and welcome to the forum! I have no idea where that white piece of plastic comes from. The only white plastic I see in my BM1000 is item 37 in the service manual, the "dial rear wall" that reflects the light of the light bulbs that illuminate the frequency indicator. Item 253 labelled as "screen for on/off switch" is actually just a piece of insulating shield between the 250V switch and the transformer. Here you can see the item and its mounting position: As far as
    Posted to The Workbench (Forum) by manfy on Fri, Oct 23 2020
  • Re: Beomaster 1700 (type 1701) revisited - Tech Help needed

    [quote user="Pete"] To add to my story: The two aluminium capacitors on the power supply have now been replaced (par for the cause) without problems but am now hesitant to unwire the 40 watt bulb before connecting to my uncles (inherited) “Mission” speakers Q; Will the “idle current” on the power amp board need adjusting after removal of 40 watt tungsten bulb? - Maybe fear after success is cutting in! [/quote] Good that you ask. Yes, it probably will change - not
    Posted to The Workbench (Forum) by manfy on Wed, Jun 17 2020
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