Beomaster 5000

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  • #4407
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Thought I would check the fuses out too before powering up…..this is what I found.

    P1016802

    #4409
    hcraig244
    Beoworld Member
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    Removed the link and cleaned up the fuseholder…new fuses installed. Gingerly applied power from the variac up to 220v……and nothing happened, not necessarily a bad thing…there was no smoke or sudden popping of new fuses…..so a little fault finding exercise required….as for now a glass of wine is called for

    P1016812

    #4410
    mexking
    Beoworld Member
    • Topics Started 1
    • Total Posts 19

    Keep them coming, I like your work, think about chancing the Fairchild (black drop) transistors, Frede, Classic Audio recommend changing them

    • This reply was modified 2 months ago by mexking.
    #4421
    hcraig244
    Beoworld Member
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    This is true Soren….I received this from Frede some time ago:

    Craigh,

     

    It is actually a ”short list” 😊

    BC 550B for npn

    BC560B for pnp

     

    When the Beolab was designed (before 1967) only a few transistors were available is really low noise versions – therefore B&O have chosen a number of different types of coarse also being able to be used and meeting the actual voltage level. But I have for many years used the above type in the pre-amplifiers.

    And I am using the transistors type B because higher gain in classic electronics design is not a good idea (this is my opinion 😊)

    B U T — for the power amplifier and the power supply – I only use the original RCA types !!!

    For the output power transistors and psu transistors — I am only using the original Motorola or RCA (there are to many “fake” 2N3055 out there).

    When I am writing the original it is actually the original because I re-use these transistors from Beolab 5000 which is scrapped.

     

    #4423
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Started by checking the 240v supply to the transformer…..all good, 32v output to the new rectifier and around 40vdc out of the rectifier. Checked the 20vdc supply and found it was around 29vdc…adjusted the new trimmer I installed and brought it back to 20vdc……checked the voltage to the power ON lamp and that was good too…..so replaced the lamp and of course it illuminated ;¬)

    Connected a antenna and adjusted the tuning dial, the stereo lamp flickered as it passed through live broadcasts which was very encouraging…..however the tuning meter stayed hard down throughout.

    • This reply was modified 2 months ago by hcraig244.
    #4425
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Thinking I may have damaged it during cleaning I took it out, looked ok and when I put my multimeter across it to check the moving coil continuity the needle deflected 3/4 up scale, as you would expect from the current from the meter set to ohms. I got out a meter I recently replaced due to severe clouding of the lens to compare….and found this curious thing……

    P1016806

    #4426
    hcraig244
    Beoworld Member
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    • Total Posts 70

    The polarity of the meters are opposite, someone has erased the + / – markings from the left hand side meter and marked them up opposite to what they where…….the right hand side meter is the one with the milky lens and still has the + / – markings unchanged,

    The negative marking can be seen against the right side post, the meters have different shapes too….change in design down the years I expect.

    P1016804

    • This reply was modified 2 months ago by hcraig244.
    • This reply was modified 2 months ago by hcraig244.
    #4428
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    However I extended the + wire and soldered the cloudy meter in place and ran another test, all worked fine

    P1016807

    #4429
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Deciding the way forward was to replace the cloudy lens with the not so cloudy lens on the one I had just installed I set about dismantling the not so cloudy meter and discovered the internal connection from the + post was loose….tightened it up put it back together and having removed the newly extended + wire I soldered it back in place…..and yes everything worked fine!……spent a couple of hours on this

    P1016811

    #4447
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Completed all the component replacements….including the “fairchild black blobs”, fitted BC550B’s.

    P1016815

    #4448
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Hooked up to a Beolab 5000 and an antenna, and I have to say that in spite of the occasional unexpected minor issue this tuner sounds tremendous….crystal clear and very stable….all that remains is to put it all back together ;¬)

    P1016814

    #4462
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    Made a start on the front panel and curser…..takes quite a bit of fiddling around to get the felt pads back in along with the nylon studs on which the curser rides…..

    P1016820

    #4503
    hcraig244
    Beoworld Member
    • Topics Started 3
    • Total Posts 70

    All complete and fully tested…..does sound very good for an old girl, I think it can now be identified as restored……

    P1016835

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