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Repair stereo transformer ~ possible?

Discussion in 'Troubleshooting and Repair' started by gbd1010, Jun 10, 2021 at 3:48 PM.

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  1. gbd1010

    gbd1010

    4
    0
    Thursday
    Hello,

    I have a stereo that is labelled as Planetron 2000.
    ~ I believe that my stereo is also the same as the Brother BR-5.

    Issue:
    Unfortunately, my 120V stereo was plugged into a 220V socket directly and my testing indicates that the transformer which supplies the amplifier and radio is blown (at the very least)
    (the offender had the wherewithal to use a plug adaptor but not a voltage transformer...sigh!)

    I'm aware that there could be other issues, but I'd like to replace or repair the transformer first and then see how things are.

    I have trawled the Internet and posted on a number of different forums but unfortunately I have being unable to track down a service manual or schematic for the stereo so I am unsure what voltages the step down transformer supplies. I have also been unable to track down the transformer based on its labelling. (see photo attached). Therefore, at this point I am unable to replace it.


    So, I'm hoping that somebody can advise on the possibility of repairing the transformer.
    Perhaps the input wire on the transformer is melted/shorted (see testing results below) and I could replace the wire...is this possible? Is it simply a case of unwrapping the wire and counting the number of turns and replacing it with a similar wire with the same amount of turns? Note that I opened up one side of the transformer (the side with the 2 white wires) as I read that some transformers can have fuses, but I saw no sign of one.


    The transformer
    - See photo attached
    - It's labelled as AC-159C (but I cannot find any reference to this on the Internet).
    - There are 2 wires (both white) on one side which I am assuming are the input wires (assume 120V).
    - There are 5 wires (2 x red, 1 x black, 1 x green and 1 x yellow) on the other side which I am assuming are the output wires. I have no idea what voltage they provide.


    Transformer Testing
    I removed the transformer from the stereo and tested the resistance between all the wires.

    - White -> White = No measurement (Open circuit I assume)
    - White wires to all other wires = No measurement (Open circuit I assume and expect)
    - Red (#1) -> Red (#2) = 3ohms
    - Red (#1) -> Yellow = 2.2ohms
    - Red (#1) -> Green = 3.2ohms
    - Red (#1) -> Black = 3ohms
    - Red (#2) -> Yellow = 2.1ohms
    - Red (#2) -> Green = 3.2ohms
    - Red (#2) -> Black = 3.2ohms
    - Yellow -> Green = 1.6ohms
    - Yellow -> Black = 0.9ohms
    - Green -> Black = 1.9ohms
     

    Attached Files:

  2. PETERDECO

    PETERDECO

    140
    36
    Dec 19, 2019
    Welcome to the forum. If you can, remove the shell on the white wire side. You may be lucky and find a fuse inside.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
    2,619
    Nov 17, 2011
    I agree. Although it is unusual to have the primary side and the secondary side on the same connector.
     
  4. gbd1010

    gbd1010

    4
    0
    Thursday
    Hi, thanks very much for responding.
    I already opened up the shell on the white wire side and there was no sign of a fuse.
    See photo attached.
    Is there anything else I can check or do?
    Is my suggestion of unwrapping the wire and counting the number of turns and replacing it with a similar wire with the same amount of turns madness?!!
     

    Attached Files:

  5. Martaine2005

    Martaine2005

    3,408
    926
    May 12, 2015
    Are there any references to voltages on the PCB?. Near the connector?
    There seems to be 3 or more outputs, any capacitor max voltages on each rail? Voltage regulators? Just a thought..
    I see you didn't have any luck on the audio/hifi forums.

    Martin
     
  6. gbd1010

    gbd1010

    4
    0
    Thursday
    I can't see anything obvious in relation to what voltages the transformer is supplying. The output from the transformer plugs into a socket which then feeds into the proverbial rats nest of wires and components ~ I am very much an amateur/novice and I have seen the inside of a few systems but this one is proving too hard for me to follow. So much of it is unlabelled.

    "I see you didn't have any luck on the audio/hifi forums." ~ Ha ha ~ No I didn't! But I'm nothing if not determined!:)

    Does anyone have an opinion on my suggestion of unwrapping the wire and counting the number of turns and replacing it with a similar wire with the same amount of turns?
     
  7. Bluejets

    Bluejets

    4,748
    999
    Oct 5, 2014
    Forget it.
    There are possibly a thousand turns on there and wound close together to minimise the finished size.
    These are wound on a former initially and then fitted to the laminations, not the other way around.
    I have done it a few times so have some idea.
    Before you do any damage, you could take it to a motor winding shop and have them do it.
    They would obviously rewind the whole thing, not just the primary for obvious reasons.
    You would need deep pockets though.
    Other alternative is to keep an eye out for a second hand unit.
    They are out there, however being collectable these days, would be difficult.
    Perhaps old radio stereo sites would be a good place to start.
     
    Last edited: Jun 11, 2021 at 11:57 PM
  8. gbd1010

    gbd1010

    4
    0
    Thursday
    Thanks Bluejets ~ that's one avenue of repair ruled out!

    I have been looking out for spare parts on the web. Unfortunately, these stereos are not very common and tend to be sold as complete units rather than broken up for individual parts. This is looking very much like a long term project! Thanks again.
     
  9. Bluejets

    Bluejets

    4,748
    999
    Oct 5, 2014
    Transformers these days as a whole are becoming rare.
    Yes I realise one would need to buy the complete s/hand unit, not parts.
    Pioneer blu ray I had here turned out the same.
    Much cheaper and less hasle to buy a s/hand unit.
    Depends how badly you need to hold on to the past.

    Waited for a cartridge for the one below for 6 months and it is a common part to many different brands.
     

    Attached Files:

    Last edited: Jun 14, 2021 at 12:25 AM
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
    2,619
    Nov 17, 2011
    Have you repeated the measurement white<>white directly at the transformer?
    upload_2021-6-14_7-56-50.png
    Just to rule out a defect within the white wires
     
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