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F-6013 Variant: what's this 2.2k resistor doing here, and more...

Discussion in 'Exclusively Sansui' started by jberger, Nov 22, 2018.

  1. jberger

    jberger AK Subscriber Subscriber

    Messages:
    2,105
    Location:
    Long Beach, CA
    I have a 5000 that I'm restoring, and it had the F-1040 boards. I ordered a set of F-6013 boards that arrived, and I'm trying to follow Service Bulletin CE-037A to install it.

    Meanwhile, my boss gave me (!) his dad's 5000a; while the schematic shows F-1040, this has F-6013s that look original.

    Two things puzzle me: first, on the replacement board, there's a 2.2 k resistor hanging off the back of TR-805, that is not on the board installed in the 5000a.

    2018-11-22 09.38.24.jpg
    This is the resistor in question. One board has a white wire cut off, the other has a black one.

    2018-11-22 09.42.00.jpg
    And this is the same spot on the installed board, with no resistor.

    So, is this needed, or not, and if so, where is the black (white) wire going to?

    Second question: as I read it, Service Bulletin CE-037A removes C027, C028, R041 and R042 from the system entirely, as well as the gray/white blue/black pairs of wires from them; is this correct?
     

     

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  2. jberger

    jberger AK Subscriber Subscriber

    Messages:
    2,105
    Location:
    Long Beach, CA
  3. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,570
    Location:
    Long Beach, CA
    Not having been in any of the 5000 variants can't say for sure what is going on bu it's not unusual for Sansui to modify boards during production. If the 5000A with the 6013 board looks original, that should make a good template for your 5000 upgrade.

    I have an ancient photocopy of a 1972 bulletin called Stabilization of the Power Amplifier, 5000A. Here's what it says:

    1) Remove the blue and gray leads (Marked on the schematic as C') from both channels. They are not necessary when using the F-6013. Also remove resistor R-036 and R-037 (6.8k ohm) {It looks like these resistors are on the blue and gray wires that you are removing here}
    2) Protector Lead B on the F-1040 board should be connected to the F-6013 board. A 2.2K ohm resistor should be added between the Protector Lead (White and Black) contact and the collector of TR-805 (2SA566). {This is your mystery resistor}
    3) 8C and 8D on the schematic of F-6013 should be shorted. {This is just jumpering two points together, look to see if your board has those edge terminals marked}
    4) Add 330 ohm resistor between C005 and C006 (2000uF 80v negative) and chassis ground. {Add this wire from the negative terminal of these caps to chassis ground.}
    5) After the complete replacement, adjust bias to 15mA +/- 2mA.

    This looks pretty straight forward for the 5000A. I don't know if it applies directly to the 5000. I don't see any reference to removing C027, C028, R041 and R042 in this bulletin.

    - Pete
     
  4. jberger

    jberger AK Subscriber Subscriber

    Messages:
    2,105
    Location:
    Long Beach, CA
    Thanks, Pete, I'll dig some more with this info.
     
  5. camfreak

    camfreak AK Subscriber Subscriber

    Messages:
    8
    Location:
    Iowa City, Iowa
    Hi Pete, this service bulletin is news to me. CE-037A is the only service bulletin I was aware of other than CE-005 that pertained to the fuses. CE-037A was for the replacement of the F-1040 with the F-6013 driver boards. It doesn't mention anything about adding 2.2k resistors between the protection circuit wires and the collector of Q805. Would it be possible to get a copy of that document? Years ago I worked at an authorized Sansui service center and have replaced many of these boards and honestly don't recall anything regarding these resistors. I was under the impression that the protection circuit was no longer used since it was not part of the procedure in service bulletin CE-037A. The protection board is not even on the schematic for the 5000X! Any documentation or feedback you could provide would be greatly appreciated. Thank you,

    Phil T
     
  6. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,570
    Location:
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    It's more of a service letter than an actual bulletin. Sadly, this photo copy is so faded that it won't show up when scanned. I got it with a group of service manuals I bought years ago on eBay. It was stuck inside a 5000A manual. Stapled to it are two letter size photo copies of schematics that are also so faded they won't copy. These schematics show before and after and have hand drawn notes to better illustrate the contents of the bulletin. I don't know if they were included with the service letter or done by the Tech that originally had these documents.

    My earlier post has the complete content of the bulletin text. You should be able to figure it out from that and a schematic.

    - Pete
     

     

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  7. tom3

    tom3 Super Member

    Messages:
    1,950
    Location:
    So. Ohio
    Maybe this? Not a real good copy either, sorry.

    sansui 6013 letter.jpg
     
  8. tom3

    tom3 Super Member

    Messages:
    1,950
    Location:
    So. Ohio
    Ran across this too, kind of interesting. Like to buy a couple of those driver boards for that price now.

    sansui 6013 letter 2.jpg
     
  9. tom3

    tom3 Super Member

    Messages:
    1,950
    Location:
    So. Ohio
    Looks like there was an alternate method for installing that resistor rather than putting on the driver board? (this is all I could find on this)

    sansui 6013 letter 3.jpg
     
  10. camfreak

    camfreak AK Subscriber Subscriber

    Messages:
    8
    Location:
    Iowa City, Iowa
    Thanks Pete, your instructions are quite clear. I would have just liked the document for reference purposes. I like lots of documentation! I'm not quite sure if I should incorporate this mod or not. I've always questioned the protection circuit design, since all it does is remove B+ from all boards feeding the input to the pre-driver. It's not going to prevent a catastrophic failure. And they removed it completely on the 5000X. I would love some feedback on this issue........thanks
    Thanks Pete, I really appreciate your time doing this! Funny thing is we were a warranty station for Sansui and they provided the F-6013 boards free of charge. I'm pretty sure they also covered labor, but that I'm not exactly sure of.
     
  11. LBPete

    LBPete Rolling Along Subscriber

    Messages:
    11,570
    Location:
    Long Beach, CA
    Yup, that's the document I have. Thanks Tom.

    - Pete
     

     

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