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9090 or 9090db is one better than the other?

Discussion in 'Exclusively Sansui' started by lilwing, Apr 5, 2018.

  1. CDFixer

    CDFixer Number 1 USC Trojan Fan

    Messages:
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    A couple of notes. On 9090 the newer driver boards will work in older units but not vice versa. The older units without the fuses on driver board had a jumper on board connected the fuse replaces that jumper so and older board will not work in newer chassis without the jumper being added. I believe the cadmium plated chassis was added mid year 1977, might be wrong I have to see what I have.

    The fuses replacing the fuse resistors were added to make the units shipped directly to US, UL approved. Most multi voltage units were built for the US Military with some for Europe. Single voltage units were built exclusively for NZ/AU, GB, which did not have outlets in rear of the unit.

    Yes those printed circuit “cables” between switch board and Dolby were a nightmare.

    Some of the really early driver boards used in 9090 had the suppressor coils mounted on driver board but these may have only been used in other Sansui amps same vintage. I have found that the printed board for the 8080/9090 is much more subject to soldering damage the most other PC boards.

    Pete unless I am doing a complete restoration, I only fix Dolby board feed thrus that are defective.
     
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  2. LBPete

    LBPete Rolling Along Subscriber

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    Great information. It's a safe bet that the cadmium plating of the chassis was introduced to the 9090DB in 1977. Although production of the 9090DB started in around October of 1976, most of what we have on file in the database were built in 1977. All the 9090s had zinc plating.

    Jim, have you actually seen a 9090 driver board with coils on it? Although the board has a place for them, Neither the parts list in the service manual nor the schematic show them. Sansui used variations of that F-2436 board in several other receivers prior to the introduction of the 9090. For example, the F-2436 board in the 881 has those coils. The are called out in the parts list and the schematic for the 881.

    There is another recent thread that talks about the variations of the F-2436 driver board.

    - Pete
     
  3. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
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    9 times out of 10 if you tap on the Dolby board a channel will drop out, revealing bad feed thrus. The 10th one has either already been fixed or has the new feed thrus. I don't like recalls.
     
  4. 55trucker

    55trucker New Member

    Messages:
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    Location:
    Toronto, Ontario
    It's been approx a year since i last posted with the Dolby issue with my 9090db.....(which as of yet has not been solved).


    Pete how does one distinguish the year date of the improvements to the Dolby board?


    Steve
     
    Last edited: Apr 17, 2018
  5. lilwing

    lilwing CAGE FREE AUDIO ZOO Subscriber

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    While you bozos were hijacking my thread I was out doin' stuff. JK:D[​IMG]
     
  6. LBPete

    LBPete Rolling Along Subscriber

    Messages:
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    The first improvement is easy to see, the green flex pc board connecting the push switches to the Dolby board were replaced with black ribbon wire. That happened around the time they switched to the yellow zinc plating on the chassis. Somewhere around the end of production they deleted the rivets in the pass thru holes. Don't know when exactly that occurred but my best guess is around the time they stopped shipping multi voltage units to the US.

    We have not been tracking these changes in the serial number database but we can. To do so, people with these units need to report which mods their unit has along with the serial number. I can tag this information to newly reported or serial numbers that are already in the database. With enough reports we can narrow it down to the month of production.

    Also, sorry about the thread hijack but you opened a can of worms.

    - Pete
     

     

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  7. 55trucker

    55trucker New Member

    Messages:
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    Location:
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    Thx Pete,
    I'm not going to take any more of JK's thread, I'll start a fresh thread & supply you with all I can.


    Steve
     
  8. lilwing

    lilwing CAGE FREE AUDIO ZOO Subscriber

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    JK = Just Kidding
    It's really ok.
    Hope we can see pics of what y'all are talking about.
     
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  9. lilwing

    lilwing CAGE FREE AUDIO ZOO Subscriber

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    Well I just watched BLUEGLOW's youtube video about rebuilding the dolby board. Looks kinda hard but do-able.
    My db is smokin' along just fine so I'm not about to fix something that ain't broke yet.
    I haven't been able to do a "sound" comparison yet but I'm not worried and I doubt my old ears could tell the difference.
     
  10. LBPete

    LBPete Rolling Along Subscriber

    Messages:
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    The traces on the Dolby board are tiny and lift very easily. You need pretty good soldering skills to service it without damaging it.

    - Pete
     
  11. lilwing

    lilwing CAGE FREE AUDIO ZOO Subscriber

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    That's exactly what I'm going to do. Tomorrow I'm dropping my 9090 and 9090db off at QRX restore. Lucky I guess that no shipping is involved.
     
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  12. lilwing

    lilwing CAGE FREE AUDIO ZOO Subscriber

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    I have my 9090 back from QRX and it sounds huge and lush and detailed.
    I'll be dropping off the 9090db this week for the same restoration and dolby bypass.
    So it's possible that my comparison won't be fair since I'm told by them that the dolby "colors" the sound somewhat and the dolby bypass eliminates that effect.
    I think my original question of which is better has been answered by "J" at QRX. He prefers and uses as his personal rig the 9090db. (bypassed)
    BTW: The team at QRX certainly has their customers' satisfaction as their goal. Nice guys too!
     
    Last edited: Jun 12, 2018
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