New project. Sansui 8080 recap. Advice appreciated.

Discussion in 'Exclusively Sansui' started by RR--, Apr 4, 2018.

  1. RR--

    RR-- Active Member

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    Update.
    I decided to recap the tuner as I had almost enough spare capacitors lying around and needed to buy more parts to qualify for free shipping from Mouser. All those new Wima caps look nice too!
    I also added an extra heat sink to the Tuner power supply transistor, even with the additional heat sink it gets very hot.

    [​IMG] [​IMG] [​IMG] [​IMG]

    I also decided to remove the Tape Rec/Play port and install a switch to change between stock and modded backlight states, I generally prefer to leave the tuner lights off but on occasion I like to show them off.
    The original port is taped up and tucked away inside in case the mod needs to be undone, I made it completely reverse able.


    [​IMG]

    Current pic of the bottom of the receiver showing all mods, I'm currently repainting the power transformer and will have a top pic when it's done.
    [​IMG]
     

     

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  2. RR--

    RR-- Active Member

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    So I think my next step is to replace some old noisy transistors, I have been using the receiver with the -20db mute enabled as it reduces the background hiss considerably but occasionally I like it unmuted and then the noise is annoyingly loud. After replacing a heap of transistors in my AU-719 the background hiss is almost nonexistent it's impressive.

    Looking at the schematics I noticed there's a few 2SC1313's on the Triple Control Tone board I can replace with some KSC1815's.
    I also noticed on F2436 that TR02, and TR04 don't match TR01 and TR03 so I think they should all be replaced, do you have any recommended transistors that should be replaced and some modern equivalents to purchase? [Edit, the schematics say they're 2SC1708(G)] remember you recommended replacing some transistors a while ago that I forgot about, any recommendations on what to replace those with too? http://audiokarma.org/forums/index.php?attachments/upload_2018-4-8_0-48-3-jpeg.1157685/some
    I don't mind replacing more than necessary, also I'll try and stick to RS Components this time as I won't be buying much. (I hope)

    Thanks again.

    [​IMG]
     
    Last edited: Jul 6, 2018
  3. petehall347

    petehall347 the brandy coffee man Subscriber

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    RS is free shipping here i feel bad when shipping costs more than my order
     
  4. RR--

    RR-- Active Member

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    Yeah that's why I do too, I prefer Mouser as they have more options but $25 shipping can hurt for individual components, unfortunately RS Components often only sell transistors in quantities of 200 so it's often a pain. At least I have plenty of spares.
     
  5. petehall347

    petehall347 the brandy coffee man Subscriber

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    tone boards should be fine for 1815 . i have more than a lifetimes supply of 2sc1815 here
     
  6. RR--

    RR-- Active Member

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    Thanks. I have three spare which should just cover it including the volume control board, they came out of another amp when troubleshooting the problem so I think they're still good.
     

     

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  7. Hipocrates

    Hipocrates Anti-Muppet

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    maxhifi and RR-- like this.
  8. RR--

    RR-- Active Member

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    Wow that post is a goldmine thanks! and thanks to Tnsilver.

    So it looks like I'll need to do the following:
    • Replace 2x 2SA818 at TR05 & TR 06 with KSA1381ES (in upper pin hole position)
    • Replace 2x 2SC1628 at TR09 & TR10 with Zetex ZTX694B (backwards orientation)
    • Replace 2x at TR11 & TR12 with On Semi NPN 863-MJE15030G (Same position)
    • Replace TR13 & TR14 with On Semi PNP 863-MJE15031G (Same position)
    TR01, TR02, TR03 & TR04 still puzzle me though, on my board TR01 and TR03 seem to be much older with the marking C639 while TR02 and TR04 say C1400. My thinking is that the C1400's have been replaced in the past although the soldering doesn't look like it has been altered.

    Any thoughts on what to do here? Searching through the forum KSC1845FTA seems to be the correct replacement for all four transistors.

    Also looks like I'll be paying extra for Mouser again, I'd buy more from RS if their minimum order quantities weren't ridiculous.
     
  9. Hipocrates

    Hipocrates Anti-Muppet

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    That's why I end buying some dozens always, if all my projects are done, and have leftovers, I would just buy another unit to use them :rolleyes: (oops now I see why the hoarding).
    I think I used KSC1845FTA too, HFE matched If memory serves me right.
     
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  10. RR--

    RR-- Active Member

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    Thanks again Hipocrates, I'll go with the KSC1845's for all four although I wont be able to HFE match them, that shouldn't be a problem should it? Strange that the two transistors at TR02 and TR04 (right side) were replaced with C1400 transistors, but this driver board sure has been butchered a lot in the past so anything goes really.
     
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  11. Hipocrates

    Hipocrates Anti-Muppet

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    I don't think it will be and you will be probably getting same batch. And yes I remember that board, some weird values. Anyway KSC1845 will do the job
     
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  12. RR--

    RR-- Active Member

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    Hey quick question, My parts have arrived and I'm currently installing them. When removing the transistors mounted to heat sinks no thermal compound seems to be present although some have been slightly oily.
    How should I go about mounting the new transistors to the heatsinks?

    Below is a picture for reference (TR02)

    Thanks
    [​IMG]
     
  13. RR--

    RR-- Active Member

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    Also I was planning of replacing the four BiPolar capacitors on F-2546 with regular Nichicon Gold electrolytics, however I just noticed they're rated at 85° where the BiPolars are at 105°, is this a bad idea?
    I got the idea from this post http://www.tapeheads.net/showthread.php?t=49795
     
  14. Hipocrates

    Hipocrates Anti-Muppet

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    I cleaned them and put a tiny amount of thermal paste and spread it on the back of the transistor, that's just to help thermal conductivity.
    I don't think it will be a problem.
     
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