Pioneer SA6200 Rebuild Project

Discussion in 'Pioneer Audio' started by colinhepburn, Oct 4, 2010.

  1. colinhepburn

    colinhepburn New Member

    Messages:
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    Location:
    Scotland UK
    Hi All
    Well having a look around EBay I can across a pioneer SA 6200 which I snapped up for a mere £22.00 $34.00 I had one of these Amps years ago when I didn’t know too much a about Hi Fi sound then and gave it away. I seen to remember it sounding good at the time so thought I’d have another play with this one for a bit of fun. The seller did say it has a fault in one channel he described the sound as muffled and intermittent anyone have a idea of the cause or causes of this fault While I await delivery of the amp

    Intended Work plan is to do a full recap using Elna Silmic RFS and Elna Cerafine Electrolytic and polypropylene Caps in the single path maybe Mundorf MLytic SI electrolytic for the Power supply Caps and a rewire And as I an still a beginner at this restoring game I would gratefully for a guiding hand though the process from the pioneer boffins I’m OK with a soldering iron and reading schematics
    But I am inexperienced on the testing side of things like correct currents ext. But keen to learn from the members here and my biggest confusion is soring and selecting the best Transistors equivalents I just don’t know enough about this side of thing I look forward to reading everything you all can tell me about this Amp :music::music:

    OK I had a crack at sorting the transistors would someone pleas advice if I have this right if wrong would you mind posting the best one from this site if possible in stock
    http://www2.cricklewoodelectronics.com/Cricklewood/search.php?mode=search&page=1


    SUBS 2N6126/2SA733/2SA1740
    SA2600 POWER AMP
    Q11/12/13/14.
    2SA489/2N6126/PNP 8OV 4A 40W
    Q9/10
    2SA720/PNP 60V 500mA 200MHZ
    Q5/6/7/8/15/16
    2SC1318 NPN 50V 0AS 500mA
    Q1/2/3/4
    2SA726/2SA733 60V 100mA 200MHz
    Control Board
    Q1/2/3/4/5/6 2SA1740 50V 0A1 180MHZ
    Phono Board
    Q1/2/3/4 2SA1740 50V 0A1 180MHZ
     
    Last edited: Oct 4, 2010

     

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  2. colinhepburn

    colinhepburn New Member

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    :smoke:Well 29 views so why no response i would kinda like an response to my post before i take delivery of the amp as i do requirer some help with this amp thank you:smoke:
     
  3. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    WHY no response? And why not RIGHT away...

    First - the lack of service information for the sa-6200, that ate an hour of time before I gave up the FIRST time.

    Second, not only do you want me to come up with substitutes, you name unfamiliar (to me) transistors that doubles my work, first I figure out what the originals are doing, but then I have to figure out whether the replacements you specify will work. First tracking down THEIR specifications. Compounding that is your desire to use capacitor brands (that while are perfectly adequate) that are unfamiliar to me. Then I end up fighting unfamiliar search engines in Foreign parts suppliers. NO quick easy answers all round. That's where the personal pivotal decision point is in what I do, build upon the foundation of familiar circuits, equipment and replacement parts. Otherwise it eats up a tremendously larger chunk of time. I'm NOT paid to do this.

    Third I had to decipher the post itself.

    Fourth, the unit is IN TRANSIT. When it arrives, it could be smoked out ruins inside. There is no rush. I will NOT be rushed.

    SO, after several hours of effort in other posting sessions, with nothing material to add from my(separately invested and frustrating) hours of efforts on your behalf, I stay silent (so others would not be dissuaded from chiming in, saying "If MTF has hit a wall, fuhgedaboudit") and am apparently upbraided for it.

    BUT FINALLY, The HELPFUL thing I have noticed is that it is a relatively uncomplicated model, VERY similar to the sx-525. There are parts lists on here for the 525, but even that has problems, as I specified On-Semi parts for the output transistors that had characteristics that caused us problems, thus fairchild replacements or a circuit change was recommended.


    You want to get faster answers, do some of the legwork.

    for the original transistors and the replacement transistors, post their:
    case type (optional)
    npn/pnp for the 2n devices
    Vceo
    Ic
    Pd
    Hfe
    Ft

    you have a start in your first post already...

    This is how I do replacements and comparisons.

    my replacements re sa-6200 / sx-525:
    2sa764/2sa726 to92 ecb/bce 30v 50mA 0.2w 250hfe 120mhz
    512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

    2sa820 / 2sc1318 to-92 ecb 60v 0.5a 0.625w 85-340hfe 200mhz
    512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
    512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

    2sa489 / 2sc789 to-220 bce 60v 4a 30w 40-240hfe 3mhz
    512-KSB596Y pnp to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62
    512-KSD526Y npn to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62
    NOT the 863- part numbers.
     
    Last edited: Oct 5, 2010
  4. colinhepburn

    colinhepburn New Member

    Messages:
    30
    Location:
    Scotland UK
    Hi All
    Well still no replies it seems that the pioneer amps must have going out of favour or maybe it’s just the SA6200 I Am going to document this Restore of the SA6200 on this thread with Wright ups and images on the progress but to do this I will need the help of other here with answers to my questions and perhaps help with sourcing parts But there won’t be progress if now one posts :boring::boring::boring:
     
  5. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    my post 6:23pm

    his post 6:32 pm.... how could he miss all that???

    Joined Feb 2007, 4 posts, but he can't claim noob-ness.....

    btw everybody, I think that the stereomanuals .com manual to be used should be the sa-620 manual.
     
    Last edited: Oct 5, 2010
  6. Glenz75

    Glenz75 Sansui and Pioneer Freak

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    Location:
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    Hi, I think some patience is required here, you will get replies eventually and like Mark said, do some of the homework yourself :)
    The SA6200 is a pretty straight forward basic amplifier and its a good base to start with if you are wanting to restore and learn from the experience. I had one myself years ago and it was a good little performer. Good luck!

    Cheers
    Glen


     

     

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  7. colinhepburn

    colinhepburn New Member

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    Right first thank you for your replies
    Just so you all know I am not a total novice at this I have built a couple of pre amp pass B1 and A bridge of Zen pre as well as a Valve phono Stage and a Valve Headphone Amp And now collecting part for a Moondog 2A3 valve amp I have also tweaked most of my audio kit with audiophile parts i.e. resistors and the caps I referred to in the first post
    I am aware this amp will not win any awards but it will serve as a good foundation to learn more about solid state
    Ok I have the SA 6200 Schematics PCB layouts part values and voltages as for transistor I am still not good at understanding how to read the datasheets making the reason for my limited info in my first post you say to do the leg word first but I have to ask the questions first so I can learn how to understand to doing the leg work
    As this is the pioneer thread I did think these transistors would be common across the SA range of the pioneer amp so thought they would de know to most of you who repair them as you also have said your fighting unfamiliar search engines in Foreign parts well all I can say on that is sorry about that but the same is true for me as well on this side of the pond
    So I will promise to do more on the leg work but I still wish for help in a step by step guide on how to setup the amps currant at VR1 and Vr2 i.e. how and where do I connect the MM meter to read off the current and what should the current be running at I think somewhere between 30/40 mA but not should can you give me an ball park figer for this see Schematic
    Thank you for your time is appreciated
    Colin
     

    Attached Files:

  8. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Some of what we do here is to "teach to fish," instead of "giving a fish"

    The idle current is measured across either one or both of the 0.5 ohm resistors at the output. Then use ohms law (0.5 ohms or 1 ohm) to translate (milli)volts to (milli)amps. Then adjust using the variable resistor for that channel.

    Although the pin numbers are different, the sx-525 service manual (in our database or posted in digital docs) provides almost exactly what you need, and you should quickly spot the similarities to your power amplifier stage.
     
  9. colinhepburn

    colinhepburn New Member

    Messages:
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    Location:
    Scotland UK
    :beerchug::beerchug:

    Yep I can run with that but I need to know the fish I need to catch first
    Thanks Mark a Little at a time like this is a good start for me Cheers
     
  10. colinhepburn

    colinhepburn New Member

    Messages:
    30
    Location:
    Scotland UK
    Hi all
    Is seems the SX-525 you pointed me to is a tuner did you mean SA-525 or the SA-5200 can you post a link to it
    Thanks
     
  11. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Location:
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    The sx-525 receiver has an amplifier section very very similar to the sa-6200.

    Unfortunately the manual does NOT have an idle current setting procedure or explicit idle current target value.

    It does say 60ma on a certain wire, shared unequally 3 ways, assuming a mix of 10, 25 and 25, gives 25mV across 1 ohm or 12.5mv across 0.5 ohms

    ohms law example:
    20ma through 1 ohm measures 20 millivolts across the resistance.
    20ma through 0.5 ohm measures 10 millivolts across the resistance.

    Some of Pioneers older stuff was set at 7 millivolts, some at 15 millivolts both across 0.5 ohms. 12.5mV seems reasonable.

    As the idle current setting is increased, it will decrease distortion , until it hits a point where the increase ceases to change the distortion as the idle current increases, thus just generating waste heat with no benefit.

    Factory specified settings strive for slightly after this point.

    Adjust the 100 ohm VR1 or VR2 pot as appropriate for the targeted channel.
     

     

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  12. colinhepburn

    colinhepburn New Member

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    Yep got that it was just the word tuner that throw me of balance thanks again for the info on the idle current setting procedure I have even located the test points 16/17 18/19 Close to the 2Watt R35/36 when recapping would you recommend upping the cap uf values on the amp boards and PSU for example PSU smoothing cap from 4700uf to say 6800uf or even 10.000uf
    Colin
     
  13. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Most cap values have a distinct purpose, changing values willy-nilly is a no-no :nono:

    Should you wish to increase the value of the big power supply capacitor you will need to put in new rectifiers to handle the increased peak inrush current on power up. The old rectifiers will just die mysteriously sometime in the future...

    Those rectifiers will be larger, and have thicker leads, so you will also probably have to enlarge the holes that they pass through on the circuit board.

    The amplifier output capacitors characteristics are considered and integrated into the design, changing them can have serious repercussions. Might seem fine until the wrong set of speakers presents the wrong load to the amp, pushes it over the edge and -blooie- .
     
    Last edited: Oct 6, 2010
  14. colinhepburn

    colinhepburn New Member

    Messages:
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    Location:
    Scotland UK
    Hi
    Lookining as both the SX525 and the SA 6200/sa 5200 there are some wide cap differences in uf values between them like 100uf on the amp boards and 1000uf difference on the large coupling cap[s and psu cap any time I have up rated cap uf values in amps or CD players often I have noted a marked difference in performance of course you can go too far and the amp can sound slow

    I am considering up rating the PSU cap to 6800uf x2 with a 0.5 or 1ohm resistor in parallel this should lower impedance and improve the ripple current and also bypass the cap and increase the coupling caps to 4700uf and bypass them the only speaker impedance will be either 6 or 8 ohms only

    And the Rectifier Diodes up rated to something like 6amp MUR fast recovery types talking about Diodes am I correct in thinking I can replace the 1S2473 with a 1N4841 and the SV-4A with three 1N4841s plus the 1SBO1-01 with a 1N4001/2 but again a fast recovery type
    Colin
     
  15. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    I freely acknowledge that very very similar is NOT identical.

    you want to see different, :D look at a sx-3900 Non-Switching amp... :D

    I'm not going to argue mods. I don't have THAT much time.

    The amplifier could oscillate itself to death and so far it seems to me you are not equipped to detect it, no less kill it solo. i could be wrong... meh...

    this is what I had in mind for the diodes:
    512-1n4004 conventional rectifier 1a 400v $0.06 ea
    512-1N5404 conventional rectifier 3a 400v $0.19 ea

    fast recovery rectifiers generate more noise than general purpose 60hz like those guys... and the unit is already equipped with capacitive snubbers.

    wanna argue/discuss mods, I'll bet DIY will LOVE you...

    but I won't get into fixing modded circuits, it's nasty enough giving advice on fixing the factory stuff for 5 to 20 different units at a time.
     
    Last edited: Oct 7, 2010
  16. colinhepburn

    colinhepburn New Member

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    Location:
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    Hi
    Ok Respect as you don’t seem to be in to modding that fine but I can say I have never experienced what you have described in your post I have only witnessed t a better amp I will be modding the amp but first I just want to get it up and running can you confirm the replacement diodes for the 1S7473 to be 1N4841 and three 1N4841 in series for the SV-4A and a 1N4002 for 1SB01-01
    Colin
     

     

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  17. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    not really...

    The diodes In the amp should be left alone, especially the SV-4a. Guys go through a lot of trouble to preserve them, and that diode string trick is a last resort to keep the amp from becoming a doorstop.

    The 1s2473 can be replaced by the 1n4148
    the SIB01-01 can be replaced by a 1n4002
    I would replace these only if transistors in the amp have been replaced, and to reiterate: leave the sv-4a alone...
     
  18. colinhepburn

    colinhepburn New Member

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    Location:
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    OK the SV-4A will stay i now have the amp and it works but we do have a problem
    Well amp is working but i noted a hiss from the right speaker between tracks like a background hiss like a cheap phono stage can be but at a lower midrange and soft sounding then fading off a little and fading back in with an intermittent sound like it’s about to start motor boating but fail to do so then repeats the process over and over turning the balance all the way left don’t do anything turning the volume off and the hiss stays
    OK t got the DMM out and did some checks
    DC offset at switch on bounce up to 28mA with rapped drop back to 0mA
    Idle Current
    DMM set to 200m left channel @ 13.4mV /0.5R = 26.8mA
    Right Channel @11.5mV/0.5R=23mA
    The serves Manual don’t say what the total current is apart from two places on the schematic adding them together we get 102.3mA but still not sure what the idle current t should be set at
    So any ideas of the fault could it be a noise emitter resistor or bad Cap

    PS Control amp and head amp are allso working ok feeding the NAD 352C power Amp


    I am running the amp from its pre amp out into the NAD power amp and I have just lost the right channel volume dropped by half its level as if I swung the balance over to the left
     
    Last edited: Oct 7, 2010
  19. colinhepburn

    colinhepburn New Member

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    Location:
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    Just to update this post

    I have just switched it on in same configuration as last night running control amp and it working fine from Cold I will leave it running see how long it works for before trying its main amp odd a leaky Cap perhaps I will do some voltages tests later and report back with my finding
     
  20. colinhepburn

    colinhepburn New Member

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    Location:
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    Well I Can Confirm that the power Amp is working a treat Driven by the NAD 352C pre Amp sounds very good now where the problem with Pioneers pre-Amp as you still get sound from the right speaker but its low level coming from underneath the hiss
     

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