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  1. eradoncic

    20 Years

    ;)Wow, as usually, I’m a bit late on the party, but hey- I just realozed I’m also kind od veteran here! May 31st 2004. was also mine first post here. And then, the famous post about seeking help for LAPT-3 OT:oops:. I thought I joined the forum much later, 2006 or so…:eek: Fun fact: I discovered...
  2. eradoncic

    Sansui AU-α607 MOS Premium 1991 [recovered schematics]

    Very good! One question: why the resistors kR2/3 are (somtimes very) different in various generation of Alpha? In 14th generation (701/901) we have 3,3k…then 3,9k (X1111mos), and here and in several morels after -6k8? I notived also that in bigger model there is top-quality resistor type, and in...
  3. eradoncic

    Newbee to alpha series 907 vs 711 mod

    Well...yes. Some differences are unfortunately unbridgable when compared 711 and (any) Alpha907. Simply put: alpha 907 is kind of statement model, the best parts inside, meticulous and obssessive engenering, etc. On the other hand, the 711 and similar smaller amps (so called "607" models on...
  4. eradoncic

    Leestereo's Restoration & Upgrade of a Rotel RA-970BX

    Sure. Either for 980/985 and 1070- the schematics is very similar to RA970. Just these days, I’m refreshing one of the mentioned models (RA-1070). Replaced all signal DC blocking caps as mentioned using Nichicon ES, 10uF/50V, since to my ear these sounds much better than Wima MKS (somewhat...
  5. eradoncic

    Alpha AU-a907NRA a907NRA a907 907 NRA the last big Sansui

    @All I wish to share something I run over my head recently…I remember when I have wrote my first post here in AK, I had a big problem back than and nobody have had even clue how to resolve it. And realized that Alphas actually are completely unknown to vast majority Sansui enthusiasts here...
  6. eradoncic

    Alpha AU-a907NRA a907NRA a907 907 NRA the last big Sansui

    Excellent and very rationale job done there. Wellcome to our (now not so small Alpha owners) community here, glad you joined AK
  7. eradoncic

    Alpha AU-a907NRA a907NRA a907 907 NRA the last big Sansui

    My vote for bad contact of the bias compensation transistor. To me it always seems a bit tricky to ensure a good contact and heat transfer. Also, if you have not done already- resolder these transistors and correspinding resistors.
  8. eradoncic

    Alpha AU-a907NRA a907NRA a907 907 NRA the last big Sansui

    Idle current for 907NRA should be also 8.8mV +/- 1mV, for sure.
  9. eradoncic

    Alpha AU-a907NRA a907NRA a907 907 NRA the last big Sansui

    At least, with C1216 type you have 200W (4x MT200) less maximum disipation in 907NRA than in 907MR (8x125W=1000W max disipation)
  10. eradoncic

    Sansui AU-X701 help

    One probe to middle leg, and other…anywere on metal part of the amplifier. Hope the pics bellow are enough illustrative: Edit: very nice and clean restauration work there!
  11. eradoncic

    Sansui AU-X701 help

    Much easier access at this point (especially in x701) is: DC offset (hot/cold): - multimeters probe on the middle leg of the neighbor emitter resistors (big white rectangular) for each channel (you’ll see clearly made distinction for L/Rch) HOT/GND: - after adjustment above, let one probe on the...
  12. eradoncic

    Leestereo's Restoration & Upgrade of a Rotel RA-970BX

    Well, I doubt it is oscillation- 970BX is well decoupled, and in other similar model to my expirience both mentioned op amps does not oscillate. Even a LM6170 stands good at that place and it is 100MHz/2000V/uS unit. Something else is made noise there, check the socket, use quality one. Having...
  13. eradoncic

    Leestereo's Restoration & Upgrade of a Rotel RA-970BX

    Wha op amp you’ve put instead? As far as I remember, the original was AD827?
  14. eradoncic

    AU X901 distortion and PS voltage problem

    Watch those Wima PPS/SMD- rich natural sound. But still difficult to find 2,2uF (the biggest on their catalogue). Can be easily soldered underneath directly accross the legs of MV-103/SV03, which are 15mm.
  15. eradoncic

    AU X901 distortion and PS voltage problem

    The Panansonic I tried are ECWFE series, highly regarded exactly for sound quality and excellent price. Nothing wrong with them, on the contrary, sounds really good. To me, I would use for any such position in a heartbit. The only problem is they are somewhat big, and lead spacing is some...
  16. eradoncic

    AU X901 distortion and PS voltage problem

    So, just to finish this thread and to share some thoughts and ideas, here is an update how this story ended. I Asymmetrical voltage of the regulated PS: 1. the voltages of the driver section went to normal after fixing the problem of the virtual ground resistors 2. the resistors nominally 6k8...
  17. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    C’mon- you have almost served points of measurement here :) Just put the grasping leads of your multimeter on the leg of the emitter/drain resistor which easily accessible as it can be seen on this photo, Jim. You have more than enough space between the geeen foil cap kC28 and the resistor kR52...
  18. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    Why you didn’t go to some computer service/shop? They have tons od such/simillar connectors for sure, you can adapt something certainly.
  19. eradoncic

    Alpha's a607-a707-a907 can you hear a difference?

    Have had several years back during relatively short time 707DR and 907DR…607DR never heard but have x701 which is 607i. and also x901, which is 707i, as we all knows on this forum. The difference: 607 is “enough”, sound, for not too demanding listeners, and easy driving speakers. It is the...
  20. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    Ecxellent synthesis. As far as I can see- you’re ready! You have located all the points correct, have DMM and even jumper which will alleviate all the measurements. I think as I already suggested previously, the main thing now is to release the protector, so a rough adjustments will be ok in the...
  21. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    That means nothing special- just location of the different boards. You have 4 (k)VR on each power amp board- two for bias (grey) and two for hot-cold/hot-ground. They has to be adjusted with balanced/direct switched control on the face plate on the amp. When these are ok, it sholud be...
  22. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    So even though this diagram is for one(or more) of the other Alpha's with different boards the VR's and TP are the same? That’s same on almost each and every Alpha’s. Years back I found and uploaded my own copy of MRX on hifiengine (also posted here in AK for our fellows), since it is only...
  23. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    Nice! Did you measured/found something unusual? Any update of the initial problem?
  24. eradoncic

    Alpha Penultimate / Ultimate : AU-a607NRA II / AU-a607 MOS Limited

    Don’t worry, this Golden bird will sing again, I’m sure. We all here in this forum are learning, that’s the part of Sansui fun:thumbsup:
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