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bias

  1. rdeining

    BA-5000 Bias woes - Unable to set bias

    Hi all, I have changed all the transistors on the F-2518 Driver Boards and everything seems to work fine, at least on the left channel. I am able to adjust the bias on either board on the left channel, but the right channel reads 0 mv on both boards. To me, that means that both of the boards...
  2. N

    SX-890 Bias and Protection Issue

    Trying to wrap up a refurb of an SX-890 and can't get one channel to bias (DC Balance) and it won't get out of protection. At one point it would get out of protection but wasn't stable on on either channel when trying to DC Balance At this point, on the Right Channel I get ~ -35V at pin 12 and...
  3. audio_exp

    G-5500 No Bias On Right Channel

    I have no Bias on Right channel when I measure across R71/R77? I get some audio but it's distorted. Left channel is fine. Audio is clear in headphones until I put an 8ohm load the right channel. I have checked all the resistors around the driver section and the 2 driver transistors look good...
  4. K

    Technics SU-8088 heating too much?

    Hello all, Thank you to all the members, both seekers and helpers, who make this website a living reference for hifi and audio related care. I just bought a Technics SU-8088 in its original state, no revisions or repairs done (supposedly, ever). I tried it with headphones, played 3 or 4 songs...
    • karma_
    • Thread
    • advice bias heat su-8080 technics
    • Replies: 1
    • Forum: DIY
  5. Burialcloud

    SAE 2400L dc offset question along with recap, restoration tips and recommendations.

    I bought a SAE 2400L this week for 350. It was in “working” order but I figured it would probably need an overhaul before use. Got it on my bench today and channel B seems great. Was able to get the offset and quiescent dead on. (Don’t have a distortion analyzer to check bias unfortunately)...
  6. T

    6060 running hot

    It's been a long journey with this 6060, mostly centered around the 2647 Driver board. After replacing the 2SA726 Transistors and a recap of that board, I get clear sound on all inputs from both channels and the bias on both sides adjusts to in spec per the service manual. I'm not sure if the...
  7. jefferylhenr

    Bias adjustment PL700 where is R47?

    Is there a typo in the manual? I have looked multiple times can’t locate R47
  8. david winter

    Luxman M-2000 can't adjust bias

    Hi, I'm trying to find out why the bias on both channels can't be adjusted. The amp was recaped, I cleaned the relays which work fine (the first clicks within one second after powering up, followed by the second relay (which turns the VU lights on) 3 seconds after). The voltages going to both...
  9. G-901

    Sansui G-9000 in protection dc offset

    The receiver is in protection, speaker relays do not click on. Was testing DC offset at terminal 27 and 28 and am getting -2.5vdc tried to adjust it on driver boards but would only get down to -2.2 Vdc I’m at a loss as to what it could be. Any help would be much appreciated
    • G-901
    • Thread
    • bias dc offest g-9000 g-901 protection mode protection problem
    • Replies: 6
    • Forum: Exclusively Sansui
  10. tusntuk2

    HELP! Can't set BIAS on Kenwood KA-3500

    Greetings fellow Ak'ers! This puzzle has me stumped - any good puzzle solvers out there wanna try it? I have rebuilt a Kenwood KA-3500 amp with a full recap, many transistors, resistors and diodes, and new Bournes trimmers, too. This is my 12th recap of this model, but I'm stumped. The Left...
  11. Racingh11

    OnSemi ThermalTrak power transistors

    OnSemi finally did what so many have suggested and put a matched bias diode junction in the same case as the output transistor. They call them ThermalTrak and is a 5-pin TO-264 case. No more bias lag issues. I will have to try these out. Datasheet attached.
    • Racingh11
    • Thread
    • bias onsemi output temperature thermaltrak tracking transistor
    • Replies: 10
    • Forum: Solid State
  12. PROJECT 2501

    Model 32 amplifier with 100mv DC offset in the right channel

    Left channel is steady at 35mv Right channel went from 75mv to 98mv Right channel produces a disgusting buzz/humm through the right speaker that is constant no matter the amount of attenuation. Needless to say that it's in need of repair, that's a given. I'd just like to know if these...
    • PROJECT 2501
    • Thread
    • amplifer bias dc offset magic smoke marantz model 32 recap repair restoration
    • Replies: 2
    • Forum: Marantz Audio
  13. G

    quadraflex 180r Bias

    I picked up a Quadraflex 180r today cheap, it had a noisy transistor on the right channel which I replaced, but I can't find any information on how to check and set the bias, any info would be appreciated. I also noticed the lamps are dim, I measured 8vac on the line, can anyone confirm what the...
  14. P

    Basic Question about DC OFFSET and BIAS for the SX-737

    This subject has been discussed so many times, but there is one information missing I like to find the answer. Every reply covering DC Offset and BIAS points to a millivoltage range with 20mVDC for Bias and DC Offset close to 0 mVDC. BUT sometimes it’s very hard to get the DC Offset close to 0...
  15. Stereoboy70

    Sansui 350 Bias and offset

    Does anybody have the adjustment procedure for this receiver ?? I have a service manual but it doesn’t show how to set the offset or bias current. Any help would be appreciated. I just got this receiver and fixed a couple of issues. The headphone jack was giving me issues with the L...
  16. goldswimmerb

    M-60 Class A Bias Question

    Hey, just a simple question here, is the 110mv +- 10 number given in the SM correct for class A bias on the M-60? I've noticed, of the several I've seen, they always seem to top out around 85-90mv. Hoping someone with a bit more engineering knowledge may be able to weigh in...
  17. THD

    L-09M test points?

    So...I have my 2 L-09Ms that are recapped and refurbed and ready to be used, but all the shitty service manuals online show a horrible rediculous picture of where the bias & offset test points are on the back of the circuit board. A dot matrix of bullshit. What? Is it some kind of secret puzzle...
  18. robz2000

    Bias Help Sansui 661 (771)

    Hey everyone. My issue, and I have had this happen twice now, is a sansui 661 (or 771) the bias sits at 29 to 31 and doesn't move past that up or down. If I turn the trim pot, it'll go up or down 1 mv. Same behavior both channels. The correct number is 19mv and I cannot get close to that. The...
  19. robz2000

    Sansui bias help

    Hey everyone. This is my first post here so apologies if in the wrong place. My issue is, and I have had this happen twice now, on a sansui 661 (or 771) the bias sits at 29 to 31 and doesn't move past that. If I turn the trim pot, it'll go up or down 1 mv. Same behavior both channels. The...
  20. zastin17

    Sansui and Their Mis-worded Service Manuals. AU-666

    Here is the Sansui Au666 Current Adjustment Instructions. And I am not making sense of their wording. It says to put the Meter in place of "F003", but also to point 27"which I believe is filter block, and Point B1,and B2. But I can't do both at the same time right? Also point "27" only exists...
  21. Spendor

    Help with DC offset and Bias on amp. Soundcraftsmen circuit?

    I have a power amp made in Australia that i believe was used as an install amp in Cinemas. It's made by Auditec or AVE. It sounds kind of good, but on checking DC its showing around 350mA. There are 2 1k adjustment pots which i assumed were for DC and Bias but they're wound fully anticlockwise...
    • Spendor
    • Thread
    • 2sk176 bias dc offset soundcraftsmen
    • Replies: 11
    • Forum: Solid State
  22. P

    MC240 Using bias probe - some interesting observations...

    Did some measurements and that need explaining to me please. I had a matched set of JJ 6L6GC in my MC240 and they were showing ma readings per tube of approx 20ma on each tube on one side and approx 15ma per tube on the other....this was weird - also the fact that when switching sided those...
  23. Mike244

    No DC Bias in 8010

    Hi, I start serviced my "new" 8010 (Europe version of 771) and saw some minor (I hope) problems: noise from both channels on minimal volume position, variable DC voltage on output- 2-15 mV, and most strange thing - no DC Bias!!! On both channels its 0 and not changed during adjustment with...
  24. jFF_Bulbo

    Help with marantz 2245

    hello AK'ers. I´m working on 2245. on P750 power amps, i recapped both boards. DBT pass ok on both unit i´ve changed all electrolitic caps. BIAS is imposible to set properly on both channels. h756/h757 are extremely hot on both. When i blow on to the board, bias downs for a while, after few...
  25. NickArchdale

    Harman Kardon HK430 refurbishment - DC offset problems

    Hi there, I hope someone can help please. I'm restoring an HK430 twin PSU receiver and appear to be falling at the last hurdle. There was crackling and switch/pot noise so after some consultation here, I have replaced all the angular 2SC458, 2SC1344 & 2SC1345 transistors with new KSC1845 (from...
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