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bias

  1. D

    Sansui au777 oscilloscope settings

    Hello everyone. After a lot of patience I was able to score an au777 with wood case. When it arrived I was surprised to see that no metal cover was under the woodcase...was the woodcase an option? No idea... inside was super dirty and a blown fuse. Checked the outputs... 1 of the d143 was blown...
  2. ocdecio

    Biasing a Model 1200

    To what extent the 240/250 procedure of biasing by checking the voltage across R531/R532 at 12-15mv applies to a 1200? The 250 has a higher rail voltage (58V vs 52V) given that it is 125WPC whereas the 1200 is 100WPC. The reason I ask is that it seems like setting it to 12-15mv distorts the...
  3. ocdecio

    Model 1200 - bias doesn't go above 0mV

    I just finished rebuilding the left amplifier channel of a 1200. I checked voltages connected to a DBT, and they all seem to be pretty close. Light dims, and when I connect it to a signal generator I get a clear, amplified wave in the output. DC is close to 0mv. However no matter what I do I...
  4. joestcyr

    After Burn-in...........?

    Question; after a full recap (in my case au20k) lets say I’ve set bias and came out very close to spec. In a perfect world, it sounds fantastic. Then I do a standard(?) burn-in, Does burn-in Alter bias? To the point it requires adjustments? ?:bowdown::bowdown:I await wisdom of the AK...
  5. Gian Luca

    AU-517 checkup

    Hello, I purchased a 517 and I’m trying to check if all it’s ok. Now first of all as for DC adjustment on left and right channel, I have to check the the dc voltage on speaker terminals. How to proceed for this? I know that the volume must be at minimum level and input selector to AUX. The...
  6. Fleime

    Rotel RB-990BX fluctuating bias

    Hello, First off, I am a electrical novice. I guess I know the basic stuff an average person does. I have actually learned most here on AK, but forgive me if I'm not using the correct terminology as of yet. I have a multi-meter. After acquiring some Infinity Kappa 8.1, I was advised on the...
  7. Devileyes

    Am I checking the Bias right? Sansui 990

    My 990 has been running hot since I bought it a few months ago. It’s been recapped and had the trim pots replaced by the dude who I bought it from. Anyway I checked the DC offset first, using the SM and the sticky thread. RC was 37.0 and LC was 8.9. I adjusted those both down to as close to 0...
  8. sean sweeney

    Kenwood KR-6600 restoration etc.

    I have been working on this Kenwood a lot of this week. A friend sold it to me cheap, as it was stuck in protect mode... I kind of listened in on the amp section and heard that there was a lot of noise from bad transistors, in this case it was the 2sa733's as the differential pairs and others...
  9. A

    Sony TA-N77ES gets hot and right channel fades out?

    Hi. Just purchased this after years if hunting. The unit runs hot and the right channel fades out... Leaving it to cool down it works again. Could it be the DC offset or the Bias that needs to be adjusted?
    • ATN
    • Thread
    • bias hot repair sony ta-n77es
    • Replies: 1
    • Forum: Solid State
  10. S

    MCS 3223 - Right channel louder than left

    I recapped the power supply, changed the fuses and changed the bulbs of my MCS 3223. Now I realized that the right speakers sound a bit louder than the left ones. What could be causing this/how can I fix this? I also noticed that sometimes when I'm listening to records, the left channel...
    • sabalennon
    • Thread
    • bias dc offset louder louder than other speaker mcs receiver vintage
    • Replies: 0
    • Forum: Solid State
  11. D

    HK 450 with very low Bias, should I be concerned?

    Hi all, I have a Harman Kardon 450 that I really like, but I've always felt that the left channel is kind of weaker/thin than the right, reading up on DC offset and Bias I finally gathered some courage to give it a try to adjust the DC offset for the first time. The trimpots were a bit flaky but...
  12. Ray122

    Lafayette LR-1515 Idle Current Adjustment

    Hey everyone! Just finished recapping and cleaning up a Lafayette LR-1515 and it sounds great, but the heat sync gets really hot. Like too hot to touch. My guess is the idle current is way too high after re-capping the unit. Usually, this isn't a big deal for me if I have the service manual...
    • Ray122
    • Thread
    • adjust idle current bias bias adjustement diy help idle current idle current test point lafayette lr-1515 lr-2020
    • Replies: 5
    • Forum: DIY
  13. D

    NIKKO NR-719 Power Amp Distortion

    Hello all, First post! Schematic here: https://www.hifiengine.com/manual_library/nikko/nr-719.shtml I have a Nikko NR-719 that passes signal through both channels, but the left side is distorted when pushed, especially with lots of bass. I don't have a scope but characteristically, it...
  14. S

    Pioneer SX-50 suddenly very unstable, going in and out of protection mode.

    My SX-50 has suddenly started acting really weird. This afternoon, I turned on the stereo, and the relay took around 10 seconds to click on. About 5 seconds longer than usual. I hit the speaker A switch, and was greeted with loud, scary pops through my speakers as the relay started clicking off...
    • Saffire
    • Thread
    • bias diy issue pioneer
    • Replies: 19
    • Forum: DIY
  15. S

    Is it necessary to adjust the bias after replacing filter caps?

    I'm currently rocking a Pioneer SX-50, which works and sounds great. It's almost 40 years old, and I'm wanting to replace the filter caps just for reliability reasons. I have a pair of Nichicon's coming in next week, and I've heard about AK'ers adjusting their bias after a recap. Should I be...
  16. Taavip

    Kenwood KA-5500 left channel repair

    Hello from Estonia! Hope you are all well. Got my hands on this really sweet '77 year Kenwood amp. Unfortunately left channel is dead. I really like this amp, so I would like to repair and restore it. Hopefully you can give some little guidance needed to bring this amp back to life. Before I...
  17. L

    Bias, EQ, HXPro, Dolby, Chrome tapes with 120 us EQ

    Hello, a new user here! Got some questions regarding tape recording, would be nice if someone in the know could explain whatever I am not getting :) -- Bias So bias is, basically, a sort of a shakeup to ensure that low-amplitude (or low-frequency? or both) signal is recorded sufficiently well...
    • Late Boomer
    • Thread
    • bias chrome dolby equalization hxpro
    • Replies: 19
    • Forum: Tape
  18. duncan

    Denon POA 2200 repair/recap - some notes

    Nothing earth-shaking here but thought I'd post some pictures and notes for anyone who runs into a similar situation. I acquired a POA2200 power amp last year. The previous owner gave full disclosure that it seemed to have intermittent problems, but I couldn't make it misbehave. Actually the...
    • duncan
    • Thread
    • bias denon protection recap relay servo zener diode
    • Replies: 19
    • Forum: DIY
  19. Johnny_Law

    Sansui AU-517 Bias Current Always 0 SOLVED: Amp R23/R25

    The right channel amplifier stays at 0V bias no matter the position of VR03. The left channel amplifier adjusted correctly to ~20mV. Both channel DC offset has been adjusted to 0mV. The unit has been re-capped, comes out of protection normally, and plays fine at normal volume levels (from...
  20. david winter

    Technics SE-A5 with random fault (supposedly bias)

    Hi, I'm stuck on this amp. The input board has been recaped. I also changed two small electrolytics on the power stage board. Right channel works fine, and bias adjusts without trouble. Left channel will intermittently work well with stable bias once adjusted. However, when the problem happens...
    • david winter
    • Thread
    • amplifier bias distorsion output stage se-a5 technics
    • Replies: 7
    • Forum: Solid State
  21. Jeff Howard

    Sansui AU-717 DC Offset & Bias Help

    Hey Audio Karma. I am new to the Hi-Fi Audio world and am in need of some of your knowledge. I am almost through re-capping a Sansui AU-717, and am curious about adjusting the DC Offset and Bias of this amplifier. Does anyone have experience in this or know a thread with good info? Much obliged!
  22. P

    Some questions for the power supply on a SX-750

    I got an untouched SX750 a few days ago and started already to work on the different boards. Before disassembling I took the AC and DC voltages at the Power Supply Assy AWR-099 and AWR-100. Pin 12 and 16 should be +/-48 vdc but pin 12 hat +53.9 vdc and pin 16 -55.5 vdc. The only thing I changed...
    • pa_200
    • Thread
    • awr-099 awr-100 bias dc offest power supply sx-750
    • Replies: 13
    • Forum: Pioneer Audio
  23. david winter

    1060 - Can't get half voltage at output caps

    Hi, I have done this model more than once and don't understand the problem. It's fully recaped as usual with Nichicon / Elna. I replaced all 2SC458/1000 on the phono stage, as well as both 2SD438 on the output board (the two new ones I have in stock have a gain of 152-155 so no idea if this is...
  24. PE9ZZ

    Replacing VFETs with MOSFETs

    Many people said it couldn't be done so I saw a challenge. On the Audiofreaks forum I documented (in Dutch) my efforts in getting a dud Sony TA-4650 going again without having to resort to tying to get unobtanium 2SJ18/2SK60 SIT transistors. I decided to use IRFP(9)240 instead. Of course the...
    • PE9ZZ
    • Thread
    • 2sj18 2sk1057 2sk60 bias irfp240 ltspice mosfet sony ta-4650 vfet
    • Replies: 79
    • Forum: Solid State
  25. QSilver

    Pioneer A-9 Biasing instructions wrong?

    I'm going through the procedures for setting this bias on an A-9 and having some trouble. Some history: I got it as a non working piece some months back and found it had many poor repairs in the all the regulator boards. I've now been right through the whole amplifier and slowly and surely...
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