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bias adjustement

  1. mhz

    KR-3090 Adjusting DC Offset

    Hello everyone, I'm working on a KR-3090 and currently looking at bias + DC offset. This receiver was on the cheaper end, so adjusting the transistor bias involves swapping a fixed resistor and as far as I can tell there is no adjustment procedure for DC offset. Luckily, transistor bias seems...
  2. mcaddie7

    Eico 2536 Receiver - How to Bias

    Hi all! received an Eico Tube receiver that looked pretty cool for cheap. I checked all of the tubes (same replaced in 69) and they all pass, albeit the 4 matching pairs highlighted in red appear to have more of an “open” according to my tube tester. Anywho, replaced all electrolytic caps and...
    • mcaddie7
    • Thread
    • bias adjust bias adjustement tube amp tube amp help tube receiver
    • Replies: 3
    • Forum: Tube Audio
  3. tutor_turtle

    Heathkit AA-71 data?

    I have a pair of Heathkit AA-71's in the shop for a general check-up/tube testing. It would be nice to know the bias/balance settings and measuring points. Does anyone have any data (build sheet) on this guy?
    • tutor_turtle
    • Thread
    • bias adjustement heathkit aa-71 schematics needed
    • Replies: 3
    • Forum: Tube Audio
  4. U

    Need Bias Current Help with Sansui AU-20000 (0 mv)

    Hi everyone, I'm experiencing an issue with my Sansui AU-20000 amplifier. When I set the low pass filter on the front panel, the amp goes into protection mode, and a loud pop is heard from the speakers. The amp is quite old, so I decided to recap all the boards and change some transistors...
    • Utk
    • Thread
    • au-20000 bias adjustement bias current sansui sansui au-20000
    • Replies: 42
    • Forum: Exclusively Sansui
  5. mcaddie7

    HarmAn Kardon 930 Bias Adjustment Help

    I want to preface this with I'm a pretty big nob and have never touched a transistor or biased anything. I have however recapped my Harmon Kardon 930 to what seems great success. There are several guides on this site for biasing this receiver but non include pictures and thus I really can't...
    • mcaddie7
    • Thread
    • bias adjustement harmon kardon harmon kardon 930 hk twin power receiver
    • Replies: 21
    • Forum: Solid State
  6. F

    Accuphase P-266 bias adjustment

    Hi everyone! I have changed all of the capacitors in this power amplifier, including the filter capacitors, as the old Elna's were very swollen. In addition, I've replaced all relays as well. I am very happy with the results! Now, I need to adjust the bias in the "Normal mode" (class AB) and...
  7. J

    Tape for Pioneer rt 909

    Hi Guys, I've bought a Recording The Masters SM900, and i've a Pioneer RT909. SM 900 https://static1.squarespace.com/static/62798251da32f57e31bea13d/t/62f2149f22e6b6134c31427e/1660032161030/fiche_sm900_rtm_2022.pdf https://www.recordingthemasters.com/audiotapes Could you please help me to...
    • juniorgroove
    • Thread
    • bias adjust bias adjustement recordingthemasters rt909 tape
    • Replies: 13
    • Forum: Tape
  8. Hyperion

    Bias Circuit Operation - explanation

    Here are some tips which you might find useful when you have a bias problem. Below is a schematic snip of a driver board for an AU-517. TR06 (centre left) is the bias control transistor, just below it is VR03 the bias trimmer, the transistor and the trimmer are vital to the operation of the...
  9. U

    Sansui BA-2000 Bias Adjustment Q/A

    Hello Folks, I found a BA-2000 at a thrift store and was trying to restore it. I swapped all fuse resistors, relays, and caps. It took me a month to do all this. I was excited about finally using it with my JBL's but when I tried to adjust the bias, C37 on F-2661 blew open. My Mistake was...
    • Utk
    • Thread
    • ba 2000 ba-2000 bias bias adjustement sansui sansui ba 2000 sansui ba-2000
    • Replies: 2
    • Forum: Exclusively Sansui
  10. richiem46

    Marantz 2275 P700 Component Selection Affecting Bias Setting

    I read a number of threads about bias issues with the P700 amp boards in the Marantz 2275 and in other Marantz units. A lot of great information freely shared by other members. I came away not completely clear on the best approach to restoring the P700 board and thought I would start another...
  11. T

    Mc302

    Hi all, after reading miles of posts I decided to ask you something: Last week I've bought from a friend a MC302 poweramp and a C220 pre (this is still under official warranty 'till 2023). He has not used them for months and decided to sell them. They are in really near mint condition, but...
  12. J

    MC 2255 & C29 service maintenance or component upgrades

    I'm taking my 2255 amp & C29 pre-amp for service and cleaning to our local technician in our area as the potentiometers are scratchy and sometimes the left channel gets distorted intermittently. Our local technician has done LED upgrades, DC offset, bias adjustments, power meter...
    • jervz
    • Thread
    • bias adjustement c29 led conversion maintenance mc2255 mcintonsh recap restoration vintage amp vintage preamp
    • Replies: 16
    • Forum: McIntosh Audio
  13. Stereoboy70

    Sansui G3500 bias adjustment

    I’ve been trying to adjust the bias on this receiver but when I clip the leads on R77+ And R79- I get no readings. It should be around 10mV dc when it’s adjusted correctly I’m getting absolutely no v reading. I’ve got good sound in both channels now after replacing some junk components but I...
  14. jefferylhenr

    Thoughts on setting bias Luxman R-1050

    I have a mint original R-1050 that I am tuning up and I want to set the bias. My PB-1062 board has no fuses? They were jumpered out at the factory it appears as the solder points are undisturbed. Do I just cut the jumpers?
  15. J

    Marantz 1060 - Can't set bias, output cap overvoltage

    Hi I have recapped my 1060 and powered up to set the bias but I am seeing C006 (Nichion 6800uF 63v) go to ~70v. Adjusting the R723 makes no difference. I have checked that the pots are all working. The other channel is at a reasonable level. Have any of you come across this before or able...
  16. B

    AU-666 +20V DC offset on each channel?

    Hi AK I have an old AU-666 that has been recapped and gotten new transistors all around since it was in a really bad shape. However when i turn it on now it has a DC offset of around -28V on both channels measured with no load, and I have run my head into the wall as to why.. All new...
  17. Ray122

    Yamaha CR-1020

    Hey everyone! Hope you're all enjoying the holidays! I once again found myself in a repair pickle and asking for the sage wisdom of members much more experienced than myself. Recently re-capped a Yamaha CR-1020 for a friend and first I ran into the issue with the misprinted polarity sign on...
    • Ray122
    • Thread
    • amplifier amplifier repair bias adjustement distorion help repair repair help service help. yamaha yamaha cr1020
    • Replies: 41
    • Forum: Yamaha
  18. P

    BASF D6075 idle common problem

    aka NEC AUA-8000E aka MCS3865. Found two similar treads: https://audiokarma.org/forums/index.php?threads/help-with-idle-current-adjustment.578811/ https://audiokarma.org/forums/index.php?threads/idle-current-question-nec-aua-8000e-amplifier.893200/ but with no solution, couple of guys tried...
    • Poskok2010
    • Thread
    • basf d6075 bias adjustement idle adjust vu meter
    • Replies: 12
    • Forum: Solid State
  19. HowlerMonkey

    dynaco ST-70 w/ou bias sets

    I have this great ST-70 that i bought from a fellow Ak'er. It is a very clean kit with the only "non standard" difference that the front sockets to check the bias have not been wired. I am debating if i have the skills to wire them myself (i might need step by step instructions like the ones you...
  20. 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
  21. S

    Cayin A50T bias for KT77

    Hi guys, newbie to this forum. I’ve been using a Cayin A50T doe a good 7 years now. Recently been thinking of upgrading to Genelax GoldLion KT77. I was wondering what I should set my bias to once I’ve upgraded. The Cayin manual states 0.30 - 0.35vdc however I believe that is for EL34. can I...
  22. Cergei

    Yamaha M-4 | Bias Calibration do not last

    Hello ! I noticed that my M4 Bias current needs to be re-calibrated somehow “often”. All electrolytic capacitors were replaced recently. Any idea ? Thanks
    • Cergei
    • Thread
    • bias adjustement yamaha m-4
    • Replies: 11
    • Forum: Yamaha
  23. M

    Sparks on nad 304

    Hello, after finishing a long recap and resistor upgrade on my NAD 304, I was following the alignement procedure for offset and idling current. I did it one time and after listening some music for 10 minuts, I disconnected the speakers for a 2nd and final adjustment. While I was doing it the...
  24. Strgazr1967

    Welborne Labs ST70 bias, caps and tube questions

    I picked up this ST-70 a few weeks ago and have been cleaning it, going over it and deciding on tube choice for when I set it up after Christmas. The wife's decorations require I take my system out for the holidays. I have a few questions. While going over the amp I noticed that whoever did the...
    • Strgazr1967
    • Thread
    • bias adjustement capacitors dynaco gold lion st-70 tube amp bias issues tubes
    • Replies: 1
    • Forum: Tube Audio
  25. scootsity5

    Sansui 5000X channel mismatch

    Hello all I just recapped my Sansui 5000X and at the end noticed a massive channel unbalance. The right channel is outputting about 10-20V (peak-to-trough: when the left channel was at -20 to 20, the right was at - 10 to 10 using a 1khz sine) less than the left channel. I hadn't noticed because...
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