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bias

  1. Dr. Drawbar

    Mcintosh MA230 Bias Voltage Resistors

    I've had an MA-230 for about 3 years. It recently began humming as things this old will, so I put it on the work bench and popped the bottom off of it. First thing I noticed was three out four 15 ohm bias resistors were cracked, two of them severely so. Checked the schematic and it shows...
  2. P

    Denon PMA-700V - problems and failures

    Hi, First - apologize for a lengthy post. I got this mystery going on with my amplifier Denon PMA-700V. Bought it recently, cleaned deoxited etc. and performed some checks. DC offset in both channels is acceptable - 9.4 and 9.6mV. Now - what I did was probably dumbest thing ever. I noticed...
  3. G

    TEAC A-430 auto bias operation

    Hi guys, A friend of mine brought in a TEAC A-430 for servicing, as it needed new belts. While the new belts are on their way, I installed a temp replacement to check the other functions. I'm especially intrigued by the auto-bias function and it's motor driven knob. Unfortunately, I'm unable...
    • Gertjan90
    • Thread
    • a-430 auto auto-bias bias tape teac
    • Replies: 4
    • Forum: Tape
  4. S

    Help with bias adjust on Luxman LV 109

    Hi, I'm trying to set the idling current on a Luxman LV109 but I am confused. The instructions say: 3. Adjust VR7602A so that voltage between TP1 and TP2 reaches 45mv 4. After connecting TP3 and TP4, adjust VR7601A so that voltage between TP1 and TP2 reaches 15mv. I've done step 3, but I...
    • Sam Gray
    • Thread
    • bias luxman lv-109
    • Replies: 1
    • Forum: DIY
  5. A

    Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

    Hey all. I have this Marantz model 1030 amplifier with some problems. Problem 1: Left channel has extreme distortion under any kind of load. If you crank the bass control, it distorts to hell and gone. Problem 2: When attempting to set the bias voltage for the left channel, it's ENTIRELY too...
  6. Shrugg

    Yamaha R-9 - Strange bias and offset issue

    Hello all, I am getting some very strange voltages on my Yamaha R-9. After testing it both on headphones and speakers and verifying that it sounded ok, I measured the offset and bias. For the offset, the left channel was a solid 18 mv, but I was getting a strange fluctuating voltage on the right...
  7. Stack

    Kenwood KA-801 bias and preamp DC Offset questions

    Hi, I've recently recapped my KA-801 and wanted to fine tune things. I've had specific problems with the bias and DC offset, and was wondering if anybody could lend ke some friendly advice. For the preamp DC offset (which I'm now thinking I should've left alone in the first place) the spec...
  8. Stack

    Problems adjusting Preamp Offset, Power offset, Bias on Kenwood KA-801

    Hi, For those people wanting to attempt to calibrate their KA-801 or similar Kenwood machine after a recapping project, I wanted to document the troubles I faced and ask for advice on a few key points. A side note: for this project, you will need a multimeter. I used an early 2010s Radio...
    • Stack
    • Thread
    • amp bias dc offset ka-801 kenwood kenwood ka-801 preamp
    • Replies: 1
    • Forum: Solid State
  9. K

    Marantz 1060 power amp gets weird when speakers are attached

    I've been wrestling with this 1060 on and off for a few months. When I acquired it, the left channel was fine; the right channel was always very distorted. After an initial tune-up (cleaned the pots and replaced most of the caps/trannies/diodes), the left channel sill works fine and the right...
  10. K

    Dynavector 20x2-L: seeking bias/tracking force advice

    My system: Rega Planar 3 2016 Dynavector 20x2-L cartridge Phenomena II+ I just installed a new Dynavector 20x2-L cartridge on my Rega turntable. To set the bias and tracking forces, Rega recommends setting the tracking force to the upper end of the tracking force recommended by the manufacturer...
    • Kronius
    • Thread
    • 20x2-l bias dynavector tracking force
    • Replies: 5
    • Forum: Turntables
  11. A

    68 Magnavox AstroSonic Bias Help

    I have an 68 astrosnic console chassis number: R220-02-BA My amplifier has a unique silicon npn/germanium pnp output stage pictured below. Unfortunately, my germanium is leaking on my left channel and subsequently, the output power is very low. The old transistors are bandix 111p1 and the...
  12. Sci525

    Overhauled AU-101, right channel failed after 20 min

    Hi everyone, I overhauled my 1971 AU-101 yesterday. New electrolytic caps, small transistors, and power supply diodes (transistor substitutions below). Sounded good for 20 minutes before the right channel went out. Turned it off and back on and the right channel was on for 5 min before going...
  13. t_munz10

    Yamaha CA-800 Bias Problems After Cleaning

    Hey Guys! Some of you may remember, I was taking apart a CA-800 for cleaning to see if that would fix the very scratchy output. I've cleaned all the pots and switches with Deoxit and have semi reassembled everything (enough to test). Looks like the cleaning helped a little, but I may still be...
    • t_munz10
    • Thread
    • bias ca-800 yamaha
    • Replies: 23
    • Forum: Yamaha
  14. Mike Sweeney

    2245 etc bias transistor upgrade

    Here is the final outcome of my own version of the round to TO transformation. All I did was reverse the bend for the diode, get a longer screw and put the new transistor on some lead extensions. And yes, there is a mica insulator between the heatsink and the body of the transistor with a dab...
  15. viennadad

    Saved a Model 11 III from the dump but......

    Was at a local office store the other day. They accept electronics for recycling. As I was leaving I saw a fellow walking in with a cartful of various devices. On the bottom was a BIG brown case. I asked if I could take a look. I pulled it out and its a Model 11 series III. I asked if it turned...
  16. Mike Sweeney

    Bias transistor revisited

    I read with interest this thread - http://audiokarma.org/forums/index.php?threads/solution-for-2270-high-bias-early-serial-number.770102/page-2#post-10572328 And I liked it well enough to go back to my two boards and redo the two transistors I had just soldered in last night :) But I made a...
  17. tcdriver

    Output Tube Bias Using a Micro-controller

    In a thread in the AudioKarma Manufacturers Forums > Fisher a discussion was started on tube bias. Link: http://audiokarma.org/forums/index.php?threads/fisher-500-c-bias-a-case-history.843474/ This discussion turned to using an Arduino or something similar automatically set output tube bias...
    • tcdriver
    • Thread
    • auto-bias bias micro-controller tube bias
    • Replies: 26
    • Forum: Tube Audio
  18. tcdriver

    Fisher 500-C Bias - A Case History

    Fisher 500-C Bias The Story: Recently, I pulled my Fisher 500-C out of the barn, where it had been stored since 1985. Cosmetically, it still looked to be in pretty good condition. I knew the challenge would be in getting it operating again, after 33 years sitting in the barn. The first task...
    • tcdriver
    • Thread
    • 7591a bias fisher 500c
    • Replies: 21
    • Forum: Fisher
  19. N

    Kenwood KA-9X fluctuating high DC on one channel

    Hi, I'm trying to repair a friend's Kenwood KA-9X integrated amp. He says the protection relay sometimes remains open (or closes after long time ~10mins). I measure DC fluctuations of ~+/-2V at the left speaker terminals. Even with this, the relay closes normally (when I test it and with no...
    • NabMan
    • Thread
    • bias idle idle current test point ka-9x
    • Replies: 4
    • Forum: Solid State
  20. RogerMod

    Burning Amp 2018, Fort Mason, CA

    We had a nice turnout this October in San Francisco. Thanks to all the DIYers who brought their work to show off. Thanks to Linear Systems, makers of really low noise FETs and other SS devices, for hosting the event. Here is a link to their site. All the presentations can be seen there. See...
    • RogerMod
    • Thread
    • bias class a class ab idle current power output tubes
    • Replies: 5
    • Forum: Tube Audio
  21. RogerMod

    When we bias a tube amp what are we measuring?

    There seems to be some confusion about biasing a tube amplifer. I would like to ask the readers here to give their thought on what are we adjusting and what are we measuring when we adjust a tube amplifer's bias. If one were discussing his amplifier with another person what would be the...
    • RogerMod
    • Thread
    • bias bias voltage bias voltage at zero idle current tube amps
    • Replies: 93
    • Forum: Tube Audio
  22. Kingsin7

    Mcintosh MA230 Bias Voltage

    I've begun to notice a slightly louder than usual hum coming from my Mac MA230 that I use daily in my office setup. It has been about a year since I last reset the bias, so I decided to take it out of it's wood case today to make adjustments. After reviewing the manual, a voltage of 0.7v is...
    • Kingsin7
    • Thread
    • bias bias adjustement mcintosh tubes
    • Replies: 20
    • Forum: Tube Audio
  23. J

    Fender Deluxe Reverb -Tube malfunction takes out screen resistor

    The shop amp is back on the bench for repairs after an event during use which was a loud pop followed by red plating of a finals tube. The amp was shut down and the tube replaced but to no avail. There was nothing more to be heard from it. I focus my troubleshooting with a visual...
    • JRUBIN
    • Thread
    • 6v6 bias fender deluxe reverb hickok 6000 matching repair resistor screen troubleshoot
    • Replies: 6
    • Forum: Tube Audio
  24. tusntuk2

    Is KSA916Y a good choice for replacing 2sa915 on KA-7100 Bias circuit?

    Is KSA916Y a good choice for replacing 2sa915 on KA-7100 Bias circuit (Qe7-10)? Other suggestions? Trying my best here, but I want to double check with anyone who has replaced these before. Funny it's so hard to find with so many recaps of this great amp. One thread said KSA992's were too...
  25. kintave

    Kenwood KR-7200 repair problem

    I got a free KR-7200 with a scratchy, intermittent right channel and some hiss. I replaced nearly all electrolytic capacitors in the entire unit (pretty much all of them were leaking). I cleaned the relay and the contact pins on the main amp board, and I replaced all the amp resistors (Rq1-4). I...
    • kintave
    • Thread
    • amp bias channel distortion kenwood kr7200
    • Replies: 34
    • Forum: Solid State
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