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bias

  1. ekimezeerf

    CA-800 Bias Problems After DOA Rebuild

    Hey everyone, long time lurker, first time posting. A friend brought me a dead CA-800, would not power on and many signs of heat stress on main amp and power boards. Our thought was the PO has dumped a bottle of cologne on it due to it's aroma and the goop present everywhere inside. I've...
    • ekimezeerf
    • Thread
    • bias bias adjustement ca-800 rebuild yamaha
    • Replies: 23
    • Forum: Yamaha
  2. J

    Marshall JCM 800 2203 Guitar Amp - Tube Swap and Re-Biasing

    Chris from Cornerstone joins me again for this Marshall re-biasing video. This is an all original JCM 800 - 2203 that is receiving new tubes all around. Of course, a quick inspection is in order. Measurements of the electrolytic caps show that most of the caps are good, one of the filter...
    • JRUBIN
    • Thread
    • amplifer bias jcm 800 marshall rebias robotube
    • Replies: 0
    • Forum: Tube Audio
  3. 1mike161

    Pioneer CT-F950 Bias Problem

    My Pioneer CT-F950 is not recording properly on the Left channel. The recorded level of the left channel is significantly less than that of the right. I think I have traced the problem to the bias amp. I determined that the recording signal is good (balanced on all tape types and across many...
  4. Mike Sweeney

    Seen before? 2285B bias question

    I replaced the pots with new ones and everything dials in perfectly except the rigtt channel floats about +- 1mV instead of zeroing out like the left does. Just enough to be annoying. Doesn't seen to be hurting anything other than my pride :) Ideas before I go into a rabbit hole?
  5. TellMeWhy

    Marantz 2270 volume low?

    Good evening people... Does anyone have an idea why my Marantz 2270 puts out less volume (per same position on the dial) than my Marantz 2230? Sound is fine on both... Marantz 2270 runs much hotter.... I didn't check DC offset or bias... but I wonder, could it be a cold solder joint on the...
  6. sajjad amer

    KA-7100 No Bias voltage on Right Channel

    Long Story Short Recapped, changed Bias and DC offset variable resistors. Broke Speaker Selector switch and managed to get it working , only Channel A and Channel B work, A+B do not work. Speaker A was working fine, so I started listening to it, 2-3 notch on volume, forgot that I have not...
  7. H

    McIntosh MC60 Circuit Differences / Restoration

    I am recapping a pair of MC60 amps for a friend and the serial numbers are 3XXX and 7XXX there are lots of differences between these two amps. The board layout is completely different and the bias section is different as well. The first amp I replaced the selenium rectifier with silicon and...
    • Hi-FiGuy
    • Thread
    • bias m-171a transformer mc60 mcintosh recapping restoration
    • Replies: 2
    • Forum: McIntosh Audio
  8. R_F

    Things you should know about tubes — Robert Tomer

    Something may have changed since 1960. If so, please correct anything that has with direct sourced evidence. I made screen captures from parts of the book to try to focus mainly on the most relevant bits to audio. I edited out extraneous stuff like references to figures not shown. I did this...
    • R_F
    • Thread
    • bias cathode fixed longevity tips tomer tubes
    • Replies: 33
    • Forum: Tube Audio
  9. Elemental

    Biasing Question on Mx110 Preamp Section

    Technical question: I'm troubleshooting distortion on a McIntosh Mx110Z and wanted to rule out incorrect biasing of the 12AX7 tube (V15) which is the first stage of the preamplifier section. Looking over the schematic, something doesn't make sense. The schematic says that on, say, the right...
  10. J

    Marshall 6100 LM Output tube meltdown troubleshooting event

    My almost unedited troubleshooting event of this 30 year anniversary amp that was eating final tubes for breakfast, before I get yelled at be sure to review the constraints of this project, so YES, i would have done it different, given the choice Enjoy,
    • JRUBIN
    • Thread
    • 6100 6100lm amplifier bias capacitor marshall
    • Replies: 0
    • Forum: Tube Audio
  11. DanGuitarMan

    Dynaco ST-35 bias voltage skyrocket

    A few years ago I rebuilt a Dynaco ST-35 using Dave Gillespie's boards and I've encountered a problem that I haven't been able to figure out. I've reached out to Dave and he has been very helpful so far, but I thought it couldn't hurt asking the rest of the AK community. A few weeks ago a tube...
  12. Homer4beer

    Idling current adjustment help - Marantz PM7200

    Hi guys, I managed to fix this amp and am now trying to adjust the bias. I am measuring the voltage across the two legs as per the service manual. I've attempted to adjust the bias now. For the bias for AB, set from cold, I can set both variable resistors to measure 0.4mV < 1 min. For the...
  13. ExcitableOne

    So my brand new JVC RX-517v from Goodwill is having a few issues...

    Now to start this off, I don't even know if this is the right place to put this since my JVC isn't exactly "vintage". It's from 1993 and actually looks newer, so I honestly don't know. Second, I'm new here...as you can probably tell. Alright, now on to my problem. So a while ago my poor JVC was...
  14. tusntuk2

    KA-5600 variable oscillation - where do I look?

    Still puzzled about finding the cause of the variable oscillation in the Audio board after recapping electrolytics. Low/high tap gets faster with more volume or more bass after unit is warm, no noise when cold. I'll be changing the bias trimmers to multi-turns, and I wonder if changing the...
  15. tusntuk2

    Kenwood KR-5600 Intermittent noise - is it bias related?

    This is the third thread on this interesting receiver. Previous threads helped fix a relay problem and questions about recapping - thanks again! Now I have replaced all electrolytics in the PS and the Audio board (power amp) and the amp sounds amazing with the FM radio. (Yay!) BUT - here's...
  16. tusntuk2

    Kenwood KA-3500 bias needs help

    Hello again, just love this forum and the gracious help here! I just finished completely recapping a Kenny KA-3500, and the DC offset shows -6mv on one side and 56mv on the other. Not terrible, even if a little unbalanced, I understand, but when I check the bias it seems to wander from about...
    • tusntuk2
    • Thread
    • bias bias trimpot replacement ka-3500 kenwood
    • Replies: 3
    • Forum: Solid State
  17. T

    Question about Optonica receiver idle current

    I was helping my buddy clean up and adust the DC offset and idle current on his Optonica SA-5606. We set the DC offset first and that was fine. When setting the idle current, our goal was 10mv between two test points. The left channel had zero voltage between the test points, regardless of where...
  18. copezone

    MARANTZ 19 (channel issue)

    Ok, so a guy brought a 19 into my shop with the left channel out. Two prior service attempts by others (new caps, yadda, yadda,) and still, no left channel, EXCEPT during "power down". While powering down the left channel kicks in. ANY IDEAS???
  19. dlucy

    SOLVED: Intentionally-loose wires in SX-626 help check the bias

    I've just started restoring my first SX-626 and I'm carefully recording all the caps, transistors, etc. to compare against the service manual... and there are two loose wires, just hanging out in space, apparently intentionally. Why? These look like they came this way from the factory, they...
    • dlucy
    • Thread
    • bias pioneer sx-626 sx-626 recap pioneer
    • Replies: 11
    • Forum: Pioneer Audio
  20. tusntuk2

    How do you set bias or dc offset in SX-727?

    Hello the the Pioneer group! I'm a recent old member, just reintroduced myself from Arkansas. I successfully repaired a NAD with fellow AK er's help, and it inspired me to recap a SX-727 - wow! I'm stunned by the clarity, it's like, um, retirement, you know? There's this big build-up to it...
  21. J

    Hafler se-120 Bias

    Greetings- I have a Hafler SE-120 amplifier and one side of the amp gets hot even when at Idle. I suspected that the bias needed adjusting. The manual states that the bias should be set at 100ma so I measured the settings according to the service manual and the left channel was spot on at 100ma...
    • jonsand
    • Thread
    • amp bias hafler
    • Replies: 24
    • Forum: DIY
  22. baretta

    What's your opinion about hard, medium and soft power tubes?

    I'm talking transconductance (Gm). My Marshall amps prefer low transconductance EL34s. What about you home audio people? Are your tube receiver/amplifiers as particular? Or are you able to properly bias almost any Gm output tube type?
  23. zeste

    Sansui au222 bias adjustment issues and crackling

    Hello, I have recap my sansui au222, replaced the 2sc871 with bc550c, and the trim pots. I set the bias ajustment at 20mA. It woks fine for a couple of month. And it started crackling and sound being fuzzy. I replaced some resistances(the 0,5 ohm 2w and others) but nothing change. Then I...
  24. bibota

    Changing 2230 trimmers

    R765 trimmer behaving unreasonably while being adjusted did quite some damage on my right P750. I intend to replace all pots now. Not at all sure about the power rating though, in the specifications are all marked as "B". Any advice please? This series available at Digikey seems to be...
    • bibota
    • Thread
    • bias dc current p750 pots r765 trimmers
    • Replies: 6
    • Forum: Marantz Audio
  25. Johnny JJ

    Kenwood KA-6100 help with bias too high

    Hey guys, I recently acquired a ka-6100 that had no sound. Opened it up and found 2 fuses blown Fm2 & Fm4 and a bad diode (burned & shorted closed) in the bridge rectifier for R channel. Also found a bad regulator transistor (Qm29). So I replaced both voltage regulator transistors (Qm29 & Qm30)...
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