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dc offset

  1. 70smidfiguy

    Sansui 5900Z - DC Offset - One channel goes high after a minute

    Hello all, I acquired a 5900Z which had a bad output transistor and a few dead components through to a burned resistor on the main board. I measured tested and replaced the bad components which on startup gives me a good offset of about 10mv but after about a minute rises to 250mv. I...
  2. David_NC

    Sony STR-7025 DC Offset

    I picked up this nice little receiver yesterday. It seems to work really well, though I noticed a bit of hum on the left channel. A multimeter tells me there's 24mv of DC on the right channel outputs and 250mv on the left channel. I've adjusted this on an old Marantz receiver, but I'm not...
  3. 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...
  4. 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
  5. Isaac C.

    Lafayette LR-3500 DC Offset and Speaker Relay Question

    Hello everyone, I acquired a Lafayette LR-3500 back in February in working condition. Upon acquiring it, I performed some basic servicing. I created this thread in order to figure out how to adjust the bias and did so with success. This receiver does not have a dc offset adjustment but only...
    • Isaac C.
    • Thread
    • dc offset drift lafayette lafayette lr-3500 speaker protection relay transistor speaker relay
    • Replies: 1
    • Forum: Solid State
  6. WillRobinson

    Onkyo M504 Protection Mode Problem

    Hello all! I recently picked up an Onkyo M504 and P304 pair from a local estate. Both were in very nice shape, they were stored in a closed cabinet where they collected very little dust. I opened them up, blew out what little dust there was, did a quick visual inspection and saw nothing out of...
  7. D

    Sansui 9090 Red Protection Light

    Hello All, First time poster on AK (longtime lurker!). I just got a 9090 (not a 9090db) from a thrift shop, so not sure about its history. Was definitely in a smoker's house due to tar all over it. VERY dusty/dirty inside so I vacuumed it out and did basic clean up. Got the dial lights working...
  8. Corktowner

    Stuck on a JVC JA-S55 DC overload problem

    Hi all! I've gotten stuck and I need to reach out for some help. I am working on a JA-S55 which a friend of mine owns. He described the problem as scratchy, then a pop and then no sound. The unit looked like it had not been worked on previously except perhaps to change the light bulbs. I...
    • Corktowner
    • Thread
    • dc offset jvc ja-s55 shorted output
    • Replies: 11
    • Forum: DIY
  9. 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...
  10. ELzekio

    JVC RX 950v High DC OFFSET

    Hello everyone, So I have recently been spending time working on a JVC RX 950 that had some weird issues. Seemed I was only getting sound on one channel, but after re doing some cold solder joints on the pre driver board and replacing the caps on the pre driver, I was able to restore the...
    • ELzekio
    • Thread
    • dc offset high dc offset jvc jvc rx 950v jvc rx 950v high dc offset
    • Replies: 16
    • Forum: Solid State
  11. spark1

    KA-7002 Nearing the Finish Line...Just Need a Little Push, Please

    Hello again. With the friendly help of expert members along the way, I'm just about done updating my Kenwood KA-7002 amp. I've replace all the electrolytics, all of the 2sc458 and 2sc871 transistors, the trimmers and a few other components. Also put new paste and insulators on the outputs...
  12. T

    SAE 2200 amplifier 1vdc offset - how would you proceed

    I have a SAE 2200 that works, but it has 1.0 vdc to 1.4 vdc offset on channel 2. Bias adjustment does not do anything. The amp works and sounds ok, I do not want to run long enough to see how it sounds , but it does work ok. The VU meter shows the offset also about 30% of the vu meter lights up...
    • Trebolo
    • Thread
    • dc offset offset issue sae 2200 sae amplifier offset
    • Replies: 27
    • Forum: Solid State
  13. D

    Primare Pre30 kicks relay of power amp when turned on/off

    Hi, I got a Primare PRE30 a while back that was totally dead, no lights, no commands, no sound, but the power supply was working. -First step was the micro controller chip, got a new one from primare and that gave me a very nice faceplate with all the leds lit up and a dash on the display...
    • depaj
    • Thread
    • dc offset power off power on primare pre30 relay
    • Replies: 7
    • Forum: Solid State
  14. A

    Phase Linear 400 - DC offset problem

    I've recently replaced the output transistors on one channel of a PL400 I'm working on but I now have a big DC offset. When I got the PL400, it arrived with no main fuse. On DBT (with fuse) it drew too much current. Measurements indicated that three of the connected outputs on one channel were...
    • audiogymp
    • Thread
    • dc offset phase linear 400 pl400 problem
    • Replies: 139
    • Forum: Solid State
  15. c.coyle

    Testing speaker protection circuit

    I replaced the differential pair transistors in an amplifier and, when I tested offset (with no speakers connected, thank the stars), I got 38 volts at the speaker terminal on that channel. I went back and figured out that I had an open solder joint on one of the new trannys. That fixed the...
    • c.coyle
    • Thread
    • dc offset differential pair relay speaker protection
    • Replies: 1
    • Forum: Solid State
  16. runnin'

    Harman Kardon HK395i with issues

    Hi, I posted in an existing thread in the solid state section, but on second thought figured I should start my own thread. So the 395i, upon power up, pushes out the woofers of the connected speakers before they return to normal in about a second. Measuring dc offset at the speaker posts(all...
    • runnin'
    • Thread
    • dc offset harman
    • Replies: 7
    • Forum: DIY
  17. Johnny_Law

    Pioneer SX-636 Intermittent DC Offset How to Diagnose?

    Have an SX-636 on the bench. It was acting like an output transistor had shorted, giving me ~20VDC offset across the right channel at one point. Got it to the bench (a couple days later) and checked all the pins on the Power Amplifier board (AWH-034) and the Power Supply board (AWR-060). The...
  18. 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...
  19. xrayspex77

    HK 730 with Odd DC Offset problem

    HK 730 has High DC Offset on the L Channel for the 1st 60 secs after Power On. It seems to be partly related to the state of charge of the Main Caps. Readings are from the Speaker Terminals. If the Main Caps are fully discharged the sequence is -> 4-5 Secs then 16V which drops until after 60...
  20. bibota

    Readjusting bias current and DC offset - Marantz 2230

    I'm currently in the midst of my first project, recapping a Marantz 2230 and meeting quite a few difficulties along the way. All of them feeding into the learning curve, to put a positive spin on it. I keep reading that after recapping the tuner boards, a "readjusting of the bias current in the...
    • bibota
    • Thread
    • am rf board bias adjustement dc offset marantz 2230 p150 recapping sound after recapping
    • Replies: 21
    • Forum: Marantz Audio
  21. grindfix

    Marantz 2225 DC offset issue

    Hello everyone. I'm trying to adjust DC offset and R711 trimmer is maxed out at -0.080 VDC (negative) between pin 723 and 722 (ground). Opposite channel is adjusted to 0.0VDC no problem. Bias adjustment was difficult due to error in the schematics but is good now (0.020VDC) on both channels. Can...
  22. W

    Rotel RSX-972 Pops Upon Power Down. Advice?

    I'm working on this Rotel unit that had an output transistor blown on the right channel due to accidental crossed speaker wires. The offending transistor (and its matched partner and the emitter resistor) have been replaced. The amp now turns on and plays... However the DC offset on the output...
    • W.T. Holt
    • Thread
    • dc offset dc to speakers pop noise on shutdown receiver rotel rsx-972 stereo
    • Replies: 4
    • Forum: Solid State
  23. S

    sansui 881 bias adjustment issue

    so I've recapped my Sansui 881. I did one board at a time and always checked her on a dim bulb tester and did a basic function test between each board. I am now setting the final DC offset and Bias adjustments before buttoning her up and putting her back into services. I have the DC offset...
  24. B

    Marantz 140 Adjusting DC offset and bias ?

    Hello guys,im new to this kind of things regarding electronic repairing etc etc, can someone tell me how can i adjust the bias on my Marantz 140? Where do i connect dvm, on which pins ?I have the manual, but to me its unclear where should i connect the digital multimeter in order to adjust the...
    • Bogdan1986
    • Thread
    • bias dc offset help marantz 140
    • Replies: 6
    • Forum: DIY
  25. QSilver

    SA-6500II Rebuild high dc offset.

    Picked up one of these with a few problems. Had some bad crackle on one channel which i think i have tracked down to the outputs. I pulled out the outputs and the crackling has gone from my scope. On the left channel, i had a dc offset of 80mv and 20mv on the right. I started working the left...
    • QSilver
    • Thread
    • dc offset pioneer refurb restoring sa-6500ii
    • Replies: 8
    • Forum: Pioneer Audio
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