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oscillation

  1. jd3rdcoast

    SX-1050 strange hi frequency noise on regulated power supply lines

    I have an SX-1050 I'm restoring and I am getting a strange high frequency sine wave on all regulated power supply lines (AWR-103). This seems to be an ongoing issue with this unit from before I got it. Some background info: 1. Initially received with an EMI Filter box spliced into the main AC...
    • jd3rdcoast
    • Thread
    • oscillation power supply noise power supply oscillation sx-1050 sx-1050 noisy power
    • Replies: 36
    • Forum: Pioneer Audio
  2. D

    Kenwood KA-9100 oscillating

    Hello everyone, first post, I'm from France and passionate about renovating old audio gear, from turntables to tuners and of course vintage amplifiers. I started my journey in this passion about 5 years ago with an SU-7700 from Technics which is still working beautifully to this day. In the...
  3. 2385 Phono stage oscillation.MOV

    2385 Phono stage oscillation.MOV

    2385 amplifier oscillation when phono stage is used.
    • Rick churay
    • Media item
    • 2385 amplifier oscillation oscillation phono stage oscillation
    • Comments: 0
    • Category: Member's Systems
  4. U

    Project/One Mark IV protection

    I've come across a strange one. When the unit came in for repairs, one channel had shorted outputs. I replaced the outputs and found a weak coupling capacitor and the unit fired up. I had it on a Dim Bulb Tester, thankfully, since 30 secs after firing up, it thumped, the bulb lit up and the...
  5. faccan

    Another F-2624 bias problem

    Hello, I'm working on a 7070 that the relay doesn`t "click". I had changed both 1 omh fuse resistors in power supply board, all the fuse resistors of the F-2624 and deoxided the presets. I tried to set bias current of one channel starting from maximun resistance in preset ( It have the F-2624...
  6. ocdecio

    Parasitic oscillation?

    After rebuilding the left channel on a 1200, I finally was able to get some bias (connected to the DBT). However as soon as bias start to inch up, the output waveform gets all distorted. When I turn it off, for some seconds the waveform cleans up before fading away. Have anyone seen this...
  7. E

    SA-7800 C18/Q24 question

    Hi guys, I bought the pretty faulty SA-7800 (looked nice but it was burnt a lot inside) couple years ago. ONLY because of your knowledge and experience which I found in the forums I was able to repair it during last two months. (Replaced all power transistors, Q6 in the phono part, bad trimmer...
  8. tusntuk2

    Can you help me use a 'Scope to find oscillation?

    Looking for a patient teacher to walk me through using a 'scope to find an apparent oscillation in a Kenwood KR-5600. I'd love the help if anyone has the time to try! There is a sudden hum/buzz current draw at the full open position of the Treble control. I'm thinking it could be oscillation...
    • tusntuk2
    • Thread
    • buzz current draw humm kenwood kr-5600 oscillation treble pot
    • Replies: 0
    • Forum: Solid State
  9. tusntuk2

    "Treble Max" Problem - Can you help with this puzzle?

    Hi y'all, hope you are staying healthy at home! My main home activity has been to recap/rebuild a Kenwood KR-5600, and things are going pretty well for a difficult layout - except the inevitable mystery problem has cropped up. Maybe someone else has heard of this? It goes weird when the...
    • tusntuk2
    • Thread
    • feedback kenwood kr-5600 oscillation recap treble
    • Replies: 14
    • Forum: Solid State
  10. tusntuk2

    Kenwood KR-5600 Strange Tone Problem - Know what this is?

    I'm rebuilding a Kenny 5600. Original description was "one side out", and all the lamps are out. This improved some with deoxing the controls, but there were two anomalies. The FM had terrible distortion on one side, and while checking a signal thru the AUX, the Treble control, when turned...
  11. M

    Jadis JP80MC info needed

    Hello friends. So I made my Defy 7 work, and it sounds great. But now my vintage JP80MC has developed noise in the left channel only of its MC stage. It’s “motor-boating”, which to me indicates either a bad capacitor, or a bad regulator. On my unit regulator markings are sanded off. On later...
    • marknoir
    • Thread
    • jadis mc motorboating oscillation phono stage power supply preamplifier regulator
    • Replies: 0
    • Forum: Tube Audio
  12. tusntuk2

    Need help figuring out probable oscillation in SWR Studio 220 Bass Amp.

    I'm restoring an SWR Studio 220 bass amp. The amp had a bad hum, so I replaced all diodes, zener diodes and all electrolytics. I boosted the main caps from 4700 to 6800. Grounding is a possible hum issue due to the design, but more on that later. When I powered it up (DBT) it seemed to whine...
    • tusntuk2
    • Thread
    • bass amp bass player oscillation studio 220 swr
    • Replies: 8
    • Forum: Solid State
  13. tusntuk2

    Now just how do I use this new Oscilliscope to find a problem?

    Got a "new" (old used) scope to help diagnose a voltage/oscillation problem in a KR-5600 receiver, and I'm learning how the scope functions. How, exactly, do I use the scope inside the amp? I'm trying to diagnose a vexing problem with apparent oscillation or voltage runaway as the volume...
    • tusntuk2
    • Thread
    • component testing kr-5600 oscillation oscilliscope
    • Replies: 55
    • Forum: Solid State
  14. tusntuk2

    Having trouble finding oscillation/bias problem - where do I look?

    Please help me find the cause of an apparent oscillation problem. It seems to be related to the bias circuit, or at least it's manifested there. This is a recently recapped Kenwood KR-5600. Great help from AK folks helped me spot a faulty diode and fix the relay, and the audio board and power...
    • tusntuk2
    • Thread
    • bias drops hot output kr-5600 oscillation
    • Replies: 56
    • Forum: Solid State
  15. 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...
  16. tusntuk2

    Pulsing buzz varies speed with Volume/Bass. Any ideas?

    Kenwood KR-5600 receiver, just finished recapping Audio and Power Supply boards. After resetting bias it started making buzz/hum in a rhythmic pulse that would vary speed as either the Volume or Bass control was moved. Right channel only. Maybe some transistor oscillation? Haven't had one...
    • tusntuk2
    • Thread
    • buzz changes speed changes with volume hum kenwood kr-5600 noise oscillation pulse rhythmic noise
    • Replies: 5
    • Forum: Solid State
  17. QSilver

    SA-8800 Oscillation?

    Went to switch it on today and it took longer than usual to come out of protection. Then I heard a slight crackling noise from inside the amp. Turned it off, and smoke came out from the front right corner of the amp. Damn. So I took it to the bench. R80 had burned up. I changed it and replaced...
  18. Tangerine

    Pioneer A-9 in parasatic oscillation after repair - HELP!

    I've already posted this under my blog that covers the re-build of the A-9: Having fitted the new transistors: 2SA1295 2SC3264 to the (GWX-593/4) Driver Assemblies (that's a post on its own) and recapping the (GWH-148) Power Amp Assembly we now have parasitic oscillation (PO) present running RF...
  19. Richs_Trains

    Marantz 4230 Oscillation

    Hey guys, Latest project is a 4230 I actually bought for the decoder and the wood case, so the receiver cost me about $100.00. I was billed as LED upgrade, De-Oxit and functional. What I get is functional until you start to turn it up, then the power oscillates (sound up and down, lights up...
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