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protection circuit

  1. mgrisoli

    Pioneer QX-9900 Protection board

    So, this is the third QX-9900 I'm working on. I'm still to see a protection board as called out in the SM: None of the units I worked on have this board. This time I took the proper time to reverse engineer and document the board that is actually in the receiver: And now I am sharing with...
    • mgrisoli
    • Thread
    • pioneer protection board protection circuit qx-9900
    • Replies: 0
    • Forum: Pioneer Audio
  2. O

    Kenwood KA-7100 comes out of protection only when warmed up (a lot).

    Got a KA-7100 that I had to re-do the on/off switch on, and replace the LED. That work came out fine. Now... the system comes out of protection ONLY when it REALLY gets warmed up (like over 5 or 10 minutes on). Once it gets warmed up like that, I can power it off, then power it up, and it...
  3. S

    Project: Solid State Relay (drop-in) replacement for speaker protection

    Hey guys, I have been working on a quick project: A (drop-in) solid state relay replacement for relays with the footprint of Omron's MY2 (and similar) used as speaker protection relays. Today I'm too lazy to write a long post, so Q&A it is: Why? Because I don't think I have seen a compact...
    • SebastianH
    • Thread
    • protect protection circuit relay solid state relay speaker protection relay ssr
    • Replies: 0
    • Forum: Solid State
  4. electrotek

    Onkyo A-9130 Volume Increase Causes Protection

    Hi legends! I recently acquired a 5 year old Onkyo A-9130 amp from a first-time owner who found it would cut out (assumably protection circuit) after the volume reached above about 10 o'clock (1/3rd power) if, and only if, music ("input") is playing. However, using headphones does not cause the...
    • electrotek
    • Thread
    • a-9130 amp amplifier onkyo power protection circuit
    • Replies: 0
    • Forum: Solid State
  5. Stereoboy70

    Onkyo TX 870 speaker protection circuit issues.

    I’m working on an Onkyo TX 870 receiver. The main rectifier blew up and took out some other transistors. It was blowing the main fuse every time but now it’s ok sisnce I’ve replaced several components. The issue now is the speaker relays won’t close. The 2 100uf caps and the big 3300uf cap...
  6. tutor_turtle

    9090 no bias current one channel

    I fixed the bias issue (2sc984 bias control x-stor was bad) I have a 9090 (not db) that came in for shorted outputs (in protection). Rebuilt the driver board, replaced the outputs. Comes out of protection, bias and offset are good, but I don't get a green light. Sound quality is good. Pulled the...
  7. J

    Help with SA-7700 protection circuit

    Hi, I just joined this forum in hopes of getting some help with my Pioneer SA-7700 amplifier. The amp protection relay suddenly stopped closing on start-up. I've read up on the protection circuit and everything I can find on this forum. The PA3004 pin readouts are as follows: 1: 12.4v; 3...
  8. john cronin

    Sansui AU-317 Protection Circuit / RED LED issue

    Hi All I bought a 317 on eBay. The most filthy dirty unit Ive ever seen but I can see it will scrub up nice. Both main fuses on the PCB had blown etc so I just got stuck in on the restore and clean up. Cut along story short I replaced the standard components that normally needs changing on...
  9. C

    AU717 power stays on

    My amp stays on even when power turned off.Must be in the protection circuit, maybe.Red power light on always. Any idea?
  10. T

    Nikko NA 550 Amp Works Well But Won't Go Out Of Protection

    Working on a Nikko NA 550 Amp. The amp works well, I jumped it from the center point on both channels and the sound was as it should be. The center point DC output voltage is a good low 10mv from either channel, so that isn't an issue. I reset the bias so it is running nice and cool. To put it...
    • tonebrain
    • Thread
    • nikko na 550 protection circuit relay
    • Replies: 16
    • Forum: Solid State
  11. T

    Yamaha M-65 protection mode - seeking help

    Hello all! I have a M-65 that recently went into protection mode and won't get out of it. I'd really appreciate some guidance on getting it fixed. I'm not nearly as experienced as most of the people who post here are, but I have tools and the schematics and I'm willing to learn. I've never...
    • tocomplero
    • Thread
    • m-65 protection circuit yamaha
    • Replies: 33
    • Forum: Yamaha
  12. tusntuk2

    Pioneer SX-727 Blown Internal Fuse - what can I do?

    Hello AK, thanks for looking in. I'm having trouble identifying the cause for blowing an internal 3A fuse (# 2) in a Pioneer SX-727. I have reviewed other threads here and made some changes to my unit, but the fuse blew again while on the DBT, so I'm stuck, now. Can't measure voltages if it...
    • tusntuk2
    • Thread
    • fuse blow pioneer power supply protection circuit sx-727 trimmers zener diode
    • Replies: 31
    • Forum: Pioneer Audio
  13. Yamaha5000

    Yamaha CA-1000/CA1000II Power Supply and Protection Circuit Diagnostics, & Lower SNR values with the QA403

    With the DVM + lead on the Base of TR708 and the - lead on E: On the V scale I read 15.32vdc and the relay is off On the mv scale the relay coil becomes active I can use the V and mv scale selector to act like a switch to turn the relay on and off. FYI the Emitter to E measures 15.84vdc...
    • Yamaha5000
    • Thread
    • 60 cycle hum crosstalk internal hookup wire power supply power supply caps protection circuit qa403 snr yahama amplifier yamaha ca-1000
    • Replies: 358
    • Forum: Yamaha
  14. tusntuk2

    SX-727 blown fuse - please help identify parts

    Merry Christmas AK'ers! I could use a little help solving a blown fuse problem on a SX-727. This unit was my first recap project, done 4 years ago. Following AK threads I bravely dug into a SX-727 to recap it, but little did I know how hard/easy it was! I figured even if it blew up it could...
    • tusntuk2
    • Thread
    • awm-027-d blown fuse diode help identify internal fuse power supply protection circuit recap sx-727
    • Replies: 2
    • Forum: Pioneer Audio
  15. tusntuk2

    SX-727 Schematic changes for AWM-027 D Protection Board

    Holiday Greetings, AK'ers! My beloved Pioneer SX-727 blew an internal .5 fuse, so I checked it out. AK threads suggested the power supply or the protection circuit were common culprits. You might remember that the Protection Boards in the SX-727, and several other SX and SA series amps, are a...
    • tusntuk2
    • Thread
    • awm-027 awm-027d pioneer protection circuit sa-8100 sx-727
    • Replies: 0
    • Forum: Pioneer Audio
  16. Ray66

    SX980 with PA3004 chip PCB substitute

    An SX980 that I’m restoring has a problem with the protection board where the relay does not energize. I believe the problem is with the PA3004 IC so went ahead and replaced the it with the ‘substitute PCB’ designed by merlynski and alexhastings (see PA3004 chip PCB substitute). A big thanks to...
    • Ray66
    • Thread
    • pa3004 pioneer protection protection circuit
    • Replies: 33
    • Forum: Pioneer Audio
  17. Ray122

    Testing Protection Mode

    So this might be a bit of an odd question seeing as there doesn't seem to be too many posts about it. Naturally lot of post have been about getting amplifiers out of protection mode, but what if I wanted to get my amplifier in to protection mode. Crazy right? This question primarily centers...
    • Ray122
    • Thread
    • amplifers diy pioneer pioneer spec 4 protection protection board protection circuit protection circuit issues spec 4
    • Replies: 5
    • Forum: DIY
  18. PE9ZZ

    Sansui AU-719: how does the protection work?

    I have this amp on my workbench and it went into protect after some time. As per complaint. The thyristor SCR601 was bad. I should have replaced it with a replacement (MCR100) but since this was not present in my tray and there is time pressure I replaced it with a DIY thyristor consisting of an...
    • PE9ZZ
    • Thread
    • 2sf656 au-719 mcr100 protection circuit scr601 thyristor
    • Replies: 13
    • Forum: Exclusively Sansui
  19. merlynski

    Pioneer PA3004 chip PCB substitute - link

    Here is a link to an open source replacement pcb for the Pioneer PA3004 Protection SIP. It is available with Gerbers, Eagle files and BOMs for both SMD and Through hole versions. This is collaborative project by AK members. PA3004 chip PCB substitute | Audiokarma Home Audio Stereo Discussion...
    • merlynski
    • Thread
    • pa3004 pioneer protection board protection circuit protection ic
    • Replies: 1
    • Forum: Solid State
  20. alexhastings

    PA3004 chip PCB substitute

    After discovering a failed PA3004 chip on my SA-7700 rebuild, and paying $35 for a single replacement, I asked @merlynski to help me design a PCB substitute, so we can all keep rehabbing these old units without paying exorbitant prices for new "old stock" chips. Our design goal was to replicate...
    • alexhastings
    • Thread
    • pa3004 pioneer protection protection board protection circuit protection ic protection mode protection problem protection relay relay click
    • Replies: 66
    • Forum: Pioneer Audio
  21. S

    Optonica SA-5605

    Hey Everyone- First Time Post. Been Lurking. So, I got a HH Scott, LK-72 last year, recapped it, almost works good. Decided I would set it back, and go through it further later. Then, I was at an estate sale and picked up a dirty Marantz 2245. Cleaned it, recapped the power board, and it...
    • shawnmgray
    • Thread
    • no sound optonica protection circuit protection relay sa-5605
    • Replies: 3
    • Forum: Solid State
  22. J

    Restore of AU-7900 - Thank You!

    Just wanted to say a heartfelt thanks to the collected knowledge here on AK. Using the information on these forums, I was able to successfully restore a Sansui AU-7900 that was experiencing periodic pops and clicks - bad enough that the protection circuit would kick in. Final restoration...
  23. Cergei

    Yamaha M-4 | Relays not connecting after recapping

    Hello everyone, I completed the replacement of all electrolytics on my unit purchased in 1980, and noticed that once I power up the relays are not connecting. I measured on Left channel the voltage, instead of getting +65, I got 28.5V, while on the Right channel I got 44.4V instead of 65V. I...
    • Cergei
    • Thread
    • protection circuit reccaping relays yamaha m-4
    • Replies: 32
    • Forum: Yamaha
  24. Juanbanzai

    Pioneer SX-850 almost there; tripping protection circuit

    First, I want to sincerely thank everyone who assisted me in bringing my 850 around to working condition. The first issue was the low output volume, the second being on how to work with the final amp board. Both of these threads were addressed elsewhere, so with this new question, it's best to...
  25. Tangerine

    Pioneer A-9 - Goes into protection all the time, with loud pops in speakers

    Hello all. Hope you've been keeping well and that you and yours are safe. :) Problem Well last time I was here I was getting this A-9 beast back up and running, and running quite well these past couple of years, with one minor issue. That being the machine randomly going into protection (the...
    • Tangerine
    • Thread
    • a-9 diagnosis faulty pioneer protection circuit
    • Replies: 2
    • Forum: Pioneer Audio
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