Help me identify this capacitor

  • Thread starter JoshB.
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  • #26
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oh sorry - didnt know you had to signup for it.
Anyone know of a good free hosting site?
 
  • #27
Wes Tausend
Gold Member
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oh sorry - didnt know you had to signup for it.
Anyone know of a good free hosting site?
Josh,

The 32 page pdf manual did download, without sign-up, on my miserable atom-powered 10" netbook with Explorer 8, but I can't magnify it enough to read it decently without crashing. The site did complain about my ancient browser but I am not sure my meager chipset can handle any more data from a newer version. And I don't trust microsoft to let me back out without re-installing my op sys..

I think I did see a set of output IC's (IC123's 1, 2) fed by a single IC pre-amp (IC12). They terminate FR and FL which seems to indicate a stero output section for front right, left. From there a feedback path is fed back to IC12 pins 5 and 25, but I don't see a decoupling capacitor on these.

Another detrimental feedback path is sometimes inadvertently established by a power feed where the current draw of an output stage overloads the stability of a normally steady dc supply and this wavering cycle is fed back to the power supply feed of an earlier amplifier stage. There again a local filtering capacitor to ground from the supply line may have failed, but this is also true of the main supply in some cases. In any case, a leaky power transistor may also draw too much current for the voltage divider circuit design to filter smoothly. Discreet transistors are not used much anymore, except for outputs. I thought IC's 123 might each be a black-box push-pull set combo.

Does your feedback whine travel through all audio channels equally? I'm imagining you don't have a lot of test equipment to work with. You might be able to measure (or hear) a higher audio ac voltage on one channel more than the others with an ordinary multimeter. If so, it might be possible to isolate a single channel as the source of unwanted feedback generation. Don't know what else to tell you.

I need an updated computer. Even the new PF forum software no longer renders correctly, making posting a chore. The above drop-down tabs often get stuck on my screen and, after saving a prospective post to clipboard, I must laborously reload the page to get rid of them.

Good luck.

Wes
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