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Post by thespianator on Dec 30, 2015 23:26:51 GMT -5
OK. So those are the secondary caps you are referring to. I found 3 caps on that board that have high ESR, one of them I previously mentioned. But you said before that might not be the cause.
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Post by thespianator on Dec 29, 2015 19:39:48 GMT -5
yes, the preamplifier has its own PSU. This response, I don't understand. There are 6 same size filter caps adjacent to the case. I am assuming those are what you are calling the main filter caps. So then are you saying that any other electrolytic caps are the secondary caps? Thanks.
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Post by thespianator on Dec 27, 2015 15:58:15 GMT -5
First check DC if its stable. To check AC ripple you need a oscilloscope. Preamplifier PSU, you can check with DVM. Then the secondary filter caps you are referring to the caps OTHER than the 6 main filter caps just outside the cage?
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Post by thespianator on Dec 26, 2015 18:42:44 GMT -5
First step: check over filtercaps outside the caged box (secondary side filter caps). If voltage is stable and no high AC ripple, then theres no need to open caged box. SMPS = Switch Mode Power Supply How do I determine if there is AC ripple? What would that look like with a DVM?
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Post by thespianator on Dec 25, 2015 16:27:27 GMT -5
I didn't mean speaker output. You have some different voltages from PSU that feeds the amplifier. Something like +-15-18V rail that feeds op-amps and main amplifier rail +-100-200V. The preamplifier has its own PSU. The amplifier PSU is probably SMPS. You can check over filter caps. Yes, they are in parallel to increase powerbank. My main language is not english, so bare with me No problem with language, since I don't speak schematic very well (LOL!). Your communication is fine. What is SMPS? Also, in order to get to the PCB in that caged area where the main PS is, I have to remove one of the main caps to get at one screw and all 6 of the power transistors have to be unsoldered from the main board. This is a lot of work just to access the main PSU!
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Post by thespianator on Dec 23, 2015 13:07:59 GMT -5
You need to check DC voltage from psu, if you have high AC ripple. That 10uF cap has to high ESR. But i dont think its your main problem. Reassembled, tested for DC voltage at the speaker output. It reads almost 400mv DC at the speaker output. What's next?
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Post by thespianator on Dec 22, 2015 21:05:08 GMT -5
Checked the main filter caps for ESR. All OK for ESR However, the caps are rated at 1000uF but each measured around 2800-3000. Does that mean they are wired in parallel?
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Post by thespianator on Dec 22, 2015 17:18:58 GMT -5
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Post by thespianator on Dec 21, 2015 15:15:27 GMT -5
OK, got plate amp out. Nothing obviously burnt or leaking, nor shrunken shrink-wrap. Going through it with ESR meter. Hard to know what is the appropriate ESR value for small caps, but found one 10uF 50V cap with an ESR of 4.6 ohms. Seems high.
Would that be possible to cause the motorboating/buzzing sound or would that more likely be a main filter cap? Anyone know? Could be IC?
Thanks
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Post by thespianator on Dec 20, 2015 16:20:32 GMT -5
Thanks, MT! Have a great Holiday to you and yours, and of course everyone here.
Thanks, Masterdoor - I'd be happy to find obviously bad filter caps (I have an esr meter for the others), but access isn't easy.
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Post by thespianator on Dec 19, 2015 21:00:53 GMT -5
While picking up a tuner from CL, I also got a deal I couldn't refuse (I gotta knock that off) on two Velodyne HGS10 servo controlled subwoofers, with one having an obvious problem: it makes a motorboating noise when plugged in to AC after about 3 seconds (no signal applied). Apparently no schematics are available on the net. (hopefully the second sub works ok).
It's a 45 lb sub with a 1000 watt amp and a 310 ounce magnet structure in about a 1 cubic foot box. They were quite highly rated back in '01 when it was made, so I figure it was worth a shot.
MT, any ideas where to start? (besides not dragging this stuff home?)
**HAPPY HOLIDAYS EVERYONE**
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Post by thespianator on Dec 14, 2015 17:41:54 GMT -5
I've recapped several receivers, tuners, amps and been pleased with the improvement in sound. But what about upgrading other components, using Fast Recovery Epitaxial Diodes, Schottky Diodes, etc. Does one need to know precisely when/where to use them? Modders like Musical Concepts mention that they upgrade diodes and also use hi-quality resistors in specific places.
Any clues as to proper use of these upgraded components? Is it possible to denigrate the sound with wrong selection of upgrade parts (well, yes, probably - so what are the pitfalls and how does one avoid them?)
Thanks!
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Post by thespianator on Nov 24, 2015 18:03:43 GMT -5
Thanks MT! Got the tool. Pulled the chip, stretched the contacts ever so slightly. Cleaned up all the contacts on the chip and the socket with D5 Deoxit. They seemed a little dull but not visually oxidized beyond that. It's playing now, and it will have to go thru several days or weeks worth of on/off cycles to confirm whether it freezes again. I'll withhold further comment until this repair has had a chance to proof out and I'll report back. Many thanks!
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Post by thespianator on Nov 21, 2015 13:54:57 GMT -5
I've looked for PLCC pullers, and online there are several styles. Some have a black plastic spring/lever around the claw. Locally I can pick up the style that is just an insulated u-shaped claw. Would that one be OK or is the one with the black plastic lever safer to use? (Radio shack used to carry them but they appear to be out of stock and some locations are closed).
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Post by thespianator on Nov 18, 2015 23:37:53 GMT -5
**BUMP** Thanks!
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