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M1 requires trouble shooting
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T3owner
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PostPosted: Sat Nov 17, 2018 10:46 am    Post subject: Reply with quote

yoshi88 wrote:
My power supply board is KLM 1268 117CN
Cap #18 was shot and replaced.

Replacement cap should be low-ESR type meant for switching supply frequency, and 105 degree C rating is preferred.

 
yoshi88 wrote:
Excess glue removed from this region. There is plenty of old glue still around caps by CN#9 of 1268.

Glue around the caps usually isn't a problem if it isn't touching other component leads. Make sure the +5v and +/- 12v are correct and stable. Try breathing on the area with the glue (to provide moisture) and verify that the voltages remain stable. If not, remove the glue and recheck.

 
yoshi88 wrote:
I will find a good ground and test ( 1261 ) in regions B , C , L and M Correct?

Yes, measure those points to ground (CN12 pins 2, 3), as well as points D, E, G, H, J, K. Post what you measure.
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yoshi88
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PostPosted: Sat Nov 17, 2018 5:17 pm    Post subject: Reply with quote

"glue around the caps usually isn't a problem if it isn't touching other component leads. Make sure the +5v and +/- 12v are correct and stable. Try breathing on the area with the glue (to provide moisture) and verify that the voltages remain stable. If not, remove the glue and recheck. "

What is the preferred way to this 30 yr old remove glue.
There is a resistor on the power board that has its legs buried in it.
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T3owner
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PostPosted: Sat Nov 17, 2018 7:21 pm    Post subject: Reply with quote

yoshi88 wrote:
What is the preferred way to this 30 yr old remove glue.
There is a resistor on the power board that has its legs buried in it.

Scrape as much off as you can with whatever tool you prefer. It will come off in larger chunks if you freeze it first with cold spray. Any small amount remaining can usually be removed by a solvent such as lacquer thinner (acetone, etc.), but avoid getting the solvent on plastic parts.
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yoshi88
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PostPosted: Sat Nov 17, 2018 9:33 pm    Post subject: Reply with quote

Acetone or lacwuer thinner on electronic components seems harsh.
Would one use hair dryet for heat
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T3owner
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PostPosted: Sat Nov 17, 2018 10:18 pm    Post subject: Reply with quote

yoshi88 wrote:
Acetone or lacwuer thinner on electronic components seems harsh.
Would one use hair dryet for heat

A small amount of solvent, applied carefully with a cotton swab, is unlikely to cause problems. I've successfully dealt with that glue in numerous pieces of equipment, so I know what I'd do. However, I suggest that you do some online searching about the yellow glue on pc boards, then come to your own conclusions.
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yoshi88
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PostPosted: Tue Nov 20, 2018 8:38 am    Post subject: Reply with quote

T3owner wrote:
Many distortion problems are caused in the DAC circuit, which is sensitive to voltage. The KLM-1261 board has a power supply area (at lower left on the schematic) where the +/- 12v from the kLM-1269 is further filtered, and regulated down to +/- 5v. What voltages do you see on all the points labeled "B" through "M" on that part of the schematic? Please give readings to two decimal places.

Also, do you have an oscilloscope?
NO Osc.

R26 = 11.97v
R25 = 11.96v
C48 = 0.0
C50 = 11.97v

I will continue but was interrupted.
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T3owner
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PostPosted: Tue Nov 20, 2018 11:14 am    Post subject: Reply with quote

yoshi88 wrote:
R26 = 11.97v

OK

 
yoshi88 wrote:
R25 = 11.96v

Please pay attention to polarity - "C" voltage should be negative with respect to ground.

 
yoshi88 wrote:
C48 = 0.0

Are you certain? Voltage at "M" would be 0 volts only if LC1 is open. Make sure you're measuring from ground to the negative side of that cap.

 
yoshi88 wrote:
C50 = 11.97v

OK
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yoshi88
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PostPosted: Mon Dec 10, 2018 8:31 am    Post subject: Reply with quote

Checked the AD board 1261.
All capacitors and resistors are good.
Voltage values are good.

Distortion still present.

Could there be an issue on the power supply board still. Capacitor was replaced. When completed sound was restored although distortion still present.

Thoughts :

Shall I check all resistors and capacitors again on ps?
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T3owner
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PostPosted: Mon Dec 10, 2018 2:52 pm    Post subject: Reply with quote

yoshi88 wrote:
Checked the AD board 1261.
All capacitors and resistors are good.
Voltage values are good.

Please be specific (not just "good") - what are the voltages with respect to ground at all the points B, C, D, E, G, H, J, K, L and M?
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yoshi88
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PostPosted: Mon Dec 10, 2018 5:25 pm    Post subject: Reply with quote

Do ALL connections to the KLM 1261 board with orher M1 circuits need to be complete before testing voltages at those points?

Or... can the tests values remain true with only the power being supplied to the klm 1261?
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T3owner
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PostPosted: Mon Dec 10, 2018 9:36 pm    Post subject: Reply with quote

Just power via CN12 should be sufficient. Use pins 2/3 of that connector (or something connected to those pins) as common for the measurements.
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