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Old 2nd December 2013, 06:43 PM   #1
svs88 is offline svs88  Finland
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Default Creek OBH-21 SE problem

Hi,

I recently got faulty Creek OBH-21 SE headphone amplifier. When it is turned on, first couple minutes it has weird "clipping" with 2 - 3 second delay. Also the power led flashes with the same pace. Also the sound distords a little bit.

After the amplifier warms up the clipping noise disappers but sound still distords.

I opened it and saw that the channel 1 headphone jacket was broken, so i soldered it out but it did't fix the problem. It seems that amp has been dropped..

I think the next move would be to measure the voltage from power supply and voltage at the power led. I tried to search schematic but had no luck. Only found schematics for OBH-11, would it be little bit similar with this amp?

I would really appreciate the help. Thanks in advance. I will post the solution here when it founds.
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Old 25th December 2013, 04:41 PM   #2
svs88 is offline svs88  Finland
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Time to upgrade this one.

Measured input voltage from the circuit and it was around 8 VDC then dropped to 5 VDC and went back up to 8 VDC and kept looping the voltage. Also the voltage after LM317 regulator was driving around 4-5 VDC. That was quite od when the CREEK OBH-2 power supply seems to be 24 VDC.

Measured power supply and it shows CONSTANT 23,9 VDC without any load. Found cheap 24 VDC power supply from garage and plugged it in. Now input voltage is steady 23,9 VDC and after regulator 17 VDC and amp seems to work very good.

So the project changes from fixing OBH-21 headphone amp to OBH-2 Power supply.

Teared up the power supply case (i think creek really hoped anyone would not open this) and by eye it seems to be ok. Anyone know where to start? Never been playing with power supplies. See attached pictures.

PIC1
PIC2
PIC3
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Old 25th December 2013, 04:49 PM   #3
Mooly is offline Mooly  United Kingdom
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Is the regulator not flush with the heatsink ? It looks it from the picture. That's a simple PSU, if its been dropped then look for cracked and damaged print.
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Old 25th December 2013, 05:01 PM   #4
svs88 is offline svs88  Finland
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The regulator is just screwed to hatsink and it seems that it screw was also not tightened all the way. Could that damage the regulator by overheat? Theres no any markings on the regulator also..
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Old 25th December 2013, 05:04 PM   #5
Mooly is offline Mooly  United Kingdom
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It is possible it could damage it. If there are no markings on the device then you would need to trace and draw the circuit out to determine what the device might be
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Old 26th December 2013, 10:34 AM   #6
svs88 is offline svs88  Finland
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Found part list for OBH-2 from this forum.

It turns out to be LM317. Ordered all new parts, including panasonic FC series caps (dont know if those add anything good in PSU's).
Btw, how i can measure the noise PSU makes?

It seems that Creek uses ONH-21SE same panasonic caps.. would it add anything by changing those to ELNA SIMTEC II caps?
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Old 26th December 2013, 10:52 AM   #7
Mooly is offline Mooly  United Kingdom
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You need a suitable scope to measure the noise but its going to be very low. What many don't appreciate is the fact that noise at the regulator output can be degraded ten or a hundred fold at the regulators final destination due to circuit board resistance, wiring resistance and inductance etc. More realistic tests are are done by loading the regulator with a variable load (variable and high frequecy) and seeing how it all performs then.

You won't have a problem though with noise on a headphone amp.

I'm not a fan of boutique parts tbh
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Old 26th December 2013, 10:54 AM   #8
svs88 is offline svs88  Finland
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Ok thanks for fast answer and helping

I must ask, what do you mean by boutique parts?
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Old 26th December 2013, 11:00 AM   #9
Mooly is offline Mooly  United Kingdom
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For me (and this is just my personal opinion and view) its parts with a high price tag compared to normal top quality commercial grade stuff. Often they are parts of totally unsuitable physical dimensions, and often parts that are specified with no other reason other than some supposed magical audio properties that conveniently can't be measured or quantified

I'm just not a believer in that sort of thing...
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Old 26th December 2013, 11:10 AM   #10
svs88 is offline svs88  Finland
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I think youre right, theres a lot of shitty stuff on Hifi markets.
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