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svs88 2nd December 2013 05:43 PM

Creek OBH-21 SE problem

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.

svs88 25th December 2013 03:41 PM

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.


Mooly 25th December 2013 03:49 PM

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.

svs88 25th December 2013 04:01 PM

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..

Mooly 25th December 2013 04:04 PM

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

svs88 26th December 2013 09:34 AM

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?

Mooly 26th December 2013 09:52 AM

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 :)

svs88 26th December 2013 09:54 AM

Ok thanks for fast answer and helping :)

I must ask, what do you mean by boutique parts? :D

Mooly 26th December 2013 10:00 AM

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 :D

I'm just not a believer in that sort of thing...

svs88 26th December 2013 10:10 AM

:) I think youre right, theres a lot of shitty stuff on Hifi markets.

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