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Creek OBH-21SE doesn't power up
Creek OBH-21SE doesn't power up
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Old 16th May 2018, 03:54 AM   #1
Alexandru is offline Alexandru  United States
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Default Creek OBH-21SE doesn't power up

Creek OBH-21SE doesn't power up after I've connected the DAC output during music playing to the headphone amp's output (RCAs). What did I do?! Could you help me please?

photo of the circuit board below

P.S: Creek's engraved msg on the back of the amp: "No user serviceable parts inside" is very discouraging.
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Old 16th May 2018, 08:36 AM   #2
merlin el mago is offline merlin el mago
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Arrives DC to the unit?
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Old 16th May 2018, 01:12 PM   #3
Alexandru is offline Alexandru  United States
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Yes, The DC source puts out 24V. I’ve measured it with a meter.
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Old 16th May 2018, 02:36 PM   #4
merlin el mago is offline merlin el mago
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Do you have a schematic? Check if VR1 is regulating OK?
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Old 16th May 2018, 04:58 PM   #5
Alexandru is offline Alexandru  United States
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Merlin, thanks for your help so far. Unfortunately I don’t have the schematics.

The first advice I got outside the forum: “Likely, you've cooked the op amps for the input circuit, and depending on their failures maybe other parts in series as well”
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Old 16th May 2018, 10:25 PM   #6
Alexandru is offline Alexandru  United States
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I've measured the DC voltage from ground to Vcc+ and the Vcc- of the 14-pin TL04CN chip and there are completely dif values. As far as I understand the two voltages should have the same magnitude (within a tenth of a volt).

Is this correct?
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Old 17th May 2018, 12:47 AM   #7
Alexandru is offline Alexandru  United States
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I've been trying to troubleshoot the 14-pin TL074CN.
Please let me know if I'm doing it correctly. Thank you

- With the headamp's DC power OFF
- Multimeter in diode mode
- I've measured each pin to ground:

1(1OUT): 0.74V
2(1IN-): .0L
3(1IN+): 0.0V
4(VCC+): 0.95V
5(2IN+): 0.0V
6(2IN-): .0L
7(2OUT): 0.74V

8(3OUT): 0.74V
9(3IN-): .0L
10(3IN+): 0.0V
11(VCC-): 0.54V
12(4IN+): 0.0V
13(4IN-): 0L
14(4OUT) 0.74V

===

With the amp's DC power ON
Multimeter in V mode,
I've measure the VCC+/- to ground:
VCC+: 0.54V
VCC-: 0.0V

Last edited by Alexandru; 17th May 2018 at 01:01 AM.
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Old 17th May 2018, 09:51 AM   #8
merlin el mago is offline merlin el mago
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Measurements without power aren't necessary. It seems the power doesn't arrive to your IC, have you checked the voltage regulator VR1 as I said in post 4?

Last edited by merlin el mago; 17th May 2018 at 09:54 AM.
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Old 17th May 2018, 12:33 PM   #9
Alexandru is offline Alexandru  United States
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Sorry, I did and I found the following values:

DC Power on:
Ground to Vin: 0.48V
Ground to Vout: 0.49-0.51V
Ground to Vadj: 1.15V

Last edited by Alexandru; 17th May 2018 at 01:02 PM. Reason: I measured it wrong
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Old 17th May 2018, 01:02 PM   #10
merlin el mago is offline merlin el mago
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It's arriving voltage at regulator?
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