Author Topic: QRV-08 hum  (Read 13384 times)

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Offline CapRock

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Re: QRV-08 hum
« Reply #45 on: April 01, 2011, 02:57:32 PM »
here are the jumper positions that I used bare wire jumpers (is that the same as a tin jumper?) are these causing the problem?

J1
J2
J4
J5

Offline peranders

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Re: QRV-08 hum
« Reply #46 on: April 01, 2011, 03:26:43 PM »
I see that I have forgotten to mention these jumper. You should have one jumper at the time. This is for the input bias current adjustment.

http://sjostromaudio.com/pages/hifi-projects/36-hifi-projects/92-qrv06-headphone-amp?start=4 Here I have mentioned this.
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Offline CapRock

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Re: QRV-08 hum
« Reply #47 on: April 02, 2011, 06:11:59 AM »
I checked the link and that was for the qrv 06. And I did not see anything about jumpers on the page. Can you list all the jumpers I should be using so I can take off the ones that I don't need.

Offline peranders

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Re: QRV-08 hum
« Reply #48 on: April 02, 2011, 02:45:46 PM »
The described a patch which I designed in. Remove J1, J2, J4, J5. You could remove the J3 and J5 but it's necessary. J3, J5 is for selecting desired output impedance.
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Offline CapRock

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Re: QRV-08 hum
« Reply #49 on: April 04, 2011, 05:42:23 AM »
ok I removed the jumpers and here are a list of my voltages.  LEDS are still dark



input voltage: 119.8 VAC
TR2 pins 6 and 7: 11.57 VAC
TR2 pins 9 and 10: 12.35 VAC
TR1 pins 6 and 7: 11.86 VAC
tr1 pins 9 and 10: 12.69 VAC

BR3: 11.17 VDC
BR4: -12.03 VDC
BR1: 11.23 VDC
BR2: -12.30 VDC

Offline peranders

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Re: QRV-08 hum
« Reply #50 on: April 04, 2011, 09:25:24 AM »
Better but 12 VAC should generate 15-16 VDC

What about the voltages out from the regulators? You can measure this at J1, J2, J4, J5. The pads  in mind are those closest to the designators. You measure with respect to ground.
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Offline CapRock

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Re: QRV-08 hum
« Reply #51 on: April 05, 2011, 04:35:01 AM »
ok here they are in VDC

J5: -9.59
J4: 8.64
J2: -9.37
J1: 8.48

Offline CapRock

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Re: QRV-08 hum
« Reply #52 on: April 09, 2011, 08:05:03 PM »
I posted the DC voltages you had asked for.  Is there anything else I need to test?

Offline peranders

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Re: QRV-08 hum
« Reply #53 on: April 10, 2011, 03:56:52 PM »
Values of the smoothing caps, C27, C28? 2200 uF? Do you have any oscillscope? It would be interesting to se how much ripple you have on the raw voltage. With 12 VAC, you should have approx. 15-16 VDC at least. Do the red LED's shine?
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Offline CapRock

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Re: QRV-08 hum
« Reply #54 on: April 15, 2011, 03:35:11 AM »
Hi,
   LED's do not shine and yes I am using 2200uf for the c27, c28, G27, G28 snap in caps on top of the board.  And then on the bottom side of the board I have 2200UF caps for C29, C30, G29, G30.  I do not have a scope, is this something I will need for further testing?

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Re: QRV-08 hum
« Reply #55 on: April 15, 2011, 09:02:47 AM »
You don't need smoothing caps on the solder side but it won't hurt electrically. The regulators may work but the input voltage is too low. I'm also really suspicious about your high ripple voltage voltage. It should be rather flat since you have 4700 uF as smoothing. With nearly 13 VAC, you should have 17 VDC. Are the amps working? Much hum?

You must get in touch with an oscilloscope owner.
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Offline CapRock

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Re: QRV-08 hum
« Reply #56 on: April 18, 2011, 05:47:40 PM »
Hey per can you give me a list of everything you need me to test with the oscilloscope?  I know an owner but he is not very close to me so I would like to try and do this in one trip if possible.

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Re: QRV-08 hum
« Reply #57 on: April 18, 2011, 06:52:49 PM »
Since you have around 12 VAC, you should have 12*1.4 as top voltage after rectification and the min voltage should be maybe 1-2 volt under. The frequency must be 100 Hz for 50 Hz or 120 Hz for 60 Hz. If you have 50 or 60 Hz the rectifier bridge may be broken.
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Offline CapRock

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Re: QRV-08 hum
« Reply #58 on: April 21, 2011, 04:49:33 PM »
Hmmm. Is it really possible that all of my rectifier bridges broke in the same exact way?  So if I get ahold of a scope where is a good spot to test the frequency of power?  Or am I not understanding and I need to test something else. I will hook everything back up today and see what it sounds like

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Re: QRV-08 hum
« Reply #59 on: April 21, 2011, 07:11:53 PM »
The rectifier bridges might be Ok but your raw input voltage needs some investigation.
/Per-Anders Sjöström, owner of this forum

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