Author Topic: QRV-08 hum  (Read 26969 times)

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Offline CapRock

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QRV-08 hum
« on: February 01, 2011, 03:52:46 AM »
Hi Per,
     I just completed the QRV-08 and got it mounted in its case and all wired up.  I wanted to test it in the most basic way so I hooked up the AC power inlet to the terminal (X3) and hooked up my trs jack for the headphones to X2 and powered it up.  As soon as it powers on I get a really loud hum.  I am in the U.S. and I am using the transformers from you BOM (Hahn 230/40) even though we are on 115.  LED's H4 and H2 illuminate at power up but H1 and H3 stay dark.  The parts in your BOM that said do not use I left those spots blank, the parts that said short with tin jumper I jumped with a leftover lead from through hole resistors.  What do you think I need to do to get it working?

Offline peranders

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Re: QRV-08 hum
« Reply #1 on: February 01, 2011, 06:56:45 AM »
All LED's must be on. Do you have +- 12 volts in both channels? How much is your AC voltage really? 230/24 is better since I used 230/12 with 230 VAC in.
/Per-Anders Sjöström, owner of this forum

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Offline CapRock

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Re: QRV-08 hum
« Reply #2 on: February 01, 2011, 06:14:08 PM »
My Mains voltage I measured at 120.5 VAC.  I will check for 12 volts on the board later.  Where is a good place to check for 12 volts?  The transformers I am using are 230V 50-60hz, will these be ok for me?

Offline peranders

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Re: QRV-08 hum
« Reply #3 on: February 01, 2011, 06:27:44 PM »
It could be anywhere where you have 12 volts, please consult the schematics where you see 15V_R, 15_L, -15V_R, -15V_L.
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Offline CapRock

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Re: QRV-08 hum
« Reply #4 on: February 02, 2011, 06:48:29 AM »
I just checked the voltages around the board.  My input voltage was 121.6VAC and everywhere that was labeled 15V on the schematic I was getting between 4.16 and 4.39v which is obviously bad.  I also attempted to adjust the trimpots P1/P2 to read 0V across R1 and turning them either direction had no effect on the voltage reading across R1/E1.  Any Ideas?  Will these transformers work with the voltage I am getting here?  could I have damaged any parts by powering it up with these transformers? 

Offline peranders

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Re: QRV-08 hum
« Reply #5 on: February 02, 2011, 08:19:22 AM »
You must first make sure that your power supply is working. What is your raw DC voltage? Should be 20-25 V.
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Offline CapRock

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Re: QRV-08 hum
« Reply #6 on: February 02, 2011, 06:26:31 PM »
I checked for 25V at the positive leg of the bridge rectifiers.  Here are my results

BR3: 10.16
BR4: 0
BR1: 6.78
BR2: 0

Offline peranders

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Re: QRV-08 hum
« Reply #7 on: February 02, 2011, 06:30:40 PM »
You should measure at the NEG pin for the negative voltages.

+ pin is GND for the negative voltages, please check the schematics so you see where you should measure.

Can you measure the AC voltage on all four windings?
« Last Edit: February 02, 2011, 06:41:59 PM by peranders »
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Offline CapRock

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Re: QRV-08 hum
« Reply #8 on: February 05, 2011, 06:17:52 PM »
ok so today my mains input voltage is 119.1 VAC.  BR1: +14.2, BR2: -8.47, BR3: +21.5, BR4: -6.61.  Ac voltage at tr1/tr2 prim 1 is .2 V.  Ac voltage at prim 2 for both is 119.1
secondary voltages are as follows:

TR1:
sec1: 7.7
sec2: 7.5
sec3: 0
sec4: 0

TR2:
sec1: 12.8
sec2: 12.7
sec3: .3
sec4: .5

Offline peranders

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Re: QRV-08 hum
« Reply #9 on: February 05, 2011, 09:40:55 PM »
Do you have two primary windings?
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Offline CapRock

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Re: QRV-08 hum
« Reply #10 on: February 05, 2011, 10:54:13 PM »
I believe so.  I used the exact ones from your bill of materials.  both transformers primary 1 was .2V, and both primary 2 were 119.1V.  Am I measuring something wrong? I cant find a data sheet for these transformers.  Hahn BV EI 382 1194 are what I am using.

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Re: QRV-08 hum
« Reply #11 on: February 05, 2011, 10:58:00 PM »
My transformer has only one primary winding and there are also only two holes in the pcb.
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Offline CapRock

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Re: QRV-08 hum
« Reply #12 on: February 06, 2011, 12:45:07 AM »
ok, mine is mounted on the PCB so it is only one primary then.  The pole that is pre varistor is 119.1 on both transformers, the pole that is post varistor is .2 on both transformers.

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Re: QRV-08 hum
« Reply #13 on: February 07, 2011, 06:37:51 PM »
You should have 115 VAC across the varistor and also at each transformer. Personally I'll doubt that you can use 230/40 transformer. You should have 24 V.
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Offline CapRock

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Re: QRV-08 hum
« Reply #14 on: February 08, 2011, 04:42:38 AM »
Ok do you know of a suitable replacement if I can desolder them from the board?  Something that would fit in the same holes would be great but mounting it to the case is ok too. thanks