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Old 24th April 2011, 11:20 AM   #1521
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Richard Murdey
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cc. email, posted here since others probably have the same problem:

See page 9 of the catalog.

For 115V nominal:

Primary
AC live: black, violet
AC neutral: yellow, red

Secondary
to ~ of first rectifier: green, red
to ~ of second rectifier: brown, blue

The voltages wont measure correctly until you actually connect to the VSPS. When you do, you can expect V++ to be about 17 V and V-- to be about -17 V.

Rest of the connections as per the guide.
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Old 24th April 2011, 10:20 PM   #1522
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Quote:
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...

I will go through the components on that board tomorrow to make sure nothing died from the first time I played and both channels played.

...
I checked all the components visually to make sure nothing was installed incorrectly and double checked against the working board. Everything *looks* correctly installed.

The only difference between the boards was that I ran out of prp 68k 1/4w resistors for R19/20 and used takman carbon film 68k 1/4w instead. You can tell because the takmans are pink with regular resistor color codes. I will replace them when I get to order more prp's.

The board that doesn't work is the one closest to the connectors in the photo (the one with the takman's).

It is getting input power.

Are there any key test points where I could check in the pcb to isolate the problem?

Thanks again.
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Old 25th April 2011, 04:01 AM   #1523
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From the photo I can see everything looks quite neat and tidy, with no obvious problems.

Try the obvious: switch the phono cable R and L channel, to confirm the problem is not upstream.

Then confirm that power has reached the op amp socket (pin 1 and pin 7). About 10V typically.

Then replace or switch the op amp.

If the op amp is working and powered, the problem must be a signal connection inside the VSPS box or a bad solder joint on the board, or, unlikely but possible, an open circuit component in the signal path. C3 for example got smoked with you soldered it in place.

Using the multimeter, test for continuity all along the path from the input RCA to the op amp socket, and along the output path on both sides of the capacitor.
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Old 26th April 2011, 06:23 AM   #1524
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Quote:
Originally Posted by rjm View Post
Try the obvious: switch the phono cable R and L channel, to confirm the problem is not upstream.
Connected the vsps to the amp directly and it's the vsps.

Quote:
Originally Posted by rjm View Post
Then confirm that power has reached the op amp socket (pin 1 and pin 7). About 10V typically.

Then replace or switch the op amp.

If the op amp is working and powered, the problem must be a signal connection inside the VSPS box or a bad solder joint on the board, or, unlikely but possible, an open circuit component in the signal path. C3 for example got smoked with you soldered it in place.

Using the multimeter, test for continuity all along the path from the input RCA to the op amp socket, and along the output path on both sides of the capacitor.
Before I even attempted to check the opamp I checked the resistors to make sure they were all ok. On the bad board, I can't get resistance from R1, even if I put the multimeter leads on the resistor legs. The good board I get 46.8k. Thinking the resistor was bad I took it out, measured it and it measures ok!

I put it back in and can't get a reading, meter just shows 0.000 either on the upper, lower parts of the hole or on the legs of the resistor. R2, R3 and R7 around it measure correctly... R1 on the good board measures ok.

I checked the opamp between legs 1 (trim offset) and 7 (vc+) and I get 0.5vdc on both opamps. I think I misunderstood what you wanted me to measure...

Thanks again.
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Old 26th April 2011, 11:34 AM   #1525
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Quote:
Originally Posted by palmito View Post
Connected the vsps to the amp directly and it's the vsps.
I was referring to the connection from the turntable to the VSPS, not the VSPS to the amp.



Quote:
Originally Posted by palmito View Post
Before I even attempted to check the opamp I checked the resistors to make sure they were all ok.
I hope the VSPS was unplugged and fully powered down when you were doing those measurements. Otherwise it's all null and void.

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Originally Posted by palmito View Post
I checked the opamp between legs 1 (trim offset) and 7 (vc+) and I get 0.5vdc on both opamps.
Sorry, pin 4 and pin 7. pin 4 is V- pin 7 is V+. Remove the op amp from the socket and power up the VSPS to make the voltage measurements. Black test lead to COM/ground.
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Old 26th April 2011, 12:31 PM   #1526
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Quote:
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I was referring to the connection from the turntable to the VSPS, not the VSPS to the amp.
Sorry, I did those too but forgot to mention it. The turntable plays fine (both channels) through my preamp using the preamp's phono stage.


Quote:
Originally Posted by rjm View Post
I hope the VSPS was unplugged and fully powered down when you were doing those measurements. Otherwise it's all null and void.
Yes it was.

Quote:
Originally Posted by rjm View Post
Sorry, pin 4 and pin 7. pin 4 is V- pin 7 is V+. Remove the op amp from the socket and power up the VSPS to make the voltage measurements. Black test lead to COM/ground.
Will do tonight when I get home.

Any idea why R1 would not give me a valid resistance when installed?

I've just come to realize that anyone who sells pcb's/kits and gives this kind of support over the forum/email must do it because they love it. Because by now, if you pay yourself by the consulting hour, this would've have wiped out any profits from the sale of the pcb/parts... Your help it very much appreciated. Thanks again.
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Old 27th April 2011, 12:26 AM   #1527
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Quote:
Originally Posted by rjm View Post
ISorry, pin 4 and pin 7. pin 4 is V- pin 7 is V+. Remove the op amp from the socket and power up the VSPS to make the voltage measurements. Black test lead to COM/ground.
Pin 7 (+vcc) & pin 4 (-vcc) with op amp removed using xlr connector's common:

Good board:
pin 7: -7.54v
pin 4: 15.83v

Bad board:
pin 7: 15.84v
pin 4: -7.97v
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Old 27th April 2011, 12:52 AM   #1528
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Seems like you have voltages the wrong way around. Could it be that your Q1 and Q2 are swapped or reversed?

Last edited by woodturner-fran; 27th April 2011 at 12:57 AM.
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Old 27th April 2011, 03:13 AM   #1529
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Originally Posted by woodturner-fran View Post
Seems like you have voltages the wrong way around. Could it be that your Q1 and Q2 are swapped or reversed?
No, but could it be that I wired the input RCAs in reverse? Thanks for the suggestion woodturner-fran, I went back to look at Q1/2 at your suggestion and noticed that the input rca's had their +/- reversed... Apparently yellow and black wires do not offer enough color contrast for my brain to process into +/- . The outputs were wired correctly. Sorry to waste so many nice people's time.

The op amps now have the right polarity, but the voltages are still 15.8v for one and 7.6/9v for the other pin. Does this qualify as "around 10v" or do I still have something wrong?

I only listened to one song, but it sounds very good (in stereo no less...).

Thanks again for your help.
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Old 27th April 2011, 06:23 AM   #1530
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I'm glad you found the problem with the RCA input wiring, but you are not out of the woods yet.

With respect to COM, the V+ and V- measured at the op amp pins should be about 10 V, let's say 8-10 V, while the V++ and V--, measured for example at the point where the power supply connects to the board, should be about 16-17 V.

As Fran suggested, you have a problem with the transistors Q1 and Q2: they are either reversed (BD135 for BD136 position), reversed (rotated 180 deg so BCE instead of ECB), or blown.

I think there is a typo in what you wrote earlier and you probably have

Good board:
pin 7: 15.83v
pin 4: -7.54v

Bad board:
pin 7: 15.84v
pin 4: -7.97v

This means the positive rail (V++) is not being regulated by the X-reg but passed as-is to the op amp. The negative rail appears to be fine. So the most likely thing is you have Q1 reversed. (pin 1 into the base instead of the emitter, BCE instead of ECB)
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Last edited by rjm; 27th April 2011 at 06:25 AM.
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