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Author Topic: Voltages 1/2 [resolved]  (Read 3288 times)

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Offline hbonilla

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Voltages 1/2 [resolved]
« on: October 17, 2015, 06:02:34 PM »
This is my first DIY amp.

I checked all the OHMs and everything seems ok. However, when I put voltage only the small bulbs light up and my measurements are exactly half the voltage in the manual. Any ideas?

Thanks

Hector
« Last Edit: January 12, 2016, 03:58:32 PM by Caucasian Blackplate »

Offline fullheadofnothing

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Re: Voltages 1/2
« Reply #1 on: October 17, 2015, 06:19:32 PM »
Were your power transformer secondary voltages (p.31-32) correct?
Joshua Harris

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Offline Natural Sound

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Re: Voltages 1/2
« Reply #2 on: October 18, 2015, 05:54:38 AM »
I agree with Josh. Sounds like you have the primary of the power transformer set for 220 but feeding it with 110. That would give you roughly half the voltage on the secondary.

Offline hbonilla

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Re: Voltages 1/2
« Reply #3 on: October 18, 2015, 03:04:02 PM »
 :) Thanks. I checked my wiring on  pages 28 and 29 and found a mistake. I had connected 2 to 48U rather than 3 to 48U. Connection is correct now but my readings are still exactly half of what they should be.

My input voltage is 122.5

I reviewed my notes and the Power Transformer Secondary test was on target +- 10%

Any other thoughts?

Thanks again
« Last Edit: October 18, 2015, 03:12:26 PM by hbonilla »

Offline Paul Joppa

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Re: Voltages 1/2
« Reply #4 on: October 18, 2015, 03:30:50 PM »
Look at the high-voltage rectifier connections (and orientation).

If you don't see anything there, somebody will get more meticulous once the work week begins. <eanwhile, it never hurts to re-flow all the solder connections, and that fixes more than half the problems...
Paul Joppa

Offline Paul Birkeland

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Re: Voltages 1/2
« Reply #5 on: October 19, 2015, 04:41:35 AM »
What is the AC voltage between terminals A1 and A4? (Put one probe on each terminal to measure)
Paul "PB" Birkeland

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Offline hbonilla

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Re: Voltages 1/2
« Reply #6 on: October 19, 2015, 09:31:33 AM »
AC Voltage between a1 and a4 is 2.0V

Does this make any sense?

« Last Edit: October 19, 2015, 05:30:32 PM by hbonilla »

Offline Paul Birkeland

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Re: Voltages 1/2
« Reply #7 on: October 19, 2015, 06:12:37 PM »
What's your line voltage?
Paul "PB" Birkeland

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Offline hbonilla

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Re: Voltages 1/2
« Reply #8 on: October 19, 2015, 06:50:08 PM »
122.5 V AC

Offline Paul Birkeland

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Re: Voltages 1/2
« Reply #9 on: October 20, 2015, 07:13:35 AM »
Can you post a photo of your mains wiring?

122V on 120V mains should give more than 2V.  I suppose it's also possible that your meter can't resolve the next digit, so if you had 2.4V, it might just say 2V.

-PB
Paul "PB" Birkeland

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Offline hbonilla

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Re: Voltages 1/2
« Reply #10 on: October 24, 2015, 06:46:56 AM »
Hi, sorry for my late reply. Here are the picture please let me know if you see something.

Thanks

Hector
« Last Edit: October 24, 2015, 06:56:45 AM by hbonilla »

Offline Paul Birkeland

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Re: Voltages 1/2
« Reply #11 on: October 24, 2015, 07:28:30 AM »
That all looks correct.  How about a photo of the terminal strip with the UF4007 diodes and pair of caps.

-PB
Paul "PB" Birkeland

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Offline hbonilla

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Re: Voltages 1/2
« Reply #12 on: October 24, 2015, 10:38:53 AM »
Thanks

Offline Paul Birkeland

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Re: Voltages 1/2
« Reply #13 on: October 24, 2015, 12:30:54 PM »
What AC voltage do you have between terminals 19 and 20 on the power transformer?
Paul "PB" Birkeland

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Offline hbonilla

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Re: Voltages 1/2
« Reply #14 on: October 24, 2015, 02:32:56 PM »
It is 161.7.

Thanks

Update Sunday Morning.

Yesterday I tracked back all my steps. I resoldered a few connections that I thought might be better and, voila, my numbers improved a lot. My only real problem now is number 7 which throws 407v rather than 170-230. I resoldered but to no avail.
« Last Edit: October 25, 2015, 07:13:24 AM by hbonilla »