Voltages 1/2 [resolved]

[hbonilla]

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

[fullheadofnothing]

Were your power transformer secondary voltages (p.31-32) correct?

[Natural Sound]

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.

[hbonilla]

  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

[Paul Joppa]

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 Birkeland]

What is the AC voltage between terminals A1 and A4? (Put one probe on each terminal to measure)

[hbonilla]

AC Voltage between a1 and a4 is 2.0V

Does this make any sense?

[Paul Birkeland]

What's your line voltage?

[hbonilla]

122.5 V AC

[Paul Birkeland]

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

[hbonilla]

Hi, sorry for my late reply. Here are the picture please let me know if you see something.

Thanks

Hector

[Paul Birkeland]

That all looks correct.  How about a photo of the terminal strip with the UF4007 diodes and pair of caps.

-PB

[hbonilla]

Thanks

[Paul Birkeland]

What AC voltage do you have between terminals 19 and 20 on the power transformer?

[hbonilla]

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.