120V to 220V higher readings, 2nd problem noticeable hum both channels

[Jimb0]

I assembled a S3X with C4S upgrade wired for 120V. All voltages checked out fine. However, when I modified it for 220V I am getting higher readings. I assume the voltages would be cut in half but a few of the terminals are now reading higher. Other terminals seem to be ok. Using 120V AC line voltage

2 is reading ~250V
OA and OB are reading ~250V

I resoldered all the wiring on the main transformer but still got the same readings

 

[Paul Birkeland]

These issues are not from your rewiring of the power transformer wiring unless you have many, many other voltages that are all out of whack.

What are you getting a terminals 3/17?

Can you carefully measure the DC voltage at pin 9 on each tube? 

It could also help if you posted photos of the build if the problem is not immediately apparent.

 

[Jimb0]

I rewired it back to 120v to retest the voltages. Everything checked out normal. Wired to 120V, pin 9 read 2 or 3 volts

 

[Jimb0]

-

 

[Jimb0]

-

 

[Paul Birkeland]

I rewired it back to 120v to retest the voltages. Everything checked out normal. Wired to 120V, pin 9 read 2 or 3 volts

Is that in the 220V configuration?

 

[Jimb0]

That's in the 120V configuration. I'm going to try the 220V configuration today and check it again and post my readings

 

[Jimb0]

Tested it on the 220v configuration again.

2  243v
3  3v
4  0v
5  0v
6  249v
7  263v
10 260v

Pin 9 A/B  2v

16  159v
17  4v
18  0v
19  0v
20  241v
21  261v
24  257v

H2, H5  +2v
H4, H7  -2v

 

[Paul Birkeland]

Can you do the test on page 35 and let us know what you find?

 

[Jimb0]

4v at 7 and 9
103v at 11 and 12

 

[Paul Birkeland]

What is your incoming AC line voltage?

 

[Jimb0]

120v

 

[Paul Birkeland]

OK, so why are you wiring your amp for 220V of incoming voltage? 

 

[Jimb0]

I built this for a customer who lives in the UK and don't have a step-up transformer to test it. I could get one if that's what I really need but I thought the voltages would come out lower not higher on some of the readings

 

[Paul Birkeland]

Yes, you need to use a step-up transformer to test the amp once you've wired it for 220V.  Without adequate heater voltage, the tubes won't conduct, so most of the voltage readings are pretty meaningless.

 

[Jimb0]

Thank you Paul. I will look to get one

 

[Jimb0]

I was able to test it on the step-up transformer and everything checked out fine. Thanks for the help as always Paul!

 

[Jimb0]

Hi Paul. I did not do a listening test on the 220v until now. I'm getting a hum on both channels. I was not getting a hum on the 120v configuration. Any thoughts why this is happening?

 

[Paul Birkeland]

What are you using for a step-up device? What are you using for a source?

 

[Jimb0]

I'm using a Seyas 120v to 220v 500w step up converter. Source is a Schiit Modi Multibit hooked up to my desktop