Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: Jimb0 on July 31, 2019, 12:31:41 PM
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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
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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.
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I rewired it back to 120v to retest the voltages. Everything checked out normal. Wired to 120V, pin 9 read 2 or 3 volts
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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?
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That's in the 120V configuration. I'm going to try the 220V configuration today and check it again and post my readings
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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
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Can you do the test on page 35 and let us know what you find?
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4v at 7 and 9
103v at 11 and 12
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What is your incoming AC line voltage?
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120v
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OK, so why are you wiring your amp for 220V of incoming voltage?
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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
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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.
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Thank you Paul. I will look to get one
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I was able to test it on the step-up transformer and everything checked out fine. Thanks for the help as always Paul!
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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?
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What are you using for a step-up device? What are you using for a source?
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I'm using a Seyas 120v to 220v 500w step up converter. Source is a Schiit Modi Multibit hooked up to my desktop
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Try using your phone with a 1/8" to RCA cable as the source to see if the hum goes away.
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tested it on my phone but still having the same issue
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I also want to mention that I went ahead and rewired it back to 120v a few hours ago and tested it with my headphones. I was getting a hum as well.
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Are the voltages still OK? Is the hum in both channels?
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Rechecked the voltages, everything seems okay. Could it just be a cold solder joint? I'm resoldering any suspect joints right now
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Rechecked it after resoldering the joints. Still getting the hum. The hum increases when I raise the volume as well. It is in both channels.
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If you have no hum with the pot all the way down, but hum with the pot all the way up, I would be looking at the grounding wires around your RCA jacks, and ultimately I would check on the grounding connections from the IEC power entry module.
Ultimately you could simply have a wire that has broken in the process of rewiring the power transformer.
-PB
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PB,
The hum is there as soon as I turn on the amp. It then gets louder when the headphones receive the signal from the amp.
Resoldered all the grounding wires on the RCA jacks, even tried replacing the wire from the IEC power entry to terminal 13 on the transformer.
There's a hum even with nothing plugged into the RCA, it's immediate as soon as I turn the amp on.
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You definitely have a loose wire, broken wire, or something not well connected. If it's there right when the amp is on, then I would suspect some kind of issue around the H terminals as a strong possibility.
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Paul,
I carefully inspected and resoldered almost every wire on the amp, paying close attention to the ones on the IEC power entry module and H terminals and I'm still getting noise. Is it possible there is another reason for the buzz, possibly one of the tubes has gone bad? I remember having a similar issue with a Crack when I was removing and reinserting the tubes several times. Could this be it? Is there anyway to test it?
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One of the tubes won't make both channels hum. You could also double check the resistance checks to see if anything looks odd there. You could also get hum if a power supply cap became disconnected, but in order for that to happen in both channels, you would also see improper B+ voltage.