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PostPosted: Wed Feb 01, 2017 11:27 am 
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Joined: Sun Oct 16, 2016 10:27 pm
Posts: 2
Hi just finished my first build.
18w sIII with VRM
Everything is perfect, sounds better that i could ever imagine.
The only thing is the Voltage.

If i check the voltage chart i am off all the way.
The v3 PI is the weirdest one.
Is it normal or there is something really wrong with my amp?

Thanks!

V1: Pin1: 155, i have 128. Pin 3: 1.0 - 0.89 Pin6: 155 - 127 Pin8: 1.0 - 0.82

V2: Pin1: 180 - 163 Pin3: 1.5 - 1.5 Pin6:272 - 244 Pin8: 180 - 166

V3: Pin1: 220 - 181 Pin2: 52 - 34 Pin3: 75- 72 Pin6: 217 - 183 Pin7: 62 - 35 Pin8: 75 - 73

V4: Pin3: 12 - 11.9 Pin7: 345 - 330 Pin9: 340 - 319

V5: Pin3: 12 - 11.9 Pin7: 345 -329 Pin9: 340 -317


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PostPosted: Sat Feb 04, 2017 3:42 pm 
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Joined: Wed Feb 11, 2015 5:55 pm
Posts: 17
Location: frozen northern Minnesota
it looks like the activity on the forum has been really low so don't get upset with no one giving any advice or possible issues to look for. sometimes everyone gets busy and it can be a few days before help comes. The first thing you will hear is pictures always help, maybe what tube manufacturers and type, they can have an affect on your voltages. Other peoples build have had a little different voltages than what is listed so I would not get too hung up on your numbers. V3 is a little low and it sticks out like you say. check your wires and resistor values are all correct. I had lower voltages on my build for a lot of the numbers. I found others did too. these are average voltage numbers figures, using a certain manufacturer and type tubes. I found just like the sound changes, the voltages change with nos tubes and new tubes and from different manufacturers. When you use different types of rectifiers tubes from different manufactures is one example or 12au7 instead of a 12ax7. I also found as you put hours on your amp the numbers will change, tubes wear out parts break in. There is a lot of really knowledgeable amp people on this site so help will come. They probably will know right where to look. again pictures will be the first thing they ask for. it is great that you got your amp done and looking for issues will teach you even more. Cheers


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PostPosted: Sat Feb 04, 2017 10:07 pm 
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Joined: Sat Dec 04, 2010 3:42 pm
Posts: 519
Location: Qualicum Beach, BC
Sounds like things are working pretty well. The B+ is a bit low compared with the voltages on the schematic. What do the following voltages measure with the VRM up full:
Incoming line voltage (AC, live to neutral)
Pin 1 of V6 (AC)
Pin 7 of V6 (AC)
Pin 3 of V6
Input to VRM
Output of VRM
Center tap primary side of output transformer
Positive terminal of C14
Positive terminal of C13
Positive terminal of C11
Positive terminal of C12


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PostPosted: Sat Feb 04, 2017 11:13 pm 
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Joined: Sun Oct 16, 2016 10:27 pm
Posts: 2
Thanks!

Bear with me.
First build and didn't even ever solder nothing before and did not know what a resistance was.
Learned with this project.
Rectifier and power tubes are JJ's Preamp are V1 Tung Sol V2 and V3 EH.
PI Values are Top One: 57.9k - Right: 510k - Middle: 800 - Left: 510k

Image


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