Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: DustDoggy on April 30, 2022, 01:31:11 PM
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Hey so while doing the voltage check on my stereomour Im pretty sure I shorted the probe across terminal 31 and 32. There was a spark and a pop. All the voltages until then where good. Now I get 143 VDC on terminal 31. Terminals 34,36,37,39,40 all now read 0. Looks like the 2a3 tubes no longer glow but its hard to tell with how bright it is right now. I really hope the damage isn't too bad and It's fixable. Thanks.
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Is the fuse still intact?
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Yup it looks just fine.
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Can you post some pics of your build? I would wait for all the voltage to bleed down out of the kit and then check the DC resistance of your 120 ohm resistors in your power supply.
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Let me know if ya need a closer view of anything.
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Which terminals would I find the 120 ohm resistors attached?
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Which terminals would I find the 120 ohm resistors attached?
This information is readily available by searching the PDF of the manual.
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Under the high voltage power supply section I see 130ohm resistors. Are we talking about those ones?
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Pretty hard to get in there with the capacitors in the way but it seems the two on the left measure correctly but the two on the right measure overload on my meter.
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Yes, you're correct they are 130 not 120.
What DC voltage do you get if you measure between 41 and 45?
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I'm reading 209 Dc Volts between terminals 41 and 45.
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How about the AC voltage between 19 and 20 on the power transformer terminals?
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It is 161 AC Volts between 19 and 20 on the power transformer.
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There's a loose connection on that 41-45 terminal strip somewhere that is causing your problems.
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I checked and reflowed all of the connections on the 41-45 strip and the problem persists. Is it worth ordering some of those 130ohm 2W resistors and replacing the ones that measure incorrectly?
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No, the 41-45 terminal strip is a voltage doubler that works off the AC winding of the power transformer. You have the correct AC voltage coming out of the power transformer but you don't have the appropriate DC voltage appearing at that terminal strip. Since you have about half of what I would expect, you are inadvertently half-wave rectifying what's coming out of the PT rather than full wave doubling it. Most of the time this happens from a loose connection not allowing everything to conduct properly when it's supposed to.
Beyond that you also have a distribution problem beyond this terminal strip, but you need to address the issue above before looking for other problems.
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Just thought I would post an update. After much reflowing, prodding, reflowing and head scratching I wasn't really getting anywhere. I then read a thread where someone had the same problem and decided I would replace the 130ohm 2W resistors. All voltage checks where spot on and the amp is working perfectly and sounds amazing! I'm excited to start the reduction build and get the vinyl spinning.
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Just wondering, was that thread from me? I got my amp working last weekend, and it has been amazing. Big thank you to PB because I would have not been able to do it without his help.
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I hadn't seen that part of your thread yet actually. I did come across this thread though https://forum.bottlehead.com/index.php?topic=8730.0 Glad ya got it up and running!