Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: kjwcb2 on June 14, 2020, 06:49:06 AM
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Hi! I have a reading of 124.9DCV at 1A on the C4S board. 1B is fine at 220.2VDC.
Any clue what might be causing this? Presumably an issue with the shunt regulator board.
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Is this an Eros 1 or Eros 2? Is this the board above the D socket?
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It's an Eros 2. Yes, it's above the D scoket.
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IA and IB are wired together with a piece of wire.
Either your piece of wire is broken, or it isn't connected between those terminals.
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I've got the jumper between 1A and 1B. It seems to be fine, but I'll replace it anyway and see what happens.
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You can't have a wire between IA and IB and have a difference in voltage of 100+ V. The wire has to be broken, out of place, or poorly soldered.
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Hi, I replaced the wire between 1A and 1B. No real difference. The readings now are: 1A - 148VDC / 1B - 214VDC. A 65VDC difference +/-
Interestingly, the reading at the MJE5731A transistor next to 1A is 219.8VDC, compared with 152VDC at the MJE5731A next to 1B.
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You can't have a difference in voltage between IA and IB with a piece of wire connected. This is a physical impossibility. 100V across a piece of wire like that would dissipate thousands of watts and the copper would evaporate and possibly explode loudly in the process (though the power transformer wouldn't support this).
Can you post some build photos?
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What photos would you like?
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The top and bottom of the C4S board above the D socket.
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Here they are.
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Are they clear enough? I removed the heatsinks to test the transistor voltages. The board is a bit messy in places from all the soldering and desoldering.
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What type of solder are you using, what wattage is your soldering iron (is it adjustable), and are you using any additional flux or anything?
What DC resistance do you get between OA and OB with your meter?
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I'm using the best solder I can find locally. I don't think it's anything special but I've made 3-4 amp builds with it without any problem. I've got a Hakko soldering station - adjustable - set at 250 degrees.
The resistance between OA and OB is 441.4 KΩ. DC = 0.
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That's with the board disconnected.
Sorry for spoiling your Sunday!
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What's the resistance between IA and IB? Can you show me a photo of your solder? If you have a Hakko FX-888, set it to 899 degrees (that's where I have mine set). Do note that with this station, it is incredibly!!!! easy to think you are turning the temperature up and actually be calibrating the temperature so that the station thinks that wherever you have the iron set is whatever temperature you are setting on the screen.
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Your 250C setting on the Hakko is way too low. That's only about 480F for the US readers. PaulB's temperature is nearly twice that, about 480C. I find that a bit too high for work on a printed circuit board where solder pads can burn off, but he's the expert. I personally solder at about 400C - 420C when I work on PCB's. You should probably wash the circuit board with alcohol when you're done soldering.
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Yes, I wouldn't solder that high on a single sided board with no through hole plating, but our boards hold up OK at those temps.
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It's all about the dwell time of the tip on the work. If you have been doing boards for a number of years you tend to work quickly and only hold the tip on the pad for a second or two, You can get away with a pretty high temp that way.
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The short dwell time is why hot is good. The components actually heat up less that way, but only, if the dwell time is really short.