Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: Twodawgzz on August 09, 2020, 12:39:34 PM
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Getting plenty frustrated. A1, A4 voltage reading was fine. D1, D4 reading was zero. Checked all solder joints and added solder to a couple. D1, D4 reading was fine. Moved chassis to frame and turned on. Wouldn't play and only one 2A3 heated up. Back to the table. Rechecked everything about 6 times and can't get any voltage reading from D1, D4. Stuck at this point with no idea what to do next while enjoying great sound from my Transcendent Sound amplifier.
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Can you post some photos of your installation?
Definitely do not try to listen to an amp that doesn't pass its voltage checks!
There are many things that could cause 0V related to the DC filament upgrade board. On the offending side, I would measure the AC voltage at the input terminals (that connect down to the power transformer), then measure the DC voltage at the output terminals (that go to the socket).
If you have one backwards cap or diode, that would cause this problem. If you have a broken wire, that would also cause this problem. A bad solder joint on the filament filter choke on the board would also cause this problem.
Visually, be sure everything on that board is consistent between sides.
-PB
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Here is a picture of the installation.
https://drive.google.com/file/d/1X5eeqg2mzomftPA2cHkC1ibyJX8eyWnh/view?usp=sharing
I just checked AC and DC voltages on the DC filament upgrade board. A, which was giving good voltage readings, read AC 3.24 and DC 2.99. D, which gave no voltage readings, read AC 3.35 and DC 0.
Any suggestions as to what to look for next?
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I would pop both wires out of the "DC" side of the board, unscrew the board, lift it up, then post a photo or two of the bottom.
Having proper ~3V AC at the input and 0V DC at the output would mean a short dragging the output down (unlikely) or something not well soldered on the bottom of the board.
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Looking at the photo the right side DC out looks as though the POS + terminal is not properly soldered, flow it out and see if that solves your problem.
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AB2KH might have found your trouble spot. You can try that first and if it doesn't work you can still pop those wires out and check underneath.
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Flowing solder at the DC Pos + terminal did not fix the problem.
Here are photos of the underside of the DC Filament board and the wiring. Anything see anything suspect?
https://drive.google.com/file/d/1iGEWe-dMyxuyYqRGlYJwTNxcnqfgc3CB/view?usp=sharing
https://drive.google.com/file/d/1nnVe9Tbky1WKv7yeMpQmsXBqhI48W3pD/view?usp=sharing
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You can apply a whole lot more heat to those solder joints on the bottom of that board. This is especially true for the choke and diode solder joints.
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You can see how the solder didn't flow to the bottom of the PCB around the green wires. That is a sign of not enough heat. It is very likely that some of the other joints have the same problem. Apply more heat until you see the solder flow and get sucked in. At first the solder just sits there as you reheat the joint and then most of it seems to disappear. Now you have a good joint. That change is very visible to someone with young eyes and to older eyes with good light and magnification.
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Okay, I flowed more solder onto the choke, diode, and DC joints. I now get voltage readings for AC and DC, but they're outside of the ranges in the instructions.
Voltages are supposed to read between 2.375 - 2.625.
My AC voltages are both 3.19. My DC voltages are 2.86 and 2.88.
Is this okay? Or do I need to swap out resistors as mentioned in instructions?
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With one probe on A1 and one probe on A4, what DC voltage do you get?
With one probe on D1 and one probe on D4, what DC voltage do you get?
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Oh yeah, duh.
Voltage readings were 2.49 for A1/A4 and 2.54 for D1/D4. So I'm good to go.
Thank you so much to Paul Birkeland, grufti, and AB2KH for your help. I'm really appreciating how a solder joint must be hot hot hot and substantial.
Now on to the next upgrade.
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The tough part to learn is how much heat some of these components take. Something like our little HLMP diodes have no mass to them and very little metal to draw heat away from the solder joint, so they can be soldered in a few seconds. Something like those filament chokes on that PC board have thick wires winding through them sitting on top of a metal core that will also tend to soak up some heat, so it is just more difficult to get the joint up to temperature because you are fighting the parts themselves. This effect is amplified if you're using an iron instead of a station, as a soldering station can just add more power as the tip of the iron requires it.
In any case, I'm glad you got things up and running!
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Hooked everything up after voltage readings were correct. Now I get sound out of only one speaker. Same thing when I switch cables, switch L&R inputs (1, 2, or 3), switch L&R outputs on my preamp, and change sources.
Any clues as to where to look for the problem?
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Check your DC voltages in the kit.
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All voltages and resistance levels match up with specs. Could a component be faulty? When I built my Crack headphone amp, it came with a dead tube (I don't remember which one, but I think it was the 12AU7).
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It's likely a loose connection, maybe even something as simple as a loose speaker wire.
You can swap the 2A3 tubes from side to side and the 12AT7s from side to side to rule them out.
Actual components like resistors, transistors, and capacitors will tend to produce wildly off DC voltages and smoke when they fail, so you definitely do not want to start pulling parts because you think one is bad. This kind of effort will generally make more problems that also need to be solved.
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Swapped tubes and that didn't change anything, so tubes are fine.
Next step was to flip the chassis over and poke around with a wooden skewer to hopefully find a poor connection.
When I flipped the chassis over and turned everything on, the problem was gone, and the amplifier played both channels just fine. Then I flipped it back upright, and everything was still fine.
So I guess I'll proceed with the next upgrade and look for a bad connection later if the problem resurfaces.
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Did you poke around with the chopstick even though it was working? That might save you from having to do this again when the problem resurfaces
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Poked around and found the intermittent contact at C3. Probably needs to be resoldered.
Thanks again for the help everyone.