Is Doc a Saint or .... ??
- Thread starter ALL212
- Start date
Rocketman248
New member
I did have two minor issues while building it. The first was during the power supply tests. I kept getting around 3.5 volts on both the 6.3v pads and the 275v pads. I rechecked everything, reflowed every joint. Racked my brain for a while, and ended up just going to bed. I took a look at it the next morning, and realized I was trying to measure AC volts on DC test points. There's a slight typo in the manual on Page 38. On the second step from the bottom, it says "You should see around 6.3VAC on your meter." I was reading quickly, and it didn't even click in my head that everything else on that page, and even printed on the board said DC. There's a lot to be said for the whole "Looking at things with a fresh set of eyes" thing. :
The other issue is with the coarse attenuator. When I first finished it, all of the resistance and voltage checks were spot on, but I was only getting audio on the right side. It didn't change with volume, and it was the same on both inputs. I checked everything in the output path, touched up a few questionable solder joints, and tried swapping tubes. Still no joy. Then, while listening, and adjusting the coarse attenuator, the sound came back to both ears. That's when I discovered that there was a slight play in the shaft on that attenuator. Looking at it closely, the swiper on the top side of the switch moves with the shaft, and is likely losing contact when I wiggle the shaft. I tried tightening the contacts by pushing on them with a toothpick, but it didn't change anything. I'm not too worried about it though. If I move the knob slightly to the front of the chassis, it works just fine. Someday, I might look at replacing it, but I'm not in a hurry.
Aside from those two issues, it was a fairly easy build, and it sounds great! I hope you get yours working soon, ALL212!
The other issue is with the coarse attenuator. When I first finished it, all of the resistance and voltage checks were spot on, but I was only getting audio on the right side. It didn't change with volume, and it was the same on both inputs. I checked everything in the output path, touched up a few questionable solder joints, and tried swapping tubes. Still no joy. Then, while listening, and adjusting the coarse attenuator, the sound came back to both ears. That's when I discovered that there was a slight play in the shaft on that attenuator. Looking at it closely, the swiper on the top side of the switch moves with the shaft, and is likely losing contact when I wiggle the shaft. I tried tightening the contacts by pushing on them with a toothpick, but it didn't change anything. I'm not too worried about it though. If I move the knob slightly to the front of the chassis, it works just fine. Someday, I might look at replacing it, but I'm not in a hurry.
Aside from those two issues, it was a fairly easy build, and it sounds great! I hope you get yours working soon, ALL212!
Can you confirm that the R1 resistors on the offending side are in the correct places? They are pretty easy to swap, and can cause anomalies like this.ALL212 said:
Additionally, the center leg of those MJE5731A's can take a lot of heat to solder well. If one is not well soldered, you will also get this type of behavior. Shorts are another potential cause of this, and the most likely place for this would be on the solder joints for the PN2907 on the "B" portion of the high current C4S.
-PB
ALL212
New member
R1's are good, board completely reflowed, no shorts AT THE BOARD!
Just before putting it back I put the magnifier on the socket. I had a cutoff shorting 5 to 6.
I have the same results at the board after this but what may have died by shorting pins 5 and 6 at the socket?
Would I be safe by reversing the outside boards? Or could I blow something else up in the process?
Sneak peak:
Just before putting it back I put the magnifier on the socket. I had a cutoff shorting 5 to 6.
I have the same results at the board after this but what may have died by shorting pins 5 and 6 at the socket?
Would I be safe by reversing the outside boards? Or could I blow something else up in the process?
Sneak peak:
ALL212
New member
Thanks to the BH crew all is well - or almost. The fine volume control is one click off so I have max volume at -7.5 position and no volume change at the 0. Fixable but I'm almost liking it. I can be at minimum attenuation on fine and with one click go to the maximum attenuation. Got to spend some time thinking through this...
Converted my MrSpeakers Alpha Prime's to a balanced connection. Almost did the HD650's but then I wouldn't be able to play them on the B.A.Crack. With the S.E.X. going to the office I don't have anything else to play the MrSpeakers (low impedance) on anyway. Not sure if there is any difference - maybe a bit more L/R separation but nothing major that I can hear.
I think that's the end of this story. But... Now that I've seen what BH can do with headphones I'm thinking of replacing the Reduction with an Eros.
Thanks BottleHead for another great amp!
Converted my MrSpeakers Alpha Prime's to a balanced connection. Almost did the HD650's but then I wouldn't be able to play them on the B.A.Crack. With the S.E.X. going to the office I don't have anything else to play the MrSpeakers (low impedance) on anyway. Not sure if there is any difference - maybe a bit more L/R separation but nothing major that I can hear.
I think that's the end of this story. But... Now that I've seen what BH can do with headphones I'm thinking of replacing the Reduction with an Eros.
Thanks BottleHead for another great amp!
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