Issues with Crack after speedball install

[crochese]

I recently installed the Speedball on a well functioning Crack and have run into a couple of new issues:

• I get ringing/microphonics when I touch or tap the Crack
• I've gotten a few large pops. Mainly in the right ear
• I actually noticed a flash/spark in the 6080 the last time I heard a pop

I've gone through a rechecked everything. All LEDs, resistance and voltage measurements are within the appropriate range. The only things that are the least bit suspicious are:

• I do see the voltage at the headphone out spike a little above the 20V that is specified in the Speedball manual, but it's hard to catch since my DMM is slow. How high is too high here?
• Pins 7,9 don't show a reading when doing resistance check. I was thinking this is expected because now the path to ground is through the new transistors vs. a resistor in the base crack. I may be wrong though.
• Pin 13 starts in the Megohm range then counts down, then when it gets to about 1Mohm, it drops to the low kohms and counts up to 270k. It did this both before and after the change. I reflowed those joints (12 and 13) because those were tricky and messy when I built the crack and still see the same thing

Anything I'm missing? Is it possible a tube crapped out when I installed speedball?

 

[Paul Birkeland]

I suspect that you have a flaky solder joint outside of the Speedball that go disturbed during the installation.  I would go back through the amp and reheat all of your solder joints.

-PB

 

[crochese]

Thanks. Will do.

Can you confirm my suspicion about 7 and 9? Should I be getting some kind of resistance reading at those two? My original statement below:

"Pins 7,9 don't show a reading when doing resistance check. I was thinking this is expected because now the path to ground is through the new transistors vs. a resistor in the base crack. I may be wrong though."

Also, any guidance on how high is too high for the voltage rise on the tip or ring terminal should be? The manual says "It could climb briefly to about 20 volts and then drop to zero. If it climbs much higher and/or does not reduce to zero do not plug in headphones until you have worked out the issue and the voltage drops to zero". In that statement, it says "much higher". Is 30 much higher? 40?

 

[Paul Birkeland]

If the voltage never goes back down to 0V, then you have a problem.  Otherwise, you can ignore the tip and ring voltage.

The resistances at 7 and 9 do change from the Speedball installation, which is why there are no resistance checks in the Speedball manual.

-PB

 

[crochese]

I finally got around to reheating everything and also replaced a wire that had a burnt spot (likely from the iron inadvertently resting against it when I was soldering for the speedball) on the insulation.

I listened for a few minutes and noticed a bit of scratchiness, but things were mostly cleaned up. However, when I turned it up a little louder, I got another one of those very loud pops in the left channel.

Any more ideas? If you think it's still a bad solder joint, can you help me narrow it down to the connections that handle the signal path for the left channel? I couldn't tell from the schematic and that would at least allow me to focus the rework a little better. Pins 2,4,6, 8 and the tube pins are hard to get to with the speedball so I don't want to poke around more than I need to and risk more damage.

 

[Paul Birkeland]

Try taking a wood chopstick and poking at every connection with a pair of junk headphones on your head.  When you find the culprit, it will make a pop for you.

 

[adydula]

I had a loid popping noise on one channel as well a long time ago....it happened several weeks of flawless operation.

It turned out to be a cold solder joint on one of the pins of the smaller signal tube. One of the leds would go on and off as the loud pop occurred, I forget the pin number but it was one like 7 or 8....I would check and reheat all the pins on this smaller tube socket.

Good Luck
Alex

 

[crochese]

Thanks for the tip on the small tube socket. I'll take a look next chance I get.

However, I think at least one problem could be the final filter cap on the power supply (between pins 12/13). It wouldn't quite explain why I get microphonic/ringing in one ear, but when I tap the top end of it I do get distortion. They now are including taller Nichicon caps in the kits (they look different than the pics in the manual) and it rubs against the side of the wood base. I'm not sure if that causes anything, but I can definitely tell it's rubbing, because if I lift it gently out of the base while it's on, I get a bunch of static. I'm guessing that's coming from that cap.

 

[Doc B]

It's not coming from the cap itself. It's coming from the bad solder joint on the cap lead.

 

[crochese]

Alright, seems like I'm almost there. I completely redid 12, 13, and 14. No noise or anything from there any more. I have not seen or heard a single pop/spark/etc. in quite a while. I'll keep my eye on it, but so far so good.

However, I still hear that ringing sound. Here's a little more detail. If I knock on the desk that the crack is sitting on or even type on the keyboard on the desk while no music is playing, I can hear ringing in phones. Sometimes it's limited to the right, but sometimes the left. It sounds similar to making a wineglass ring by rubbing the rim. Sometimes it will hang around for a while, but sometimes it will die out fairly quickly. It's more pronounced if I tap the volume knob, headphone jack, or 12au7. I can jiggle the 12au7 in the socket a bit and that will sometimes quiet it down for a while and make it a bit less sensitive to tapping.

Is this still seeming like a bad connection/solder joint problem? or is a bad tube possible? I'll repair anything I need to in the circuit, but am trying to avoid excessing poking around and potentially causing further damage.

 

[Paul Birkeland]

Ringing is a little bit of tube microphonics, it isn't harmful and can be very common on certain types of tubes.