Crack with Speedball - loud pop and damaged driver [FIXED]

[Lowercase]

Hi guys! I just finished building a Crack with the speedball upgrade. I had an absolute blast building it! Still waiting on some supplies to finish the base. However, the other night when I put on my headphones, currently use a Sony MDR-V6 and waiting to take delivery of a Sennheiser HD6XX. About fifteen seconds after turning it on the right channel made a loud pop. Of course I had a nice ringing in my ear for 30 seconds or so after. Immediately turned everything off and waited till morning to look over everything. All voltages within normal range and did a quick chopstick test to see if anything was amiss. No dice! Interesting thing was a similar pop happened before the one that toasted the driver on my headphone. Shortly after startup and in the right channel, but didn’t think anything of it at the time, it was pretty quiet.

Could this be a result of a bad tube or my shoddy soldering? Did a search through the forum and didn’t see anything similar to my situation. Obviously want to be sure everything is functioning 100% before plugging in the right headphones. The Crack before the speedball upgrade was working just fine too and all checks passed with flying colors. Also, all LEDs are on. Thanks and let me know if I can provide more details.

Update: New tube and all is working as it should be. No more sparks or pops and sounds incredible!

[Paul Birkeland]

Could you post some build photos?  Often times stuff like this is related to a soldering issue.

-PB

[Lowercase]

HiPaul,

Thanks for helping out! Here are some images below. Let me know if you want something more specific not listed here.

Sorry having issues embedding images so here is a gallery:

Remove_https://imgur.com/a/fEcoZ2l

Remove the “Remove_”

[Paul Birkeland]

The junction of the 2.49k resistor and the red wire on the headphone jack looks suspect. 

Terminal 7 does as well.

[Lowercase]

Thanks Paul, just reflowed Terminal 7 and all pins on the headphone jack, just in case.

REMOVE_https://imgur.com/NcKvQwJ

REMOVE_https://imgur.com/RH3HFKC

Any idea of what may have happened? Since you suspected the headphone jack connection could that have caused the driver to pop? My first though was a crossed wire, but I think I kept things fairly tidy. Nowhere near as good as some of these other builds I’ve seen. Almost makes me want to start all over!

[Paul Birkeland]

It sure sounds like a flaky solder connection.  A tube issue causing a pop should produce visible fireworks inside the 6080, and it shouldn't stop.  This kind of thing can happen when a 6080 gets gassy and stops working properly.  Beyond that, if the 100uF coupling cap on the right channel wasn't well connected (which includes all the connections between the octal socket and headphone jack), then it could cause a pop as it suddenly charges up. 

[Lowercase]

Thanks again Paul!

In addition to the reflows already done I cleaned up the wires a bit at the terminals and reflowed terminals 1-10. Fired it up and got the following voltages.

Big board
B+ 184.4
G 0
0A 105.5
0B 100.9

Small board
0A 65.7
0B 71.9

Is it normal for some variation in the reported voltages between A/B? Looks like it falls between specs listed, but didn’t know if it’s normal for one channel to be higher/lower. Also is it normal for some of the LEDs to be somewhat dim. The small board looks darker than the big board and the 9-pin socket.

Any other checks I should make before plugging in headphones again?

[Paul Birkeland]

Yes, that's normal.  The big PC board runs more current through the LED's (by necessity).  They should be about as bright as the two mounted to the 9 pin socket, while the four LEDs on the small PC board will be dimmer.

The wire that goes from B5 to B2 gets sort of close to B3.  You don't want those to touch!

[Lowercase]

Wiggled that wire away from B3! Thanks again, will do a test run soon before the good headphones arrive. Can’t wait to listen again! Even with the V6s I couldn’t believe how incredible this amp sounded. Looking forward to what the 650s will sounds like.

[Lowercase]

So I’m back a again with issues. Listening last night I noticed a brief arc in the 6080 tube with a quiet pop. Removed my nice headphones and when plugging in my cheaper headphones I noticed a pretty big arc inside the 6080. Figured maybe another reflow of joints was needed again so turned off and waited till the next day.

Fast forward to this morning. Reflowed some joints again and went back to testing. Noticed an arc again in the 6080 while plugging in the headphones back into the jack. Turned it off flipped it over everything looked good. Flipped it back over turned it on, success! But then thirty seconds in brief arc in the 6080 again, but this time popping the right driver again on my headphones similar to last time. Luckily they were not over my ears this time.

I will say during the period of the last reflow and yesterday evening, about two weeks, the amp performed flawlessly. Am I looking at another shoddy joint or something else?. Not sure what would have happened between the original issue and now. All voltages with the speedball are spot on too.

As always, really appreciate the help!

[Paul Birkeland]

Yes, shoddy joints.  The one that most people miss is where the black wires meet on the headphone jack.  It's very common to see one black wire there that's well soldered to the jack while the other isn't.

[Lowercase]

Hey Paul,

Thanks again for the quick reply. Here is another image of the jack again:

Remove_https://imgur.com/n8gFAAR

The joints were looking good after the first reflow but went ahead and reflowed and held for a bit.

Looking good? Like I said it looked about the same before reflow. I know this is the same spot as last time you pointed out as being a tricky spot too.

And just to confirm the black wire loops through all three jacks on the right side facing the connectors?

[Paul Birkeland]

If your soldering iron is adjustable, where do you have it set? If it's not adjustable, what wattage is the iron itself?  It may be that you just have cold joints, as those joints on the headphone jack look a little on the lumpy side, which is indicative of insufficient heat.

[Lowercase]

60 watt and set it to 400°. Max is 450°, I’ll reflow again or should I get something with a higher temp?

[Paul Birkeland]

Is that C or F?

450C should be hot enough to get good joints.