Can't get Speedball to stay stable.

D

danosol

New member
Just went to Bottlehead today and got a new B board and the fixings and it was working fine when I left. I get it home and it works for about two songs and then I hear this static noise and swooshing.  So I lower the volume all the way and power down and the headphones get a loud pop.  The first time it did this the LED's on the B board stopped working.  I heated all the connections with the iron and thought i had it fixed the second time but the same static and swooshing.  This time when I turned it off I still got the pop but LED's are still on.

Help!
 
Triple check those 2.49K resistors on the headphone jack, just to be safe.

You could get popping and swooshing from something heating up and misbehaving, did any of this occur before installing the Speedball?  Knowing that Doc B. built the board (with a fresh tip in the iron I noticed), I might suspect a 12AU7 being a little fussy.  I'd recommend leaving the Crack on overnight with no headphones plugged in to let the tube cook a bit, that may end up remedying the problem on its own.

-PB
 
No it sounded great and no issues pre speedball, but I didn't have it that way for long.  I have no problem leaving it o over night but if the LED's go out on the B board and the amp is on all night will that be a problem?

Could a bad 12AU7 cause those issues?
 
Went back and checked the 2.4k resistors and noticed the LED's on the B board went out.  I powered down and reheated the two 2.4K resistors and when I powered the Crack back on the LED's were back on.

Went back and checked the LED's again and they were out on the B board again.  Powered it up a minute later and they went on again.  I think you are right.  Something is heating up and causing the LED's to go out.  But what?
 
Anyone out there?

Fired it up this morning and lights went on and out a few moments later.  I tried 2 other 12AU7 tubes and nothing different.

Help!
 
OK, this narrows the potential issues down to:

1.  LED connection/functionality (shouldn't be a problem since the amp was working pre-Speedball).
2.  A poor connection from the wire leaving the center lug of the volume control to that particular channel (worth double checking).
3.  Issues within the C4S itself.  I would quadruple check the ground connection to the board.
4.  Issues with the wire leaving the "O" pad on the PCB, and heading to the 12AU7 (same as #2, just give it a good look over).

You can always do the chopstick test, find a wood or all plastic poking implement, then poke each transistor, LED, resistor, and wire leaving the offending PC board while the amp is running and the LED's are out.  At some point, you will poke the right part and it will reveal itself as the problem.

-PB
 
Well I heated up the first LED again and pushed it a bit away from the board and they both lit up.  Gonna leave it on for a bit and see what happens and I'll report back.
 
2 plus hours of listening later and no dropouts.  Crossing fingers but I think getting the LED a bit off the board helped.  In the process of doing this I decided to rewire transformer terminal 4 to 22 and then move it back to terminal 14U.  In the process I accidentally burned a wire on the power socket (No Prob) when I went to put a new wire there it wouldn't take solder and I ended up melting the tab in to the socket a bit.  It all works, but would you guys sent me a new power socket.  I would sure appreciate it.
 
dan...

Hang in there.  Those LEDs are physically delicate but I soldered and resondered my old C4S board LEDs almost a dozen times, seriously.  I ended up putting in current HLPM 6000 LEDs which were swapped a number of times themselves.  My problem was I had the input and output wires swapped.

Just be patient.
 
Well after a day of not using the Crack I fired it up and the LED's went out again >:(.  This is getting old fast.  Super disappointing.  I just want to listen to some music!
 
It is probably worth rolling in a different 12AU7 if you have one.

You should also have a look at the 12AU7 itself, to see if one half of it goes dim when you're having your issue (half of the heater could be getting crusty once it's warmed up).

-PB
 
Just reheated the LED again and It's working, but for how long.  If you're looking from the back it seems to be the LED on the left cause when they are out the one the right is lit but very very dimly.
 
Ajay, if you could leave it with us for a day I'm sure we can carve out some bench time to go over it more rigorously and sort it out for you. Maybe the 2N2907 or an LED was stressed when the MJE350 was in backwards and is having some kind of intermittent issue or something. If that is the issue we can build up a new board and install it for you.
 
I'll see how this goes.  It's a bit expensive taking the ferry over.  You guys have been very generous however, and I appreciate that.  I think it may be the LED's but why would it work for a full day and all of a sudden stop.  I don't think it's the 12AU7 I tried another 12AU7 prior to this and it made no difference.  I also metered the transistors and they all tested OK.  I'm currently about a half an hour into the re-flow of solder on the LED that I think is the culprit so I'll be a bit more patient.
 
My hunch is that it may be a thermal issue. It might be that when the amp goes through a warm up and cool down cycle that a solder joint that looks good shifts ever so slightly and a connection is opened. Reflowing the joints on the C4S is indeed a good place to attack the problem. Luckily the components on the board are all pretty heat proof so you don't need to worry about reflowing the pads if necessary.

 
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