Problem with speedball upgrade

[xiawei]

Before the upgrade all readings were right and both LEDs (A3 and A8) lighted.

However, after the upgrade, the voltage reading of terminals 5 (-380mV) and 9 (50V) are not right. The rests are spot on. Also the LED connecting A3 doesn't light.

During the building of the speedball, the 3 pads of B+ that connects individually with 2U, the resistor and the other B+  are too close, during the soldering I wasn't sure if they touches each other. I assumed they were the same. And  I haven't tested how it sounds yet….

Thanks a lot for the help!

 

[Paul Birkeland]

During the building of the speedball, the 3 pads of B+ that connects individually with 2U, the resistor and the other B+  are too close,

The "I" and the "O" pads need to not be soldered together.

The "I" pads and the closest leg of R1 are all connected on the board, so that's not a problem.

The LED on A3 not lighting and 0V on T5 means that you need to reheat the center leg of the MJE350 on the right PC board.

 

[xiawei]

During the building of the speedball, the 3 pads of B+ that connects individually with 2U, the resistor and the other B+  are too close,

The "I" and the "O" pads need to not be soldered together.

Thanks for the quick reply!

What does 'The "I" and the "O" pads need to not be soldered together' mean?

 

[xiawei]

I just re-wet the middle foot of MJE350 but the A3 LED still does not light..

 

[xiawei]

Any ideas? Could be any defect parts?

 

[Grainger49]

The I and O pads are the input and output of the C4S board.  Having them soldered together jumpers around the whole board.

There are IA and IB, OA and OB solder pads marked on the top of all three boards.

 

[xiawei]

Is and Os are quite far, I didn't short cut between Is and Os. They were the 3 B+ pads that are too close and I was sure they was together.

Any ideas why the A3 LED doesn't light? Before speedball upgrade everything was fine. I double checked and found A2 touched A1 ,which I believe happened during I made spaces for the nylon standoffs. I separate them but everything stays the same, voltage readings and the non-lighting A3 LED.

Thanks a lot for the help!

 

[Paul Birkeland]

Any ideas why the A3 LED doesn't light?

A3 won't light if the board that feeds that half of the tube isn't functioning. 

0V out of the board generally means that parts aren't well soldered on that board.

-PB

 

[xiawei]

Any ideas why the A3 LED doesn't light?

A3 won't light if the board that feeds that half of the tube isn't functioning. 

0V out of the board generally means that parts aren't well soldered on that board.

-PB

Thanks! Although I doubt a bad solder could occur, I will re-do the solder connecting O pad to T5 and that connecting T5 to A2 after the work. Hope this is where the problem is..

 

[xiawei]

I re-solder every parts of the speedball and reconnect it with the amp. But the same problems remain.

The right channel sounds ok but the left hums with lots of noise, which changes little when I touch the aluminum plate. even more changes when I touch the small tube. Could it be a bad tube socket? The reason I'm saying this is A2 accidentally touched A1 when I turned it on the first time after the upgrade?

Please help! Really frustrated here.

Thanks

 

[Grainger49]

It is probably not a bad tube socket or a bad part (unless it was damaged in installation).

Most likely it is a problem with the ground.  Go to the Crack folder read and follow the sticky thread about checking the ground path.

 

[xiawei]

It is probably not a bad tube socket or a bad part (unless it was damaged in installation).

Most likely it is a problem with the ground.  Go to the Crack folder read and follow the sticky thread about checking the ground path.

It passed all ground tests. Could improper ground cause the A3 LED not to light? How to test the A3 pin is OK? Or maybe a broken LED?

My stock build that was sounding so good - and my work only turned it into something that doesn't work at all….

 

[Grainger49]

Yes, the A3 LED should have a wire to ground from the center pin of the tube socket.  So a ground problem would keep it from lighting.  But if the other LED glows that verifies the ground is good.

"Humming with lots of noise" is often a grounding problem or an open hot lead from the RCA jacks.  In my experience, an open hot lead has a hollow sound to it rather than the normal hum.

 

[xiawei]

yes, all other 9 leds light. i would describe the left channel muffled, with very low volume and some hums. now i doubt the led is dead, anyway to verify that without taking it off? also could it be the a3 pin or the correspoding leg on the tube?

 

[Grainger49]

If your meter has a diode check position read the manual and see how it should be used.  Then check the LED.

If not, set it on a resistance range like 200 Ohms and check first with the red lead at the tube pin and the black lead on the socket center pin.  Better yet, put the black lead on the top plate; this verifies continuity to ground.  This reading should be a measurable resistance.  Report it back.

Then put the black lead on the tube pin and the red lead on the tube socket center pin you should have infinite resistance, or something above 1M Ohms.

Report your findings back.  We can at least verify that last LED and move on to the circuit boards.

 

[Paul Birkeland]

I must emphasize that messing with the LED's on the socket is absolutely the last resort, and rarely an actual problem.

Please swap the smaller PC boards left to right and see if the issue follows one of the boards.

-PB

 

[xiawei]

I must emphasize that messing with the LED's on the socket is absolutely the last resort, and rarely an actual problem.

Please swap the smaller PC boards left to right and see if the issue follows one of the boards.

-PB

Good suggestion, I'll do after the work.

 

[xiawei]

If your meter has a diode check position read the manual and see how it should be used.  Then check the LED.

If not, set it on a resistance range like 200 Ohms and check first with the red lead at the tube pin and the black lead on the socket center pin.  Better yet, put the black lead on the top plate; this verifies continuity to ground.  This reading should be a measurable resistance.  Report it back.

Then put the black lead on the tube pin and the red lead on the tube socket center pin you should have infinite resistance, or something above 1M Ohms.

Report your findings back.  We can at least verify that last LED and move on to the circuit boards.

I tried to do exactly as you are describing here. But I only managed to get reads from 3 out of 10 LEDs. Don't know why I can measure some even they light..

 

[xiawei]

I must emphasize that messing with the LED's on the socket is absolutely the last resort, and rarely an actual problem.

Please swap the smaller PC boards left to right and see if the issue follows one of the boards.

-PB

Thank you so much Caucasian! Now I see the hope!

After I switched the pc board, A3 lighted but A8 did not. Looks like it's the PC board. I also noticed they are always the LEDs on the faulty board light up first after the power is on.

But I already reosolder that board! Now how to pin-point the problem…

Really appreciate your help!

 

[Doc B]

The transistors were possibly damaged by the A1/A2 short and may need to be replaced. You can request more at [email protected]