Problem with speedball upgrade

[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]

[xiawei]

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

Thank you Doc!

You mean both the MJE350 and 2N2907?  Anyway to test them?

[Paul Birkeland]

You mean both the MJE350 and 2N2907?  Anyway to test them?

If you replace them, and the board works, then they were bad

Really though, it's no problem to assist with some replacement parts, the transistors are sensitive enough that it's a good idea to replace them both and not worry about one failing later.

[xiawei]

You mean both the MJE350 and 2N2907?  Anyway to test them?

If you replace them, and the board works, then they were bad

Really though, it's no problem to assist with some replacement parts, the transistors are sensitive enough that it's a good idea to replace them both and not worry about one failing later.

Thank you all for the great helps I got here! I'm ordering replacement now.

[xiawei]

Sorry Doc just one more question! I switched the pc boards although A3 lights now but the sounds of both channels are gone. Before the switch the right channel sounded fine to me.

Could anything else be wrong?

[Doc B.]

Could anything else be wrong?

Sure, but you need to make this fix before you move on to other issues.

[xiawei]

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

Sent an email yesterday. How can I know the order was received?

[xiawei]

Got the parts! The shipping was fast! Amazing service! Thank you Bottlehead!

 I'll install them either later today or tomorrow. And post the result here...

[xiawei]

Could anything else be wrong?

Sure, but you need to make this fix before you move on to other issues.

Thank you Doc for quick delivery of the parts. Unfortunately, after replacing both transistors on that small board, nothing changed! A3 LED still doesn't light up.

When the bad board was on the right side, terminal 5 read 0v and terminal 9 read about 50v. Now after switching of the boards (bad one on the left) and replacing of the transistors, T1 reads 0v and T7 reads 55v.

I'm puzzled! Please guide me!

Have a great weekend!

[xiawei]

Looks like it's the small board. But what also can go wrong with it? Or something else that is beyond my understanding? Please help.....

[Paul Birkeland]

When we get our next batch of boards in, we can send you a single replacement board and all the parts.  (Since this has been narrowed down to be the issue)

I'd shoot an e-mail to replacementparts(At)bottlehead(doht)com

-PB