Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: TRTim on February 10, 2015, 05:46:31 AM

Title: Help with Speedball Mod [Solved]
Post by: TRTim on February 10, 2015, 05:46:31 AM

I may have fried the transistor on the large Speedball board. Originally, I installed the LEDs backwards on the left side of the board. I have corrected that issue but the voltages I am getting are off. They are:

Term 
1   179
2   180
3   0
4   180
5   77.9
6   0
7   172
8   0
9   112
10  0
11  0
12  0
13  181
15  199
20  0
21  216


I completed the Crack headphone amp and ran in the amp for about 20 hours before adding the boards, so I think the base wiring is OK. Can you please help.

Thanks
Tim

Title: Re: Help with Speedball Mod
Post by: Paul Birkeland on February 10, 2015, 07:10:40 AM

179V on terminal 1 would indicate:

The 2N2907 not being installed (did you swap it with a 2N2222 on the big board?)
The R1 resistor being swapped with an R1 resistor on the big board
The center leg of the MJE-350 needing extra heat to solder properly
Other issues present before Speedball (shouldn't be the case in your repair)

-PB

Title: Re: Help with Speedball Mod
Post by: TRTim on February 10, 2015, 09:52:55 AM

After a quick test of the resistors R-1 with my ohm meter, I had indeed put the wrong one on board "A". I swapped them back and all of the voltages went to their correct value. I am now playing Bach's solos for unaccompanied cello by YoYo Ma and life is good.

Thanks!
Tim

Title: Re: Help with Speedball Mod
Post by: Nathan on February 10, 2015, 12:48:51 PM

Quote from: TRTim on February 10, 2015, 09:52:55 AM

After a quick test of the resistors R-1 with my ohm meter, I had indeed put the wrong one on board "A". I swapped them back and all of the voltages went to their correct value. I am now playing Bach's solos for unaccompanied cello by YoYo Ma and life is good.

Thanks!
Tim

Good reason to measure each resistor and check each part more than once before committing to installation.