Help with Speedball Mod [Solved]

TRTim · 1991

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Offline TRTim

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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
« Last Edit: February 10, 2015, 06:23:44 PM by Caucasian Blackplate »



Offline Paul Birkeland

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Reply #1 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

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline TRTim

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Reply #2 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



Offline Nathan

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Reply #3 on: February 10, 2015, 12:48:51 PM
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.

Crack/Speedball, SEX 2.1/C4S, Bryston BHA-1

Sennheiser HD600/Cardas cable, Beyerdynamic T1 2nd Gen, Hifimam HE560/Hifiman balanced cable