Speedball voltages [solved]

[tamarind]

Here are my voltages after adding the speedball to my working crack.

For a start, just attaching the ground to 12 with 200 on the DMM gives me ~0.5 and is roughly what i get for all the 0 terminal values.

1 and 5 seem quite low and out of the 10% range?

Should I look over something? Thanks.

Terminal/expected/actual


1 75-90 55
2 170  179
3 0      0.6
4 170  179
5 75-90 57
6 0      0.6
7 100    97
8 0        0.5
9 100    95
10 0      0.5
11 0      0.4
12 0      0.6
13 170  177
14 0      0.5

 

[Paul Birkeland]

1 and 5 do seem low, tell us about the 12AU7 you're using?

Low voltages at these terminals generally means higher than normal emissions, which is actually a good thing to some degree, but this voltage does influence the operation of the 6080.

 

[tamarind]

Hi.  I'm just using the 12AU7 that came with the kit if thats what you mean?

Going back a step I had a couple of the R1 resistors on the wrong board causing 182 at T1 and the LEDs on board A dark. I swapped the resistors over and retouched the middle terminal near the LEDs and it started working with the voltages listed above.

I've been using the standard crack without issue before doing the upgrade. Is there something I could have introduced? I'm not sure where to trace this back to on the board.

Should I avoid the headphone test before sorting this out?


Thanks for your help.

 

[Paul Birkeland]

No, it will very likely function with headphones.  You may just have a very, very strong 12AU7 that's throwing things off a bit, let us know how it sounds.

-PB

 

[tamarind]

I guess the only thing is that the readings for the original crack were all within 15%.  If the 12AU7 is the cause I would expect to have seen similar numbers at the time.

I'll take a listen and see what I get.

Thanks.

 

[tamarind]

I just did a final check before hooking it up. I was poking around terminal 21 trying to find a good contact point and there was a really loud snapping sound. There was no smell of smoke.

Does that sound like something has blown? How should I proceed now?

 

[tamarind]

Ok I did another round being more careful using some alligator clips rather than poking around with the probe and the numbers seem close enough. The sound is coming through fine as well. I think the $5 DMM might have been a false economy, the LCD isnt even showing properly.

Time to hit the CD collection again. 8)


Cheers
M