Speedball Voltage Issue

[tchevy]

Hi everyone.

I built the standard crack about a month ago. Build went smoothly, all resistances and voltages checked, been working perfectly. (Love it)

Built the speedball upgrade today and I've had a few issues. I also added padding to the pot during at this time.
- Had a shoulder washer backwards on one of the TIP50 transistors, fixed this rigth away.
- Foolishly connected the black cable (that runs from 3U to right side board terminal G) to the terminal above G (directly beside the 2907 transistor). I correctly this as well.

Current Issue:

- As far as I can tell theh LED's on board B (right side) do not light up. It is difficult to tell given how dim they seem to be.
- Voltage on Terminal 5: ~150
- Voltage on Terminal 9: ~150

Thus far I've reflowed most of the joints on board B, in addition to Terminal 9, and several joints on the large PCB. I've searched the forums and seen similar voltage issues in a few posts but I'm unsure where to go from here. I'm wondering if I blew a component with a previous error. Any help would be appreciated.

 

[tchevy]

Pictures.

 

[Paul Birkeland]

So, this is a really old Speedball kit.  Where has it been stored for the last couple of years?  Has it been exposed to a humid environment? 

The first step to debugging would be to remove the 6080 and retest the voltages at terminals 1 and 5.  You need to get those to be correct before doing anything else. 

With that voltage at terminal 5 being 150V, either you will have one dark LED on the 9 pin socket or one LED on the 9 pin socket that is substantially brighter than the other.  Let me know which case you have.  In either case, do not mess with the LED, it is likely indicating a problem elsewhere.

 

[tchevy]

Hi thanks for the reply.

I did purchase the kit a few years ago. Finally got around to building it, something good out of lockdown I suppose. That said the box has been sitting in my house the whole time so I can not imagine moisture would be a factor.

Removed 6080 tube:

- Both LEDs on the 9 pin socket appear to be lit. The bottom LED closest to A3 does appear significantly brighter.
- Voltage on Terminal 1 has not changed at ~75.
- Voltage at terminal 5: ~195

 

[Paul Birkeland]

This information would tend to suggest that you have one pair of R1 resistors swapped.  These can be measured with your meter while installed on the boards.

-PB

(PS - I am still catching up on projects that piled up pre-lockdown)

 

[tchevy]

Hmm I rechecked the resistors in R1 on both small boards and the large PCB.
- Both small board R1 measure at 237 ohm
- R1 on large board are ~31 ohm

Those seem to be ok. ANy other thoughts?

 

[Paul Birkeland]

Try resoldering all of the joints no the MJE350 on the offending side, paying special attention to the center leg as it is connected to the metal tab on the device intended for thermal dissipation.

 

[tchevy]

Well it turns out when I attached this B side board I must have incurred a concussion since it turns not only did I attach the ground lead incorrectly as I mentioned before, but I had the 4U and 5U connectors swapped. Apparently just needed to look at this on a new day.

So I properly connected 5U to terminal O and 4U to terminal I. Suprise suprise, problem solved.
All voltages and now in range, no fluctuation on terminal 1 or 5 with 6080 removed.

Really appreciate the help Paul. This kind of support form the community makes it significantly less daunting to undertake these projects when you have minimal experience.

- On a curious note are there any significant differences on the new speedball kits. Was wondering how u could tell it was old.

 

[Paul Birkeland]

On the new kit, we made a single small PC board up front, the two pairs of R2 resistors look dramatically different physically, the 2N2907 was swapped out with a PN2907, which is also physically very different than a 2N2222/2N2907, we reduced the number of jumpers to the big board, we split up the installation instructions to do the small board first, then test, then do the big board, and we provided some diagnostic flow charts in the manual to help with debugging.  We also switched the big board R2 to a 47K/2W resistor, which was intended in the first revision but it just didn't fit!

The error you made would be very, very difficult to do with the new Speedball board, as the PC board up front has holes that line up with each terminal strip terminal, and it's just a short piece of wire that connects between each one.

 

[tchevy]

Ah very interesting, that does sound significantly more streamlined. Not that I'll be looking to change this setup anytime soon but did you get sonic improvements with that revision.

If you dont mind I do have one final question:

- When measuring the voltage on TRS jack while starting up I dont see the voltage change at all, just stays at 0. I am measuring this gold portion of the tip. I think this is how I measured it previously. Is this correct or am I out to lunch agian?

 

[tchevy]

I certainly hope you didnt read my last reply as I was obviously stupid.

Thanks again man, really appreciate the help.

 

[Paul Birkeland]

The new Speedball and old Speedball sound the same, the new one just trades 5-10 common installation errors for 1 new common installation error (it's now easy to put the PN2907s in backwards).

As far as the voltage spike goes, wire all three outer headphone jack terminals together, then there won't be any spike at all.