Speedball Resistance and Voltage

[ganoosh]

Hi!

Been using Crack for a few months now. Got around to assembling the Speedball tonight and after passing the resistance check on the large board, I did the voltage check and got the following results:

OA: 114
OB: 2.2
G: 0
B+: 199.9

Also two of the LEDs didn't go on. So I checked and a few leads were loose. After re-soldering them and re-checking all the connections, I did another resistance test. OB was fine but this time the Ohm readout on OA didn't deviate from "1" while set to the highest resistance. And the subsequent voltage readouts all were 0. So I'm definitely missing something here now but I'd love some help in determining where to start.

Thanks in advance!

JJ

[ganoosh]

Wasn't letting me attach photos so put them on imgur: https://imgur.com/a/U3trMME

[Deluk]

Maybe the moderator can move this to the Crack section?
Pictures made me say to myself "what a lash-up". Sorry about that. One of our experts may be able to see something obvious, but if it was given to me, a decidedly non-expert, I would remove the Speedball board and rebuild the basic crack to look as close to the manual as possible. Lots of tidying to do with many leads to be trimmed back. Only then I would start to fit the Speedball. The actual board is currently very untidy too so I'd start there. Over to you.

[Paul Birkeland]

Is there a reason that the wire included with the kit didn't get used for the big board?  It looks like maybe the wire you used is stranded, which can definitely cause reliability problems.  There are also many joints in the amp that look like they could use a little more time from the soldering iron to flow out properly.

Some example joints:

B3 - the solder hasn't been allowed to flow down around the lower hole where the wire passes through.
5U - there's solder, but the wire isn't wrapped around the terminal.  I bet you can pull the wire right out.
10L - cold solder joint, this needs to be heated up till that solder flows into the hole in the terminal strip.
1U/2U - the teflon wire passing through these terminals is not bent up and looks to be poorly soldered.

I would reflow the joints on each TIP50 as well.

[ganoosh]

Hi Paul,

Appreciate the feedback. I originally used the wire included with the kit but in trying to troubleshoot the failed resistance test, I tried out a new wire to see if that would improve anything. I ran out of the wire included with the speedball. What gauge wire is it, by the way? Could I use the wire included with the original Crack kit? I have some of that left over.

I agree that the soldering job rendered here is unsatisfactory. I believe the soldering tip I was using last night was too big and thus unruly most of the time. Am going to get an iron with a thinner tip today and see if I can re-solder some of these joints. Will report back.

JJ

P.S. Upon closer examination, two of the joints on one of the TIP50s may be touching. I suppose that could be a major problem as well?

[Paul Birkeland]

The wire with the Speedball is 22 AWG, but the size is far less important than the wire being solid core and tinned. 

[ganoosh]

Update: Cleaned up many joints including the ones you pointed out and re-soldered all the joints leading to the large board with new wires (leftover from the Crack assembly). Also addressed the TIP50 joints as you suggested. Passed its resistance check this time, but here were the voltage readouts:

OA: 50
OB: 74
G: 0
B+: 88

Two of the LEDs also didn't light up as well. Here are some updated photos I took tonight: https://imgur.com/a/ZxJIFdK. Is there somewhere you recommend I start first, or is it still looking like a botched mess that requires a general overhaul? 

[Paul Birkeland]

This honestly looks like a job attempted with the wrong tools.  It looks like you can't get in to properly trim any of the leads (which happens if you have big wire cutters instead of side cutters), and your iron isn't getting things hot enough to properly flow out the joints.

I would either recommend borrowing some better tools to trim and reheat every joint in the amp, or I would send it in for repair and I can do all that for you.

-PB

[ganoosh]

Hi Paul,

Thanks for your advice up to this point. I updated our tools which made it much easier to cut and strip the wire and bought a Milwaukee soldering iron which helped a lot. I went back through and cleaned up all the solder joints on the large board and replaced the four wires with 22 gauge tinned single strand and made sure the connections were all tight. But still the voltage readouts were the same as below, with two LEDs still being out.

Due to time constraints, I was unable to re-solder all the joints in the amp, but prior to attempting the Speedball upgrade, the amp was working without a hitch for two months. So the question I have is, is there anything "upstream" from the large board that I should be checking, in terms of ohms or voltage? Could it be something having to do with a component on the board itself? It appeared something had shorted (sparks flew out briefly) during the second voltage test we conducted (after the first one failed) but it hasn't happened again.

Lastly, you had mentioned that you could repair the amp--what would be the price estimate to do so?

Thanks,

JJ

[Paul Birkeland]

My services are part of the flat rate repair service.

You can measure the DC resistance between each pair of leads on each transistor on the board to check them.  A pair of shorted leads means you have a blown transistor.

Does the small PC board still produce the appropriate voltages?