Speedball Issues [solved]

[Au70]

Greetings everyone,

My friend built his Crack and got it working and he loved it. Later he decided to install the Speedball upgrade. He wasn't able to get it working so he came to me for help.

I've spent the last few hours scouring the forums looking for posts that would help me solve the problem, but I can't find any that solved the problem I'm having.

Here is my attempt to explain the issue.

When he first turned it on, he saw smoke and turned it off right away.

Here are the symptoms that I can describe.

When I turn it on:

• the A3 and A8 LEDs slowly fade on, and then A3 slowly fades to dark.
• When A3 and A8 are fading on, the LEDs on boards A and B fade on, but are dim
• Once A3 fades out, the LEDs on the large board nearest the transformer fade on, but the other set nearest the audio jack never turn on
• The 270 ohm resistor that sits across the transformer heats up and creates a burning smell

I have checked and reflowed all of the transistor joints on both the main board and the smaller boards. I also reflowed all joints that hadn't penetrated both sides. I also looked everywhere for a short, solder bridge, or misconnected component. I couldn't find any.

The voltages are as follows:

• T1: 55 - Starts over 200 and then falls
• T2: 63 starts high and then falls
• T3: 0
• T4: 65 - starts high and then falls
• T5: 21 - starts over 200 and then falls
• T6: 0
• T7: 27 - starts low, jumps to around 87, and then falls
• T8: 0
• T9: 19 - starts lower, slowly reaches 19
• T10: 0
• T12: 0
• T13: 215
• T14: 0
• T15: 215
• T18: 76
• T19: 75
• T20: 0
• T21: 223
• A1: 15 - starts around 75 and then falls
• A2: 0
• A3: 2
• A4:
• A5:
• A6: 80 - starts around 200 and falls
• A7: 0
• A8: 2
• A9: 0
• B1: 78 - starts around 200 and falls
• B2: 207
• B3: 16
• B4: 20 - starts higher and falls
• B5: 78 - starts around 200 and falls
• B6: 20
• B7: 0
• B8: 0

I realize that some of those are way out of spec and aren't right, but I (being new to tube amps, and amps in general) have no idea where to sart.

Any help you can provide will be greatly appreciated <3

edit: I forgot to sign my name. I'm Paul Klopping! Thanks again!

[Paul Birkeland]

Hello Paul,

This is the best first post I have ever seen!

Anyway, I'd pull the 6080, then measure terminals 1-5 again. 2 and 4 will be higher than they should, but 1 and 5 are what we are interested in.

-PB

[Au70]

Thank you for the compliment!
I read several posts and always saw the same initial feedback and questions. Before I posted I figured the least I could do would be to try everything I could and answer as many of those initial questions as I could.

I popped out the 6080 and retested the voltages. Here they are:

• T1: 220
• T2: 215
• T3:
• T4: 218
• T5: 75 - starts around 215 and falls
• B1: 78 - starts around 215 and falls
• B2: 215
• B3: 8
• B4: 75 - starts around 220 and falls
• B5: 215
• B6: 7
• B7: 0
• B8: 0

[Paul Birkeland]

Well, those aren't terminals1-5, but that tells me that T1 and T5 have 78 and 75V, and that T2 and T4 have 215V.

The issue then is with 100% certainty related to the big PC board.  We often see builders leave off hardware when mounting the TIP-50 transistors that prevents them from touching the heatsink.  If they touch the heatsink, the 6080 will draw all the current it can, which draws down the power supply voltage and eventually overheats the 270 Ohm resistors to the point where they fall apart. 

I'd look over the manual very carefully when it comes to the big board instructions.  I'd also check the solder joints on the bottom side of the board, just to be sure that no 2 legs of any of the transistors are accidentally soldered together.

-PB

[Au70]

Sorry, I realized that I posted the wrong voltages a minute ago and updated my response to reflect T1-T5.

Yesterday as I was looking it over I checked to make sure that the large transistors weren't grounded to the heatsinks and that the screws were using non-conducting washers. They checked out just fine.

Later today I'll go through and triple-check all joints on the bottom to make sure that they're not soldered together.

[Au70]

Okay, I found the issue.

After meticulously going through the instructions and re-checking all of the wiring on all three boards I found the culprit.

3U was connected to O, and 9L was connected to G, instead of vice-versa.

I don't know how I missed that the first time around (probably fatigue/frustration), but after I corrected it the amp started behaving normally. All LEDs turned on (the mainboard faded on slower than the others, but they turn on) and my voltages are listed below.

• T1: 77
• T2: 175
• T3: 0
• T4: 175
• T5: 78
• T6: 0
• T7: 106
• T8: 0
• T9: 106
• T10: 0
• T12: 0
• T13: 174
• T14: 0
• T15: 193
• T18: 76
• T19: 74
• T20: 0
• T21: 212

• A1: 78
• A2: 0
• A3: 2
• A4: 0
• A5: 0
• A6: 77
• A7: 0
• A8: 2
• A9: 0

• B1: 77
• B2: 175
• B3: 106
• B4: 78
• B5: 174
• B6: 106
• B7: 0
• B8: 0

Even though my headphones are low impedance, I tested it with them and there are no stray noises and music comes through. My friend is going to bring in his high impedance headphones tomorrow and give it a proper test.

Thank you PB!
I appreciate your time and your help in isolating the issue!

[Paul Birkeland]

Good catch on the miswire.  It often can take 2-3 times of looking things over to find these things.

-PB