Speedball problem [SOLVED]: LEDs unlit, 270Ω 5W resistor overheating

[Yoga Flame]

After enjoying my stock Crack for many months I decided it was time to try some upgrades. Rolled an 8505 tube and swapped in some Axon 91

[vetmed]

It sounds to me like you have short somewhere after the power resistor(s). Also, since none of the leds light up this would indicate that no high voltage is getting to them. You must have moved something when installing the boards since it was working before. I also notice that your post was early in the morning, a decent night's sleep may make your problem more evident! Hope this helps.


Robert Lees

[Yoga Flame]

You're right! Got some sleep and today I looked at it again and realized I had mistakenly connected the black wire from 3U onto the B+ pad instead of the G pad. That was embarrassing. Still could not seem to find any other shorts though.

I will probably need to desolder and remove the Speedball boards to get unobstructed access for a better inspection. But first... I connected the power again for the voltage check again, and the LEDs still failed to light up. So I cut the power after a couple seconds rather than waiting to see if the magic smoke would come out again.

Tested the LEDs with a multimeter. The D1 LEDs seem to be dead. The D2s are all right. The tube LEDs are fine as well. I guess I'll be getting new D1s on my next Digikey order.

Is the resistance check from the Crack manual still good for checking with the Speedball installed? My readings are a bit different:
3: 0
6: 2.4KΩ
7: ~25MΩ
8: 0
9: ~25MΩ
10: 2.4Ω
12: 0
13: ~10MΩ
14: 0
20: 0
22: 0
B3: ~25MΩ
B6: ~25MΩ

[Laudanum]

It does take a little while for those LED's to light up.   Just guessing maybe 15 seconds (give or take a couple)  before they start to light up, some coming on a few seconds later than others.  I mention this because you stated that you shut it down after a couple of seconds when they didnt light up.   You arent the first to get that B+ and ground mixed up, and you probably wont be the last.  It happens.

[Yoga Flame]

Thanks! I tried powering it up again and sure enough the LEDs came on after a slight delay. That's a relief. Also shows that my LED checking may need some work, LOL.

Now to check those voltages...

[Yoga Flame]

Everything seems to check out. Thanks again for your help vetmed and Luadanum, and also Doc B. in the other thread.