Might have ruined the rectifiers? (Resistance check failure help) [solved]

[senpai3330]

Well I cleaned up the leads a little and listened to music for about 10 minutes. Went straight on to the speedball.

All the LEDs lit up fine except 1 LED on the smaller speedball board to the left (looking with the transformer further away from you). It was the LED closer to the 2N2907 transistor.

I tested voltages and every test point came up fine except terminal 20 which read ~70V instead of 0V expected.

I removed the LED to make sure of the orientation again, but it seemed it was right the first time. My DMM on continuity testing mode manages to make the HLMP-6000s light up with the probes across it, but I couldn't light up this one so it might be dead. Worst part is I sneezed and dropped it. Spent 20 minutes on my knees looking for it with no luck.

[Paul Birkeland]

If one of the LED's on one of the small boards doesn't light up, you will not have proper voltages.

Either terminal 1 or terminal 5 will not have the correct voltage.

I'd say 1 out of 1000 times, the LED is the issue, generally it is another cause that is indicated by whether the voltages at terminal 1/5 are excessively high, or 0.

If you have 70V at terminal 20, this is a separate issue that should have presented itself before installing the Speedball.

Terminal 20 is (eventually) wired to the chassis, which is where you have your black meter probe.  So if you have 70V there, you have a bad ground connection somewhere.

[senpai3330]

Either terminal 1 or terminal 5 will not have the correct voltage.

I'd say 1 out of 1000 times, the LED is the issue, generally it is another cause that is indicated by whether the voltages at terminal 1/5 are excessively high, or 0.

If you have 70V at terminal 20, this is a separate issue that should have presented itself before installing the Speedball.

Terminal 20 is (eventually) wired to the chassis, which is where you have your black meter probe.  So if you have 70V there, you have a bad ground connection somewhere.

The weird thing is both terminal 1 and 5 tested fine (83V and 84V respectively with an expected of 90V). I'm beginning to suspect the LED was very faintly lit. It did seem to look slightly different with the amp completely powered off.

Also, very stupid mistake there. I meant terminal 19, not 20. Terminal 19 read abnormally with 70V instead of 0 expected. Terminal 20 read 212V with 206V expected, so that one is fine.

[Grainger49]

The Bottlehead "favorite" LEDs are pretty good at producing 1.7V DC across them.  If you get that when it is on they are good. 

[fullheadofnothing]

I think you are reading one terminal off. Terminal 20 should be 0. Terminal 21 should be 206. 19 is not called out in the manual I have in front of me (you could have a different version- the voltage checks have changed). You also didn't call it out in the list of voltages you gave on the previous page.

[senpai3330]

Oh man I really hope I wasn't just a terminal off, but my manual has 19 and 20 listed

I'm using the 12/17/2013 Crack manual and the 4/23/2013 Speedball manual. The voltages given on the previous page were what the Crack manual asked for. 19 isn't listed. However, 19 is listed in the speedball manual.

So here's the weird part:

Crack Manual lists:
20   0
21   206

Speedball:
19   0
20   206

I doubt it's a typo or else someone would've caught it by now. I don't know how the speedball kit would interact with those terminals to make things any different though.

I don't think I could really retest voltages now that I've gone and lost the LED. I won't be able to work on the crack until I'm back home from college again. I guess the project will have to sit on hiatus for 6 weeks. I hope you gentlemen will be just as helpful then. I'll get a replacement LED in the meantime.

**The 2012 version of the crack manual and the 2010 version of the speedball manuals are this way as well.

[Doc B.]

Josh is the keeper of the manuals and the best bet is to go by what he says - 20 at 0 and 21 at 206. I can assure you that there is no statute of limitations around here on a typo being missed.

[senpai3330]

Doc that's both great and terrible news.

I might've had a working speedball then. Now I won't know for 6 weeks!

[senpai3330]

Someone get me a gold star sticker for tenacity. I found the LED after sweeping the garage and sifting through the diust pile.

It is a typo in the manual then. The voltages checked out with 0 volts at terminal 20 and 213 volts at terminal 21. Music played through just fine!

[Grainger49]

Consider the Gold Star issued!

Beautiful music, I bet.