Troubleshooting Speedball install - unable to pass voltage checks

[defenestration]

had a stock Crack that was working fine and then I attempted installing the speedball upgrade

unable to pass following voltage checks, all others check out fine as far as I can tell

terminal 1 - 155V (expected 75)
terminal 7 - 146.7V (expected 100)
terminal 19 - 83.5 (expected 0)
terminal 20 - < +/- 1mV (or approx zero - expected 206)
A6 - 139.6V (expected 75)
B1 - 142V (expected 75)
B3 - 148.8V (expected 100)

hooking up headphones results in a seemingly clear and strong left channel but a weaker and distorted (especially when I start to crank the pot) right channel

would be nice if I had some spare tubes just to rule those out - it's possible I damaged a tube while being clumsy? have spent many hours checking/re-flowing all of my joints and making sure everything is connected correctly

I have also taken pictures of my build and have posted them here - http://s1087.photobucket.com/albums/j479/concatenation/CRACK%20AND%20SPEEDBALL/

thanks all!

[Noskipallwd]

Hello defenestration,
Just finished troubleshooting my speedball, I'm new so I am probably not going to be much help. I can let you know that there is a misprint in the manual. There is a post from Doc B. Called speedball corrections, terminal 19 is irrevelant, your terminal 20 good, it should be zero. If your meter is in autorange you will get +- very small millivolts for zero. Terminal 21 should be 206. Are all the LEDs on the boards lit? This info will help others with more experience who read your post. Sorry I am not much help.

Shawn Prigmore

[defenestration]

Hey Shawn thanks for responding,

all the LEDs are lit up, when I get a chance sometime tomorrow I will check the voltage on terminal 21

[defenestration]

did the voltage check for terminal 21, checks out fine @ 207 - 207.5 VDC

have tubes coming so I can try and rule those out before I go digging again

[defenestration]

haven't done the voltage checks yet but fresh tubes seems to have done the trick nicely, if it had failed I probably woulda ripped out the speedball upgrade just to go back and verify my first build again... and then I would have started replacing transistors on the speedball boards

haven't checked the 12AU7 yet either (I put a fresh tube in each socket) but my hunch is that it's fine... I probably hosed one side of my 6080 power tube?

I put this guy http://thetubestore.com/sed6as7g.html in along with a NOS Philips 12AU7 and the sound is a bit smoother but that might have to do with the speedball upgrade

on another note, when I was verifying voltages on the power supply I slipped and caused a short that fried the fuse - the F1A1 fuse that came with the kit is quick blow fuse, but at the local hardware store all I could grab was a T1A1 which is a slower blow fuse, is it bad news bears to be operating without a quick blow fuse?

[Paul Joppa]

Slow blow fuses are more reliable with tube gear, since they are more tolerant of high inrush current when the device is first turned on. But they are generally more expensive than the fast blow ones. Time constants are all over the place, depending on the metallurgy used by the particular manufacturer at the particular current. It's not really a science! Sometimes a smaller fuse will work better that a higher-current one, just because the time constant is more suited to the application.

If it does not blow, and it does not exceed the current rating of the supplied fuse, it is probably OK.

[Laudanum]

Sounds like you're on your way but definitely verify with the voltage checks. 

And when you are good to go, check the big "Tube Rolling with Crack" thread.   12AU7 and 6080 variants are listed as well as lots of good advice and tube reviews/impressions.  Of the 12AU7's I have tried, my favorite is an Amperex (Herleen) but If you want to try some other relatively inexpensive NOS tubes, check out the GE 12AU7's and the RCA 6AS7 or RCA Jan 6AS7.  YMMV because so much is dependant on the rest of your gear and personal preference but from a personal perspective I really like the GE 12AU7 as a very nice tube in Crack (and real good bang for the buck) as well as the RCA 6AS7's.  I picked some of these tubes on ebay for relatively little money.  The first couple GE's I picked up were in a lot with a couple RCA's and a few other 12AU7's for less than 20 bucks with shipping.  By the way, the RCA 6AS7's have the cool ST shape like the Russian made tube in your link.  My favorite 12AU7 of those that I have tried is actually an Amperex (Herleen) manufactured tube. 

Speedball does have a clearly audible impact on the sound.  Tube differences are generally more subtle than Speedball.  So what you are hearing is probably most attibutable to the Speedball upgrade.  Listen with Speedball and your current tubes for a while.  Then you will be better able to know what differences you are hearing between tubes and pick some favorites.  The most easily distinguishable audible difference for me was with the Speedball upgrade.

Enjoy

[defenestration]

verified the voltages, everything checks out amazingly - with the speedball and my fresh tubes it appears my voltages are scarily close to specification, less than a volt off spec generally, sometimes only a tenth or twentieth of a volt

[Laudanum]

Great.  Larger variations dont necessarily mean much unless they were outside of 15% in either direction.  Just the line voltage being high or low will change the voltages but again, they should be within 15% of the printed values.  You are golden my friend!

[Grainger49]

The line voltage being off can change everything except regulated voltages.  Like the voltage above an LED. 

[Laudanum]

Thanks for the specifics Grainger.