New Asteroid Build

[5dollazz]

Hi everyone, I'm new here and I'd like share some pics of an Asteroid I finished over the weekend. This is my first real build and first real post here and I wanna thank everyone for all the things I've learned (and am learning) surfing TAG. Also a big thanks to RJ for the chassis, trannys, and other small parts. I can't wait to build another amp.... This is gonna be trouble. I'm thinking Rocket.

Anyway, I did something really stupid that I thought I'd also inquire about. I played it for about 5-10 minutes last night, increasingly louder, and then it arced from pin 3 to 2 on one of the power tubes and popped the HT fuse. Before that it sounded pretty amazing and a lot like a real K60 that I occasionally get to play. I did some digging and I think that I may have reversed the color coding of the OT primary wires and had the amp set at 4 ohms into a 16 ohm cab. So dumb, I should have measured them first. Is it correct the the wire with the highest resistance (about 0.8 ohms in this case) is corresponds to the 16 ohm tap? If this is the case, the wire colors on my OT are backwards from the layout that I used (I think, I could just be an idiot) and probably the cause of the arcing, right?

I'm going to replace the tube socket this week as there's a carbon trail on it, but is there anything else that I should do before I fire it up again? I gather that flyback spikes can take out an OT. I did a quick check and found that the resistance across the primary was about 89 ohms and each half was half of that. The 89 ohm reading concerned me as it is a few ohms lower than when I first installed it. Do you guys think I should do more extensive testing of the OT?

BTW, all my voltages were consistent with what people have posted on here - 485 B+, etc. One deviation from the original schematic I had to make was in the bias circuit. I had a 20K linear pot and had to use a 22K resistor to ground to get the bias voltage within range. Is this OK? It seems to work just fine, though it's pretty touchy.

Thanks for any thoughts or help anyone can offer. And thanks again (everyone) for all the info. I've had a great time working on this project and I owe it all to this site.

[martin manning]

Looks like a good candidate for this test: http://www.premierguitar.com/articles/14403

[5dollazz]

Thanks, I'll give that a shot tonight.

[5dollazz]

I'm happy to report that the OT passed the neon bulb test with flying colors. Or flashing colors. Thanks Martin!

[Colossal]

Good looking build! Carry on!

[ampgeek]

That is a VERY nice looking build! If that is your Freshmen effort....I can't wait to see you next one!!
Rock on,
Dave O.

[Synchu]

That is an excellent looking build!

Got me inspired into searching what it is and thinking while rigging for the planned SSS build (it seems to take forever, I already build another amp meanwhile) whether to build one of these

Will appreciate some sound clips.
Niki

[5dollazz]

Thanks for the kind words guys! Going into this project I was hoping that all my years of needlessly building pedals would be worth something.

I'll certainly post some clips once I get the tube socket in there and get it up and running again. I really like the way these amps sound, but it's possible that I like the way they feel even more. Whenever I play one I feel like I could noodle for hours. The touch sensitivity is just so freaking satisfying to me. My poor bandmates.

Just for the hell of it I measured the OT primary impedance last night as well and found that it varied slightly depending on which tap I used. Results were:

4 ohm tap - 5.8k
8 ohm tap - 5.9k
16 ohm tap - 6.2k

Seems like it's all close enough for jazz (I of course could be wrong), but I thought it might be interesting info.

[RJ Guitars]

Wow! Nice looking build, can we see the full pictures of it on the outside, I am curious how she turned out. Once I see the finished amp I may have to build one myself, I think I have a set of trannies left. The clips I've heard of them are really convincing and a guy can always use one more amp.

[5dollazz]

Thanks RJ, I'd be honored if this amp swayed anyone to build yet another amp. My friends laughed at the addition of this amp to my growing wall of sound, but it didn't take long before they stopped laughing and wanted to play it. Alas I have yet to put it in a box. For now it's just bolted to a 1x10 (classy) but building a box for if is the next step. I just have to beg for time at a buddy's buddy's wood shop, a rare find here in NYC.

Yesterday I rolled tubes through it and ended up with 60s Amperex Bugle Boy 12ax7s in v1 and v2, a 70's short plate GE 12ax7 in the PI, and late 70's Tesla el34s. I also really liked 6l6s (winged Cs) in there. It's amazing how much tube selection effects the tone of this amp. It seems much more sensitive to tube swaps than any of my Fenders and probably even more than my JMPs. I was also shocked to discover that VERY small bias adjustments made a huge (well huge to me) difference in tone and feel. The difference between 30 and 31 ma (481 plate voltage) was surprisingly noticeable.

Oh, and she loves greenbacks. We both do really.

[bnwitt]

I doubt very seriously that your incorrect ohm setting on the amp and cab had anything to do with the arcing tube.

Nice build. Put winged C power tubes in it. They can take a beating.

Barry