I had to go to two radioshacks to find the mounting kits. The first radioshack I went to (near work) had no idea what they were, and I couldn't find them in-store. Actually, they told me it was an "online only" item. So I got back to work, checked online, and of course - they did show as available at the very store I went to. So I called the store and asked for the catalog number. the person said "hold on, let me go check", then promptly hung up. I called back again, and a different person answered - I asked for the first one, she said "hold on", then put me on hold for five minutes - and promptly hung up. At this point I just gave up.
Fortunately the radioshack near my house DID have them - exactly two in stock. I asked them if they could keep them on hold for me and they said sure, asked me my name, and put them behind the counter.
While at work, I expanded the mounting holes slightly - from 1/8" (.125") to... 1/7? (0.140"), and also made sure to deburr the hole from the inside, as per Tomb's advice. When I got home I used some Arctic Silver Ceramique I had left over from a CPU upgrade (non-conductive). It's messy stuff, and harder to spread than I thought! A thin layer on both sides, and some fine working with tweezers and the shoulder washer... everything is in place. Flip the switch... NO SPARK! whoooo (is it bad I expect a massive spark every time I turn on the amp now?).
For posterity, I was going over the thread again last night and I came across
this post . I don't know how I didn't catch it the first time around, but it exactly described my problem.
Some quick thoughts until I can get to my nicer camera and attach my real volume knob.
- my tube LED switch doesn't really make much of an impact. I use 4.3kohm and 2.4kohm resistors (each one feeding both LEDs) connected to the switch. However, there isn't much of a brightness difference. Next time I open my amp and do some surgery I think I'll try to get the LEDs at 3mA and 10mA.
- tomb's "sea-green" LEDs are more "green" than "sea"... his picture is deceptive!
I want my money back.
- For better or for worse, the tube heaters are very dim; there's only a tiny hint of a glow at the very top of the tube. I can't see it unless I turn out the lights and turn the tube LEDs off.
- both heatsinks and tubes get nice and toasty, hot enough that I wouldn't really want to hold either for longer than a few seconds. I'll see if I can't find a temp probe somewhere in the lab to get hard numbers. EDIT: after about an hour of on time, the entire amp gets pretty toasty. I think I'll have to put finding that thermo higher up on my priority list. EDIT2: a surface temp probe tells me the temp is around 40-45C, but I don't believe it - I would say it felt closer to 50 or even 60 C. An 80C oven did not feel that much hotter than my case. I'm a little concerned about running this thing for long periods of time...
- my diode protection LEDs flash nicely when I turn on and off the amp... and with headphones connected, there's still a rather unfriendly thump, but only when turning the amp off. I guess I'll still be taking precautions when turning the amp on and off.
- my gain switch does not do a whole lot. I have it switching between 50k and 150k input resistors, along with a 50k amp. I'd say at the top end of volume, there's only about a 20% difference between the two. This is with low-impedance headphones, though, so I don't know how it reacts to, say, Sennheisers or Beyers. I hope to find out soon
- perhaps related to my gain switch, hiss becomes rather noticeable at about the 3'o'clock position for my 150kohms (low gain?) and maybe 1:30 for my 50k (high gain?). This is too bad, because the whole reason for the gain switch was to use more of the pot... oh well.
- is it just me, or is the pot really cheap? I didn't think i was putting very much stress on it and when I looked last night, the wiper pin had somehow detached itself from the pot. The whole pin! I thought it was a bad solder job at first, but I noticed the heatshrink was still on, and the end of the wire didn't look like a real wire. I put a large blob of solder here to hopefully prevent it from happening again. Just a note for people in the future, especially if you're using solid core wire - be careful with the panel components!
I think that's all for now. Back to the music!