Yesterday I did something that was long overdue since I moved to Arizona; I called my MasterCard issuer and negotiated my interest rate down. Way down...from 18.3% to 0% for six months, and prime plus 2.94% afterwards. I did this once before, back in 2000, right after I read the Motley Fool's book "You have more than you think" and I was trying to get prepared to get out of the Navy. That time, I negotiated a fixed rate, but for some reason, the credit card companies decided that once I moved (or maybe it was got divorced), all bets were off. I was pissed, but stupidly did nothing about it until now. In any case, now that's handled.
I had to re-tube my Ampeg SVT classic last week, after only about 11 months of twice a week service. I was at practice with the new band (still no name yet) and the power light started alternating red and green, which, according to the manual, indicates a power tube problem. I let the amp cool down, then fired it back up again, and after hitting a few notes, it shut itself down again.
I started searching around for a good replacement for the stock tubes, which were Sovtek 6550's. I didn't want to spend over $200 for a replacement sextet of power tubes, which narrowed things down to about two or three manufacturers. In the end, I settled on the Winged-C (formerly Svetlana) 6550C. It was really between Winged-C and Sovtek, and I was curious if maybe they'd last longer. I ordered from Antique Electronic Supply, as it was slightly cheaper, and while they're internet orders only, they do a will-call window during the week, and are located not far from where I work. Additionallhy, they would sell me a matched sextet of tubes, which the SVT requires.
I cannot stress enough what a cool feature it was for Ampeg to put user accessable bias controls and LED's to indicate proper tube bias on the back of the amp. That alone makes the cost of re-tubing this beast more palatable, because I don't have to pay a technician $75 to do it for me.
Upon visual inspection, I wasn't impressed with the new tubes. Most of them looked like the plate stacks were sort of canted a bit from vertical in the bottle. Each tube looked a little different too; it wasn't a uniform thing. Not a big deal, but it made me wonder if other things were overlooked, or if Winged-C doesn't bother because they're busy working on other stuff.
Each tube had a green sticker with a hand written pair of numbers, which, if I had to guess, denoted grid current and plate current for the particular tubes. All of the plate currect numbers matched, and 4 of the tubes had matched grid current of 4.5mA. One was 4.6mA, and the last one was 4.4mA. The SVT has six power tube sockets; three in front of the other three. Being a push-pull amplifier design, I guessed that probably the front three were responsible for one half of the cycle, the rear three for the other half. I decided to split the 4.4mA tubes between the two sides, and place the 4.4mA tube up in the front, with the 4.6mA in the back row. I fired up the amp, let the tubes warm up on standby for 20 minutes, and then again with the high-voltage supply on for another 20 minutes.
I biased the amp with both sections in the "green," but the first thing I noticed was a 60Hz hum that I could minimize, but not elmininate, by adjusting the bias pots. Knowing that that sort of hum usually comes from imbalance between the two sides, I smacked my head and realized that I place the 4.4 and 4.6mA grid current tubes in same bank; the 4.4 and 4.6mA tubes would even each other out and give each side an average grid current of 4.5mA. I turned off the amp, waited for it to cool off, and swapped two of the tubes. I turned it back on, warmed it up again, and after a little bit more biasing, managed to get the 60Hz hum almost completely eliminated.
I found the tone a little bit darker than the Sovteks, but that's OK by me. Low end response (my standard low-E or drop-D hard hit test) I think is better, but I'm not sure if that's due to the old tubes sort of being at end of life, or that I've gotten used to the softer edge compared to solid state amps. It definitely seems like I don't need to set the amp as loud in the last couple of weeks, and I've rolled off the bass on the preamp quite a bit.
The FJ seems to be delivering a pretty solid 17MPG. Sometimes I get 19, sometimes 17. The mythical 21 is probably only while traveling 55 in sixth gear. I'm OK with that mileage. I'm still torn on the premium / unleaded debate on this engine, though. Normally I'm a regular gas pusher, but the compression on this engine is 10:1. Usually anything much over 9:1 requires premium to avoid knock. Newer engines do have knock sensors to back off timing and prevent this, but I'm not keen on relying on this to save the engine. The dealer told me that regular is OK, and I think they filled it up with regular. But perhaps the fact that I got 15.3 that first tank and 17 and up with every other tank might have something to do with running premium?
Here's another thing about the FJ that I totally dig...in spite of the interior being mostly black, it doesn't get anywhere near as hot sitting in the summer sun as my Lancer did. I don't know if that's a factor of the windows being mostly straight up and down, that they're smaller, or the white roof, but whatever it is, it works.