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In Reply to: RE: They're building it impossible to work on posted by Alpha Al on February 12, 2015 at 06:29:16
I have a pair of MB-450s that have served me well since 2001. A couple of years back, I had an issue where not only the B+ fuse would go, but immediately one of the eight 6550C tubes would go supernova. Since I keep the output tubes following replacement, I had quite a few spares. I ended up smoking three more fuses and tubes before emailing VTL.Very quickly, Bea Lamm sent me an email for a couple of things to check. Mind you I'm not an EE, but have built Dyna kits and have a VOM and capacitance meter. Removed bottom cover for access to all the circuitry. Sure enough, one of her suggestions was to check the value of the output caps. One had failed. Once I relayed that information, she sent me one gratis. The cap's leads were pre-bent and precisely trimmed for fitment. It took me very little time to get it working like new.
Another area of variance I've found is ease of setting bias. I used to own an Audio Research VT100 that involved quite a procedure using matched quads. Inmate Abe Collins posted a wonderful pictorial of what to do. By contrast, the VTL allows for individual tube biasing and is easily accessible from the top plate. Admittedly, some of the newer ARC amps have front panel meters and bias points. The current version of my amp has auto bias so that is no longer an issue anyway.
Edits: 02/12/15Follow Ups:
~~!
The Mind has No Firewall~ U.S. Army War College.
I spoke to Mike Sanders and he makes some good points regarding point to point wiring. My last tube amp was an Anthem Amp 1, it was a great little amp but if a tube went it would almost always burn out the cathode resistor. Easy fix but it left burn marks on the circuit board. I replaced each resistor but didn't push the legs of the res. all the way through. This elevated the res. about a centimeter above the board so it wouldn't leave markson the board.
After going back to solid state for a few years I got back into tube amps by buying a pair of Quicksilver Mid Monos used on impulse. I usually never just buy something on impulse but I got a great deal on a mint year old pair from a guy locally.
These amps are awesome, they sound way bigger than their 40 watt rating. They are built like a tank and are the quietest amps I've ever owned, tube or solid state. I am using them with a conrad-johnson Classic 2 SE and it's a great combo.
I really wanted a c-j Classic 60 amp but with a kid in college that would have been irresponsible, so the Mid Monos only cost $200 after selling my McCormack amp. Best purchase in a long time.
I like Mike Sanders, straight up guy. He once bought a stepped transformer attenuator from my best friend. Devilishly hard to wire up and Will wanted nothing to do with it. I think Mike wanted it for his own personal use and the challenge set forth.
The Mind has No Firewall~ U.S. Army War College.
Hopefully, you won't have to deal with something like that. But engineers don't like to waste space and they are probably some components on the other side. If those parts fail, you are in for a fun time. Look at what you need to do to get at the backside. I have sold off all my amps with circuit boards partly because of my experience dealing with them, and because I now build my own. regards, Dak
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