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My new toy-cum-puzzle arrived! It's a Lafayette vacuum tube volt meter, all the way from sunny California. I haven't had a chance to get good photos, so please forgive this poor-quality cell-phone snap from last night.
To prepare for its arrival, I've been reading a few documents from the internet on VTVM theory of operation. That plus all the stuff I've learned from Michael Geier's book really helps me make sense of what's going on in there! In broad strokes, anyway.
To err on the side of caution, I'm not going to be plugging it in for some time. Not least because, on first inspection, I see that there is a blown fuse that has been jumpered around (that's the two yellow alligator clip leads in the photo). First, I'm going to trace along all the connections and draw a diagram. That will let me compare it to diagrams of other VTVMs that I've been able to locate; similarities will help me understand this particular one better. I'm hoping I'll be able to figure out a lot of component values without having to desolder and test. It would be nice to figure out what value that fuse ought to have too.
The tube sockets on the (one-sided!) circuit board are marked for a 6BN8 and a 12AU7. My reading suggests these are very typical tubes for a VTVM, but one of them is labeled differently. It's an Admiral tube, so maybe it's a comparable one with a house number; I'll try to track that down too.
The meter on this instrument is gorgeous! More pictures will follow.
(This really is, in some ways, a lot like Factorio.)
To prepare for its arrival, I've been reading a few documents from the internet on VTVM theory of operation. That plus all the stuff I've learned from Michael Geier's book really helps me make sense of what's going on in there! In broad strokes, anyway.
To err on the side of caution, I'm not going to be plugging it in for some time. Not least because, on first inspection, I see that there is a blown fuse that has been jumpered around (that's the two yellow alligator clip leads in the photo). First, I'm going to trace along all the connections and draw a diagram. That will let me compare it to diagrams of other VTVMs that I've been able to locate; similarities will help me understand this particular one better. I'm hoping I'll be able to figure out a lot of component values without having to desolder and test. It would be nice to figure out what value that fuse ought to have too.
The tube sockets on the (one-sided!) circuit board are marked for a 6BN8 and a 12AU7. My reading suggests these are very typical tubes for a VTVM, but one of them is labeled differently. It's an Admiral tube, so maybe it's a comparable one with a house number; I'll try to track that down too.
The meter on this instrument is gorgeous! More pictures will follow.
(This really is, in some ways, a lot like Factorio.)
