[sdiy] a little knowledge is a dangerous thing !

[Lanterman, Aaron]

On Apr 25, 2012, at 6:58 AM, Roger Mote wrote:

> Are you sure? Check at 8:25 the cap he says is bad is close to him. To determine this, he's probing nowhere near its leads when he makes the 48 ohms statement.


I am skeptical for three reasons:

1) A few moments prior to that he makes a reference to checking every part with his meter.

2) 47 is a common cap value. 47 is a quirky number, unlikely to pop out of someone's head, so I suspect he read it off a cap.

3) Looking at typical tube amp schematic (including, say, that of a Fender Princeton Reverb), I'm hard pressed to find a cap where I'd expect to measure 47 or 48 ohms across it, based on looking at the other resistor values. (There's also the issue that he never makes any reference to any documentation of any sort, let alone a schematic, let alone some record of resistances measured on a working amp).

- Aaron