chinacave
Its Like a Jungle Sometimes; It makes me Wonder
On your questions:
1) Wide-band audio (for an RF engineer, this is an oxymoron) signals can be read with most any of the better digital volt meters (DVM) these days. For instance, my Fluke 117 specs a 5Hz-50KHz bandwidth for AC volt measurements. Most all but the cheapest of the DVMs I've seen sport input impedance specs that are like what a VTVM used to carry. So, just getting a decent DVM is about all you're going to need unless you have very specific testing requirements. BTW, the Fluke 117 also has a frequency counter, too. Really reduces the number of instruments you need on the bench.
2) PC-based measuring devices usually have some sort of 'front end' box that does the A/D work needed so the software package can do its job. Since you can get a really functional DVM for less, that's the way I'd recommend mainly because you can take the DVM where you'll not likely get a laptop and the dongle/outboard box setup. One thing I do usually have, however, is a small USB or Firewire device so I can use the PC as an audio signal generator. Room EQ Wizard has a host of nice utilities for sweep frequency and other things that get interesting for a work bench.
3) How fried is the board? If it was due to the larger resistors being mounted close to the board, just mount new ones standing away from it and you're set.
Cheers,
David
Hi David - Thanks again for your responses -
1) Looked up the specs of the 'best' DVM I have, and the AC response is 40-400Hz. Looks like I will be looking for a better one soon. The Fluke 117 you mentioned looks good - what should I be looking for in terms of input impedance, or is it ohms/volt? As I recall , VTVM's have a very high impedance. On my cheap DVM's this is not even listed. Is there a recommended minimum figure for accurate readings with tube circuits?
2) I think you are right - I feel I am spending too much time learning and obsessing about test instruments (right now), distracting me from the task at hand of re-building the amps. I will get a better DVM and look into PC based test-ware later.
3) Once stripped of all components, the board does not look half bad, just a lot of soot. Seems perfectly re-usable, even after ham-fisted de-soldering. Man they really wrapped the leads around the terminals in a death-grip! I found a purpose-built solder-iron with integral solder-sucker - $7.95 from MP Jones, I think - seems to work pretty well.
Thanks Again!