Start-up monitoring: how crazy do you get?

[jjasilli]

In a new build or re-build, I like to monitor volatges and current draw at strat-up, and when biasing the amp.  How for do you guys go?

E.g.:  you could have 3 meters for ea power tube to monitor plate voltage, screen voltage & current draw.  That's 6 meters for a PP amp just for 2 power tubes!  OTOH an array of cheap DVM's is possible.

Alternatively, is an idea from an old electronics magazine:  build a test probe switchbox, so several sets of test probes can be routed to one meter. 

What do you guys do to monitor start-up voltages & current?

[sluckey]

I just use one VOM and start up in stages, checking for expected voltages as I go. The procedure may vary slightly depending on the circuit, But basically before putting tubes in, I turn it on and check for proper PT voltages and watch/listen for boogers. I verify the bias supply if applicable. Then I check for proper filament voltage at all tube sockets by probing the tube side of the sockets. Then I enable the power supply and check for voltages all the way down the rail. Next probe the socket plate/screen pins for B+ and grids for negative bias if applicable (again from the tube side). I will set the negative bias to maximum if adjustable. I'm not looking for correct voltage at this point (still no tubes plugged in except maybe rectifier), but the presence of high B+ tells me that the plates are probably wired correctly. Then I pop in the little tubes and check for proper plate, grid, and cathode voltages (again knowing the plates will be high because no power tubes are plugged in yet). And finally I plug in the power tubes, monitoring cathode voltage/current. Hopefully it's time to plug in the guitar and watch/listen for surprises.

And don't forget your best monitors are on your face. I'm constantly looking, listening, and smelling for abnormal signs throughout the entire startup process.

[DummyLoad]

lamp limiter and at least 2 meters - have had up to 5 at once on a new start up. bias and B+ minimum.

[jjasilli]

Lamp limiter w/o question!  Then what?  Pull the tubes and then use sluckey's procedure.  That's good.  I've been starting with the power tubes.  But I guess it makes more sense to start with the preamp tubes.


at least 2 meters - have had up to 5 at once on a new start up. bias and B+ minimum. I am not alone!   

[stingray_65]

Just one meter

lamp limiter on initial startup.

It's quicker and easier for me to trouble shoot if the smoke comes out

All kidding aside

I've had 3 meters going at once AFTER it passed the smoke test, that was for a PS issue, turned out the PT was couldn't provide enough current and would sag real crazy like. Was neat to see each node and watch them interact.

I wished they all were analog, 2 meters its difficult to monitor numbers 3 impossible for me, but if they were analog, you twist the meter so that the expected reading is 180deg from your view point. all straight up and you're good. a little left or right and you know  if you're high or low.

Ray

[LooseChange]

Light bulb limiter and a meter. No tubes, Add rectifier then power tubes then preamp tubes.  Chek voltages as I go.

[jjasilli]

Stingray_65:  I've had 3 meters going at once AFTER it passed the smoke test. . . 2 meters its difficult to monitor numbers 3 impossible for me  Good point.  I had considered maybe an array of cheap DMM's. maybe velcro them to an upright board and label them, like V4 Plate, V3 Screen, etc.  But I agree that'as too much visual info to keep track of.

if they were analog, you twist the meter so that the expected reading is 180deg from your view point. all straight up and you're good. I guess you mean to skew the Zero Adj knob so that a known good reading is moved to center scale.  That's brilliant in its simplicity!  Now the visual info is manageable.

LooseChange: Light bulb limiter and a meter. No tubes, Add rectifier then power tubes then preamp tubes.  Chek voltages as I go.  Sounds like another good procedure.  Thanks!