New Build: Start-up procedure

[Sir Cuitous]

Can anyone give me a point by point start up procedure for powering up an amp for the first time? I have a variac and have relied in the past on simply bringing the power up slowly and watching for arcing, squealing, etc. Can I start up with no tubes? All tubes? Are there certain checks that I should do?

[andrew_k]

http://paulrubyamps.com/info.html#FirstPowerUp

[tubeswell]

Hi Sir Cuitous

The way I start is with no tubes, and I measure the HT and the heater winding. Make sure the speaker is plugged in. Then I switch it off and plug in the rectifier and make sure I've got a B+ (doesn't matter what value so long as its high - anyhow it'll just keep climbing without a load, so you need to switch it off before the filter caps explode). When I'm happy that I've got a B+, I switch it back off and pop the other tubes in and then I run it for while on the bench to make sure there's no burning smell or smoke coming out. Then I check the output tube dissipation and adjust bias accordingly to taste - and do a whizz-bang check of all the plate voltages, before plugging it in to evaluate the tone and start troubleshooting any other issues (dare I mention ground loops?). And that's about it

[Sir Cuitous]

Thanks, I browsed that page some time ago, but forgot about the power-up info. I'm not sure what the difference is between keeping the PT secondaries unsoldered and just leaving the rectifier tube out. But, it's pretty straightforward.

[Diablo]

I just put it on standby, measure and adjust the bias voltage to a reasonable range, then flip the switch, make guitar noise, and last check the B+ voltage for curiosity. It works for the lazy.

[Sir Cuitous]

The least I have ever done is to simply bring the voltage up slowly with all tubes and watch and listen carefully. I may end-up doing something about halfway between the Paul Ruby "treatise" and your suggestion - just about what Tubeswell does. I do visually inspect my circuit and check off my layout to make sure I haven't missed anything. I spend a lot of time with my layouts on paper before building. I have caught mistakes on paper and I would rather make them there.

[GregS]

I did the full Paul Ruby first power on procedure for an amp I recently built. I didn't find it to be laborious or tedious at all. I also checked and re-checked my wiring and connections a zillion times before turning the power on. However, you can never be too safe or sure. It would be a much bigger pain to have to replace a blown transformer than to go through the first time power on procedure. My 2 cents.

Greg

[Five_E35]

The way I figured it, having a Variac to bring it up with means it's far less likely anything serious will be wrong

With my 5E3 build, I wired everything, stuck a plug-in SS rectifier in it(a tube won't come up right), connected an old 'disposable' speaker(important) and ran the variac up to ~60 volts with no tubes on standby. Checked the filaments & they were OK so, I took it off standby and checked the voltages down the power rail and at the tube sockets. Ran it up to 90V & got a wisp of smoke as a stranded wire whisker vapoized itself between a power tube plate and filament terminal. After checking for any more of those I redid it at 90V & checked. Shut it down, stuck a known good set of tubes in it, and fired it up on standby with the Variac at 100 volts & rechecked the filaments. Took it off standby - no bad noises from speaker, so up to 115V where I checked what the power tubes were drawing. Let it cook for about 15 minutes & then shut it down, connected a good speaker cab and just had to play it!

.... 2 days later, I stuck a 5AR4 & 5881's in it and cranked the B+ up to 400V. After resolving some noise problems and experimenting with grounds, went back to the 5Y3 & 6V6GT's and have been playing it ever since, experimenting with different tubes, etc. I don't have a scope, but I plan to put a signal generator & dummy load on it & measure the A.C. voltages & output power(official Fender schematics have those voltages), when I get around to it

[MWJB]

"With my 5E3 build, I wired everything, stuck a plug-in SS rectifier in it(a tube won't come up right)," A tube rectifier will work perfectly well from 1/3 of wall AC upwards, at <1/3 wall AC you would be very unlucky indeed to have anything go pop.

[Dave Curtis, dB AudioTech]

FWIW, with no tubes installed you really don't need a load on the OPT, except that you might forget it when you stick the tubes in, so it can't hurt.

The poor man's variac (series light bulb socket) is a lot cheaper, and IMHO, gives a better indication of a short ckt. I have one wired in series with my variac, not even as fancy as this one:
http://antiqueradio.org/dimbulb.htm