First start up

[überfuzz]

The other day I had a conversation with a HiFI-dude. Among other things he showed/explained me how he do first start ups. Quite a procedure... I also implement a high advanced technique called, well, lets call it, if it blows up it blows up. Seriously though, I just have the all familiar nervous moment before I switch the ON/OFF switch. If something goes south I think, better now then in a day or two. (During our conversation I just sort off nodded all serious like I appreciated the fact that he took it all that serious.)

Please enlighten me, how do you folks fire up your builds.

[jazbo8]

Usually with a light-bulb limiter and/or a variac on the mains. For a more detailed explanation, see this guide.

[überfuzz]

Hm, most off these checks goes into what I consider build time. I guess I'm not such a crude fella after all, ah well...

[Jack Hester]

Usually with a light-bulb limiter and/or a variac on the mains. For a more detailed explanation, see this guide.

What he said.

My lamp limiter goes on old amps, before and after repairs. And, on new construction.

Jack

[überfuzz]

When I'd read the guide you linked I did some simulation of the power dissipation in the filter resistors. Seems they take quite a beating, in every power up.

[ATTACH=CONFIG]31703[/ATTACH

This would be the resistors after the choke.

[gui_tarzan]

Light bulb limiter, I don't have a Variac yet.

[Jon434]

Usually with a light-bulb limiter and/or a variac on the mains.

This is how I intended to do it, you can even use different wattage lightbulbs as a poor mans variac, but obviously the best situation is a light bulb & variac.

[Alan0354]

When I build, I power up one section at a time. Make sure that section works before building another section. This is how I do it:

1) Put the PT in, Hook up the PT with the switch, then turn it on to check all the AC voltage.
2) Put the rectifiers and reservoir caps. Then put a 220K 2W resistor from +B to ground. Fire it up and measure the voltage. The resistor is to drain the voltage of the cap down when turn off. Always check the voltage with the DVM to make sure it's save to touch it.
3) Put in the choke and the other power supply stuff and test.
4) Do the same with -ve grid bias and filaments to verify every voltage is there. Make sure the -ve bias voltage is in range suggested by the power tube.
5) Then build the power tubes section with OT, You don't need to build the PI stage, connect the -ve grid bias to the grid leak resistors. Put a 1ohm resistor from cathode of each power tube to ground. Double check all the wiring.
6) Turn on the power and check the voltage across the 1ohm resistor. The scale is 1mA per mV. Adjust the current to spec. Check the voltage at the plate and screen grid to make sure it's all there.
7) Then build the PI stage with the feedback from the secondary of the OT back to the PI. Double check the polarity before power it up. I would put a dummy load as speaker load to do this step. Use the scope to make sure there is no oscillation.

If you get to this point, you pretty much get the critical things out of the way. Then you build the preamp section. Don't build the whole thing and try power it on. Too many things can go wrong and you don't know where to start. Bring the amp up stage by stage so if anything happens, you only have very little to troubleshoot. Double check your work every time before you power it up.

I never use a variac even I have one. You can use one to be safe, but bring it up one stage at a time. So when you run into problem, you can rest assure the former stages are all tested already, you only have the new part to trouble shoot.

This is how I build my amps, I never run into problem.

[überfuzz]

Thanks Alan! Seems simple and sensible.

[J M Fahey]

Having built well over 10000 amps (that was around 1997 and then stopped counting) I still never ever turn a new build straight on but through a bulb limiter.
Take that as a favorable vote towards its use.

Also on stuff on repair, both before (just arrived) and after (hopefully full repaired).
Go figure.

I even built a small portable one, out of an extension cord and a lightbulb socket, to carry in my service toolbox.

[big_teee]

+1 for the Dim Bulb Tester.
I have one with 2 bulbs, and use different sized bulbs, for different things.
It also works great to reduce the temp on my small Crock pot I use to melt wax for wax potting pickups.
T

[Jon434]

To me, it's one of those things where it's small and cheap and easy to make, and there is lots of upside to using it, and very little downsides. Anything that increases safety is a good thing IMO.

[JoeK]

You would be very confident if you don't use a current limiter. If it's an old amp that's been sitting in a garage for a long time or a new build that has problems I would check your mains earth is connected to your chassis. I'm in Australia so unless the appliance is double insulated (shaver etc) we have an earth. I took a 60's vox to an old amp tech for a once over as I was worried I might do damage on first power up after years of hibernation and he tested the mains earth first and found the earth was removed in the socket. These days I have a current limiter and variac.

[überfuzz]

edit, double post...

[überfuzz]

5) ... Put a 1ohm resistor from cathode of each power tube to ground. Double check all the wiring.
...

What watt rating should this resistor have..?