I've been reading about using a light bulb limiter

[SmogFighter]

Hi All,

As a noob here on this forum, I've scratched my head bald in one spot
contemplating the "Light Bulb Current Limiter".

After several hours of digging through posts I finally found it on page 4 of search results...

http://www.geofex.com/Article_Folders/SPO_Test.htm

The instructions on how to build one for yourself.

If the moderators can "sticky" the link, then everyone can benefit from
this excellent testing tool.

[Rockman]

I agree, should be a sticky, I've been thinking about building one and your link saved me time trying to search for a good reference.

[Krwkka]

Should be a sticky

Definitely should be a sticky. I built one and use it regularly. It's a great tool!

[Zouto]

It should be a sticky finally, it's a great and useful tool, I use it for a long time.

[SmogFighter]

bump

bump

[Wilder Amplification]

Simple light bulb in series with the mains...also serves as a visual indicator as to something still being shorted in a complimentary symmetry push-pull amp (if the light bulb comes on when powered up with no signal, it's not right. )

[SmogFighter]

exactly



It took me a couple of hours of reading posts before I found the instructions
on how to build 1.

I figured since it was a tool that was extremely helpful, It should be easier
to find.

[Enzo]

Enter "light bulb limiter" into google, and several articles about making one appear on the first page of hits, including RG's Geofex site.

[SmogFighter]

I concede....

Using Google, the info comes up on the first page.

[Axtman]

I built mine and use it all the time!

[oc disorder]

Some people have been using them for years

[Wilder Amplification]

Glad to see the light bulb has finally come on for some of you so to speak.

They're really useful for complimentary symmetry push pull solid state stuff as the only real simple way to fix these is to "shotgun" the whole board since they always blow random components every time they fry, but if you miss one component...BOOM! At least with the light bulb limiter, it's gonna limit the excess current enough to keep that from happening on power up. Under normal operation and no signal conditions, an amplifier should not be drawing enough current to light up the bulb so...if the light bulb comes on when you power the thing up, shut it down...something else is wrong and you just saved all your new components.

[Mars Amp Repair]

bulb limiter & variac

Well,
I fought using a bulb limiter for a long time until I realized that the variac even set at 2 volts still has the ability to provide 15amps of power at that 2 volts & still blow stuff or at the very least create one hell of a lot of current where you don't want it.

So All my techs now have a variac as well as the bulb limiter. I'm not so fond of the diagram attached in a previous post here as it requires you provide an external limter through the duplex outlet with no absolute isolation ie;DPDT mains switch. I much prefer mounting all that is needed on the same board. (see attached). you also can move this test fixture around in whole.

I also include a switch for bridging the bulb hence taking it out of the circuit once you've determined that the short has been resolved or upon initial power up, that there is no short. The switch is mounted upside down as to reduce confusion with the up-bulb in circuit' & down-bulb out of circuit- indication. I clearly mark it as shown.

The mains power switch is a double pole switch so you can leave the unit under test plugged in & be completely safe not having to constantly plug & unplug the device under test. It took a while to get to 'trust' that feature, but now I just do a visual to be certain the switch is 'OFF' & we're cool with it now.

glen

[Ronsonic]

Glad to see the light bulb has finally come on for some of you so to speak.

They're really useful for complimentary symmetry push pull solid state stuff as the only real simple way to fix these is to "shotgun" the whole board since they always blow random components every time they fry, but if you miss one component...BOOM! At least with the light bulb limiter, it's gonna limit the excess current enough to keep that from happening on power up. Under normal operation and no signal conditions, an amplifier should not be drawing enough current to light up the bulb so...if the light bulb comes on when you power the thing up, shut it down...something else is wrong and you just saved all your new components.

Here's another bulb trick, put an analog AC meter across the line on the safe side, and watch it when you power up your DUT. You can actually see a difference between an amp with shorted outputs and one where the drive/bias is screwed up and telling them to turn on. Watch the meter dive, and slam to zero or not, or dive and float back or bounce back. It's telling you something.

Remember, some amps will not like to start up with a safe light. They'll just lock up. Saw this on even a little 60W Crate. But if you jumper the bases of the outputs together then power it up with the light, you can remove the jumper and see if it runs.

There's dozens of tricks and gimmicks possible with these, experiment.

[52 Bill]

Glen:
The last one that I built used a double pole, center off switch that did the same thing. One position was limit, center was off and the third position was direct.