Forming Caps?

[gearhead]

Are there short or long-term benefits to "forming caps" as described:

http://forum.metroamp.com/viewtopic.php?t=13240

or is this just one of those things like speaker break-in?

[FUCHSAUDIO]

It cannot hurt, although a new high grade cap likely won't need it.

The easiest way to do it is a high value resistor (470-K or more), a bench power supply, and the cap. Connect the cap through the resistor to the power supply, which should be set to the maximum DC value of the cap. It will take about a day for the cap to reach the full power supply voltage (the time constant of the cap value and resistor value determines the time it will take). Once it's reached operating voltage, it's formed. Discharge through a resistor (200 or 300 ohms 5-W), and it's ready to use. Surplus or old caps can benefit more than brand new ones.

We do not form caps in our production amps, and have no failure problems with our electrolytics. We use Panasonic, Xicon or Nichicon caps in our amps.

[Structo]

Would using a light bulb current limiter on an amp start up (no tubes) qualify as forming the capacitors?

[FUCHSAUDIO]

Light bulb or variac is cool, if you don't have a bench power supply available.

af

[chocopower]

........ repeat

[chocopower]

What bulb watage do you use in a 220 volt area. I,m from Spain and maybe next week i´ll do a cap job.....


In my guitar amp, of course.... my wife is ok for the next 10 years....

[mhuss]

I don't think the voltage matters, a 60 watt bulb meant for 220 will have a higher internal resistance and admit about half the current of its 120 volt cousin, but still consume 60 watts of power.

IME a 60w bulb works fine for most amps.

--mark

[gearhead]

A light bulb? Where would you place it for an Express(no tubes of course)? Between the rectifier diodes and the first cap in place of the connector wire? Assume you would disconnect the two 100k 3Ws?

[FUCHSAUDIO]

It's put in series with the AC line, in series with one leg of the AC line.

[mhuss]

Yes, you make up a jig with an AC plug and socket, and put the light bulb in series in one line (hot or neutral) between the two.

When the U.U.T. (amp) is OK, the lamp glows dimly, and the amp doesn't get enough juice to work properly.

When the U.U.T. has a severe fault, the lamp glows at normal brightness (but typically does not blow a fuse or otherwise damage the U.U.T.)

This is a cheap and easy way to safeguard that "first time" power up of a new build or repair.

--mark

[gearhead]

Ooh OOh, I know what a UUT is (Unit Under Test). Mil background?

AC Line; you mean the INPUT to the PT and not inside the circuit?

That's great to know for a first time fireup, will try that for sure.

AFA forming caps, would you just then pull the tubes and fire up with the bulb in line?

[Structo]

Here is the D'Lite building guide.
If you scroll down near the bottom it gives the start up procedure and shows how to make a light bulb limiter.
http://bad-domain/DumbleLite/BuildersGu ... 0Guide.htm

[mhuss]

Ooh OOh, I know what a UUT is (Unit Under Test). Mil background?

Nah, I don't remember where I picked up that bit 'o jargon.

AC Line; you mean the INPUT to the PT and not inside the circuit?

Yes, the picture in Normster's build guide is very clear.

AFA forming caps, would you just then pull the tubes and fire up with the bulb in line?

No, you can leave the tubes in. The trick is to charge them "gently" the first time instead of slamming them.

--mark

[JimiB]

I actually put a light bulb socket in every amp I build.





not really






sorry

[gearhead]

AC Line; you mean the INPUT to the PT and not inside the circuit?

Yes, the picture in Normster's build guide is very clear.

--mark

Ahh, got it. Didn't know about Normsters build guide before (used Ruby's).

I wonder if Matchless Amps benefit from all those light bulbs inside? LOL.