Output Capacitor Upgrading Questions

[earwaxxer]

There, there Greg... Your story is good too! 

[4krow]

  Eric dyes his hair

[Grainger49]

John,

I know the old screwdriver across the cap trick, but I thought that military electronic schools taught you to use a wirewound resistor.

[John EH]

John,

I know the old screwdriver across the cap trick, but I thought that military electronic schools taught you to use a wirewound resistor.

There's the rub.  My guys support this electric/electronic piece of gear with zero electrical training.  Just an A school taught by guys who also have no electrical training.

[4krow]

  Actually minimal training for trainers doesn't just happen in the military. Look around you, it's the accepted level everywhere.

[Grainger49]

I can't give an opinion for today's military, but... the training my contemporaries got was exemplary!  Set this in the 1960s and 1970s.  It would be a travesty if this did not endure.

[monsterdonkey]

Capacitor DOWNGRADE question:

I'm putting together my first Crack and I've found the output caps are missing from my kit. My local electronics shop has 100uf / 160V electrolytic caps for $1.20 each. No brand name listed on the site. If I stick those in while I wait for the stock ones to arrive will my life be ruined? Any suggestions for alternatives?

Thanks
Rob

[Paul Birkeland]

100uf/160V generic caps will function in the interim.

-PB

[galyons]

Capacitor DOWNGRADE question:

I'm putting together my first Crack and I've found the output caps are missing from my kit. My local electronics shop has 100uf / 160V electrolytic caps for $1.20 each. No brand name listed on the site. If I stick those in while I wait for the stock ones to arrive will my life be ruined? Any suggestions for alternatives?

Thanks
Rob

A life without music is already ruined!  $2.40 to hear the first notes?  What's to lose?  Just tack 'em in and listen until the caps arrived.

Cheers,
Geary

[monsterdonkey]

I thought so. Thanks guys.
This is what happens when you are too lazy/excited to verify the BOM.

[wullymc]

You can measure the unstriped end of any of the black power supply caps.  Anything below 10V is low enough to work on, and the power supply is self draining, but it takes a little time.

-PB

Sorry Paul but I have another question.  How long should it normally take for the power cap to go down to 0.  I wanted to test it today so I powered up my Crack and measured the voltage at terminal 13.   It was 172V.  I next turned off the power and remeasured.  It now measures 0V.  Would this cap discharge so quickly?  I thought it would take some time (more than 1 minute) for the cap to discharge.  Does this sound right?

Thanks...Dave

[Doc B.]

Don't disconnect the meter. Leave it connected and watch the rate of drop after you turn off the switch. It might take anywhere from a few seconds to a minute to drop.

[wullymc]

Perfect!!!

Thanks Doc!  Appreciate it!!

Take care...Dave

[Paul Birkeland]

The rate of discharge depends on many things. 

If you have tubes that are warm and conducting, they can help draw down the voltage in the power supply.

If you have the Speedball installed, it will drain the power supply pretty quickly to around 3V.

If you have no warm tubes, no Speedball, and a loose 270K resistor, the power supply may never drain down

[Downhome Upstate]

I can't give an opinion for today's military, but... the training my contemporaries got was exemplary!  Set this in the 1960s and 1970s.  It would be a travesty if this did not endure.

I still remember the my USAF basic electronics instructor at Keesler airplane camp explaining the difference between two components or circuit topologies (this was 1973, can't remember details). "This is the same [as the last one we discussed], only different."