Math Formula to calculate DC power supply capacitor value?

unclejed613 · Nov 20, 2018

shortbus= said:
After reading most of your postings over the years I'm surprised you haven't won a Darwin Award, or at least been a runner up.

he's currently in the running for a Wile E Coyote award... an "ugly construction" or "ball of components" inverter, attempting to go over 1KW would certainly qualify...

shortbus= · Nov 20, 2018

MrAl said:
Hi,

Well once the shunts are removed it changes all that i think. I havent done any measurements yet though but the current should eb higher without the shunts.

Hi,
But even then, why would you change the primary instead of the secondary for low volage stuff? Which is what he is wanting in most of his threads. Why keep the ~2200 volt low amp secondary, and reduce the primary to give a lower voltage. Unless I'm totally missing something.

MrAl · Nov 20, 2018

shortbus= said:
Hi,
But even then, why would you change the primary instead of the secondary for low volage stuff? Which is what he is wanting in most of his threads. Why keep the ~2200 volt low amp secondary, and reduce the primary to give a lower voltage. Unless I'm totally missing something.

Hi,

Oh he wanted to do that?
The way i read it was that he wanted to increase the primary turns so that the transformer could better handle the 120vac input line, which it appeared to have trouble doing right now due to the shunt removal and the fact that it's probably made for intermittent duty anyway.

[corrected as per next post]

rjenkinsgb · Nov 21, 2018

MrAl said:
lower the primary turns to lower the secondary voltage,

Sorry, but that is totally backwards?

Decreasing the primary turns increases the secondary voltage (for the same secondary).

MrAl · Nov 21, 2018

rjenkinsgb said:
Sorry, but that is totally backwards?

Decreasing the primary turns increases the secondary voltage (for the same secondary).

Hi,

Yes, thanks for catching that i must have been half asleep
I'll correct that.

shortbus= · Nov 21, 2018

MrAl said:
Oh he wanted to do that?

Yeah as usual his threads kind of ramble off into other things, so you may be right. But this started out with low voltage power supplies.

JonSea · Nov 21, 2018

This thread reminds me of these.....

gary350 · Nov 21, 2018

MrAl said:
Hi,

Well once the shunts are removed it changes all that i think. I havent done any measurements yet though but the current should eb higher without the shunts.

Power does go up when shunts are removed. I removed shunts from a 30ma neon transformer power went up to 50ma. Transformer had to be put in transformer oil to keep it from burning up wire was too small for 66% more power.

Did I mention in another post high quality auto output transformers are rates to handle 3 times more than the rating. A 100 watt tube = valve amp can handle 300 watt peaks. If a poor quality transformer cuts peaks off a class A amp it sounds like class C amplifier with power turned up high.

MrAl · Nov 21, 2018

shortbus= said:
Yeah as usual his threads kind of ramble off into other things, so you may be right. But this started out with low voltage power supplies.

Hi,

Yeah i thought we were talking about a bridge rectifier power supply for a while there
Most basic type so it's usually asked about a lot.

MrAl · Nov 21, 2018

gary350 said:
Power does go up when shunts are removed. I removed shunts from a 30ma neon transformer power went up to 50ma. Transformer had to be put in transformer oil to keep it from burning up wire was too small for 66% more power.

Did I mention in another post high quality auto output transformers are rates to handle 3 times more than the rating. A 100 watt tube = valve amp can handle 300 watt peaks. If a poor quality transformer cuts peaks off a class A amp it sounds like class C amplifier with power turned up high.

Hi,

Oh that's interesting. Also reminds me many many moons ago when i was in a rock band and i was playing lead guitar BUT using a bass amplifier with valves and two large audio transformers. During one performance, one of the transformers got too hot and whet into some kind of thermal shut down during a song and the band leader got mad at me and tried to get me to go out an buy a whole new system. He was right though, i should have
There were two channels and i wired the first into the second to get more amplification, but the second transformer had a hard time with that. It worked for a long time before that happened though so it was a BIG surprise when it shut down.

Nigel Goodwin · Nov 22, 2018

MrAl said:
It worked for a long time before that happened though so it was a BIG surprise when it shut down.

Hell of a surprise, as there's usually no shut-down mechanisms in valve amps - you obviously blew something.

MrAl · Nov 22, 2018

Nigel Goodwin said:
Hell of a surprise, as there's usually no shut-down mechanisms in valve amps - you obviously blew something.

Hi,

Yeah, to this day i cant explain it. I said there was a shutdown due to the transformer, but i dont know of any there really that could cause it.
Maybe a 'valve' overheated or something because after a few minutes it started working again and we were able to continue the concert.
Maybe there was a mechanism built into the amp circuit that would shut it down if something got too hot, but then why didnt it shut down again later.
Shame of it is that i had the complete schematic so i could have reviewed it today and even posted it online for comments right here, but it's long gone. Once i got rid of the amp head i didnt care too much about the schematic anymore.
The name of it was "Ampeg". It came with a large speaker enclosure with an 18 inch speaker inside. (Yes that is 18 not 15).
The amp head was separate from the speaker enclosure though. It was really made for a bass guitar. Date of production was probably around 1970 plus or minus 5 years.

This might have been the model:
**broken link removed**

gary350 · Nov 22, 2018

MrAl said:
Hi,

Yeah, to this day i cant explain it. I said there was a shutdown due to the transformer, but i dont know of any there really that could cause it.
Maybe a 'valve' overheated or something because after a few minutes it started working again and we were able to continue the concert.
Maybe there was a mechanism built into the amp circuit that would shut it down if something got too hot, but then why didnt it shut down again later.
Shame of it is that i had the complete schematic so i could have reviewed it today and even posted it online for comments right here, but it's long gone. Once i got rid of the amp head i didnt care too much about the schematic anymore.
The name of it was "Ampeg". It came with a large speaker enclosure with an 18 inch speaker inside. (Yes that is 18 not 15).
The amp head was separate from the speaker enclosure though. It was really made for a bass guitar. Date of production was probably around 1970 plus or minus 5 years.

This might have been the model:
**broken link removed**

Transformers these days have a thermo over load built right into the transformer soldered to the B+ wire. Old transformers never had that but some companies added them externally. Internal over load turns the transformer off before the winding gets hot enough to burn up. With external over load coil can heat up faster than the EI core then coil burns up before over load turns off. If transformer heats up slow external over loads work good.

Nigel Goodwin · Nov 23, 2018

gary350 said:
Transformers these days have a thermo over load built right into the transformer soldered to the B+ wire.

But they didn't back in the days we were discussing.

schmitt trigger · Nov 23, 2018

That is also my recollection.
Back on those days, all you had for protection were cartridge fuses.

Nigel Goodwin · Nov 24, 2018

schmitt trigger said:
That is also my recollection.
Back on those days, all you had for protection were cartridge fuses.

If you were lucky

To be fair thermal fuses in transformers are a pain in the bum, they commonly fail for no apparent reason whatsoever.

gary350 · Nov 24, 2018

Nigel Goodwin said:
If you were lucky

To be fair thermal fuses in transformers are a pain in the bum, they commonly fail for no apparent reason whatsoever.

YES I found that out. Transformer tested bad but it is not fried I pealed back the covering soldered a wire across the over load device now it works perfect. LOL

schmitt trigger · Nov 26, 2018

If I remember correctly, one of the drivers to remove replaceable cartridge fuses was the fact that many users which had experienced a fuse blowout would replace the fuse with a higher rated one....or bypass it altogether with aluminum foil.....creating a fire hazard.

Thus the NON USER REPLACEABLE COMPONENTS label printed on consumer electronics from the early 1980s (if I remember the date correctly)

Nigel Goodwin · Nov 26, 2018

schmitt trigger said:
Thus the NON USER REPLACEABLE COMPONENTS label printed on consumer electronics from the early 1980s (if I remember the date correctly)

Except usually the only change was the addition of the label, although occasionally they replaced the clip-in fuse by a soldered in one.

schmitt trigger · Nov 26, 2018

Indeed, Nigel, that was the first step.
But eventually they went with fuses embedded inside the transformer itself.

Math Formula to calculate DC power supply capacitor value?

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