Re: bridge rectifier error?!

by aminoacid on Wed May 30, 2012 4:03 am

ill look in to the zener (d43) shortly. however its followed by a npn transistor. is that gonna make the zener work at one voltage drop higher??? should i add a diode for this aswell?

another thing i thought about is that in the 303, the ac from the transformer is rectified by only one diode. while the xox rectifies in both ways. so that should leave half wave in the 303 and full wave in the xox. am i wrong?

i thought about removing d43 in the rectifing bridge of the xox to make it halfwave, but is d43 part of the voltage doubler???
Last edited by aminoacid on Wed May 30, 2012 12:23 pm, edited 1 time in total.
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Re: bridge rectifier error?!

by gompie on Wed May 30, 2012 6:50 am

aminoacid wrote:
another thing i thought about is that in the 303, the ac from the transformer is rectified by only one diode. while the xox rectifies in both ways. so that should leave half wave in the 303 and full wave in the 303. am i wrong?

i thought about removing d43 in the rectifing bridge of the xox to make it halfwave, but is d43 part of the voltage doubler???


The lower half of the voltage doubler is used as input of voltage regulators IC20 and IC21.
The lower half is also the part which is half rectified or 'halfwave' like you mentioned.
The upper part is fully rectified, but since its on top of the lower half to get the double voltage, the doubled voltage will also suffer from the ripple created by the halfwave in the lower part. Removing D43 will put a half wave on top of a half wave for the voltage doubler. They would also be out of phase, so I don't know what kind of voltage ripple you would get on C5 which is placed there to even things out so you get your DC.

Then, do you really want a 50Hz-ish hum to modulate your tuning, VCA, VCO, Mixer?
It's checked pretty easily, but I predict the outcome to be pretty unwanted.
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Re: bridge rectifier error?!

by aminoacid on Wed May 30, 2012 3:40 pm

i would listen to anybody who is giving advice on this, im not to good with it, so ill pass the removal of d43 :)

i was thinking that i could get closer to the 303 by using half wave rectification. similar circuit with similar rippel if you follow me?!

i tried the 15V zener from r1-c5 to ground. but it didnt work. the voltage didnt get far and the zener got very hot before i pulled the power.

maybe a regulating circuit is required like in the 303... a transistor sinking the voltage doubbler perhaps...
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Re: bridge rectifier error?!

by Altitude on Wed May 30, 2012 6:40 pm

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Re: bridge rectifier error?!

by gompie on Thu May 31, 2012 1:59 am

aminoacid wrote:i would listen to anybody who is giving advice on this, im not to good with it, so ill pass the removal of d43 :)

i was thinking that i could get closer to the 303 by using half wave rectification. similar circuit with similar rippel if you follow me?!

i tried the 15V zener from r1-c5 to ground. but it didnt work. the voltage didnt get far and the zener got very hot before i pulled the power.

maybe a regulating circuit is required like in the 303... a transistor sinking the voltage doubbler perhaps...



If you want to regulate the power to 15V, use a 15V regulator, but then you will lose all powersupply ripples (to me thats good, but aparently you want them :) ). If you want more ripple, decrease the uF value of the capacitors (not the voltage), or take them out (now there's a ripple!)

on a side note: I replaced the 5.0 V regulator with a "R-78B5.0-1.5" I did that because this one generates no heat. The 5 volt regulator has to burn so much energy to stay at the 5.0V with a decent current, that thats the reason why the heatsink is on there. The tuning circuit should be temperature independent because of the extra diodes that were put in, but I'd like the circuit to compensate for amient power and not trapped hot air from a heatsink all across the circuitry.

Cheers
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Re: bridge rectifier error?!

by evostars on Thu May 31, 2012 4:59 am

Gompie, where did you buy that R-78B5.0-1.5? Looks good to me.
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Re: bridge rectifier error?!

by evostars on Thu May 31, 2012 5:00 am

Altitude wrote:This might be useful: viewtopic.php?f=12&t=17037&p=86295

Thanks!
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Re: bridge rectifier error?!

by gompie on Thu May 31, 2012 5:13 am

evostars wrote:Gompie, where did you buy that R-78B5.0-1.5? Looks good to me.


You can order it online from RS or Conrad. Mind you that it is not a very banned component.
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Re: bridge rectifier error?!

by evostars on Thu May 31, 2012 5:22 am

gompie wrote:
evostars wrote:Gompie, where did you buy that R-78B5.0-1.5? Looks good to me.


You can order it online from RS or Conrad. Mind you that it is not a very banned component.

Thanks, but RS? whats that? oh I guess Radio shack?
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Re: bridge rectifier error?!

by gompie on Thu May 31, 2012 7:07 am

evostars wrote:Thanks, but RS? whats that? oh I guess Radio shack?


Nope, RS-components is like Farnell.
For banned components online in your area I'd suggest dickbest [dot] nl
Funny name, but the prices of their components and shipping costs are also a joke :)
I would have bought the R-78B5.0-1.5 regulator there, were it not that they did not have it....
One of the few companies that offers the option to ship your components via letter post instead of charging for a complete package while ordering one or few small components!
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Re: bridge rectifier error?!

by evostars on Thu May 31, 2012 7:10 am

gompie wrote:
evostars wrote:Thanks, but RS? whats that? oh I guess Radio shack?


Nope, RS-components is like Farnell.
For banned components online in your area I'd suggest dickbest [dot] nl
Funny name, but the prices of their components and shipping costs are also a joke :)
I would have bought the R-78B5.0-1.5 regulator there, were it not that they did not have it....
One of the few companies that offers the option to ship your components via letter post instead of charging for a complete package while ordering one or few small components!

Thanks! Cool :-)
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Re: bridge rectifier error?!

by aminoacid on Fri Jun 01, 2012 5:13 am

wouldnt a 5Vac adapter be better by the way???

closer to 15V after the voltage doubler and less heat loss in the 5v reg.
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Re: bridge rectifier error?!

by evostars on Fri Jun 01, 2012 5:21 am

aminoacid wrote:wouldnt a 5Vac adapter be better by the way???

closer to 15V after the voltage doubler and less heat loss in the 5v reg.

(5*1.4)-1.1=5.9v *2= 11.8v
No its not enough. The diodes drop the voltage by 1.1V
The opamp needs 13.9v at least
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Re: bridge rectifier error?!

by MMM on Fri Jun 01, 2012 9:42 am

I'm a bit late to the party, I know. Last week I was thinking pretty much along the same lines when getting into the power supply issue.

I wonder what the rationale was behind the design (as a whole). After all, using AC power adapters is comparatively uncommon (there are many more devices using DC adapters).

The power supply in the original 303 and 606 used a very different design for the "early stages". It involved an (impossible-to-find) DC-DC-converter. But theoretically there are modern substitutes for it.

Edit: I've also been wondering why the input to the first opamp is always below 5.33v for the output to reach 5.33v. On the power supplies I'm having around at the moment the input is about 5.20v but the output is 5.33v. Theoretically the opamp should be just a buffer, right?
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Re: bridge rectifier error?!

by evostars on Fri Jun 01, 2012 10:23 am

MMM wrote:I'm a bit late to the party, I know. Last week I was thinking pretty much along the same lines when getting into the power supply issue.

I wonder what the rationale was behind the design (as a whole). After all, using AC power adapters is comparatively uncommon (there are many more devices using DC adapters).

The power supply in the original 303 and 606 used a very different design for the "early stages". It involved an (impossible-to-find) DC-DC-converter. But theoretically there are modern substitutes for it.

Edit: I've also been wondering why the input to the first opamp is always below 5.33v for the output to reach 5.33v. On the power supplies I'm having around at the moment the input is about 5.20v but the output is 5.33v. Theoretically the opamp should be just a buffer, right?

Its wired as a buffer. Cant be right to put 5.2 in and get 5.33 out.
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