Bauman PSU
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pmroz
Well-known member
Depends on your power trafo output. From Joe's post above..
1. Figure current(I) that the 5V rail will supply. This rail powers the leds and relays on pres. no relays here, so i estimated Imin = 50ma.
2. Figure Vdrop through the 7805... depends what Vavg you have at R1/C1, which depends on your power trafo.
... i get 33V Vavg here, and the 7805 wants maybe 9 volts to make 5, so 33-9 = 24V.
24V/.05A = 480ohm
24v * .05A = 1.2W
In my mind (may be wrong) it made sense to use both min and max current calculations. Then use V/I from min current = resistor, (the 7805 will always get the V it needs) and use max current for the wattage rating (max current= as hot as it will get) and go a little higher. Then figure heat dissipation for 7805 and a big enough heatsink for that.
If you leave R10 on the 48V rail, you have to figure Vdrop from 48V to 9V, etc...
Yeah, Greg could confirm this... look under the board and see which leg of R10 has a trace that goes straight to REG_SW (LM7805), just like on the schematic. Leave that leg there... the other leg is the one you want to attach to C1/R1
Greg
Well-known member
I use 470R 5W for R10 :thumb: !!! I lifted the lead as pmroz said and connected a wire from R10 the + of C1.
pmroz
Well-known member
... another question... almost done with PSU. Regs are on the edge of the board next to wiring terminals. i'm thinking of bending the reg leads (carefully, the bend would be 1/4 in or so above PCB) so that the regs go 90deg flat off the side of the board, to allow for bigger heatsinks and less worry about frying wire insulation.
...does this sound ok? or bad idea...
...does this sound ok? or bad idea...
pmroz
Well-known member
louder, thanks, i wondered about that too. to be sure, vr= voltage regs?
How about bending reg leads? ok, or no-no?
How about bending reg leads? ok, or no-no?
pmroz
Well-known member
... well thanks, pedro... now the P.S. will be done tonight.
what is your config? like trafo, opamp etc.
is it the canil boards?
Over here, pres stuffed, PS tonight, then start opamps. test box drilled, jacks etc. (for me, the easy part) but no wiring yet. switches and 2 trafos en route.
2x Altec 1:4/ 1731fabio/ Melcor 400-17-2, (maybe similar to old Mel channel?) and
2x Cinemag/ 252BCfabio/ Profile out/ (maybe sound like a*p*i?)
haven't ordered cinemag, probably 1:8
Matched the small stuff for 4ch, so similar 'sets' of pres to A/B opamp and trafo combos. There's an old 'Audio Acoustics' card here with plastic Beyer trafo (1:5?) and 400-17, so try Beyer in canil pres. also map5002 and other (2351?) black-box thingy coming, also A/B a few different caps on unbal out. Need sonic reference for what i read here.
I'm new to diy, trying to study first, then build. When yours are up, post how you like them, or sound/pics observations etc. i'm interested in the different configs people are trying...
what is your config? like trafo, opamp etc.
is it the canil boards?
Over here, pres stuffed, PS tonight, then start opamps. test box drilled, jacks etc. (for me, the easy part) but no wiring yet. switches and 2 trafos en route.
2x Altec 1:4/ 1731fabio/ Melcor 400-17-2, (maybe similar to old Mel channel?) and
2x Cinemag/ 252BCfabio/ Profile out/ (maybe sound like a*p*i?)
haven't ordered cinemag, probably 1:8
Matched the small stuff for 4ch, so similar 'sets' of pres to A/B opamp and trafo combos. There's an old 'Audio Acoustics' card here with plastic Beyer trafo (1:5?) and 400-17, so try Beyer in canil pres. also map5002 and other (2351?) black-box thingy coming, also A/B a few different caps on unbal out. Need sonic reference for what i read here.
I'm new to diy, trying to study first, then build. When yours are up, post how you like them, or sound/pics observations etc. i'm interested in the different configs people are trying...
alo
damn,too good to be true.
problem with the 5v rail.
if i don`t connect psu to main boards,everything okay.
when i connect psu to main boards,i only get 1.5v instead of 5v,and i can swear i saw some smoke.
i connected r10 to r1/c1 junction,and at that point i get 39v,but at the other side of r10,there is only2v.i
i did not put yet led`s.
help
best regards
pedro
damn,too good to be true.
problem with the 5v rail.
if i don`t connect psu to main boards,everything okay.
when i connect psu to main boards,i only get 1.5v instead of 5v,and i can swear i saw some smoke.
i connected r10 to r1/c1 junction,and at that point i get 39v,but at the other side of r10,there is only2v.i
i did not put yet led`s.
help
best regards
pedro
Can you measure again voltage between R1/C1 and ground? Can't be 39V ....
For a 12+12VAC power trafo you should get around 15VAC at R1/C1...
I'm not using R10 anymore, just connect the R1/C1 to the input of 7805 and that's all.
I have around 27VAC at R1/C1 so the voltage diff over 7805 should be 22V, and that's ok.
let me know.
Fabio
[/quote]
alo
well.lets start at the beggining:
toroid tranny-80vac
prim:230v-brown-blue
sec;first winding:12v/3,3amp-red-black.
sec;second winding;12v/3,3amp-yellow-orange.
this is what i did,at the secundarie:
connected black/yellow togheter(ct).
now,at the psu there is 4 in`s;ac in/gnd/gnd/ac in.
red,at ac in.
ct,not connected.
orange,at the other ac in.
values i get:
between red ac in and gnd=29,5vac.
between orange and gnd=0
between ct and gnd=14,6vac.
dc values:
phantom=44,3Vdc
opamp rail=+15/-15vdc
relay/led`s rail=5,1vdc
r1/c1 junction=39,6vdc. at this point,i`ve connected a 470 ohm resistor(4w).connected to 7805 in.
now the trouble:
when i start fiddling with the polarity/pad switch`s,in all 4 channel`s,voltage starts to drop at the 5volt rail,and i only get about 2vdc instead of 5vdc.
note:i used a 1amp fuse(slow).
sorry for my bad english.
what`s wrong?
hope you can help me,cause i don`t know nothing about electronics.
best regards
pedro
well.lets start at the beggining:
toroid tranny-80vac
prim:230v-brown-blue
sec;first winding:12v/3,3amp-red-black.
sec;second winding;12v/3,3amp-yellow-orange.
this is what i did,at the secundarie:
connected black/yellow togheter(ct).
now,at the psu there is 4 in`s;ac in/gnd/gnd/ac in.
red,at ac in.
ct,not connected.
orange,at the other ac in.
values i get:
between red ac in and gnd=29,5vac.
between orange and gnd=0
between ct and gnd=14,6vac.
dc values:
phantom=44,3Vdc
opamp rail=+15/-15vdc
relay/led`s rail=5,1vdc
r1/c1 junction=39,6vdc. at this point,i`ve connected a 470 ohm resistor(4w).connected to 7805 in.
now the trouble:
when i start fiddling with the polarity/pad switch`s,in all 4 channel`s,voltage starts to drop at the 5volt rail,and i only get about 2vdc instead of 5vdc.
note:i used a 1amp fuse(slow).
sorry for my bad english.
what`s wrong?
hope you can help me,cause i don`t know nothing about electronics.
best regards
pedro
pmroz
Well-known member
Hi Pedro,
can't help with much, except to say 80V Toroid would make lots of extra heat. But i think you said before it's hard to find a smaller one where you are.
can't help with much, except to say 80V Toroid would make lots of extra heat. But i think you said before it's hard to find a smaller one where you are.
Rob Flinn
Well-known member
The transformer only supplies the current that the circuit its feeding requires. The transformer would not generate extra heat if it is supplying the same circuit, & if it had a higher VA rating than required would get less hot than one with a lower VA rating.
pmroz
Well-known member
Sorry, maybe i was wrong. For 'generate a lot of heat' , didn't mean the toroid would get hot. But for +/-18V (36Vtot) rail, i was thinking, an 80V toroid would generate a lot of heat at the REG+/- (and series resistors) on Fabio's PS.... due to trying to regulate V to +/- 18v. We were talking about this earlier with regard to LM7805. Don't the extra volts have to change to heat?
...i'm new to this, so straighten me out. May have to go back and relearn... which is fine
...i'm new to this, so straighten me out. May have to go back and relearn... which is fine
Rob Flinn
Well-known member
The VA rating of the transformer will have no effect on how hot the regulators get. Unless you stick the regulators to the side of the transformer!!!!!!!!!!!!!!!
The VA rating is purely how much power the transformer is capable of delivering before it catches on fire.
The regulators get hot for 2 reasons. The current they are supplying & the difference between the input & output voltage. Since power = VI this in a nutshell is saying that the regulators get hot depending on how much power they are dissipating.
pmroz
Well-known member
Oh, ok, my bad.
I thought this spec meant Pedro was using
80VAC = (Volts AC) toroid, not
80va = current rating
...that's where i was confounded.
if he meant 80va, why the 'c'? Pedro?
I thought this spec meant Pedro was using
80VAC = (Volts AC) toroid, not
80va = current rating
...that's where i was confounded.
if he meant 80va, why the 'c'? Pedro?
Rob Flinn
Well-known member
You could be right there, if so, I stand corrected
alo
sorry,it`s 80va.
as you can see,i know very little about this.
i`ve been thinking about removing r10,and connect r1/c1 straight to the vin 7805.only doubt i have,it`s cause 7805 max input voltage it`s 35v.
right?
best regards
pedro
sorry,it`s 80va.
as you can see,i know very little about this.
i`ve been thinking about removing r10,and connect r1/c1 straight to the vin 7805.only doubt i have,it`s cause 7805 max input voltage it`s 35v.
right?
best regards
pedro
