so...about lilliput and 83, need your help!!!
what do you think of this?
I put a switch for 83 pre-heat, and another for V+ and 6,3V(ecc88 and 6080 filaments).
There is also a 15k 10W resistance to give a minimal load to 83, waiting for ecc88 and 6080 filaments.
Do u think it is ok, or I made some mistakes?
and what about GZ34?
I am not expert with tube rectifiers and choke input.
why GZ34 datasheets put the choke in center-trap of transformer?
And why many projects put choke in V+, insteed?
what do you think of this?
An externally hosted image should be here but it was not working when we last tested it.
I put a switch for 83 pre-heat, and another for V+ and 6,3V(ecc88 and 6080 filaments).
There is also a 15k 10W resistance to give a minimal load to 83, waiting for ecc88 and 6080 filaments.
Do u think it is ok, or I made some mistakes?
and what about GZ34?
An externally hosted image should be here but it was not working when we last tested it.
I am not expert with tube rectifiers and choke input.
why GZ34 datasheets put the choke in center-trap of transformer?
And why many projects put choke in V+, insteed?
Fuling said:
ok, thank you very much!
but what about the schematics? I am noob about tube rectifiers...
It's ok(5H choke, 470uF cap, 15k 10W resistor for a little load and 2 x R56 10w for protection of rectifier)?
And it is better to put choke in V+(like schematic) or in the center of transformer(as gz34 datasheet say)?
Thanks again.
Download and read this:
http://213.156.45.208/primo/materiale/20_060_040_001_Lee_cap3lowres.pdf
The best reference about tube power supply. A little thought but worthwile.
http://213.156.45.208/primo/materiale/20_060_040_001_Lee_cap3lowres.pdf
The best reference about tube power supply. A little thought but worthwile.
plovati said:
Thank you for nice link!
Btw reading it I can't undestand why, for example, old datasheets of tube rectifiers and old books about tube power supplies put the choke(in choke input filters) in center of transformer(0V). On the contrary many schmatics of amps(and also PSU Designer II) put the choke in V+ position(after filaments of rectifier).
And I have many doubts about the 2 plate-protection resistances.
I planned to use 2 x 56R-10W, but I don't know if value and power are ok.
In old datasheets the cap after the choke is little value(often about 60uF). I don't know if using 470uF can give problems to rectifier.
PSU Designer indicates big ripple using a 60uF cap(and also too high V+). Using a 470uF will have little ripple but a big peak in current at start.
BTW 470uF seems to be ok for Gz34(and also for 83), but You know, it is only a simulation...
About the 15k-10W resistance(to give a minimum load to rectifier, waiting for slow filaments of 6080/E88CC) I don't know if 10W is sufficient. PSU Designer give 260V(with initial load of15K) so dissipation is about 4,5W for this resistance...
Helpppppppppppppp!!!!
No matter where you put the choke as long as you pick output voltage ACCROSS the second cap.
I mean, the ground is the minus terminal of the SECOND cap when the choke is at the center tap of the tranny.
Both works the same and the PSUD simulation is applicable regardless the choke location.
An advantage of putting the choke here is that it's near of ground potential and thus releives from insulation problems.
Yves.
Yvesm said:
Thanks very much!
So, no differences between the 2 positions of chokes.
Anyone can help me with the other questions, about plate-protection resistences, 470uF cap and load resistence?
Thanks.
Hi,
In the figure, I beleive that Rs represents the resistance of the winding in the tranny and Rl the resistance of the choke.
You don't need to add this components, you just need to know their values.
Too large caps after a choke could make the PSU instable, that is the output voltage swings a long time before to stabilize after the load change.
This is easy to simutate in PSUD using "delayed" constant current loads.
However, iIf the load is constant (like in an A class amp) you don't really need to use choke input filtering.
Yves.
In the figure, I beleive that Rs represents the resistance of the winding in the tranny and Rl the resistance of the choke.
You don't need to add this components, you just need to know their values.
Too large caps after a choke could make the PSU instable, that is the output voltage swings a long time before to stabilize after the load change.
This is easy to simutate in PSUD using "delayed" constant current loads.
However, iIf the load is constant (like in an A class amp) you don't really need to use choke input filtering.
Yves.
Yvesm said:
Thanks Yves.
yes, Rs and Rl are the resistances of transformer and choke windings.
BTW it is a good idea to protect tube-plates with 2 resistances(to limitate current). And also, if rectifier will short, transformer is proteted by the 2 resistances. 😉
Now the problem is: 2 x 56R - 10W are good for purpose?
For the other questions the problems are:
1)with little cap PSU give a lot of ripple. 470uF seems good for ripple, but I don't know if it is good for GZ34(or 83).
There is an "expert good soul" in the forum that can answer this question, please?
Indeed PSU Designer II indicates that it is all ok, I think this program has a big limitation in simulating real situation. In fact the program take care only of the max. current peak supported by rectifier(GZ34 = 750mA). It seems to not take care of the normal working condition supported by the tube(250mA). To see this, I tryed to lower the load resistance... Putting 250ohm as load I not received particular advices, in spite of a constant current of 610mA in the load! The risk is to have a good simulation with the program and a bad working condition for the rectifier in real, because the GZ34 can support 750mA anly for a very short time(0,2ms).
2)I must use a choke input filter because I have 2 new transformers in junk-box 270V-240V-0V-240V-270V. With this voltages I can't use cap input filter, because of the big voltage I'll get. Lower the voltage with a resistor is very crazy, because it must be very big in power dissipation.
I know choke input filter need a minimum load in every condition, because without a sufficient load the V+ will grow fastly up to V*1,4, and diode interdict.
So to protect this situation(I am not sure that filaments of GZ34 will be ready as slow as filaments of 6080...) I have to add an additional resistance, but I don't know if 15k - 10W is correct. 🙁
Helppppppppp!!!
Ohm's law !
2 W is large enough and so they have a chance to blow as a fuse if some short occurs.
Let see, assuming you have 250V B+, you will have (I = U / R) 16mA into.
And the dissipated power will be ( P = U x U / R) 4.16 W.
Simulating in PSUD with just that load and you'll know the resulting voltage.
Yves.
2 W is large enough and so they have a chance to blow as a fuse if some short occurs.
Let see, assuming you have 250V B+, you will have (I = U / R) 16mA into.
And the dissipated power will be ( P = U x U / R) 4.16 W.
Simulating in PSUD with just that load and you'll know the resulting voltage.
Yves.
Re: Ohm's law !
Thanks again Yyves.
yes, I know the dissipation will be about 4-5W, but I am not sure that a resistance of 10W can be good for a long time...
BTW the big problem is the 470uF cap. I hope it will not make exceed the max values of GZ34...
I will try soon in real, but sometime is not so simple to see if the rectifier work well or is "over-working".
Yvesm said:
Thanks again Yyves.
yes, I know the dissipation will be about 4-5W, but I am not sure that a resistance of 10W can be good for a long time...
BTW the big problem is the 470uF cap. I hope it will not make exceed the max values of GZ34...
I will try soon in real, but sometime is not so simple to see if the rectifier work well or is "over-working".
ok,
I made the circuit with 240V-0V-240V, GZ34, 10H/70ohm choke, 470uF cap. Choke in the center of transformer(0V).
I hope the GZ34 will survive for long time...
It seems to sound and work, Voltage is lower than PSU Designer simulation, and I have a little "hum"(100hz?).
So, now I have to eliminate the "hum". Don't know how I'll do this... 🙄
I made the circuit with 240V-0V-240V, GZ34, 10H/70ohm choke, 470uF cap. Choke in the center of transformer(0V).
I hope the GZ34 will survive for long time...
It seems to sound and work, Voltage is lower than PSU Designer simulation, and I have a little "hum"(100hz?).
So, now I have to eliminate the "hum". Don't know how I'll do this... 🙄
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