Maida style Reg

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skal1

Well-known member
Joined
Jun 4, 2008
Messages
1,282
Location
Birmingham,uk
Ok guys, i have been playing with this voltage reg for a couple of months now ,and i can not get it to work , the way i would like it too.

Main issue's not regulating i think and  no adjustment from the pot,

has anyone ever build this Maida style Reg,  it is not set up for my application maybe  that is the problem, if not could anyone with Solid state knowledge comment on what i maybe doing wrong ,

Input voltage 400Vdc

no current draw at the moment


cheers

skal
 

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skal1 said:
Ok guys, i have been playing with this voltage reg for a couple of months now ,and i can not get it to work , the way i would like it too.

Main issue's not regulating i think and  no adjustment from the pot,

has anyone ever build this Maida style Reg,  it is not set up for my application maybe  that is the problem, if not could anyone with Solid state knowledge comment on what i maybe doing wrong ,

Input voltage 400Vdc

no current draw at the moment


cheers

skal
Schemo is ambiguous; it doesn't show connection between the LM317 output and the 200r resistor. This connection is needed.
Now the 200r resistor defines a current of 6.25mA, which may be not enough for the LM317. You should make the measurement with at least 10mA of load current.
As PRR suggested, measure voltages at all nodes.
Finally, I don't like the idea of using these low-voltage regulators for high-voltage application. The LM317HV or TL783 are better suited, IMO.
 
abbey road d enfer said:
Schemo is ambiguous; it doesn't show connection between the LM317 output and the 200r resistor. This connection is needed.

Yes the 200r  resistor is  connected to the ou put node

abbey road d enfer said:
Now the 200r resistor defines a current of 6.25mA, which may be not enough for the LM317. You should make the measurement with at least 10mA of load current.

measuring the voltage across the 200r resistor i get 1.4 vdc  no load on the  output of the regulator, current works out to be 0.007mA .

How would i calculate the resistor need for the 10mA load?



abbey road d enfer said:
Finally, I don't like the idea of using these low-voltage regulators for high-voltage application. The LM317HV or TL783 are better suited, IMO.

I am using the LM317HV

cheers

skal
 
skal1 said:
measuring the voltage across the 200r resistor i get 1.4 vdc  no load on the  output of the regulator, current works out to be 0.007mA .
By design, normal voltage across this resistor should be 1.25V.
This is not normal, since its tied to a very precise internal reference, so either your measurement is off or the reg is duff. This is not one case where voltage tolerance is +/-10 or 20%.

Anyway, can you check the other voltages, since it seems wrong.

Since there's already 6mA, the TIP50 should dissipate about 1.5W, so should be significantly warm - don't touch it for confirmation!!!!!!!!!!! :eek:.
How would i calculate the resistor need for the 10mA load?
According to the schemo, nominal output voltage should be about 275V. There's already 6mA in the 200r, so you need to draw about an additional 5mA. A 2W resistor of about 50-60kohm should do. You could do that with a string of 8 off 6.8k quarter-watt in series or whatever suitable combination.

 
Ok i try about 5 lm317hv's all measure a round the same voltages across the 200r resistor 1.4, 1.37, .

when i apply the load resistor 56k to the out of the regulator , the voltage across the the 200r resistor is now at  1.254vdc, would this suggest that the 200r resistor needs to be change out for a different value?


cheers

skal
 
skal1 said:
Ok i try about 5 lm317hv's all measure a round the same voltages across the 200r resistor 1.4, 1.37, .

when i apply the load resistor 56k to the out of the regulator , the voltage across the the 200r resistor is now at  1.254vdc, would this suggest that the 200r resistor needs to be change out for a different value?


cheers

skal
What are the other voltages; is the output voltage correct and does the trimmer work?
 
skal1 said:
Main issue's not regulating i think and  no adjustment from the pot,

has anyone ever build this Maida style Reg,  it is not set up for my application maybe  that is the problem, if not could anyone with Solid state knowledge comment on what i maybe doing wrong ,

Input voltage 400Vdc

no current draw at the moment


cheers

skal

I built several for exact same reason as you. Once they have minimum current, HV LM317 and pretty complicated circuit for application, they work. Questions about it surface very often, it is at least good learning experience.
Got more joy and used less material with TL783 for anodes, after that capacitance multiplier (don't even need heatsinks for preamp) for screens. I've seen people using them after TL783 and similar regulators to make really quiet psu. Don't think things like this are really needed outside of phono designs, cap bypassed hefty zeners and cap multipliers with RC filter in front seem to work very well for many. Even ony RC filter or two with zeners give good results, works well for D. Fearn's preamp anodes.
 
Ok,  i seem to have it working now,i change out the 200r resistor and replace it with a 150r resistor , voltage over the 150r  resistor is 1.254Vdc  the pot has a swing of  30vdc so its moving now .

so with 400Vdc in to the Tip50  i get 380Vdc max  with pot cw and 350Vdc min  with pot ccw from the out of the regulator.

Now that it seem to be working, i would like to change the output voltage  from 380Vdc to 300Vdc  with pot cw ,  what changes do i need to do to make this happen.

cheers everyone

skal
 
skal1 said:
Ok,  i seem to have it working now,i change out the 200r resistor and replace it with a 150r resistor , voltage over the 150r  resistor is 1.254Vdc  the pot has a swing of  30vdc so its moving now .

so with 400Vdc in to the Tip50  i get 380Vdc max  with pot cw and 350Vdc min  with pot ccw from the out of the regulator.

Now that it seem to be working, i would like to change the output voltage  from 380Vdc to 300Vdc  with pot cw ,  what changes do i need to do to make this happen.

cheers everyone

skal
Lower the value of the 180k.
 
ok ,i spoke too soon :(

well this is what's happen at the moment  , iam using this Maida style Reg to power a signal for a compressor , voltage is steady at the output  thats cool but when i apply  the CV voltage on the grid the voltage of the regulator goes high , this does not seem normal.

i know what the problem is but i do not know how to rectify it.  { load current not constant } anyone got any idea where i should to looking

cheers

skal
 
skal1 said:
ok ,i spoke too soon :(

well this is what's happen at the moment  , iam using this Maida style Reg to power a signal for a compressor , voltage is steady at the output  thats cool but when i apply  the CV voltage on the grid the voltage of the regulator goes high , this does not seem normal.

i know what the problem is but i do not know how to rectify it.  { load current not constant } anyone got any idea where i should to looking

cheers

skal
It just means that for some reason the regulator does not regulate. I asked you twice to measure all the voltages; that's the only way to understand your problem.
 
What I would do is to take the schematic and start marking down measured DC voltages at each node right on the drawing.

For a smaller circuit like this, having it all labelled in one place right in front of you can be a big help.  Knowing roughly what should be going on at each node (or at least at the major ones) it usually becomes pretty quickly apparent where things are not going as planned, and that's usually going to be a bad or missing connection, and then less often will actually be a bad part.

At least start at the nodes around the regulator, but I'd go ahead and just measure every node in that circuit.  It'll be a useful learning tool in understanding exactly how everything is working as well as probably showing exactly where something isn't.
 
ok here is the voltages i took of the reg hope this helps


cheers

skal
 

Attachments

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skal1 said:
ok here is the voltages i took of the reg hope this helps


cheers

skal
Something's really wrong wit the TIP50; the base voltage is lower than the emitter voltage. That suggests either the transistor is duff or cross-wired. In normal operation, the base voltage should be 0.6V above the emitter voltage.
 
You've shown two different voltages for the same output node! 295V and 317V...
 
skal1 said:
ok here is the voltages i took of the reg hope this helps


cheers

skal
That shows that the northern side of the 100r resistor is NOT connected to the output of the regulator, as it should. I already attracted your attention to this, but you seem to read only a fraction of the answers...
 
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