I have a question regarding the SR50 kit. I assembled one to power the USB card in my audio server. The card requires 5v@ 1amp minimum. I got the PS on EBAY where they advertised that the board does 8amps which I never believed but I figured it would do 1 amp easily. I am dropping my 19v linear power supply down to 5v with the SR50.
The USB card powers up and is seen by my DAC but does not work correctly. I get 5v on the output of the PS but I think that it is starving the USB card for current.
R1 is jumpered (0 ohms) per the included instructions. The USB card still works fine off the internal DC-DC convertor of the PC so I did not manage to fry it 🙂
Is this stock board really not capable of 1 solid amp? Do I really need to replace Q2 just to get 1 amp?
Best,
Paul
The USB card powers up and is seen by my DAC but does not work correctly. I get 5v on the output of the PS but I think that it is starving the USB card for current.
R1 is jumpered (0 ohms) per the included instructions. The USB card still works fine off the internal DC-DC convertor of the PC so I did not manage to fry it 🙂
Is this stock board really not capable of 1 solid amp? Do I really need to replace Q2 just to get 1 amp?
Best,
Paul
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Hi Paul,
I'm afraid the only way to get any reasonable current at 5v is to replace Q2 with a Darlington. The board was designed to cover a fairly wide range of voltages and currents, but in its standard form it will not give you anywhere near 1A at 5v, hence the current starvation you are experiencing.
If you do this modification, you will need to insert a resistor for R1 of around 0.4 to 0.5ohms to give you around 1.25A - 1A for the load and 0.25A for the shunt.
Good luck and do let me know how you get on?
Paul
I'm afraid the only way to get any reasonable current at 5v is to replace Q2 with a Darlington. The board was designed to cover a fairly wide range of voltages and currents, but in its standard form it will not give you anywhere near 1A at 5v, hence the current starvation you are experiencing.
If you do this modification, you will need to insert a resistor for R1 of around 0.4 to 0.5ohms to give you around 1.25A - 1A for the load and 0.25A for the shunt.
Good luck and do let me know how you get on?
Paul
Thanks for the quick reply!
I ordered the Darlington so we shall see if it is enough. What wattage do you suggest for R1?
Also. I have a 12v tap from my LPS which I could wire up to with a bit more effort. Would I be better off dropping down from 12v instead of 19v or will that really matter?
Best,
Paul (also)
Hi Paul,
R1 needs to be at least 1W, I use 2W to be sure.
19v supply is quite high, assuming it is post rectifier dc, as you have to drop 14v across the constant current source to get 5v, so 12v would be better and still gives plenty of headroom.
Just as well that you were not getting 1A through, the heatsinks would be cooking!
Good luck
Paul
R1 needs to be at least 1W, I use 2W to be sure.
19v supply is quite high, assuming it is post rectifier dc, as you have to drop 14v across the constant current source to get 5v, so 12v would be better and still gives plenty of headroom.
Just as well that you were not getting 1A through, the heatsinks would be cooking!
Good luck
Paul
Hi, i also bought this regulator. I thought i was well off with it being able to supply 8A........ i need about 4A at 5v. Would the the mod do the trick? Any thoughts on wich transformer would be best? ( ac secondary and amps output)
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Sent with tapatalk from a lazy chair......
Getting 4A at 5V is stretching it, but I have just simulated it and will just about do it.
You will need the following values of components, as denoted on the original Analog Metric schematic;
R1 = 0.1R
R2 = 5k
Q2 = PNP Darlington (TIP27?)
R7 = 300R
R12 = 2.5k
VR1 will need to be set at more or less it's maximum value of 20k to have 5v at the output and I would advise you start with a value of 0.33R for R1 and reduce it accordingly!
In addition, your heatsinks may need enlarging to cope with the higher currents.
Good luck!
You will need the following values of components, as denoted on the original Analog Metric schematic;
R1 = 0.1R
R2 = 5k
Q2 = PNP Darlington (TIP27?)
R7 = 300R
R12 = 2.5k
VR1 will need to be set at more or less it's maximum value of 20k to have 5v at the output and I would advise you start with a value of 0.33R for R1 and reduce it accordingly!
In addition, your heatsinks may need enlarging to cope with the higher currents.
Good luck!
Thanks! Any thoughts on the transformer? (Secondaire voltage)
Sent with tapatalk from a lazy chair......
Sent with tapatalk from a lazy chair......
Hi Guys,
I have some problems with this reg. Yesterday I assembled two units and without load I can adjust voltage without problem but when I connect load (0,7A) voltage at output drops to 0V. My test bench is transformer 0-8 VAC/3A and my desire output is 9VDC / 0,7A .. Instead of R1 resistor I'm using link
Do I have to tweak this unit to get desire output voltage ? I have seen some information that Q2 should be replaced for TIP137 ?
I have some problems with this reg. Yesterday I assembled two units and without load I can adjust voltage without problem but when I connect load (0,7A) voltage at output drops to 0V. My test bench is transformer 0-8 VAC/3A and my desire output is 9VDC / 0,7A .. Instead of R1 resistor I'm using link
Do I have to tweak this unit to get desire output voltage ? I have seen some information that Q2 should be replaced for TIP137 ?
9v ac secondary required, if you are requiring 4A at 5v then you will need 30va transformer as minimum.
You will need to replace Q2 with darlington to get the required voltage and current, I would also recommend that you do same with Q8 as this increases PSRR.
You will need value of around 0.47R for R1, this will give you around 1A total, 0.7A for your load and rest for shunt transistor Q8
Forgot to say, your ac input of 8v is barely adequate for 9v dc output, I would recommend 9 - 12v ac
THX for prompt response, fortunately I have 0-12 VAC tab in my transformer and I can use it. Semiconductors already ordered..
Thanks for help..
BTW. Analog Metric should warn potential customers about such problems ..
Regards,
Artur
Thanks for help..
BTW. Analog Metric should warn potential customers about such problems ..
Regards,
Artur
Hi Paul,
I've bought one of this shunt and I was planning to use it as a power supply for a citation 12, is a AB amplifier, 75W per channel and I was thinking using 4 of them, one for every branch could be ok with your mods. The shunt is rated at 8A....it seems a lot to me...what do you think? it looks like they are selling a lot of them but I didn't find feedback.
thank you
vito
I've bought one of this shunt and I was planning to use it as a power supply for a citation 12, is a AB amplifier, 75W per channel and I was thinking using 4 of them, one for every branch could be ok with your mods. The shunt is rated at 8A....it seems a lot to me...what do you think? it looks like they are selling a lot of them but I didn't find feedback.
thank you
vito
Hi Paul,
thank you for sharing.
I need about 33V and not more, 35V will fry the mos fet, for less I don't know what could happen, I guess just less Watt which is not really a problem.
vito
thank you for sharing.
I need about 33V and not more, 35V will fry the mos fet, for less I don't know what could happen, I guess just less Watt which is not really a problem.
vito
Hi Vito,
33v will not be a problem and current is low from what you explain?
8A is very ambitious for this design, certainly at 5v output it will not deliver more than 2A max, but I have not tried it at 33v.
If I get a chance, I will try on simulation for you, but I would advise doing the Darlington modification anyway.
Paul
33v will not be a problem and current is low from what you explain?
8A is very ambitious for this design, certainly at 5v output it will not deliver more than 2A max, but I have not tried it at 33v.
If I get a chance, I will try on simulation for you, but I would advise doing the Darlington modification anyway.
Paul
If the output is 33Vdc, then the input is likely to be around 40Vdc.
At a CCS of 8A the total dissipation of the Shunt Regulator will be ~320W continuously whenever the load is not taking any current.
That is enormous !
At a CCS of 8A the total dissipation of the Shunt Regulator will be ~320W continuously whenever the load is not taking any current.
That is enormous !
Hi Andrew,
as you can guess I'm quite novice in Electronic, those are my consideration about it...
I had the chance to heard a Jeff Rowland model 2 whit his battery psu...I've found it marvelous!!! Just my humble and subjective opinion. Unluckily I cannot afford it and at the same time is not funny just to bring it home. The closest PSU to battery is Shunt Regulator and I've found the SR50 which is sold as amplifier power supply.
The amplifier I have in mind is a Citation 12 modified by Nelson Pass, a AB class that has 2 mosfets IRFP9240/240 in 33V dc and 75w per channel. My idea is to use 2 SR50 per channel, one per mosfet and I guess everyone of them can drain 1.5A maximum per SR50 which is rated for 8A and following Nelson Pass suggestion this kind on power supply should be 10 times the needed amperage, which is not my case but if any irfp9240/240 get 1.5A I'm not too far either. Every suggestion is kindly appreciate
vito
as you can guess I'm quite novice in Electronic, those are my consideration about it...
I had the chance to heard a Jeff Rowland model 2 whit his battery psu...I've found it marvelous!!! Just my humble and subjective opinion. Unluckily I cannot afford it and at the same time is not funny just to bring it home. The closest PSU to battery is Shunt Regulator and I've found the SR50 which is sold as amplifier power supply.
The amplifier I have in mind is a Citation 12 modified by Nelson Pass, a AB class that has 2 mosfets IRFP9240/240 in 33V dc and 75w per channel. My idea is to use 2 SR50 per channel, one per mosfet and I guess everyone of them can drain 1.5A maximum per SR50 which is rated for 8A and following Nelson Pass suggestion this kind on power supply should be 10 times the needed amperage, which is not my case but if any irfp9240/240 get 1.5A I'm not too far either. Every suggestion is kindly appreciate
vito