dukasound
Well-known member
Can I replace TL783 with LM317 for +48V without changing circuit?
Thanks in advance
Duka
Thanks in advance
Duka
LM317 on place TL783 for +48V
- Thread starter dukasound
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tommytones
Well-known member
I've done it without problems but it might depend on the circuit you are using.
A Camel
Member
Yes, you can. But you must use the LM317HVT or LM317HVM version ready to work to 57V.The normal version has a ceiling of 37V only.Also, if your phantom needs aren,t too much you can use a 7824 regulator with a 24V-1Watt zener diode connected from the pin 2(normally ground pin) to ground to get 48 volts on output. :grin:
Tekay
Well-known member
Hi Duka!
LM317T will work fine as long as the in/ out difference isn't over 35V. Check the PSU schematics in the DIY section at my page.
www.vintagedesign.se
LM317T will work fine as long as the in/ out difference isn't over 35V. Check the PSU schematics in the DIY section at my page.
www.vintagedesign.se
rafafredd
Well-known member
So, what´s the real ceiling of the LM317, normal version? Can´t find the max Vout in the datasheets...
rafafredd
Well-known member
So, can I use it for lets say a 100v regulated PSU? :shock: :shock:
Well, in my mind there must be a limit...
Well, in my mind there must be a limit...
The device will regulate at almost any voltage, but it suffers from some protection issues if you violate some conditions. Like shorting it's output while it's up 100 volts. You just blew the in/out differential rule.
I use them, but put a zener from input to output to keep it constrained to the a bit below the max rating.
I only use it for phantom supply, so really, the only short is going to be the mic lines, which are already current limited. It'll do this all day.
If the output or adjust terminal caps crap out, it'll take the regulator too, but since I only pay 25 cents for it, I don't really care. In all my testing, none have failed in a catastrophic manner. A bad cap is more likely to cause distress to the circuit board. Oh yeah, I usually use a "fuse" resistor in front of the regulator that'll crap out first under real failure conditions. Like a 10 ohm metal film, that just goes "phhhttt" with no fire under overload.
It's a bit of extra parts, but they're all cheap, and I don't have to stock a non-standard part. We use 317's by the thousands around here...
I use them, but put a zener from input to output to keep it constrained to the a bit below the max rating.
I only use it for phantom supply, so really, the only short is going to be the mic lines, which are already current limited. It'll do this all day.
If the output or adjust terminal caps crap out, it'll take the regulator too, but since I only pay 25 cents for it, I don't really care. In all my testing, none have failed in a catastrophic manner. A bad cap is more likely to cause distress to the circuit board. Oh yeah, I usually use a "fuse" resistor in front of the regulator that'll crap out first under real failure conditions. Like a 10 ohm metal film, that just goes "phhhttt" with no fire under overload.
It's a bit of extra parts, but they're all cheap, and I don't have to stock a non-standard part. We use 317's by the thousands around here...
dukasound
Well-known member
Now, I am confused :?
Does LM317T can work for +48 stabilize :?:
Duka
Does LM317T can work for +48 stabilize :?:
Duka
robomatique
Well-known member
I want to know too!!! I just ordered the LM317T for the 48V output on my "Fabio API PSU". And I ordered 11 of them :?:
Thanks
Robert
Thanks
Robert
A Camel
Member
Does LM317T can work for +48 stabilize
Duka
Hi again.
Excuse my bad english, you can use it but you must be sure to avoid more than 37 volts difference from input pin to output pin this is the reason I said you must use the HVT or HVM version because if you have, let,s say, 50 volts or more on input pin and by any reason the output goes to ground or less than 13 volts, the LM317T goes beyond its limits and probably die.
Camel
Duka
Hi again.
Excuse my bad english, you can use it but you must be sure to avoid more than 37 volts difference from input pin to output pin this is the reason I said you must use the HVT or HVM version because if you have, let,s say, 50 volts or more on input pin and by any reason the output goes to ground or less than 13 volts, the LM317T goes beyond its limits and probably die.
Camel
We have had this questions several times now.
Yes, you can use the LM317 and the TL783 on higher voltages than their rating.
And yes, you will have to keep them within safe-operating-area.
Look at the G9 powersupply - and read it's description: http://www.gyraf.dk/gy_pd/g9/g9pd.htm
The same applies to LM317, just with different voltages.
Phantom with '317 is used in several standard units, like TLaudio and focusrite.
Jakob E.
Yes, you can use the LM317 and the TL783 on higher voltages than their rating.
And yes, you will have to keep them within safe-operating-area.
Look at the G9 powersupply - and read it's description: http://www.gyraf.dk/gy_pd/g9/g9pd.htm
The same applies to LM317, just with different voltages.
Phantom with '317 is used in several standard units, like TLaudio and focusrite.
Jakob E.
dukasound
Well-known member
[quote author="gyraf"]We have had this questions several times now.
Yes, you can use the LM317 and the TL783 on higher voltages than their rating.
And yes, you will have to keep them within safe-operating-area.
Look at the G9 powersupply - and read it's description: http://www.gyraf.dk/gy_pd/g9/g9pd.htm
The same applies to LM317, just with different voltages.
Phantom with '317 is used in several standard units, like TLaudio and focusrite.
Jakob E.[/quote]
OK. What min and max. voltage before LM317T we must have to good work of LM?
I will use circuit like Thomas -Neve PSU.
Duka
Yes, you can use the LM317 and the TL783 on higher voltages than their rating.
And yes, you will have to keep them within safe-operating-area.
Look at the G9 powersupply - and read it's description: http://www.gyraf.dk/gy_pd/g9/g9pd.htm
The same applies to LM317, just with different voltages.
Phantom with '317 is used in several standard units, like TLaudio and focusrite.
Jakob E.[/quote]
OK. What min and max. voltage before LM317T we must have to good work of LM?
I will use circuit like Thomas -Neve PSU.
Duka
See the components' respective data sheets for specifications..
There is also the LM317HV series that can be used for +48 power safely as they regulate up to 57V.
Jakob,
Do you have an alternate solution to the TL783 based power supply in the G9. Perhaps something built with discrete transistors to make it more "timeless".
Cheers,
Tamas
Jakob,
Do you have an alternate solution to the TL783 based power supply in the G9. Perhaps something built with discrete transistors to make it more "timeless".
Cheers,
Tamas
NewYorkDave
Well-known member
Tamas,
There was a plate voltage regulator that fits that description in the Peavey compressor schematic posted recently.
You could use any conventional discrete transistor series regulator topology (error amp, voltage reference, series pass element, foldback current limiter) as long as the C-E voltage ratings of the transistors were adequate. Look at horizontal output transistors for TV sets; these have a high C-E breakdown rating and should be suitable as series pass elements.
There was a plate voltage regulator that fits that description in the Peavey compressor schematic posted recently.
You could use any conventional discrete transistor series regulator topology (error amp, voltage reference, series pass element, foldback current limiter) as long as the C-E voltage ratings of the transistors were adequate. Look at horizontal output transistors for TV sets; these have a high C-E breakdown rating and should be suitable as series pass elements.
It could be done several ways, but I find the TL783 to be much better than most other solutions in terms of output noise and ripple. And specially the G9 input stage is sensitive to psu noise and hum.
For a simple no-frills regulation, you could use a zener+pass-transistor regulation, like the one used in G9 phantom power - only scaled up.
Jakob E.
For a simple no-frills regulation, you could use a zener+pass-transistor regulation, like the one used in G9 phantom power - only scaled up.
Jakob E.
> Well, in my mind there must be a limit...
In normal operation, just be sure Vin-Vout is less than 37V.
Note that the main reason you use a regulator is because Vin varies!. So you have to think about the extremes.
If you wanted 100V out, add about 3V for the minimum I/O difference needed to give the chip something to eat. This has to be the depth of the ripple voltage: if you have 10Vp-p ripple, you need minimum nominal DC of 100V+3V+5V= 108V. If you also see +/-10% line and load variations you need to aim at 120V nominal. Low day: 120V*90%= 108V. High day: 120V*110%= 132V. Then you still have at least 10Vp-p ripple, so the peaks are 5V higher: 132V+5V= 137V. So you can do 100Vout with 10Vp-p ripple and +/-10% line/load wobble, and be just inside the 317's 37V spec. (This assumes a custom transformer wound to give exactly 120VDC at nominal line and load!)
Now short the output (stuff happens). The 317 will have 120V in, 0V out. The current-limit will try to turn the 317 off, but the over-37V will try to turn the 317 ON. The 120V on a 37V part wins, you lose. Instead of peacefully turning off to live another day, it turns ON, absorbs all the energy in your main cap, dissipates about 1,000 Watts, and bursts in about a milliSecond. You lost your $2 bet. (Could be a whole lot more, if the musicians were in a groove when someone dropped his keys in your only power supply.)
Note that a regulator (almost) always starts-up with a "shorted output". We usually have some capacitance on the output pin or out around the stuff it is feeding. The input voltage goes up, usually pretty quick (wall outlets have POWER and a transformer can pass a lot of energy quickly), while the output cap starts from zero volts. So at start-up you have both full input voltage and maximum limited current. If the load cap is small this may not smoke the chip.
A well-built well-boxed Phantom supply is "sort of safe" because a short on the far end of the 6K8 resistors should not drag the 317 out of regulation, and if it does there won't be any infinite current or power to pop the 317. But this assumes all accidents happen on the far side of the 6K8. In DIY, that is not always a safe assumption. Of course in DIY we can always fix it, but we may not have a spare 317 on hand at a hot Saturday night gig.
A 35V Zener across the shorted 317 will keep its I/O voltage within bounds, for a while. But even a small transformer will soon smoke a 1W Zener, and then we are back to the over-volted 317. As Dan says, a "panic resistor" is a great idea. It should have low voltage drop at normal loads, and burn-up quick and clean in a dead-short. True, you've just changed the repair from a $1.20 LM317 to a $0.30 resistor; but a dead 317 looks fine, a burnt resistor is pretty clear, so troubleshooting is faster. And your nose tells you right away what happened: with a dead chip there is no clue so you will waste time checking cables etc. (In Dan's commercial products this has the added benefit of telling the idiot customer why it failed. If the chip just pops, it is a mystery and probably "crappy product". If you stomp a wire or drop coins through vents and 3 seconds later smoke pours out, the customer may realize the cause/effect.)
A more clever trick is to put a high volt transistor above the 317, biased 5V-30V above the 317 output. Use an H-sweep transistor and you can eat 1,000V this way. But in a short, the dissipation in the transistor is high and not self-limiting. With very clever electrical and thermal design, the 317 can sense the pass-transistor heat and tend to shut-down, though with a hard short on a fat cap this may not be fast enough.
And if you pull out all the stops, remember that heatsink insulation has limits. You usually need sinking at HV (unless current is super-low) and you usually do not want HV on the heatsink (specially in DIY). You can use a mica insulator or buy the plastic-coat TO220 package regulator, but somewhere around 500V-1,000V these insulations can break-down (sooner if you get fingerprints and dust in there).
Remember: the 7805/317 regulators were loved when they came out, because designing a blowout-proof regulator from scratch is a Big Problem, and they solved it. The 7805 and 317 and their kin changed regulation from a troublesome specialty to a commonplace thing. Not for first-cost (early regs cost more than a few transistors) but because you could NOT blow them up as long as they never saw more than 37V. Just this one small thing to avoid, and for most 5V-15V work it is not a problem to be sure you never have more than 35V worst-case available. But ask for more than about 24V, and you are back to the bad old days of actually designing a blowout-proof regulator.
In normal operation, just be sure Vin-Vout is less than 37V.
Note that the main reason you use a regulator is because Vin varies!. So you have to think about the extremes.
If you wanted 100V out, add about 3V for the minimum I/O difference needed to give the chip something to eat. This has to be the depth of the ripple voltage: if you have 10Vp-p ripple, you need minimum nominal DC of 100V+3V+5V= 108V. If you also see +/-10% line and load variations you need to aim at 120V nominal. Low day: 120V*90%= 108V. High day: 120V*110%= 132V. Then you still have at least 10Vp-p ripple, so the peaks are 5V higher: 132V+5V= 137V. So you can do 100Vout with 10Vp-p ripple and +/-10% line/load wobble, and be just inside the 317's 37V spec. (This assumes a custom transformer wound to give exactly 120VDC at nominal line and load!)
Now short the output (stuff happens). The 317 will have 120V in, 0V out. The current-limit will try to turn the 317 off, but the over-37V will try to turn the 317 ON. The 120V on a 37V part wins, you lose. Instead of peacefully turning off to live another day, it turns ON, absorbs all the energy in your main cap, dissipates about 1,000 Watts, and bursts in about a milliSecond. You lost your $2 bet. (Could be a whole lot more, if the musicians were in a groove when someone dropped his keys in your only power supply.)
Note that a regulator (almost) always starts-up with a "shorted output". We usually have some capacitance on the output pin or out around the stuff it is feeding. The input voltage goes up, usually pretty quick (wall outlets have POWER and a transformer can pass a lot of energy quickly), while the output cap starts from zero volts. So at start-up you have both full input voltage and maximum limited current. If the load cap is small this may not smoke the chip.
A well-built well-boxed Phantom supply is "sort of safe" because a short on the far end of the 6K8 resistors should not drag the 317 out of regulation, and if it does there won't be any infinite current or power to pop the 317. But this assumes all accidents happen on the far side of the 6K8. In DIY, that is not always a safe assumption. Of course in DIY we can always fix it, but we may not have a spare 317 on hand at a hot Saturday night gig.
A 35V Zener across the shorted 317 will keep its I/O voltage within bounds, for a while. But even a small transformer will soon smoke a 1W Zener, and then we are back to the over-volted 317. As Dan says, a "panic resistor" is a great idea. It should have low voltage drop at normal loads, and burn-up quick and clean in a dead-short. True, you've just changed the repair from a $1.20 LM317 to a $0.30 resistor; but a dead 317 looks fine, a burnt resistor is pretty clear, so troubleshooting is faster. And your nose tells you right away what happened: with a dead chip there is no clue so you will waste time checking cables etc. (In Dan's commercial products this has the added benefit of telling the idiot customer why it failed. If the chip just pops, it is a mystery and probably "crappy product". If you stomp a wire or drop coins through vents and 3 seconds later smoke pours out, the customer may realize the cause/effect.)
A more clever trick is to put a high volt transistor above the 317, biased 5V-30V above the 317 output. Use an H-sweep transistor and you can eat 1,000V this way. But in a short, the dissipation in the transistor is high and not self-limiting. With very clever electrical and thermal design, the 317 can sense the pass-transistor heat and tend to shut-down, though with a hard short on a fat cap this may not be fast enough.
And if you pull out all the stops, remember that heatsink insulation has limits. You usually need sinking at HV (unless current is super-low) and you usually do not want HV on the heatsink (specially in DIY). You can use a mica insulator or buy the plastic-coat TO220 package regulator, but somewhere around 500V-1,000V these insulations can break-down (sooner if you get fingerprints and dust in there).
Remember: the 7805/317 regulators were loved when they came out, because designing a blowout-proof regulator from scratch is a Big Problem, and they solved it. The 7805 and 317 and their kin changed regulation from a troublesome specialty to a commonplace thing. Not for first-cost (early regs cost more than a few transistors) but because you could NOT blow them up as long as they never saw more than 37V. Just this one small thing to avoid, and for most 5V-15V work it is not a problem to be sure you never have more than 35V worst-case available. But ask for more than about 24V, and you are back to the bad old days of actually designing a blowout-proof regulator.
