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LM317 2N3055 Variable Circuit Problems

heavyfletch2nd

Jun 27, 2016
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Lol sorry :D
I'm not using this as an excuse at all But I am absolutely shattered , i am on this site with you guys early hours most mornings "for a while now", im up at 730am for work so its been a while since i had a good longish sleep i only been having 2-3 hours a night its catching up on me , i seem to have a lot more to do after work too my daughter is only 19yo i been helping her with the little 1 this week , i will be back in the shed tomorrow evening about 8-9pm uk ,, and ill remember the resistor modemhead thanks:) .....4:00am again lol nite nite:):):):)
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Get some sleep. You'll be able to think better.

When you're fresh, do these things:

1) Verify with the 9v battery that your lm317 is still working.

2) measure the DC voltage across the filter capacitors with them connected to the rectifier but the 317 not connected.

3) Assuming the voltage above is less than 37v, connect the 317 circuit to it just as it was tested with the 9v battery and report the results.

4) THEN we will talk about those transistors.
 

BobK

Jan 5, 2010
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Whoa, I did not know about "cheap" meters giving massively misleading AC voltages for DC. Both of my meters will read the ripple voltage (and they were not expensive meters, roughly $20 to $30 range)

Bob
 

(*steve*)

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Whoa, I did not know about "cheap" meters giving massively misleading AC voltages for DC.

It's something good to know about your meter. On the internet it can be even more useful to know it about other peoples meters.

Perhaps we need to get people to measure batteries using the AC range on their meters whenever we have these sort of issues.
 

BobK

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Which is what I did, of course. One read 0mV the other settled over time approaching 0 (reading 6mV when I quit after about 30 seconds.)

Bob
 

ModemHead

Dec 2, 2010
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It's something good to know about your meter. On the internet it can be even more useful to know it about other peoples meters.

Perhaps we need to get people to measure batteries using the AC range on their meters whenever we have these sort of issues.
Multimeters are my favorite topic... :)

If a multimeter is manual-ranging and 200V is the lowest ACV range, it is pretty safe to say it uses some minor variation of the same old ubiquitous ICL7106 clone based design, with the offensive DC-coupling for the ACV ranges.

Even if the better ones use AC coupling and produce more reasonable results, you still need to be careful trying to measure AC ripple in the presence of DC with a multimeter. Often the coupling cap is placed after scaling and buffering, so too much DC offset may distort or swamp the AC component. When in doubt, use an external cap, or better yet a scope.

Speaking of the internet, the worst cases I've seen are weekend mechanics who have been told their alternator is bad if they measure too much AC on the battery terminals. Hair-pulling ensues.

I don't like those little "830" multimeter toys very much.
 

heavyfletch2nd

Jun 27, 2016
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Hi all , are up for another round of psu's lol.
The results for steve ...317 still working fine 1.3v pot turned down 8.3 pot turned up while connected to the 9v.
With 317 disconnected 9v removed and connected to the bridge rectifier 21.7v across caps,..
With 317 connected pot turned down is still 1.3v with bridge rectifier.
20.5v with pot turned up connected to the bridge rectifier ..
All good then .:cool:
 

heavyfletch2nd

Jun 27, 2016
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Modemhead I did the resistor thing you said. it worked fine 0.5v pot turned down off one transistor .this is starting to look promising :p
 

ModemHead

Dec 2, 2010
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Late to the party, sorry...

You probably should arrange to make the 2200 ohm resistor a permanent thing. Without a small load, it will be difficult to adjust your power supply properly with a multimeter before connecting it to something.

I guess you have full range of adjustment now without smoke? If yes, set the pot for 12V output, then attach a small load like your fan (125mA I think?) and monitor the output voltage. It will drop a little but should maintain fairly close to 12V.

Do you know how to measure current with your multimeter? For higher current testing I would use both multimeters to monitor both the output voltage and current simultaneously. The meter measuring current will need to be in *SERIES* with the output, using the 10A and COM jacks. Remember that you have a 6 amp bridge rectifier, and for a margin of safety I would not exceed 5 amp loading. Monitoring the current will allow you to shut it all down if you exceed the limit.
 

(*steve*)

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Now you have a working 317 circuit, you can use it with the 9v battery (and probably with one of the burnt pots) to check to see if any of your discarded 317s are actually OK.

Then we'll do some simple tests on your 2N3055's to see if they're ok or toast.

I'll draw something up this evening.
 

heavyfletch2nd

Jun 27, 2016
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I just woke up foe a wee and checked my phone for the time noticed a cupple of messages ,sorry im not ignoring you both lol, its hard getting each other at the right times living in defferent times of the world and you are probably buisy doing your own things too , thanks for your helps its really good learning from you been like going back to school lol :) anyways back to sleep lol
 

(*steve*)

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Yeah we know you're in a funny place. Get back to us when you can. Don't hurry on our behalf.
 

heavyfletch2nd

Jun 27, 2016
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Lol I just came on here to see if you two were on. got part through a txt and u popped up lol , what time is it where you live ?
 

(*steve*)

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I'm just leaving for work...
 

heavyfletch2nd

Jun 27, 2016
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Hi bob , its 1 in the morning where I am . Are you all just waking up lol , I got a hour or so before I turn it in , so I thought I'd come and have a go at powering up these transistors without smoking , modemhead said about using permanant resistors for a load wich would work ,I have 2 lcd screens volt / amp would these be ok for the load , did you get time to cook up somthing steeve , sorry if your going to work and buisy:)
 

(*steve*)

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Damn. I forgot to draw you a circuit.

Let me whip out my copy of DaveCAD...

WP_20160902_09_07_45_Pro.jpg

Connect the base to the output of the 317, the collector (case) to the input of the 317, and finally the emitter via a 1k resistor to ground.

Measure the voltage across the 1k resistor.

Operate this from your 9V battery.

The voltage across the resistor should vary as you turn the pot. It will be about 0.6V lower than the output voltage of the 317.

This week confirm the basic operation of the 2N3055.

If this works you should be able to connect it up to your other power supply, replace the resistor with a small load and vary the voltage to it. Beware that at low output voltages and high output currents the transistor will get hot quickly. If you mount it on your heat sink, you will be able to test it with heavier loads. Also beware that there is no current limiting or overtemp cutout, so it's not hard to break stuff!

This is not the best circuit because the output voltage is not highly regulated and it is difficult to parallel transistors correctly, but it is a good basic test.
 

heavyfletch2nd

Jun 27, 2016
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Just giving an update to my american friends , it is working good of one transistor , now has a bypass cap on pin 2 and pin 3 , I cept the led and resistor on pin 2 , I think it helps but it does blink at 1.7v I think that is the new cap in place on the pin 2 doing its job , i was going to fit a led pannel volt meter but i bought the wrong one 15-30v lol when i bought it i thought it was 1.5-30v meter , thanks to all your helps I have run one one of the turnigy chargers at 4.5A off this " while I monitored of course", up to 4.5A the only thing that got warm... well hot lol was the bridge rectifier, i expected that as its only a small bridge and it was not on the heat sink, it will be replaced with 25a bridge when it arrives along with a new 0-30v lcd... brilliant lol... you are the boys:D:cool:
 
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