Can't Regulate, Help!

mikee55 · 7th January 2007, 01:01 AM

Hi all.

I've built a dual rail supply, with a pair if 22.6volt rails. One plus one minus both need to be regulated to 15volts. I can't get the negative reg to work.

Un-regulated I have 22.6 volts either side of earth, the 7815 pos regulator gives +15 volts. The TS7915 won't work. Both regs are TO220 style cases and logic states it should work. Both centre pin 2(and tag) is 0 volts, both pin 1 in and pin 3 out. Both regs are from Maplin Electronics(UK) and I'm on my second negative reg. Take the regs out and I get + - 22.6 volts, dual rail to where pin 1 should be, 0volts where pin 2 should be?????

Help!!!

Please
cheers mikee55

darkfenriz · 7th January 2007, 01:09 AM

Add a 4.7k resistor from negative reg's output to ground.

jnmar · 7th January 2007, 01:32 AM

Hi Mike.

You are not making the right connections on the 7915 they don't have the same pinout that the 7815.

mikee55 · 7th January 2007, 01:33 AM

The regulator cooks as soon as I apply power! Can you please explain why you'd add this resistor?,is this a load?

cheers Mike

mikee55 · 7th January 2007, 01:41 AM

I connect meter leads one to tab, the other to centre pin in cotinuity check. Meter says tab connects to centre pin. Looking above left pin in centre ov right pin out????

cheers mike

mikee55 · 7th January 2007, 02:13 AM

Cheers guys, been and re-wired it to see if it was too late and the thing was dead.I got a reading of minus 4 volts then nothing.
The case was too hot to handle. I guess Maplin Electronics need a telling off. It should state that although its a TO 220 style case, its pins are not the same. Don't know if you're aware of Maplin ,but they've gone down hill over the past few years.

I will be complaining.

Many thanks for your help.

Cheers Mike

radtech · 7th January 2007, 04:22 AM

Quote:

Originally posted by mikee55
I guess Maplin Electronics need a telling off. It should state that although its a TO 220 style case, its pins are not the same. Don't know if you're aware of Maplin ,but they've gone down hill over the past few years.

I will be complaining.

I wouldn't exactly blame Maplin, it's pretty much common knowledge in the electronics field that 79xx series have a different pinout than 78xx. Generally if the manufacturer doesn't package documentation with the parts, the supplier isn't going to put it them in there either. They do however usually supply them on their websites, and leave it up to you to look them up. Here's a link to them:

TS7900 series docs (PDF) from Maplin site

mikee55 · 7th January 2007, 12:24 PM

but had a catalogue to hand. I was not aware that the pos and neg regulators had different pinouts. It seems logical to me to give them identical pin outs or to state in print if they have different pin outs.

Frustrated Mike

7th January 2007, 01:01 AM	#1
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	Can't Regulate, Help! Hi all. I've built a dual rail supply, with a pair if 22.6volt rails. One plus one minus both need to be regulated to 15volts. I can't get the negative reg to work. Un-regulated I have 22.6 volts either side of earth, the 7815 pos regulator gives +15 volts. The TS7915 won't work. Both regs are TO220 style cases and logic states it should work. Both centre pin 2(and tag) is 0 volts, both pin 1 in and pin 3 out. Both regs are from Maplin Electronics(UK) and I'm on my second negative reg. Take the regs out and I get + - 22.6 volts, dual rail to where pin 1 should be, 0volts where pin 2 should be????? Help!!! Please cheers mikee55 __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi

7th January 2007, 01:33 AM	#4
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	Hello there The regulator cooks as soon as I apply power! Can you please explain why you'd add this resistor?,is this a load? cheers Mike __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi

7th January 2007, 01:41 AM	#5
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	jnmar I connect meter leads one to tab, the other to centre pin in cotinuity check. Meter says tab connects to centre pin. Looking above left pin in centre ov right pin out???? cheers mike __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi

7th January 2007, 02:13 AM	#6
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	Thanks for your help Cheers guys, been and re-wired it to see if it was too late and the thing was dead.I got a reading of minus 4 volts then nothing. The case was too hot to handle. I guess Maplin Electronics need a telling off. It should state that although its a TO 220 style case, its pins are not the same. Don't know if you're aware of Maplin ,but they've gone down hill over the past few years. I will be complaining. Many thanks for your help. Cheers Mike __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi

7th January 2007, 12:24 PM	#8
mikee55 diyAudio Member Join Date: Dec 2005 Location: West Howe	Didn't have PC available at the time but had a catalogue to hand. I was not aware that the pos and neg regulators had different pinouts. It seems logical to me to give them identical pin outs or to state in print if they have different pin outs. Frustrated Mike __________________ If it don't work, I'll fix it in the mix! Or visit http://lsdp.proboards.com/index.cgi


<a rel='nofollow' href='http://www.diyaudio.com/openx/www/delivery/ck.php?n=aa5cb2e9&cb=504364' target='_blank'><img src='http://www.diyaudio.com/openx/www/delivery/avw.php?zoneid=3&cb=504364&n=aa5cb2e9' border='0' alt='' /></a>	We're saving for a new server - help us to serve you by Donating Today and become a friend with benefits! Ads on/off / Custom Title / 2009 Tshirt / More PMs / Bigger Images / Advanced printing

7th January 2007, 01:09 AM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: back to civilization	Add a 4.7k resistor from negative reg's output to ground.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
how to voltage regulate	space2000	Solid State	4	12th April 2008 10:02 AM
CDP tweaking - which IC to regulate?	mr_push_pull	Digital Source	1	18th November 2007 02:36 PM
To regulate or not to regulate	duderduderini	Tubes / Valves	3	24th October 2007 12:35 AM
To regulate or not?	Ryssen	Tubes / Valves	4	3rd April 2004 02:11 AM
Whats the best way to regulate a PS down?	downhere	Solid State	5	2nd December 2001 02:33 PM

New To Site?	Need Help?
Register to Participate Search Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read