Astron Power Supply Problem Connected Wrong Now Only .5 volt
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Astron Power Supply Problem Connected Wrong Now Only .5 volt
By mistake I connected a running 12 volt power supply to the Astron Power Supply and now it only puts out .5 voltage. The transformer is humming so it is working. I thought that I was connecting the power leads to the radio and instead plugged the hot lead into the Astron. The built in fuse above the power cord is OK. Any idea what I should replace?
If you backfed voltage into it, it probably took out the pass transistors and/or the control transistors or IC and other components in the voltage regulator circuit.
Start be checking voltage out of the rectifiers into the regulator circuit and then work your way through the regulator components looking for where you do not have normal voltages.
You could try just testing the pass transistors and replace if they are bad but you run the risk of blowing the new ones if there are other problems in the regulator circuit.
Start be checking voltage out of the rectifiers into the regulator circuit and then work your way through the regulator components looking for where you do not have normal voltages.
You could try just testing the pass transistors and replace if they are bad but you run the risk of blowing the new ones if there are other problems in the regulator circuit.
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Tom in D.C.
- Posts: 3859
- Joined: Tue Sep 04, 2001 4:00 pm
- What radios do you own?: Progreso soup can with CRT
Astron PS fixing...
Regulator boards are available from Astron in
finished form.
Pass transistors they use are standard units with
standard marking/nomenclature (not house numbers)
and available online from several sources.
But, like K2HZ said, find the failure point with a meter
before you go replacing anything.
finished form.
Pass transistors they use are standard units with
standard marking/nomenclature (not house numbers)
and available online from several sources.
But, like K2HZ said, find the failure point with a meter
before you go replacing anything.
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
If the SCR or diode on the output shorts, it should blow the fuse and you have zero output. But, it can burn open and you loose your protection so it should be checked as part of the repair.mike m wrote:Also check the SCR which is mounted directly across the output terminals. It's designed to shut down the output when the regulator voltage rises above 15 volts but it's not intended to take 12 volts back into it. It could be a 2N681 or similar SCR depending on the vintage of your supply
Astron Power Supply Problem Connected Wrong UPDATE
Thank you for your input. I guess feeding power back into the Astron was what I did. The model number of this ASTRON is SL-10MR 10 Volt or 7 volts continous. On the board there is 24 volts but on the red and black leads on the opposite site of the board there is only .5 volts. The voltage is the same before it gets to the SCR and the Pass thur 2N3055 transistors. I don't have a schmetic but there are very few components on this board.
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440roadrunner
- Posts: 236
- Joined: Mon Aug 16, 2004 3:47 pm
You can download diagrams for popular Astron models at repeater builder. I realize the exact model may not be there, but one of them should be close enough.
http://www.repeater-builder.com/astron/ ... index.html
http://www.repeater-builder.com/astron/ ... index.html
2N3055 transistors are only rated for 5 amps pass regulation, and I'll bet there is a OP-AMP on the regulator board as well, most likely an LM-324, which goes out very easily if the outputs are shorted.
You probably have ballast resistors across the transistor leads as well, check those to make sure they are of the same value as printed on the body.
They 'should' be ceramic bodies and rated for at least 5 watts, but maybe less.
The cases on 2N3055s are the base connection with the pins being the collector and emitter.
Also, the 2N3055 is an NPN device.
Just out of curiosity, what does the transformer output on its own, unregulated?
If 24 Volts, how much current can you sink at that voltage without 'sag'?
I'd be doubtful if the transformer was damaged as it takes more than what you did to kill it, I'll bet its all on the regulator board.
You probably have ballast resistors across the transistor leads as well, check those to make sure they are of the same value as printed on the body.
They 'should' be ceramic bodies and rated for at least 5 watts, but maybe less.
The cases on 2N3055s are the base connection with the pins being the collector and emitter.
Also, the 2N3055 is an NPN device.
Just out of curiosity, what does the transformer output on its own, unregulated?
If 24 Volts, how much current can you sink at that voltage without 'sag'?
I'd be doubtful if the transformer was damaged as it takes more than what you did to kill it, I'll bet its all on the regulator board.
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440roadrunner
- Posts: 236
- Joined: Mon Aug 16, 2004 3:47 pm
The cases on 2N3055s are the base connection with the pins being the collector and emitter
Uh, they are??
http://www.cas.uc.edu/~stepp/courses/256/2n3055.jpg
http://www.cas.uc.edu/~stepp/courses/256/2n3055.pdf
Astron Power Supply Problem Connected Wrong UPDATE
This has got me on a mission.
The transformer has 24 volts output. Replaced 2 diodes 1N4004 at
D1 & D2. As soon as its powered up it takes out the 3amp fuse and the 2 diodes. Already replaced the 2N3055 Pass transistors. For the second time I have replaced the 3 amp fuse and its back to 24 volts at the transformer with both diodes out again.? Seems like a short but I admit I am not electronic tecky.
The transformer has 24 volts output. Replaced 2 diodes 1N4004 at
D1 & D2. As soon as its powered up it takes out the 3amp fuse and the 2 diodes. Already replaced the 2N3055 Pass transistors. For the second time I have replaced the 3 amp fuse and its back to 24 volts at the transformer with both diodes out again.? Seems like a short but I admit I am not electronic tecky.
Re: Astron Power Supply Problem Connected Wrong UPDATE
I have seen the output post be over tightened and cause
a short to the panel. Try removing the output posts from
the front panel and float them till you get the supply working.
What concerns me is that it is taking out the diodes each
time. This shouldn't be happening. Normally the line fuse
will blow before any damage is done.
Jim
a short to the panel. Try removing the output posts from
the front panel and float them till you get the supply working.
What concerns me is that it is taking out the diodes each
time. This shouldn't be happening. Normally the line fuse
will blow before any damage is done.
Jim
BearMan wrote:This has got me on a mission.
The transformer has 24 volts output. Replaced 2 diodes 1N4004 at
D1 & D2. As soon as its powered up it takes out the 3amp fuse and the 2 diodes. Already replaced the 2N3055 Pass transistors. For the second time I have replaced the 3 amp fuse and its back to 24 volts at the transformer with both diodes out again.? Seems like a short but I admit I am not electronic tecky.
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440roadrunner
- Posts: 236
- Joined: Mon Aug 16, 2004 3:47 pm
First, did one of the schematics I posted fit?
If so, post the link to the specific one so we know what you are working on similarly.
About all you can do at this point is to start opening paths and checking for serious shorts. One very big failure would be a shorted filter cap. If there is a "crowbar" zener/scr on the output, I would first remove it. Try firing it up with the pass transistors out of the circuit
Is the regulator chip socketed?
Pretty hard to troubleshoot by remote control.
Let's assume that this schematic is close:
http://www.repeater-builder.com/astron/ ... rs20a1.gif
(by the way, I saved this pic, put it in my photo software, and trimmed it and rotated it so I can read it. I HATE trying to read sideways diagrams)
Pull loose the connections marked 2 and 4, which are soldered wire connections to the board. Notice that this supply actually is two DC supplys in one. D1,D2 merely supply control voltage for the regulator. the main rectifier is the capsulated unit, I can't read the nomenclacture in the diagram, looks like SR1. If D1, D2 are really failing, C1 may be shorted.
If so, post the link to the specific one so we know what you are working on similarly.
About all you can do at this point is to start opening paths and checking for serious shorts. One very big failure would be a shorted filter cap. If there is a "crowbar" zener/scr on the output, I would first remove it. Try firing it up with the pass transistors out of the circuit
Is the regulator chip socketed?
Pretty hard to troubleshoot by remote control.
Let's assume that this schematic is close:
http://www.repeater-builder.com/astron/ ... rs20a1.gif
(by the way, I saved this pic, put it in my photo software, and trimmed it and rotated it so I can read it. I HATE trying to read sideways diagrams)
Pull loose the connections marked 2 and 4, which are soldered wire connections to the board. Notice that this supply actually is two DC supplys in one. D1,D2 merely supply control voltage for the regulator. the main rectifier is the capsulated unit, I can't read the nomenclacture in the diagram, looks like SR1. If D1, D2 are really failing, C1 may be shorted.
Astron Power Supply Problem Connected Wrong UPDATE
None of the schematics matched exactly but were close. This board has the IC LM723 voltage regulator. Could this be taking out the 1N4004 diodes? I can't find any shorts within the board?
The diodes are cheap and available at RS but I can't find the IC LM723 to replace it. According to Southeast Iowa Technical Society the LM723 is an old but popular universal voltage regulator. NONE of the schematics show the 2N3055 Pass Transistors being used but most of the components are the same.
Thank you for all the help, appreciated for sure,
The diodes are cheap and available at RS but I can't find the IC LM723 to replace it. According to Southeast Iowa Technical Society the LM723 is an old but popular universal voltage regulator. NONE of the schematics show the 2N3055 Pass Transistors being used but most of the components are the same.
Thank you for all the help, appreciated for sure,
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440roadrunner
- Posts: 236
- Joined: Mon Aug 16, 2004 3:47 pm
I'm surprised RS doesn't have the regulator anymore, I'm sure they used to. They have, however, dropped a lot of small parts. Just about any supplier, such as Digikey or Mouser should have them.
I would not think that the regulator is failing the diodes, but you never know. Fer certain, get a socket for the regulator if there is none, so you can pull the regulator easily.
Those diodes just aren't that small, there should be a heavy short to take them out. I would think some ohmeter checks would show that. About all you can do, is to disconnect here and there from the board to isolate componets better for resistance checks.
Again, this is tough by remote control. By the way, wander over to QRZ.com. Someone there started a thread on power supplys, and there's some good troubleshooting links already.
http://www.qrz.com/ib-bin/ikonboard.cgi ... 5;t=142213
I would not think that the regulator is failing the diodes, but you never know. Fer certain, get a socket for the regulator if there is none, so you can pull the regulator easily.
Those diodes just aren't that small, there should be a heavy short to take them out. I would think some ohmeter checks would show that. About all you can do, is to disconnect here and there from the board to isolate componets better for resistance checks.
Again, this is tough by remote control. By the way, wander over to QRZ.com. Someone there started a thread on power supplys, and there's some good troubleshooting links already.
http://www.qrz.com/ib-bin/ikonboard.cgi ... 5;t=142213