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#21 |
Solder Sloth
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 5,700
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![]() Correct. This just means the in-out differential can be higher for the K versions but amps can't be that much higher - need beefier pass transistors to do this whether it be internal or external.
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#22 |
Member
Join Date: Feb 2013
City & State: Edina, mn
My Country: Usa
I'm a: Knowledge Seeker
Posts: 49
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![]() The power supply is from a company that is no longer in business. It was founded in 1983 so the unit is no older than 38 years. Like in the title - an old dinosaur. As the picture shows the design is simple and primitive. I must have bought in 20 years ago at a garage sale - never worked. Based on the posts it appears it is of a poor design heat sink wise.
After looking up the price of a replacement 7805 and seeing how rickety the wires and pc board is I opted to go with the $9.00 eBay solution. I will update when the package comes from China and I get the unit working. Thanks all for the input - I appreciate the comments and learned a good deal. |
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#23 | |
Badcaps Veteran
Join Date: Jul 2011
City & State: Sunny Jacksonville FL
My Country: USA
Line Voltage: 120 Volts 60 HZ
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![]() Quote:
Thanks for posting this information I did not know there was this version of this type of regulator I have an application that I could use this type of regulator do you know if there is a 13.8 fix regulator in a 10 amp format Thanks
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9 PC LCD Monitor 6 LCD Flat Screen TV 30 Desk Top Switching Power Supply 10 Battery Charger Switching Power Supply for Power Tool 6 18v Lithium Battery Power Boards for Tool Battery Packs 1 XBox 360 Switching Power Supply and M Board 25 Servo Drives 220/460 3 Phase 6 De-soldering Station Switching Power Supply 1 Power Supply 1 Dell Mother Board 15 Computer Power Supply 1 HP Printer Supply & Control Board * lighting finished it * These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10% 1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later ) 2 Hem Saw Computer Stack Board All of these had ![]() All of the mosfet that are taken out by bad caps ![]() |
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#24 |
Solder Sloth
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 5,700
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![]() I still wonder who made that "78P05", and whether or not it's a fake ...
Find datasheet? Never heard of "New Era Electronics" ... Don't think there's a 13.8V version, you'd probably can add a drop on the GND terminal on one of these if it really can handle 10A. Last edited by eccerr0r; 03-04-2021 at 11:12 AM.. |
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#25 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,417
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![]() when i worked in the arcade industry 7805's running 5a in a TO3 can where everywhere.
heatsink like a shoebox!!! by around 86 switching psu's became cheap enough to replace them! |
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#26 |
Badcaps Veteran
Join Date: Dec 2010
City & State: Alberta
My Country: Canada
Posts: 1,997
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![]() The original was LM309K 5V 1A competing with Fairchild uA7805K 5V 1A back in the day of 8080 home computers with TO-3. In the late 1970's the TO-220 package was good enough at those power levels and everything quickly went that way, much less hassle to assemble things. The LM323K was 5V 3A TO-3.
OP could just keep the original PCB and wire up a LM317T. The sad thing is the new chinese kit will have crappier quality parts. It's a good basic linear PSU for experimenting and bench use. If the LM317 has the two protection diodes in the circuit, they last years. I would add a grounded power cord, ground the enclosure. |
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#27 |
Solder Sloth
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 5,700
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![]() I'm only thinking it was homemade because it seems poorly balanced, and I suspect the "indicator lamp" over the power switch looks like a hack job.
Rectifiers are 1N4003 series 1A rectifiers... okay. 2.5mF bulk capacitor... a bit oversized for 1A (funny looking, probably two series 25V 5mF capacitors heatshrinked into one?). little tiny heatsink... will go nuclear if outputting [email protected] Lots of improvements possible... --- I have this homemade PSU that I picked up from the trash, it has a 26.8V 1A transformer, a bridge rectifier, an undersized but reasonable 500µF bulk filter capacitor, a LM317T, a meter, a DPDT switch to switch the meter between current and amperes mode, and misc "glue" components. This thing looks hideous and the LM317T is mounted on the only metal there is - the front panel. A chipset heatsink is attached via some pressure sensitive double sided tape, must be some huge thermal resistance between the LM317T and that heatsink... whether I should mod or redo this PSU I don't know, but people probably could say the same to my "real" homemade PSU... (CC/CV dual meter, 1.2V-14V, 0-2.5A, using LM317T and pass transistor, and yes I've fried that pass transistor multiple times also due to insufficient heat sinking...really insufficient...) Last edited by eccerr0r; 03-04-2021 at 06:08 PM.. |
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#28 |
Member
Join Date: Feb 2013
City & State: Edina, mn
My Country: Usa
I'm a: Knowledge Seeker
Posts: 49
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![]() Well the parts arrived from China and are now installed into the modified unit.
Attached are the photos - First is from the Top View displaying the incredible complexity of the modification. It was rather straight forward and I followed the advice given on how to keep the analog needle meter. I did pull the LED off the board and ran a jumper wire to the front panel. The second photo shows the front view. It was just a matter of using a drill, Dremmel tool and file to make the modifications to the panel. I agree the unit was some sort of kit/home brew as the PCB board has professional markings. Regardless I have an operational unit now and the cost was under $15.00 with shipping, including a spare module. Thanks to all. |
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