Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Sep Wed 19, 2018 7:52 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 15 posts ] 
Author Message
 Post subject: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 6:53 am 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 3372
Location: Florida
I have one of these 0-24 V, 1A supplies that I got from a junk shop 10 or more years ago. I don't have a schematic or PL and need to replace the voltage adjust pot (which seems to have been previously replaced with and audio taper one). I can wing it but it would be helpful to have the maker data.

Does anyone have a schematic and PL they would like to share?

Thanks,

RRM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 1:26 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7420
Location: Minneapolis, MN USA
What is a PL ?


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 1:52 pm 
Member

Joined: Apr Thu 11, 2013 11:03 pm
Posts: 433
Location: 649 Lacy Wilkerson Rd Roxboro, NC 27574
Parts List I assume.

_________________
Joel Walker


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 3:00 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1446
Location: Earth
Only a guess here, but if it's based around the LM317T adjustable voltage regulator, the adjust pot would be 5k ohms, linear taper rated at 1/2 watt.

http://www.st.com/content/ccc/resource/ ... 000455.pdf


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 9:16 pm 
Member

Joined: Dec Wed 16, 2015 2:49 am
Posts: 29
I found the manual for the "deluxe" model, 22-121
This model used the popular uA 723 / LM723 regulator.
https://elektrotanya.com/micronta_no.22 ... nload.html

Since Radio Shack often imported these from Taiwan you may find an op-amp" regulator circuit.
Later models incorporated the USA favorite, LM723 IC or as noted the LM317T series.
Micronta 22-123 Variable DC Supply.
Attachment:
File comment: Micronta 22-123
IMG_4104.JPG
IMG_4104.JPG [ 46.76 KiB | Viewed 1588 times ]

0 – 24 Volt, 2 Amp Bench Top Power Supply
DIY Project at Makezine.com : Uses the LM317T regulator.

Build a power supply from scratch.
by Michael Colombo
http://makezine.com/projects/0-24-volt- ... er-supply/


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sat 20, 2017 11:20 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10624
Location: Latham NY
I have one of these and I'm sure I have the schematic, I'll see if I can find it tomorrow.


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Sun 21, 2017 1:18 am 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 3372
Location: Florida
Thanks Lou, that would be great.

I looked inside and mine uses an LM723 and has a 5K linear pot for the voltage adjust. The reason I though the pot might not be stock is that the voltage adjust is non-linear. The output doesn't get to 5V until the pot is almost half way up and 10 V is about 2/3 of the way to max (24V). Other than that it seems to work fine overall and all the tweaks work.

The thing was so dirty and rusty I almost passed it up but it was cheap (maybe $5). I wound up throwing the cover away and making one from plywood. It's been handy.

RRM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Wed 24, 2017 1:39 am 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 3372
Location: Florida
Just a note. Even though everything seems ok now I'd still like to find a schematic and parts list if anyone has one.

Thanks,

RRM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Wed 24, 2017 1:08 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10624
Location: Latham NY
Sorry RRM, my unit is a 22-126 and uses discrete transistors and zeners instead of a chip.


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Wed 24, 2017 10:55 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 3372
Location: Florida
Thanks for looking, Lou. Looks like I need to get up the energy to trace the thing out and draw up a schematic.

RRM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Thu 25, 2017 4:31 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 2967
Location: Lincoln City, OR
Greetings to Lou and the Forum:

I used to have a 22-126; I just sold it at a garage sale.... too many low voltage supplies cluttering up the place. However, I did have to repair it when I got it and did reverse engineer it. If you would like the schematic, here it is:

Attachment:
Micronta Power Supply 22-126.pdf [52.01 KiB]
Downloaded 79 times


Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Thu 25, 2017 11:33 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 10624
Location: Latham NY
Thanks Jim, I do have the original manual for mine.


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Fri 26, 2017 1:04 am 
Member
User avatar

Joined: Mar Mon 17, 2008 5:05 am
Posts: 5354
Location: Ashhurst, New Zealand
Is the negative terminal really connected to the chassis? That limits it's usefulness somewhat, especially for older PNP transistor radios.

_________________
Cheers - Martin ZL2MC


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: May Fri 26, 2017 1:49 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 2967
Location: Lincoln City, OR
Greetings to Marty and the Forum:

I believe the upside down non-filled arrowhead or triangle symbol that I used in the drawing refers to circuit ground, not chassis ground.

Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: Micronta 22-123 Variable DC Supply Schematic and PL
PostPosted: Mar Fri 09, 2018 10:10 pm 
New Member

Joined: Mar Fri 09, 2018 10:04 pm
Posts: 1
If you still need this info, the voltage pot has the following markings on it: 1377702 996-0057


Top
 Profile  
 
Post New Topic Post Reply  [ 15 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Pbpix and 6 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB