Hello,

What number is given on the chip?
It could be a LM723 based powersupply, wich is more often used for CB powersupplies.

Bertus

 

Thanks.
One chip is NTE923, was exploded, together with a 18V zener to its pin 13 ¿? -replaced. Others are TC4027, LM324.
Unit powers up, with only 8 V out and collapses under any load. Voltage potentiometer setting on front panel unresponsive. Finals transistors show healthy junctions.

 

Bingo. The NTE923 is the same as an LM723. To us old farts, that's as obvious as an LM741.
The voltage collapses? Of course it does. One of the chips exploded.

 

Hello,

The NTE983 is an LM723.
Have a look at the pinouts:



Bertus

 

Thanks.
Yes, I downloaded their data sheets, replaced the exploded NTE923 and the zener at its pin 13, confirmed. The application data does not intend to have a zener there, that was my ¿? on the text. Perhaps on pin 12, but not 13. Goofy design ?

So what is the bingo ? Any similar principle of operation circuit you can point-to/explain, for CB or whatever ?

 

Hello,

Have a look at the following project that uses a LM723:
http://www.sentex.ca/~mec1995/circ/ps3010/ps3010a.html
http://www.sentex.ca/~mec1995/circ/ps3010/ps3010b.html
http://www.sentex.ca/~mec1995/circ/ps3010/ps3010c.html
http://www.sentex.ca/~mec1995/circ/ps3010/ps3010d.html

It will give you some insight on how the LM723 is used.

Bertus

 

My post #11 clearly says Guess. where do you get the "certain" from ?

My apologies, I seem to have missed that...

Best regards
HP

 

Look at the schematics of Astron Power supplies shown here. I'll bet it is similar...

 

Great assistance, Bertus & Mike !
There is one application note for the 723 as switching (fig.10) ; but at this point with a sure, confirmed error in the PCB layout for that Zener on pin 13 (freq. comp.) instead of pin 12 (Vcc), am not looking nor risking to chase my tail for other errors in the design, just forgetting about dealing with what appears as a goofy product.
Seems each LM324 quad section handles each output transistor base. The TC4027 flip-flop may be providing the oscillation.

Modifying it to use another driving circuit does not smell well with no filtering capacitors and a 18-0-18 VAC source transformer.

I learned something else today from your help. Thanks.

 

It is perfectly clear from the photo what this circuit is. The IC is an xxxxx, the transistor on the small heatsink acts as a yyy-yyyyyy, and the output transistors do a zzzzzzzzzz zzzzzzz zzzzzzzz. Filthy little Externet might know this if he weren't retarded.

Ragheads - really??? Where's a fffffff moderator when you need one? Oh, wait, since he didn't say "automotive ragheads," I guess it's ok.

ak

 

ak.....thank you for catching that and posting on Easter Sunday.

I have been reviewing Externet's posts, and I think you are right.

He uses a lot of "CODE" words and I think he is a bigot.

They are hard to find now.....because they know we are looking for them.

But with your sense of tonal context in the written word and my analytical skills.......we can root them out!

I especially liked your use of the word filthy.

I bet you really know what that word means.

Looking forward to working with you.