Soundtrack sequel psu breakdown

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

duende

Active member
Joined
Dec 16, 2016
Messages
43
Location
France
Hi,

After a PSU capacitor recap on the Seqel 2 psu board the + 17v and the 5V don't work. All the components are ok visually.
The transformer secondary  are 24v, and after the diode bridge i mesure 33v and 0V. I don't understand how work the IC L4977A.

I mesure 33v at D1 negative and 0V after the +.

Have you have some info on this circuit ?

Thanks.
 

Attachments

  • Soundtrack Sequel PSU.jpg
    Soundtrack Sequel PSU.jpg
    75 KB · Views: 28
What exactly do you mean by this? ???

duende said:
I mesure 33v at D1 negative and 0V after the +.

For what it's worth, the datasheet can be found here:
https://www.mouser.fi/datasheet/2/389/cd00000084-1795415.pdf
 
Hi,

Yes the polarity is correct... And the -17V is ok .

I mesure 33V at D1/R2 and OV after D1/C2.

I have changed the diode bridge the last week but the problem is the same.

Sometimes when and i turn up the power the 5V led are illuminated during 1 second, maybe a capacitor charge ?

 
shotgunning parts is not a good approach.  having the -17 volts as o.k.  and the other not o.k. could still be related to caps.  You also may have a shorted transistors, a shorted resistor or any number of components that have failed.  You may even have a failed  IC L4977A. hard to say. The Schematic is hard to read.  the  IC L4977A looks to be a regulator. The pin out was provided. Should be easy to check if that is not working.  However if you  are not sure about it, I would take it to a repair shop. We doin't want you to hurt yourself to cause further damage. 
 
Thanks everyone, i did find a bad solder and no connexion between the two layers...

The PSU work fine.

Thanks.
 

Latest posts

Back
Top