amp suddenly stopped working

[alexmatak]

I'm a real rookie at all guitar gear related things and am looking for some advice about my amp that just cut out while I was playing.
Basically it was working fine one minute and then the sound cut out and hasn't worked since. I've tried it with many different cables, and plugged it into several different outlets etc, all with the same problem. The strange thing is that the power light is still coming on but it now does this weird thing where after I hit the power button off it takes a really long time for the light to go out (it does this dim-fade out thing now, whereas before it would just go right off).
Does anyone have an idea of what might be the problem here?
The amp itself is really low end, just a little Squire 15 practice amp, but it all that I have so I would love to get it back up an running!

any advice would be great

[Loudthud]

I have a schematic for that amp from 1985. Two stage opamp preamp, diode clipping and a single transistor stage. Descrete 7 transistor power amp with +/- 21V rails and headphone jack.

Try using a pair of headphones or just insert a phone plug into the headpone jack a number of times. If that doesn't work, you probably have blown transistors in the power amp section.

[DrGonz78]

What sort of skills do you possess? Do you have DMM? Do you have skills soldering? Etc.... Etc... Etc...

This is a very simple amp to learn on and can be fixed without much money invested in parts. Look at the PCB board for bad solder joints on the filter caps or anything else that might look suspect. If you have a DMM (or any multimeter) test for DC Voltage at the speaker output leads. Test voltage on the BR or rectifier diodes/filter caps. Also, test voltage on the opamp chips. Basically, we need you to be able to take apart the amp and understand how to do these tests to help fix the problem. As Loudthud has stated it is probably the output transistor that is fried. So, test to see if you are getting voltage on the speaker output leads first to make sure.

[Roly]

@Loudthud - would you mind posting the circuit please (to save me hunting around for it)?  Thanks.

[DrGonz78]

http://www.amparchives.com/album/Fender/Schematics/slides/Fender%20Squire%2015%20Schematic.html

[J M Fahey]

Thanks DrGonz  :dbtu:
And yes, the headphone jack is a big suspect here, squirt a little contact cleaner (or WD40) in its contacts, and plug in/out some cable there, to clean its probably dirty/rusty contacts.
If worn it must be replaced by a similar one.
Just to have the schematic here:

[Roly]

Thanks guys.  As the Dr says, very straightforward little amp ('cept for the quirky Fender tonestacks of course).  {And there's that lowish input impedance again (sigh)}

In this case the headphone socket is actually bolted to the front panel (yea!  :tu: ), so the chances of a fractured solder joint on the Printed Circuit Board are much less, and (as above) it is most likely a dirty switching contact in the headphone socket, but if cleaning doesn't fix it then it is possible the solder joints have fractured and need touching up.

If you do have to replace the socket be sure to get another one that is insulated from the chassis like this one, or you will get strange hums and such.