UK Coolbox not working from mains

[Toady1]

Hi
I have a 40L Halfords coolbox which works off 12v cigarette lighter, but won’t work of the 13amp plug.
I have changed the plug fuse, but to no avail. Any ideas?
Cheers
Newbie

 

[Pete999]

Hi
I have a 40L Halfords coolbox which works off 12v cigarette lighter, but won’t work of the 13amp plug.
I have changed the plug fuse, but to no avail. Any ideas?
Cheers
Newbie

dDo you mean it won't cool stuff or it wont turn on as in it's as if there is no electric?

 

[UNG]

Hi
I have a 40L Halfords coolbox which works off 12v cigarette lighter, but won’t work of the 13amp plug.
I have changed the plug fuse, but to no avail. Any ideas?
Cheers
Newbie

Have you checked the output of the mains adapter before connecting it to the cool box

 

[Toady1]

dDo you mean it won't cool stuff or it wont turn on as in it's as if there is no electric?

Hi
The item seems to have no power when connected to the mains

 

[Pete999]

Hi
The item seems to have no power when connected to the mains

Fuse Blown, bad connection. switch turned off could be anything

 

[Toady1]

Have you checked the output of the mains adapter before connecting it to the cool box

There are two wires which can power the coolbox, one which fits into a cigarette lighter (which works). and the second goes to a normal plug, it’s this one which doesn’t work.
[automerge]1596832014[/automerge]

Fuse Blown, bad connection. switch turned off could be anything

 

[UNG]

There are two wires which can power the coolbox, one which fits into a cigarette lighter (which works). and the second goes to a normal plug, it’s this one which doesn’t work.
[automerge]1596832014[/automerge]

So having got to the electronics it's time to get the multimeter out and do some testing to narrow down the fault, crystal balls are pretty useless for fault finding no matter how often we are asked

 

[Toady1]

so it looks like these have blown
Hard to make out the letters
H40AE J3305-2?
Any ideas if this looks correct, and what items are suitable replacements?
I’ve tried to google the serial number but no luck
many thanks in advance

 

[Lucien Nunes]

Those seem to be FJP3305-2 which is a 700Vcbo, 4A NPN by Fairchild (whether those are genuine Fairchild is anyone's guess.

Presumably you've tested them and they are shorted all round, or what makes you think they are bad? There is a good chance other parts are bad too. Have you checked the driver, efficiency diodes, feedback network etc? How much experience repairing SMPSU's do you have?

 

[DPG]

Those seem to be FJP3305-2 which is a 700Vcbo, 4A NPN by Fairchild (whether those are genuine Fairchild is anyone's guess.

Presumably you've tested them and they are shorted all round, or what makes you think they are bad? There is a good chance other parts are bad too. Have you checked the driver, efficiency diodes, feedback network etc? How much experience repairing SMPSU's do you have?

I'm hoping he has some experience of these things, otherwise he will have that familiar look on his face when he has replaced most of the faulty parts, but not all of them. And them the SMPSU destroys itself the second it is powered up.

Been there several times in the past!

 

[Lucien Nunes]

You get to that point, with the thing hung on the lamp limiter, the startup kicks it over a few cycles and the lamp flickers. You think, maybe I should take that out of circuit now as it's obviously being throttled too much, so you put hard mains on it and PHUT. Then you think, why the fork would I take it off the limiter when it so obviously isn't working yet.

My worst disaster was actually not my fault but it felt like it. I had just overhauled a dead channel in a big vintage Pioneer receiver that uses unobtainable vintage ring-emitter transistors. It was all good, I set up the bias, took it off the limiter, moved it across the room and plugged it into full mains. In the process, the bias string had gone O/C at a lifted track on the board and it immediately ate all six output devices worth £50-75 each. Problem was, I had just bought a set of six to repair a channel in someone else's unit, and couldn't get any more as sources are few and far between. I had to settle for the older spec device with lower Vceo that was used in early production.