Fender Blues Deville fuse blow problem

[philm0l]

I have a friends 1993 Fender blues deville in my house at the moment that keeps blowing fuses.

I have tried pulling all the tubes and switching the amp on but it is still blowing.

I have also checked for any loose connections fom the power supply and found no problems.

The back of the amp states that it should have a F1.6A.250V fuse in.

Is there anything else I could try guys before handing it over to a qualified tech?

Thanks

[Wally]

There is nothing else for you to do. IF it is blowing fuses with the tubes removed, the problem is internal. There is a problem in the AC power circuit or the power transformer.
Side note: this is a risk when borrowing equipment. IF the power tubes were weak and failed thereby taking out the transformer, you and your friend may have serious discussions over who is responsible for the repairs. IF it is the transformer, the repair will get expensive. Sometimes things like this strain friendships. Hopefully, this is not one of these times.
Good luck with it.

[philm0l]

Thanks for the reply Wally.

I know he is not the type of guy that will blame me. We both knew the amp was blowing fuses before I said I would look at it for him.

He is purely a player and not interested in mundane things like broken amps

I just thought it was shame that this honey didn't sing anymore, so I will now hopefully find a decent tech in my area to have a look at it for him without it costing him an arm and a leg (although I suspect that will be easier said than done...!)

[Wally]

Well, then, that's a better situation than borrowing an amp and having it blow up on you. Good luck with.

[philm0l]

I also should have mentioned that he is Irish and hopefully the "Emerald Isle" gods will smile on both him and the amp...!

Here's hoping eh..?

[Wally]

If not the Emerald Isle gods, perhaps one of those fiery redheaded girls with laughing green eyes????? I might even prefer the latter over the former!

[philm0l]

My word that sounds just like his sister....!

That's the real reason I said I would have a look at the amp.

Here's hoping again eh?

Thanks for your imput Wally, that is why I love this forum so much.

[Wally]

LOL.....admirable goal, Phil.

[backline]

1. Possible stand by switch that is grounded. You need to feel comfortable on the inside of the amp.
2. Measure the resistance of the PT primary. With the amp unplugged and the power switch on you should see about 2 ohms DC resistance on the hot and neutral prong of the power cord.
3. Possible pin of the power tube socket going to ground. Check for continuity between ground and the pins of the sockets.
Good Luck

[Pepi]

I had one of these in on repair a few weeks ago. There was a shorted diode in the main power supply. I replaced all of the diodes (CR14-CR17) and the amp was fine then. Could also be a shorted filter capacitor. C34 or C35

[philm0l]

Thanks for all your help guys, I have today taken the amp to my local tech who has said he will fix it this week.

I am not that confident poking around in the back of amps when it comes to testing components and thought it best that it should be looked at by a pro.

The amp is switching on fine until the standby switch is flicked and then the fuse pops.

I will keep you all informed as soon as she comes home (and I cant wait for that...!)

[Wally]

Phil, as always we want pics......of the redheaded, green-eyed Irish beauty, that is! (;^)
And....good luck withthe amp.

[philm0l]

Just a small update guys, I have just spoken to my tech and he has isolated the problem to a dodgy HT choke. He is now waiting for a replacement from Fender (Amsterdam) and should be up and running proper next week.

Good chance it has been stored in a damp environment for a fair few years and this has led to the possible break down of the coil, or there is a good chance it is just had a fair amount of Guinness all over it I reckon.

My tech reckons he has never come across this problem before and I am happy I didn’t even try to find the problem.