AMP Blowing fuses on one channel

[Skins]

I dug out my old DAP amp as a mate wants to borrow some kit for gig in the coming the weeks.

Its a DAP Palladium 1600, now Ive never had a problem with it until today when I fired it up and it blew the two internal fuses on the right channel.

The left one was fine. So, I replaced the fuses and as soon as I power it up, it fuses and goes into protect mode.

6 fuses later I cant figure it out for the life of me. Theres no visable damage, it just seems to blow fuses for the hell of it.:confused:

It does this even before I put any audio through it, so something isnt right...

Some of you will say bin it, but it "was" a great amp and I love to get it working again...

anyone have any ideas??

Many thanks

Shaun

[Paul James Promotions]

Any liquid in it at all that could be causing a short?

[Skins]

Nothing Jamie,

The inside is like brand new, and theres nothing visible that could be shorting the boards....

Shaun

[spin mobile disco]

Seems obvious but checked cables for a short? or are the ohms correct on your speakers? I know obvious but always worth mentioning.

[deltic]

output transistors leaking probable cause-not too difficult to change not too expensive either

[Penfold42]

Where was it stored?

[One Vision]

Where was it stored?

I was just gonna ask the same question :D

[Penfold42]

I was just gonna ask the same question :D

Then you may think like me.......:D

If it was in a cold place then put in your room at room temperature....you could have caused condensation......just a thought. :)

[Skins]

Where was it stored?

Under the stairs in the house of all places..!
FYI, It blows even before Ive connected any output cables / and still blows after Ive connected the output cables.

anyone looking for a little weekend project?!

Shaun

[Shaun]

anyone looking for a little weekend project?!



You're asking DJs if they're looking for a weekend project? :confused: :d

[Skins]

You're asking DJs if they're looking for a weekend project? :confused: :d

edit: "anyone got an hour spare that they want to kill?!!!:o

S

[nigelwright7557]

You're asking DJs if they're looking for a weekend project? :confused: :d

I design and build my own amps.

You need to start logically from the front end.
1/ Is transformer working OK on its own ?
2/ Has the rectifier gone short ?
3/ Have one or more of the smooting caps gone short ?
4/ Have any of the output transistors gone short ?

If I still havent found the problem then I remove the output transistors and check the components on the driver board. The LTP, VAS, bias and CCS's. If the driver board seems OK I will fire it up and look for unexpected voltages. I will check the bias voltage coz if its too high that will pop the fuses.

[Andy Westcott]

Interesting one eh Nigel?
Odd that both supply rails should blow fuses - if an output device is damaged, it'd only blow one of the fuses as a rule.

I'd be looking for a coin or something similar rattling around inside, although if there is one it has obviously caused some damage by now.

I can't for the moment think of any likely fault which would cause this, with no input signal and no load connected - I'd be interested to know what it was when you get it fixed.

[nigelwright7557]

Interesting one eh Nigel?
Odd that both supply rails should blow fuses - if an output device is damaged, it'd only blow one of the fuses as a rule.

I'd be looking for a coin or something similar rattling around inside, although if there is one it has obviously caused some damage by now.

I can't for the moment think of any likely fault which would cause this, with no input signal and no load connected - I'd be interested to know what it was when you get it fixed.

A transistor can blow very much quicker than a fuse can.
In my experience one transistor going usually takes out the complimentary ones too which then blows both fuses.

[Skins]

righto,..

quick update,

Ive looked at every possible idea so far and cant see anything obvious. Theres nothing that I can see that causing the short, nothing seems to have blown as Ive checked for any signs of scorching on the boards.....etc:

and, as a last resort

I removed both internal fuses (for the left channel) and a green LED inside the amp comes on and the protection circuit goes OFF......

But, you guessed it

when the fuses go back in, the blow straight away and the green LED goes off.

Ive but an compressed air duster through it and still not getting anywhere fast....:bang: :bang:


next!!!!!

Thanks for those that have helped so far....

Shaun

[deltic]

nigel

i agree with that only takes one tranny to leak not neceseraly go dead short and both fuses blow.

[Skins]

if its any help,

heres the pdf

http://www.showfotos.nl/manuals/DAP-audio%20manuals/D4137-P2000-Vintage-E.pdf

have already reset the breaker switch!

S

[Jiggles]

Take it to a sparkie they may have a better idea if somethings gone

[nigelwright7557]

righto,..

quick update,

Ive looked at every possible idea so far and cant see anything obvious. Theres nothing that I can see that causing the short, nothing seems to have blown as Ive checked for any signs of scorching on the boards.....etc:

and, as a last resort

I removed both internal fuses (for the left channel) and a green LED inside the amp comes on and the protection circuit goes OFF......

But, you guessed it

when the fuses go back in, the blow straight away and the green LED goes off.

Ive but an compressed air duster through it and still not getting anywhere fast....:bang: :bang:


next!!!!!

Thanks for those that have helped so far....

Shaun

Things dont have to be scorched to have gone.
A dead transistor can look just like a normal one.
You need a ohm meter to measure across them to see if they are shorted.

[Skins]

Thanks Nigel, I`ll grab a meter tomorrow and report back.

Shaun

[Andy Westcott]

But you need to know what you are testing for - voltage drops across junctions rather than resistance, for example.

To be frank, I'd just get the amp into a reputable repair shop - "No user serviceable parts inside".

Unless you are well experienced in electronics, that is.

[Skins]

I think thats the only solution now matey,

Ive shoved my tester in and spent another hour tinkering but I`m not getting anywhere.!

Best box it up and send it off!

Thanks for all your help on this guys, I`ll report back my findings once Ive spoken to the engineer

shaun