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Rotellian 5th February 2006 07:57 PM

Rotel amp problem
I recently acquired an old (15 years) rotel amp. When i plugged it in there was no output in one channel. I eventually traced this to blown fuse. Swapping over the good fuse confirms that both channels are working, and i plan to get a replacement (6.3A 250v slow blow i believe).

Am i right in thinking that a blown fuse could be symptomatic of something more seriously wrong? (i know nothing about amps) A further look around the insides reveals a slightly blackened look on a small part of the pre-amp/input pcb. Yet everything still seems to works OK (well replacement fuse not withstanding). Should i soak test the amp after replacing the fuse? I wondered if whatever burnt out is likely to give me more problems or if it might be a part of the preamp section i dont use (phono cartridge input)

Any help/advice would be great :)

Netlist 5th February 2006 08:05 PM

It could be an indication of bad solderings, especially in the brown areas. I have no idea about your soldering skills so take care if this would be your first attempt.
Could you post some high res. pictures of the brown coloured areas? Solderside?


Rotellian 5th February 2006 08:24 PM

Hi, thanks for your reply, I havent touched the amp other than to change the fuse. My soldering is OK (ive changed op-amps, capacitors etc in cd players but not amps). The discolouring appears to be component side not solder side. I cant post pics until tomorrow. Soldering all looks pretty good as its a commercial component (although admittedly thats not always much of a guarantee!)

Rotellian 5th February 2006 08:38 PM

There is a minor amount of soot on the inside of case above where the problem area is. Perhaps one or more of the electrolytic caps failed? (il post a pic tomorrow).

Netlist 5th February 2006 08:47 PM

Fuses 'can' jump by accident but they do rarely.
If all seems ok now, I'd let the amp play at moderate volume and keep it in observation for a while. Is the fuse located in the power supply or the output?


Rotellian 5th February 2006 08:50 PM

I'll check soak test it when ive got another fuse. Fuse that had blown was in the output.

Netlist 5th February 2006 09:11 PM


Originally posted by Rotellian
Fuse that had blown was in the output.
Party? :D


Rotellian 5th February 2006 09:16 PM


Originally posted by Netlist

Party? :D


Thats what i thought! But not mine!

Rotellian 6th February 2006 10:14 AM

Here is a pic of damaged area (sorry its not better res was taken with my phone)

forr 6th February 2006 10:37 AM

Hi Rotellian
> a blown fuse could be symptomatic of something more seriously wrong?

Most often, yes, but not necessarily. A fuse can be blown because it becomes old : every time there is a switch on/off, some particles of metal leave the fusible wire, which blows when too thin.

~~~~~ Forr

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