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Old 5th February 2006, 07:57 PM   #1
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Default 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
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Old 5th February 2006, 08:05 PM   #2
Netlist is offline Netlist  Belgium
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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?

/Hugo
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Old 5th February 2006, 08:24 PM   #3
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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!)
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Old 5th February 2006, 08:38 PM   #4
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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).
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Old 5th February 2006, 08:47 PM   #5
Netlist is offline Netlist  Belgium
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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?

/Hugo
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Old 5th February 2006, 08:50 PM   #6
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I'll check soak test it when ive got another fuse. Fuse that had blown was in the output.
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Old 5th February 2006, 09:11 PM   #7
Netlist is offline Netlist  Belgium
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Quote:
Originally posted by Rotellian
Fuse that had blown was in the output.
Party?

/Hugo
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Old 5th February 2006, 09:16 PM   #8
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Quote:
Originally posted by Netlist

Party?

/Hugo

Thats what i thought! But not mine!
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Old 6th February 2006, 10:14 AM   #9
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Here is a pic of damaged area (sorry its not better res was taken with my phone)

Click the image to open in full size.
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Old 6th February 2006, 10:37 AM   #10
forr is offline forr  France
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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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