Rotel RX-1203 Needs Help!

[Owlesque1]

Hi all.
I bought a lovely big 120wpc Rotel RX-1203 about 3 months back for £3, and it has was performing wonderfully. It's easily the highest quality no compromise object I've ever owned. It looks mint inside and out, but recently went wrong.

The reciever has an amplifier circuit protection cut out, comprising a switch and 2 6.3A T fuses to the circuit board, and a 4A fuse protecting the speakers. I turned it on, the dial lit up, but the familiar 'click' of the main circuit starting did not come. this usually happens about 6 seconds after the on switch is thrown. I noticed a strand of speaker wire was shorting against another (precisely the kind of thing to blow the cut out fuses and flick the switch), so I rectified it and looked inside. The 2 fuses were blown, but they were only 3A, as opposed to the 6.3A T marked on the panel. I replaced them with the correct rating, turned her on and after a six ish seconds heard the familiar click as the switch reset and the amp circuit came on.

It worked fine for two weeks then it happened again: Turned on, no click, no music sound. The 3A fuse in the plug had blown. I thought this a bit too low and replaced it with a 5A, then trying again, the two 6.3A T fuses blew. I replaced. The amp then blows the 4A speaker fuse, but the tuner dial lights stayed on.

There is also a 2A fuse for the dial lamps. If this is removed, the amp circuit protection switch does not throw, so no sound. Two of the dial lamps were out. I struggled to find replacements for the 0.25A 6.3V pieces, the closest I could get are 0.25A 6.0V. I have replaced all bulbs with these, and they switched on fine, but the speaker protection 4A fuse blew at the same instant, so still no main protector switch reset, still no sound. I've been through 3 packs of fuses. I've ordered a multimeter from ebay......

There is a switch on the main circuit board that moves left ad right, I wonder if it's in the correct position, and whether this is the protector switch....DOES ANYONE HAVE ANY IDEAS ABOUT ANY OF THIS??? Please? It's baffling my brainbox

[anatech]

Hi Owlesque1,
I don't have a schematic for this, but it sounds like a serious problem. Installing more fuses has extended the damage if you've lost an output transistor.

So, do you know anything about electronics? If so, do you have a digital multimeter?

-Chris

[Apogee]

Check the driver transistors.

Twenty years ago I worked on a 1603 that kept blowing drivers because the design didn't like low ohm loads.

The guy who owned it had built his own speakers that measured 3 ohms and dipped lower, and the amp didn't like it.

I don't know what you're driving but it's something to consider. It showed the exact same symptoms as you described.

You are going to also have to check the outputs as Anatech mentioned because of your shorted speaker wires.

Yes, you made it worse by putting bigger fuses in. You should order a service manual for it at the very least.

You will need more than just a multimeter for this.

This family of receivers sure is beautiful to look at!

Good luck,

[Owlesque1]

Thanks for the reply. I'm learning about electronics in a hands on kind of way.

I only replaced the fuses with the ones of correct rating.

New multimeter arrives soon, I'll check those output trasistors pronto.

[anatech]

Hi Owlesque1,
The problem with replacing fuses is that they take time to blow. That means that other components are also stressed more and the damage marches through every time.

Don't do that.

-Chris

[AKN]

Hi,

Just a sidenote:

When a customer came to our repair shop with an object they often said "It is probably just a fuse"
And I answered every time "if so, there must be a reason"

And often customers had tried to replace fuses before coming, bad.

[anatech]

Hi 4fun,

And often customers had tried to replace fuses before coming, bad.

LOL
Almost every single time!

-Chris