Pioneer SX-990 dead channel

Hi everyone,
I'm a newbie. I have a problem. My dad' s Pioneer SX-990 receiver has a dead channel. When I opened, I saw two 2A fuses near the rear panel placed close to each other. One was open. So I replaced it with a new one. However my pioneer burned that new one again. So I have one channel working. Can you help me please?

Those fuses are in the B+ line for the amps! Don't put anymore fuses in until you've figured out WHY the fuses are blowing. These could be blowing due to blown output transistors, shorted driver transistors, shorted or open caps, shorted resistors, or related components. There are some VERY GOOD threads in the forum(s) for you to read on how to test components, and possibly replace them.

Read these.
http://www.audiokarma.org/forums/showthread.php?t=333423
http://www.audiokarma.org/forums/showthread.php?t=426532

The second has further links to other threads pertaining to component testing. Read them at least twice, and proceed SLOWLY, particularly if you have no or little experience with electronics. Get the Service manual and learn to read and understand the schematic, and how to take voltages(SAFELY!!), and test components CORRECTLY.

Also the following thread is important to all audio gear......"The Idiot's guide to DeOxit, revisited!".... http://www.audiokarma.org/forums/showthread.php?t=207005

Schematic and manual here.... http://www.kallhovde.com/pioneer/Pioneer/Main scan page.html . Scroll down.

Thanks larryderouin. I see it is a quite work here. I do not have the equipment and tools mentioned in the threads but I will take my chance. Thanks anyway...

sx-990

Great old pioneer, that sx-990.

I'm afaid there is no "easy" fix for that problem you have though.

I suspect blown output transistor(s). But that is a first guess.

Since the main amp board stands upright through the deck, they are tough to work on. Its hard to get to things to probe them with the board in place. Taking the board loose helps but then you need to worry about shorting against the case and such.

I have some tools and have gotten fairly good with them, but I'm no tech.
I would take the main transistors out (you have to desolder them) and test them with a DMM to see if they are blown.

If they are, I would search for good replacements (check AK threads). I would also look for replacements for all the other transistors on the main amp and make a list of all the capacitors on there. I would check all the resistors in place with the DMM and look for any corrosion (I had a problem once on an sx-990 with a bad resistor).

Then I would order all new transistors and capacitors and replace them all. Its a piece of work but its SOOOoooo worth it. The SX-990 has such a nice sound.

Luck

Thanks blhagstrom. So you say that the problem is most likely in the main amp board which stands upright through the deck? I can desolder it and test transistors with my multimeter. However I do not have any oscilloscope or any signal generator so I can not test further tests.