how long do transisors last in use?

[spooney]

I am getting ready to do a little work on an orion 280gx amplifier. It currently works fine but being over 20 years old I was planning on doing some basic stuff like replacing the caps,touching up any shotty looking solder joints, adding heatsink compound/replacing the insulators, etc . Anyways like I said the amp works fine but I was thinking of replacing the outputs and ps fets. I'm just curious if it is even worth it to replace them seeing as the amp works perfectly.How long do fets/transistors usually last in an amplifier that isn't abused?

[eclectic2k]

don't bother to replace transistors. If operated within spec and not abused, they'll likely last darn near forever.

reflowing solder joints, and replacing caps is definitely recommended (as you are planning) depending on the quality of the originals, replacing some of the critical resistors with good quality may see some gain as well...

on a related note:
If you wanted to upgrade to more modern devices, that might be a worthy goal, but that would require at least a minor bit of re-design, not just an upgrade/replacement.

[wakibaki]

Originally Posted by spooney

... the amp works perfectly...

You actually said that 3 times in different ways in your post.

Leave it alone. It probably doesn't work perfectly, but who cares, you can't tell any different. The commonest cause of broken equipment is unnecessary 'fixing'. This is why, over and again, you will hear the phrase:- 'If it ain't broke, don't fix it'.

Don't do it. If you want to fiddle about with components, build a kit.

w

[1moreamp]

Afternoon John I sent you a small epic novel on this question you asked via gmail.
Hope you get some in depth info and a good laugh also....C

[Perry Babin]

Are you going to use the amp?

As a side note, I don't think this amp used FETs in the power supply.

[spooney]

I do plan on using this amp Perry,most likely to run my mids and highs. The power supply in this particular amp uses SMP60N05's . I couldn't find an exact match for that part number but similiar part numbers(STP60N05) were all FETs.

[spooney]

Thanks for the email Cecil. Tons of good info in there

[Perry Babin]

The SMP60N05 is an FET. This must have been a late model 280GX. I'd recommend using an IRF3205 as a sub if you need to replace them.

If you're an abusive person that constantly drives their amp into clipping, it would probably be good to replace all of the power transistors. If you don't drive an amp like that, I'd recommend using it as it is. Use a 35 amp fuse in the B+ line. That should hold up to normal use and should limit the damage to the circuit board if the amp fails.

[acebaker]

I guess the stuff that looks like brown sugar at the bottom and the little bumps on the sides mean my Sprague 515(D) 50V 1000uF cap is kaput then. I've got a lot to learn still.