First Gen 225 Orion

[SS64]

Ok I have this amp im trying to fix for my friend. He hooked it up at a 1/2 ohm bridged, so needless to say it went POOF after about one song.. I took off the rails and 6 6488's are blown in the supply and 4 6491's and 2 6488's in the output section. I went and bought the 88's and 91's. I'm in the process of getting the supply up and running again. I put all the supply trans in and I went to power it up. Besides for the hissing the supply trans all run cool besides one. Now with the wire end facing towards you the one 88 that is the first one on the right gets hot. I think this has something to do with turning it on. When I hook up the remote wire the trans. gets hot and then the amp will stay on. And with the remote disconnected if I take my finger and touch the leads the amp turns on and stays on until i disconnect the power wire. And with the remote wire hooked up I get 18 volts on the rails but when the amp sticks on the rail voltage jumps to 35.
So where can I start?

[tomtomjr]

My first suggestion of where to start...

When the 2N6488 and 91's go out, change them all. It will burn again and the ones you just put in will go too.
I have had them burn 4 and leave a few still good. If I changed just the 4, it will be back the next week with the same problem. So, on the Orion's, change out all of them on that side. If one reads bad, that whole side is bad...
Also, check the resistors in front of the fets. Most of the time, they will show heat damage on the bad ones. Sometimes the ones with heat damage still check fine. Check em though...

[mike49504]

ss64 wondering if u can do me a favor theres a yellowish orange tantulam cap neer the remote wire on that amp.. wondering if u might be able to post the numbers off it. im repairing the same amp and that cap was missing so i have no cle what value goes there any help would greatly be appericated

[SS64]

That cap reads just like this
A
2u2
25


And I am going to replace all the trans along the rails. All the outputs are removed right now. I just need to find out why the one 88 that I mentioned is heating up....

[tomtomjr]

I put up some hi-res pics of the guts of my Orion 425 1st Gen. (mint) . Go to the left of the page, then you will see ---ORION 425 --- Click there, and you will see lots of closeup pics. Took one of the cap for you too. Not a 225, but a pair of 225's on one board. They made some with 2 225 boards, but I have the single version.

http://s250.photobucket.com/albums/g...DIO/?start=all

GO TO the left of the page, and you will see ORION 425 Folder.

[SS64]

Thanks for the pics. Man where do you live!!! I want to come drool!!!
I was hopeing Perry could chime in on my subject....
Could the MCT2's be bad?

[Perry Babin]

The single transistor drives the transformer windings that drive the rest of the power supply transistors. It's operating in linear mode and dropping a fair amount of voltage so it's going to run hotter than the transistors driving the power supply transformer's primary windings (when at idle).

If you look at the board, you can see that it's not connected to the power supply FETs.

[SS64]

Ok. But is it supposed to get hot enough to burn me? And the amp stays on after I activate the remote 2 or 3 times. And with no outputs in the rail voltage starts at 18.79 and climbs up from there.
Oh and I know you said FET's. This one uses 6488's in the supply

[Perry Babin]

I don't remember exactly how hot they run. I have an old 280gx here. I'll repair it and see how hot it runs in this amp.

When the rail voltage went to 35v, where was the black meter probe?

When you wrote 'when the amp sticks on the rail voltage jumps to 35', what did you mean?

You're correct, no FETs.

[Nismoron]

Sorry to Hijack, but I just wet myself. I have been looking for one of those old multi-piece zapcos for about 15 years... refering to the pics posted by tomtomjr.