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?
So where can I start?
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...
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...
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
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/gg278/tomtomjr/CAR AUDIO/?start=all
GO TO the left of the page, and you will see ORION 425 Folder.
http://s250.photobucket.com/albums/gg278/tomtomjr/CAR AUDIO/?start=all
GO TO the left of the page, and you will see ORION 425 Folder.
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.
If you look at the board, you can see that it's not connected to the power supply FETs.
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.
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.
Yes it does have the resistor. With the amp remote wire off, with the positive probe on the + input wire and the Negative probe on the resistor I get 14.75. With the amp on I get 5.72 Sometimes.... and 18.62 other times... It seems like every 3 or 4 times I turn it on the voltage changes... Could that 88 go bad? It was new.
Those are zeners by the 88 right? Could those have went bad?
Those are zeners by the 88 right? Could those have went bad?
On every repair, it's important to remove all of the soot that was deposited by the blown parts. If there is carbonized fiberglass/epoxy, you must cut it out. Sometimes even flux can be conductive enough to cause problems (especially on circuits like this one). After replacing parts, you should clean the board to remove the flux. Flux alone won't cause any problems but it can become contaminated and sometimes becomes conductive (generally when too much heat is applied). Removing it makes the repair look better and prevents other problems.
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