Is there a chance anyone would have a schematic for a Orion 220GT?
I have one that has developed a problem and would like to try and diagnose and repair it.
It looks like it is a relatively simple amplifier and may be a good one to learn a bit about amplifier repair.
Thanks!
Dan
I have one that has developed a problem and would like to try and diagnose and repair it.
It looks like it is a relatively simple amplifier and may be a good one to learn a bit about amplifier repair.
Thanks!
Dan
Attachments
Mr. Babin,
Thank you for your reply.
It is blowing the 10A fuse that I installed in line.
I replaced it and the amp came on but it blew the fuse again as soon as I connected the RCA's with a signal running through them.
I have replaced the amp with a substitute amp for the mean time and the substitute is working fine so I'm sure the problem is with the amp.
I can't see anything that looks as if it were hot or burnt inside of the amp.
Thank you for your input. I really appreciate it.
Dan
Thank you for your reply.
It is blowing the 10A fuse that I installed in line.
I replaced it and the amp came on but it blew the fuse again as soon as I connected the RCA's with a signal running through them.
I have replaced the amp with a substitute amp for the mean time and the substitute is working fine so I'm sure the problem is with the amp.
I can't see anything that looks as if it were hot or burnt inside of the amp.
Thank you for your input. I really appreciate it.
Dan
With nothing connected to the amp, what is the resistance between the B+ wire and the RCA shields on the amp?
Gently push/pull/twist the power transformer while checking to see if it changes.
Gently push/pull/twist the power transformer while checking to see if it changes.
The resistance between B+ and the RCA shields is 3.78 M ohms.
It does not change when applying tension to the transformer.
Thanks,
Dan
It does not change when applying tension to the transformer.
Thanks,
Dan
Post the DC voltage on all pins of the TL494. Copy and paste the following into your reply. Look up the datasheet for the 494 if you don't know the pin numbering configuration.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Mr. Babin,
I put the amp on the bench tonight to try and get the TL494 pin voltages.
The amplifier is now blowing the fuse (7.5A) immediately upon the application of power without anything else connected to the amplifier. The power led comes on and the fuse blows immediately. I tried a fast and slow blow fuse.
Nothing is noticeably hot in the amp.
I guess something totally failed upon the last power up or it was just taking a bit for the fuse to blow.
May I ask for suggestions?
Thank you,
Dan
I put the amp on the bench tonight to try and get the TL494 pin voltages.
The amplifier is now blowing the fuse (7.5A) immediately upon the application of power without anything else connected to the amplifier. The power led comes on and the fuse blows immediately. I tried a fast and slow blow fuse.
Nothing is noticeably hot in the amp.
I guess something totally failed upon the last power up or it was just taking a bit for the fuse to blow.
May I ask for suggestions?
Thank you,
Dan
That would typically indicate that the output transistors have failed. Check them with a multimeter set to ohms. You should not read anything near 0 ohms across the legs of any of the output transistors with any combination of meter to terminal. To be consistent, check each transistor, leg 1-2, 1-3 and then 2-3.
Mr. Babin,
Ok. I will.
Can these be checked “in circut” or should they be removed from the board?
Thanks again,
Dan
Ok. I will.
Can these be checked “in circut” or should they be removed from the board?
Thanks again,
Dan
Ok Mr. Babin. I will as soon as I get a chance. I am on my way to my daughter’s christmas concert now.
Thank you very much for your time and trouble.
I know you are really busy. I really appreciate your help.
Dan
Thank you very much for your time and trouble.
I know you are really busy. I really appreciate your help.
Dan
Mr. Babin,
Please forgive me for the long delay in my reply.
I had an unexpected cancer diagnosis and had to go in for a fairly major surgery the day after Christmas.
They think they got it all, I am on the mend and doing well.
I was able to return to testing the mosfets in the amp and it appears that one of the IRF542 mosfets have gone bad.
From my research, it appears that IRF540’s would be suitable replacements for the pair.
Does that sound correct to you?
Again, I apologize for the delay in my response and sincerely appreciate your help.
Dan
Please forgive me for the long delay in my reply.
I had an unexpected cancer diagnosis and had to go in for a fairly major surgery the day after Christmas.
They think they got it all, I am on the mend and doing well.
I was able to return to testing the mosfets in the amp and it appears that one of the IRF542 mosfets have gone bad.
From my research, it appears that IRF540’s would be suitable replacements for the pair.
Does that sound correct to you?
Again, I apologize for the delay in my response and sincerely appreciate your help.
Dan
The IRF540 should be OK. The 540N causes problems in some amps that use the 540 so make sure that you don't order those.
Hi Dan,
Sorry to hear about your situation, but it sounds like you have a good plan. And it's great that you're already getting back to fun stuff. Keep on keeping on! If you have questions, want to vent, or want to hear from others you can visit this thread or drop me a PM.
Sorry to hear about your situation, but it sounds like you have a good plan. And it's great that you're already getting back to fun stuff. Keep on keeping on! If you have questions, want to vent, or want to hear from others you can visit this thread or drop me a PM.
Tim,
Thank you for your concern and reply.
I am blessed and fortunate compared to many others.
I have ordered the mosfets for the amp and will check all of the caps and replace if necessary.
It will be nice to revive the amp and place it back into a working old school system.
Thanks again,
Dan
Thank you for your concern and reply.
I am blessed and fortunate compared to many others.
I have ordered the mosfets for the amp and will check all of the caps and replace if necessary.
It will be nice to revive the amp and place it back into a working old school system.
Thanks again,
Dan
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