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Marantz 2015 main fuse blowing

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UsedChaps

New Member
Hi all! Long time lurker, first time poster here. I recently got a pretty worn Marantz 2015 (with wood case) for 50$. Main fuse (on the back) keeps blowing on power-up. I found that the output transistors were blown, so went ahead and replaced those to no avail. Still getting blown fuses.

Any ideas? It looks like the previous owner cut the wire to the tuner indicator light, but I doubt that would be blowing the main fuse...

Thanks so much!
 
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Something else is still wrong on the amp board. Do you have a dim bulb tester? It will likely save your new output transistors. Were the original outputs shorted? Just 2, or all 4?

Did you pick this up at the audio show in Southfield last weekend? I think I looked at this unit while I was there.
 
Motnick said:
Something else is still wrong on the amp board. Do you have a dim bulb tester? It will likely save your new output transistors. Were the original outputs shorted? Just 2, or all 4?

Did you pick this up at the audio show in Southfield last weekend? I think I looked at this unit while I was there.
Click to expand...
I do have a dim bulb tester! The original outputs were indeed shorted (3 of them). I actually just realized I may have put the replacement transistors in wrong (there’s a wire that connects to the collector of the transistor — I attached it to the wrong side). Would that cause a short?

I think I may just start from the transformer and work my way through the secondaries.

I got this from Facebook marketplace actually haha
 
If the outputs were blown then you should definitely check the other transistors on the amp board. It’s likely you have a bad driver transistor still. My advice is to go through the amp board and look for other shorted transistors. Blown outputs usually take other parts along with. Check the diodes and the bias trimmers while you are in there.

What did you use for replacement output transistors?
 
Motnick said:
If the outputs were blown then you should definitely check the other transistors on the amp board. It’s likely you have a bad driver transistor still. My advice is to go through the amp board and look for other shorted transistors. Blown outputs usually take other parts along with. Check the diodes and the bias trimmers while you are in there.

What did you use for replacement output transistors?
Click to expand...

would the other transistors be the same diode test on my DMM? Could I test them in circuit? I got some plastic TO-220 ones from eBay (the ones with the three pins where you break the middle off). They test perfectly so they seem to work.
 
Is this a 2015 or a 2015b? I thought the 2015 used TO-3 but I could be mistaken.

eBay transistors are likely bad news

transistors should be removed to test properly, but you should be able to find a shorted transistor in circuit. Just might need to remove to confirm.
 
I'll go ahead and start testing transistors on the amp board and report back! Probably will have to wait till next week as I'm travelling... Very committed to getting this thing up and running as it's my first Marantz! Very excited, especially for 50$.
 
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