Marantz 2240 Blowing Fuses on Power On

[Danementzer]

Hey friends, it's been a long time, but I'm finally back to servicing and maintaining my gear.

My Marantz 2240 blows a fuse every time I power it on. Can you give me some advice on where to start looking for issues?

I'm attaching a few pics and the schematics. This sucker is very clean with no evidence of leakage or shortage anywhere I can easily see. Thanks in advance for your help.

 

[Richs_Trains]

First off, I am not a tech, just a hobbyist. I would build a DBT (dim bulb tester) and then if your power amps are modular, I would remove them one at a time and power the unit up on the DBT each time. If the bulb stays bright for more 2 seconds or so, shut it down. This will at least tell you if the problem is in the power amps. If the bulb goes bright and then dim, you have found where the short is and have a starting point. If both amps are pulled and you still have a bright bulb, try removing the feed to the power supply and test again. If it still stays bright you could have a bad filter cap (these don't usually fail, but I have had two unit with bad filter caps). It is a pain, but you can remove the power from your filter caps and test on the DBT again. The DBT should keep your fuse intact while doing these tests. I am sure there are people with better advice than me, but this is my process when there is a dead short. Good luck, Rich

 

[mbz]

+1 on DBT
Common cause is shorted outputs or driver transistors. Suggest diode test the output (heat sink mounted) transistors, amp
powered off/unplugged, hopefully your mm will beep indicating a short, search AK for how to diode test transistors...

 

[Jonstigator]

+2 DBT

 

[jd3rdcoast]

+3 on DBT, +2 on check output transistors.

 

[Steven Tate]

+4 on the DBT.
How to test transistors with a DMM:
https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/