2285b Euro keeps blowing 5A fuse on back
- Thread starter PooPoo
- Start date
Velox
Just a bug hunt, Ripley..
Well presumably some of the more active and senior members here will dive in soon and give you some directions. I can offer some simple suggestions. Firstly never put in another fuse when the one you just put in blows out. Never put in ANY new fuses to try and fix a blown fuse problem without first identifying why the fuse blew. In this case, you should not be attempting any power on without using a DBT - dim bulb tester - search on here and Google and plenty of info how to build one for a few bucks. Putting 5 amps through your Marantz that has already blown a fuse is just asking to harm more parts! Once setup with the DBT then you need to systematically isolate which area of the receiver is shorted - obviously some component is creating a short that takes out your 5 amp fuse. You say you already blew another fuse after umplugging "the driver boards" meaning I assume both power amp connectors. So with the power amp boards out of the equation, something else is shorted, most likely in the power supply. Inspect "everything else" first looking for loose wires, broken wires, wires that have become unsoldered, wires with exposed copper loss of insulation etc. You need to go over the power supply board very carefully looking for burnt, leaking, broken, smoked, cracked etc components. You can isolate the power supply by removing the input voltage to it from the transformer and then verify other cicuits are functioning normally - lamps, switched AC outlet etc. You can get a service manual at hifiengine.com and study block diagrams, schematics and part descriptions. You may have a shorted filter cap - the two big ones - look them over for damage, perforation etc. Get your digital volt meter out and make sure you know how it works, and get ready to test resistors, capacitors, transistors, diodes etc. But step one is, protect from further damage. Then on to step two, isolate the area causing the short. The on to step three, test all the components in the area of the short. Report back once DBT ready and full inspections done, I'm sure others will jump in to help, and good luck!!
5 amps is good amount of current. Those two primary filter caps are really four caps.. Two inside one case. And it's common for one or both to go bad. One for each channel ( R/L) A bad transformer could do this too.. as can a bad power supply board or a bad main amp board. But like the question that has been asked.. whats the state of this? OEM? worked on ? been restored? No idea? Pictures can be of help too to decipher if any work has been done.
. Common? yeah.. with 40+ year old caps it's common enough. Swapping could cause a bad problem to be worse. Just replace them. There are more than a few ways to do it. The only "gotcha' like we said, it's two caps in one case. Look at the diagram on the outside of the cap. I used perf-board in mine with a set of radial lead 63V Nichicon caps. These are small enough to fit side by side without having to resort to gutting the old ones or hot gluing them into place. Or for a quick test, you can lift the leads from the caps installed and jump in a set of replacement caps with alligator clipped wires.
PooPoo
Active Member
Didn’t recap the main filter caps yet just the power supply board.
Does it play awhile, then blow or is it right away? If it plays for awhile I'd look to be sure it's wired correctly for 120V operation. The fuse is supposed to be 5A, checking the US schematic so that seems alright.
If it blows right away I'd unplug the two power connectors from the bottom end of the output amp modules. They are in from the edges one connector, have 5 pins and (at least) black, red and white fat wires attached to them. Make sure they can't touch anything when you power up with your DBT inline.
As Velox wisely suggests, build yourself a DBT (dim bulb tester) if you don't have one yet and use a 100W or even 150W incandescent bulb. Do this first!
If it blows right away I'd unplug the two power connectors from the bottom end of the output amp modules. They are in from the edges one connector, have 5 pins and (at least) black, red and white fat wires attached to them. Make sure they can't touch anything when you power up with your DBT inline.
I dont agree with stuffing this particular caps. I have in the past often times with my early 30s-40s radios. But this arrangement is right next the hot plate of a power amp board. Granted, it should not get THAT hot in normal operation but if you are driving a 4 ohm load and pushing anything close to the 80-90 watts it can generate, then all bets are off. Those caps got warm and I prefer to have my caps coolGood deal. Now the fun part, adapting or rebuilding via restuffing.No... not fun!
So when I did my own 2285B, I forgot about the restuff ( also makes any future repair a real PIA) and did up a couple of perfboards with 4 new smaller caps. Everyone wins.. the caps are smaller and get more air, the amp gets more air and I get an easier job if per chance, one of the new caps decides to die an early death. It also made it a lot cleaner underneath the chassis. Right now mine are soldered in but I may get some screw mounts and re-do that part before I close everything up for the final time. I have some fish paper to put under the perf board and I'll clean up the wiring a bit more. I saw a guy made some nice PWBs to do the same thing which allowed bigger caps ( mine have radial leads vs the short PWB leads)You can see what I have right now in place
EDIT: The bigger caps also put the leads real close to the chassis unless I spaced it up which I didnt want to do. That custom PWD I mentioned looked like it was spaced up. These radial leads have alot of clearance.
PooPoo
Active Member
That’s good stuff. I might have to copy you! Btw you need any new vellum? I got a bunch I can send you a sheet to replace those toast lolI dont agree with stuffing this particular caps. I have in the past often times with my early 30s-40s radios. But this arrangement is right next the hot plate of a power amp board. Granted, it should not get THAT hot in normal operation but if you are driving a 4 ohm load and pushing anything close to the 80-90 watts it can generate, then all bets are off. Those caps got warm and I prefer to have my caps cool
You can see what I have right now in place
EDIT: The bigger caps also put the leads real close to the chassis unless I spaced it up which I didnt want to do. That custom PWD I mentioned looked like it was spaced up. These radial leads have alot of clearance.
View attachment 1164125
Funny you should ask
. The 2285B doesnt use vellum but I've another Marantz sitting waiting it's turn that does . So yes, I could use a sheet .. if you dont mind sharing.These are the caps I used for the 2285B- 63 volts and 6800 uf with radial leads. They run about 6 bucks each.
https://www.mouser.com/ProductDetai...GAEpiMZZMtZ1n0r9vR22e0BBN1kF1oiGiFT%2bMzB0yY=
