Marantz 4270 problems

[Jack Panjer]

I have a marantz 4270 that I recently aquired and upon power up it blows the main fuse, I realize it could be anything but any suggestions on where to start? I took the case off and it's quite intimidating to look at to say the least.

 

[blhagstrom]

Main fuse blow usually point to the transformer (unlikely) or the power supply. The filter caps or bridge rectifier are the primary suspects.

I’ve only seen a few truly bad filter caps in 100s of old units. I’ve seen more bad bridge rectifiers so that is the first suspect in this case.

The power supply in the US 120v 4270 tends to run hot and is a bit tedious to access and work on. Are you skilled at electronics work?

 

[catrafter]

A dim bulb tester is your new best friend.
One or more shorted output transistors is also a possibility.
I always test Stereo 2 + Quadradial 4 gear with the rear panel Power Mode switch in the X4 position.
You can switch it to X2 once you have it all working if you wish.
Never ever cycle the Power Mode switch with the unit powered on.

Tom

 

[Jack Panjer]

Main fuse blow usually point to the transformer (unlikely) or the power supply. The filter caps or bridge rectifier are the primary suspects.

I’ve only seen a few truly bad filter caps in 100s of old units. I’ve seen more bad bridge rectifiers so that is the first suspect in this case.

The power supply in the US 120v 4270 tends to run hot and is a bit tedious to access and work on. Are you skilled at electronics work?

Thanks for your help, I'm an electrician and have spent many years working on plc''s and microprocessors on medical equipment, however I only worked to board level.so my knowledge of electronics is minimal.

 

[Jack Panjer]

Thanks for your help, I'm an electrician and have spent many years working on plc''sand microprocessors on medical equipment, however I only worked to boardlevel.so my knowledge of electronics is minimal.

 

[Steven Tate]

Hang around here and you will learn a lot from the seasoned experts. If you are interested in pursuing this as a hobby, I’ll give you good advice that was given me about three years ago when I wanted to learn to restore a 2270. Set your 4270 aside, go to eBay or CL and latch on to a lower powered and cheaper Marantz like a 2215 or 2220. Start a thread and let them help you work through it. It’s less crowded and easier to work on. Get it up and running and then move to something more complex.

 

[blhagstrom]

Hang around here and you will learn a lot from the seasoned experts. If you are interested in pursuing this as a hobby, I’ll give you good advice that was given me about three years ago when I wanted to learn to restore a 2270. Set your 4270 aside, go to eBay or CL and latch on to a lower powered and cheaper Marantz like a 2215 or 2220. Start a thread and let them help you work through it. It’s less crowded and easier to work on. Get it up and running and then move to something more complex.

Good advice but there is no training that can prepare someone for quad work.
You just have to man up, put on the big boy pants and have at it.
It's a right of passage.
It also helps to be either stupid or stubborn or both.
Quads are just painful.

Here's one restore I did.
http://audiokarma.org/forums/index.php?threads/marantz-4270-restore-grandpas-machine.786556/

 

[Jack Panjer]

Thanks for your reply, interesting looking at your pictures it is obviously very involved. I'll try some baby steps, it's very clean inside that's a positive. Still can't get over how heavy this thing is lol.

 

[omegaman1954]

You are right there! I have four and learn about the mental pain. I just rebuilt the 700 boards in one . I tested every part that went into it. put it all together and hit the switch, the relay clicked and after a few seconds those two gray resistors at the bottom began heating up and smoking. there are four of these resistors at the bottom .05ohms 3 watts and those two film capacitors that look like bumblebee where can i get those?

 

[blhagstrom]

We get parts from Mouser.com and Digikey.com