[User]

please picture on the tuner pcb

[IaninOz]

I have only just this Easter weekend dragged out my old PM451 (amp) and fixed a problem that forced me to pack it away for a few years. I didn't want to get rid of it as it is part of my Marantz collection.
The problem was the speaker protection delay relay wouldn't operate after the 4 seconds and connect the load. The cause was poor soldering on the PCB. After some really close looking one of the straps that 'jumped' printed circuit tracks was under tension and poor soldering over time allowed it to fracture (probably vibration). It took a lot to find the fault as occasionally it would work, usually when first powered up, then subsequently not - caused me to think the timing capacitor was the fault.
This is the second time I have found dodgy soldering on the board in the AMP, and my tuner (ST551) also exhibits a display drop out which could be removed with percussion (that's giving it a technical tap). This too was poor soldering resulting in dry joints.
My suggestion is check VERY carefully for dry joints. Even to the point of sweating them again.

[Guest]

I have the unit you're talking about, and your best bet will be to open it up, and check for any blown up or popped capacitors. Next, unscrew the fuse, and reseat it. Set the clock and move the slider on the bottom to off. And repaint the corney flames... its vintage not punk. what are you using to input the the reciever?

[fongs]

Hi,

The contact spray wouldn't work if yours is using digital volume control.

Could be due to bad volume control IC...? U wuld need the schema to locate this IC.

[Mozgus]

Sorry, that last post was by me.

[Guest]

Hey guys! I still havent gotten around to messing with it yet but I just realized something odd about the static which might be helpful in figuring out the exact part which is at fault! Hear me out.

Ok I have digital buttons for controlling volume. Now I was listening to the static at different volume levels. I noticed that at 0% volume, there is 0% static, however when I raise it, the static raises too.

Now here is the weird part. Once the volume reaches about 20%, the static goes completely mute! Now as I continue to raise the volume, the static raises again with it, and then at about 45% volume, the static dramatically drops down to a faint noise. I raise the volume/static more, and at 60% the static drops again. Then at 80% volume, the static goes COMPLETELY mute again like it did at 20%, and it remains gone for the rest of the volume scale.

So with this knowledge, what component do you guys think is at fault? This kind of reminds me of a gear system in a car or a bicycle and I was wondering if the volume in this thing operated in a similar way?

[fongs]

Both methods should work. I personally like to re-solder with new solder.

[Mozgus]

[fongs]

Good to know that... perhaps the set has dry joint in some components??

I'd re-solder the power amp section especially the power transistors. These generate lots of heat when in operation. The soldering joint maybe bad.

[Mozgus]