Marantz PM7004 Right Speaker Outputs No Sound

[Shylok]

Hi, i picked up a 2nd hand Marantz PM7004 a few years ago on Ebay in nr mint condition. However im now finding that the right speaker outputs can intermittently cut out sound. I have plugged the right speaker in to the left output & the speaker works fine so i know the speaker itself is ok.

Any ideas what the problem is & how much in the UK would i expect a repair to cost? Ill need to find a reliable hifi technician in the Manchester area.

As a work around can i plug the the right speaker into the left biwire System B connectors on the amp because it seems to work?

 

[Kapkirk]

Have you tried both speakers in B? Could just be a bad connection on the speaker A/B switch or relay that controls it.
You could use both in the left A+B but you will only get mono output as they are both wired together internally, there is also the chance of overheating the output transistors on the left channel as the impedance will drop below 4 Ohms.

 

[Shylok]

Have you tried both speakers in B? Could just be a bad connection on the speaker A/B switch or relay that controls it.
You could use both in the left A+B but you will only get mono output as they are both wired together internally, there is also the chance of overheating the output transistors on the left channel as the impedance will drop below 4 Ohms.

Yes i tried plugging them into System B & the right speaker output still has no sound. Is this a known fault with Marantz amp?

BTW my speakers are Monitor Audio RX2 & the cables / banana plugs are connected to the LF & not HF terminals, which are linked by a metal plate. Im not sure what difference that makes.

 

[Kapkirk]

Not that I am aware. If it happens when the unit is cold but improves as it warms up it could be a speaker output relay. Another way to tell if that is the problem is to smack the amp quite hard on top and if the sound returns as you tap it then chances are it may well be bad relay contacts or even a dry solder joint.
Before you do that wiggle the input selector, volume and balance controls back and forth to see if it is one of the pots. Also does it happen on all inputs? it could be a bad RCA cable if you only use 1 input.
I have not repaired one of those Marantz amps so am not too familiar with them.
I am not from the manchester area so I can't recommend a place to send it for repair, perhaps someone else on here may know of a place local to you.

 

[Shylok]

I think i have found the culprit. When playing a cd the right speaker worked fine, but when i changed the input back to phono to which my technics turntable is plugged in there was no sound. So i unplugged the phono RCA connectors then plugged them back in & the speaker started working.

Does that mean the phono stage or connector on the amp is faulty or the RCA lead connectors from my turntable? I only have one turntable so have no option to swap it out to eliminate that possibility.

 

[Kapkirk]

Sounds like the phono lead then, from the turntable. Just replace them, or if they go directly into the turntable you have have to get someone who could re-wire it.

 

[Shylok]

How do you know its not the phono stage in the amp thats the issue?

Replacing the Technics RCA leads doesn't look to be too difficult with the use of a soldering iron checking YouTube videos. Some do a mod to get rid of the groundwire. Might be a good opportunity to upgrade them anyway. I've found these modded Van Damme cables Technics Van Damme RCA Upgrade

 

[Kapkirk]

How do you know its not the phono stage in the amp thats the issue?

Replacing the Technics RCA leads doesn't look to be too difficult with the use of a soldering iron checking YouTube videos. Some do a mod to get rid of the groundwire. Might be a good opportunity to upgrade them anyway. I've found these modded Van Damme cables Technics Van Damme RCA Upgrade

Yes of course it is possible that it may be the phono preamp but in my experience with the more budget Technics decks (the OP does mention the model) it's more likely to be a break in the lead near the phono plug end.
Although the Van Damme cable is a great upgrade for the upper tier Technics deck's the wires may be too big to fit in the clamp inside the turntable if it is one of the budget models. The job can be a little challenging to someone without soldering skills.