Discussion in 'Marantz Audio' started by Moby Dick, Feb 18, 2017.
Headphones are after power amp, same as speakers
What level is the pre out?
Can it be ran into tape or phono?
I didn't have another amp which has a power amp in connection so I plugged a Logitech Bluetooth receiver in the power amp in of the marantz using the rca cables which came with the Logitech adapter.
Then I connected my iPhone via Bluetooth to the Logitech Bluetooth receiver and played music from my iPhone.
This bypasses the preamp and all of its functions in the marantz.
There was distortion coming from the LH side which eliminates the preamp section of the marantz from being the source of the distortion.
As I mentioned earlier,
I will bias and check D.C. Offset next as well as do the deoxit cleaning.
Does the headphone jack come after the speaker relay?
I am asking because I am thinking of cleaning the speaker relay but it is difficult if not impossible to open without breaking something.
Both headphones and speakers come after the protection relay.
Your problem is in the power amp so only need to clean speaker selector switch..
Yes, the relay could be the cause but low probability. Also could be failing
transistor in LH power amp
I opened up the top and bottom casing and faceplate. I sprayed the pots and switches with crc contact cleaner. I wasn't able to get ahold of the caig stuff in time.
All the switches and pots were sprayed multiple times including rca jacks and speaker terminals.
Still had distortion in the LH channel.
I turned my attention to the speaker relay and had a very difficult time taking the cover off the relay.
Eventually brute force and persistence won the day and I got the cover off.
I took 1000 grit wet/dry sand paper and slid it between the contacts flipping the paper to get both sides.
Here is where it all went down-hill;
As I was poking around the relay assembly making sure everything works as it should, I accidentally broke-off the tinsy-tiny wire from the coil that energizes the magnet in the relay and now need a replacement relay.
So, being a graduate student of the school of hard knocks I Am undeterred and have a new relay on its way from mouser.
Once I replace the relay, if the distortion is not resolved, I will send it to a professional.
I really want to get this beauty ito my system.
Thanks for the help so far.
I've never been a fan of cleaning the relays. If it is an older, hard to get relay, I get it. But for those cheap and easy to get Omron relays, it just makes sense to replace what, in some respects, is at the heart of the audio path.
Although I have nothing to add as I am a newbie to this hobby , I will follow along and try to learn.
One step closer to a solution.
Half-way through de-soldering the broken relay switch, I decided I had dug this hole deep enough and called in the expert.
A friend of mine at work is an electronics engineer and has already done fantastic work on one of my guitar tube amps.
What he found once he finished replacing the relay was this:
I wonder if the blown output transistor was the cause of this or vice-versa?
Most probable fault scenario is people fiddling with speaker wires when the unit is powered up.
The wires touch, the amp sees a zero ohm load and tries to deliver putting huge strains/demands
on the internals to deliver the wanted current. Components overheat, finally the transistors blow
or resistors fail open circuit/flame.
If not done already, check other transistors starting with Q717 and 718 then Q709, 710. The outputs
are very robust, likely other TR's damaged along the way.
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