hifi engine

Marantz 1550 Receiver One Speaker Has No Output in Stereo Mode

hobbylots's picture

I just purchased a Marantz 1550 receiver at a flea market and I'm only getting sound from one speaker in stereo mode. I've replaced wires, speakers and cleaned it with Deoxit. In mono, both speakers output sound. Also letting it run for a while, the sound will drop down considerably. I'm wondering if anyone knows what might be the problem and if it would be worth trying to fix. It is a beautiful looking receiver and if I could bring it back to life at a reasonable cost, I would love to hear it play in its full capacity. Any input is appreciated! Mike



karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

You try it only on radio, or connecting an external source?

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Yes. It has the same results regardless of the selection. Radio, phono, auxilary all result in one speaker coming out when in stereo mode. Both speakers work in mono. Thanks for the post.

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Examined the scheme. To avoid long search for switches and sockets, I have an idea. Open the unit, volume-minimum- balance in the middle- turn on the receiver and with something metallic in hand give hum on both ends of the balance potentiometer. . Switch is set to "stereo". If you hear hum from both speakers - the problem is in some switch or socket. If you hear again one speaker-the problem is in tone amp. or in filter amp.Similarly, you can track both channels and further the scheme.But watch out for the speakers!!!
P.S. Stereo-mono switch can be a problem.If it should bypass to stereo-to check

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

HI Karodimitrov! I greatly appreciate your time and suggestion. I'm a beginner electronics guy so I'm not following your suggestion completely. I get the part with setting the volume, balance and switch to stereo. I'm not following your suggestion "with something metallic in hand give hum on both ends of the balance potentiometer." Are you suggesting trying to short across the potentiometer? I think the stereo/mono switch might be bad but it isn't a potentiometer...I don't think. Can you clarify your post. Again, I appreciate your time and interest! Have a great day!

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

When you touch with hand both ends of the balance potentiometer - one type you are apply signal on both channels, and when they are on Stereo mode-you must hear hum(BRRRRRRRRRRR) from both speakers.If it's OK-reason to lose one channel is before this point.If the problem still exists - the reason is after this point.After this point are Tone amp and Filter amp.Thus determine where exactly is the problem (in which part of the amplifier).
Looking scheme there is no way the reason is the MODE switch .In mono position it connects the two channels together and in stereo just not connected them nowhere.Now do what I described you to fix where is the problem.
To be continued...:)))

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

P.S.At the scheme switch is set to stereo mode.(SS01-4 MODE).Look the two channels-L and R.- not connected nowhere(left side of the switch).For that the reason can't be in the switch-(his left side commutates channels,right side commutates the LED).Gain must be less to protect the speakers from too loud BRRRRR.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

So I tried what you suggested. Not sure what caused the change but now, I get sporadic volume in the left speaker when in stereo mode. At one point it began playing normally in both channels but did not last but a few minutes. The left channel sound can be barely heard when balance is turned completely all the way to the left and switched to stereo mode. It's almost too low to hear but it is getting some sound. If I move the balance and tone knobs around it sometimes will jump in volume on the left channel but is inconsistent and quickly jumps down to the low volume. I removed the potentiometer knobs and sprayed them really well front and back with dexoit. Same results after the good cleaning. It seems to get less responsive the longer it is on. Does this sound like a bad or faulty capacitor?

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

I understand the problem is the tone control. May be a capacitor, but I think you should first check potentiometers tone control. They are cleaned, but some may be interrupted

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

You said that you cleaned potentiometers with DEOXID, but you have to lubricate them with some kind of lubricant. I use liquid grease in spray.You can use some kind of thick oil applied with a syringe.All potentiometers and switches.May be this is the problem.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Hi Karodimitro! Thank you for continuing to help me with this issue. It is very nice of you to do so. I applied silicon spray to lubricate the potentiometers. Unfortunately, I still have the problem with the volume. Not sure what to do at this point. I ordered replacement electrolytic capacitors to recap the receiver. Maybe one is causing the problem? I'm thinking it is a good idea anyway since the capacitors are original and nearly 40 years old. This will be a weekend project to get them replaced. Let me know your thoughts for any other ideas and again, thank you for your help!

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Is a good idea is to replace electrolytic capacitors.It would be better to measure potentiometers and switches - if no interruptions or poor contact. But - this is for the weekend.:))
There is no way not to handle it.
Regards and luck!

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

P.S.
Look the Johnysan's post below.Clean and lubricate all.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Did you clean the tape monitor switches? Most of those pushbutton switches had holes on the top; you can get Deoxit in the hole (use sparingly).

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

I have cleaned these as well. One other thing going on with the unit is the meters have both stopped working. I'm not sure if this issue could have anything to do with the speaker not working or sporadically working in stereo mode. Thanks for your post!

karodimitrov's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Check and clean carefully selector switch.Both metters take а signal from the tuner(signal streight meter and tuning meter) passes through selector switch.They are before main amp. and do not work when is phono,tape or aux.Check carefully selector swirch and tape monitor switches.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Well things have gone from bad to worse. I started changing caps today starting with the 10000uf 50v caps. After putting the new caps in, the receiver is blowing the main 5amp fuse. I've verified that the caps are wired correctly with negative going to the negative bar and the resistors wired in between pos/neg terminals. I took photos prior to making the change and I cannot see any wiring issues that would be causing the problem. One of the caps has a charge on it after the fuse blows and I'm able to short across the terminals to discharge it. the other cap does not have a charge on it or a least does not ark when putting a screwdriver across the terminals. Not sure what I have done to cause the fuses to blow but obviously something in the change has caused the current problem. After cleaning the selector switch prior, it still had the problem with the volume in the speaker.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Okay, I had polarity reversed on one of the two capacitors. My brother-in-law looked at the pics I had taken and caught this goof up. I've reversed polarity and all is working in both speakers now at the correct volume. Now, I was able to get the issue back by pushing the "tape 2" monitor button. As soon as I did that, the problem came back with little to no volume in one speaker. A few pushes cleared up the issue. I'm going to clean that switch more thoroughly. It has been playing without issue for nearly an hour, both radio and CD through the auxilary input. Sounds fantastic!!! I'm currently running it with a pair of Bose 501 speakers I had to re-foam on of the woofers. Thanks Karadimitrov and Andrew for helping get this unit working! I think it is close to fixed. I still plan to replace the other caps at some point. Mike

hobbylots's picture

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

I will try that and let you know if that fixes it! I may not have cleaned it well enough the first time around. Thanks for the suggestion.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Still having the issue after cleaning it. A friend suggested the Stereo/Mono switch could be bad. Not sure where to find one.

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

One way to clean switch I use, is ``Brake cleaner``, this clean for sure. Then as soon I use it,2to3seconds, I spray lot of ``Contact cleaner`` to dilute the ``Breake cleaner`` because it is strong cleaner and everything work good after this .Be careful, because Breake cleaner is hard on plastic.Good luck...

Re: Marantz 1550 Receiver One Speaker Has No Output in ...

Since using the deoxit and silicon spray on the switch, it has been working fine. So, as it stands now, all is good. Thanks for your suggestion. I would not have thought of brake cleaner but good to know for future use!