My 4300 Just dropped the left rear channel...

Ed White

The Nightfly
My Marantz 4300 just lost it's left rear channel. After researching my receiver in this section, I read how the unit in the stereo mode was actually the four channels combined into two...via the switch on the back.

I noticed it recently when the left channel sounded quieter than the right, and wouldn't balance as normal. Hmmmmm...it seems it was running on half the power!

I took this newfound info, and tested it by switching to four channel mode, and hooking the speakers up as rear speakers. Sure enough. right is well...right on. Left...you can barely hear. Aye carumba. My baby is gonna need an overhaul, it seems. I've had it for years, and it worked fine. Oh well. It's really clean, with the wood case. Rummage sale find...20 bucks....five years ago. It's been great, but it needs help.
 
Sounds like an output transistor, you might want to check those. If you can't, i'd suggest taking ti to a technician, a wonderful unit that deserves some TLC.
 
The first thing to do is to isolate the problem to either the preamp or the power amp by removing the jumpers in the rear and subbing another amp/preamp. Based upon my experience, you'll probably discover that the problem is in the preamp.

If so, check CE07 (22uf @ 25v) on your PE01 preamp board. Betcha it's open. As a matter of fact, it wouldn't be a bad idea to replace CE05, 06, and 08 while you're at it. Any one of these 'lytics fails open and it'll kill a channel.

If the problem is in the main amp, let us know and we'll go from there...
 
Well thanks....I''ll probably take it to somebody....I imagine it has other issues after all this time....if it was some podunk unit, I might give it a shot, but this probably deserves a little more care...thanks! Good information!
 
Good conclusion Ed, finding another 4300 is hard, and it would cost more than to have one brought back to snuff.
However, i'd recommend finding a tech that likes vintage gear, a lot of new techs just mess them up and tell you "they cannot find parts" so ask them if they know what they are doing with old gear, if so, then it should be a-ok.
I lost a beloved Pioneer SX-950 to a tech who didn't like vintage gear, he was a jerk to.
It went it with a bad channel, and came out with the output boards ruined.
Since then I learned how to do the repairs and adjustments myself, but you have to be careful.

I wonder if you could send it to echowars. You might want to PM him.
 
I know what you're saying....

I agree ....there are people who just don't get it. These are very fixable. One thing I didn't mention, is the channel is not "dead" it plays well for about three seconds, then fades to a very quiet, faint whisper. What that is a clue of, I don'y know. I think I'll check with echo to see if there's any openings in a few months. I'm getting my Fisher 400 done here in Michigan...by NOSVALVES...but the guy does principally tube gear. I'll ask him for a tip on somebody good in my area.

Thanks!
 
Awesome news.

Channel fading off, that might be a capacitor, because a bad output transistor would just be blowing fuses.

Good luck with it!
 
As mentioned before by skibjr, you need to isolate the problem before you start to play the guessing game. You can dump lots of money trying everything before you get to the simplest of resolutions --like a fuse or dirty switch.

Check fuses first, make sure you are getting proper voltages. If no fuses are open, I highly doubt that output transistors are at fault. The only failures in outputs I've seen are usually C-E shorts, which effectively blows the fuse in a rapid fashion

Also make sure that the mode selector is not dirty. If this has the power mode selector switch on the rear, clean that as well. I had a 4230 quad with intermittent left front channel that was remedied by cleaning this switch.

If you do not have a spare amp or preamp, you can test the power amp with the use of a portable device like a cdp or ipod. Just use a 1/8" stereo jack to RCAs. connect your device to the amp-in jacks, turn it on, set the volume to minimum, then power on the 4300. Reverse to shut it off. This way you can test the front and rear left and right channels.

Best of luck to you. Let us know what you find.
 
Thanks! these are good tips...I'm out of town until after the new year...I'm itching to get home and check this stuff out. Don't tell my wife....we're visiting HER family, and I have to look enthused!

Thanks for the tips!

Ed White
 
skibjr said:
The first thing to do is to isolate the problem to either the preamp or the power amp by removing the jumpers in the rear and subbing another amp/preamp. Based upon my experience, you'll probably discover that the problem is in the preamp.

If so, check CE07 (22uf @ 25v) on your PE01 preamp board. Betcha it's open. As a matter of fact, it wouldn't be a bad idea to replace CE05, 06, and 08 while you're at it. Any one of these 'lytics fails open and it'll kill a channel.

If the problem is in the main amp, let us know and we'll go from there...
Good tips skibjr. I'm repairing a fellow AK members 2325 with the same problem in the left channel. The first thing I did was to connect a CDP to Main In to determine if it's the pre or power amp. The amp section played fine.
This morning I turned the receiver on and the left channel was weak. The output increased with the volume control, so that rules out the Tone Amp, Volume, etc.
Look in the Buffer Amp since that's the first stage after the Selector switch. Electrolytic caps are the main suspect.
 
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