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New member with a Marrantz 2250b

T

Thrash50

New Member
Hi Audio Karma members,
Thrash 50 here. I'm a new member, and this is my first post. I have Marrantz 2250b stereo receiver. I picked the unit up at a garage sale about 10 years ago for a great price, with quite a bit of other gear. This is the same model I treated myself to, as a high school graduation present many, many years ago. I'll post pictures later.
The balance control quit working when stereo is selected, balance works fine in Mono. I need to find a repair shop, or repairman on the California Central Coast, any suggestions would be appreciated.
Also any member who has worked on, or can give me advice on troubleshooting the problem would be appreciated.
Thanks,
Thrash 50
 
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I also picked up a 2250B from my father-in-law and have been troubleshooting it using the posts on this forum. My left speaker wasn't working using FM radio but the right one was. Also in MONO mode both speakers were working. Today I discovered a problem in the preamp thanks to the posts and guidance from users in this website forum. The key test is to put an ipod or iphone signal into MAIN IN and see if both speakers play in stereo. Be careful to keep the volume low on the ipod or iphone since the volume knob is now not useful and is driven by the iphone. If both speakers play in stereo then you can rule out a problem with the P700 Main Amplifier boards (the ones with the heat sinks on each side). One board drives the right speaker and one drives the left. These are difficult to get out of the unit so keep your fingers crossed. In my case both speakers played fine with this test so this pointed to the Pre-Tone Amp board (PE01) as possibly the problem. This PCB is in the middle front and is long and skinny and has some of the dial knobs connected to it. First, I pulled firmly on all the knobs on the front panel and gently used a screw driver to pry the knobs off, unscrewed the 4 metal front nuts and with two screwdrivers and taped protection on the front plate around the center knob so I didn't scratch the front panel around this center knob. There is a brass colored screw now holding the front panel to the chassis. You need to use two screwdrivers to slowly and carefully turn this screw/cylinder. You'll slip a few times so don't forget to put tape around where you are working to protect it from scratches. Next I had to remove the nuts and washers around the knobs with a 7/16" wrench. Next I removed the connector to the board. There are two black plastic tabs that you have to push out to release the connector. Now the PE01 PCB should be free but there is one standoff on another board that will block you from removing the PCB. Remove it with a wrench. When I had the PCB finally out, I saw that the 220uF, 35V capacitor had blown brown snot out the side of it and it went across the board. I removed the 220uF cap (CE39) and tried to clean up the goop but it was really rubbery and I couldn't get it all off. I measured the resistance across RE13 and RE14 since RE14 was covered in goop and RE13 was not and got the same value of 380kOhms (increases slowly to 400k probably because of cap charging). Since the resistances seemed the same I think that was the only problem. While I was in there I replaced the 10uF and 100uF capacitors with new ones. Unfortunately, after replacing the 220uF cap with a new one the problem remains. I verified that both the FM and PHONO modes have the left speaker quiet so I think it's the preamp board.
 
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rBuckner said:
Did you clean the switches yet with DeOxit?
Click to expand...
No I didn't try cleaning the switches yet. I will try this. Thanks. However, since the same L speaker is out with the MAIN and REMOTE speaker switch I am thinking that the switches are not the problem. I think it's unlikely that both switches would go bad on the same speaker.

My next attempt will be to replace HE01/HE02 with the Sparkos BA312-M boards. Seems like the right thing to do even if these parts haven't failed yet. If that doesn't do it then I'll replace the HE03/4/5/6 parts. Need to find their equivalent parts with a forum search.

I'm impressed by all the labor involved in building these receivers. Can see why they cost $550 back in 1976.
 
Any of the other switches can cause your issue. As you had sound on both speakers when driving the amps directly the speaker switches, which come after the amps, were not in doubt. Your main suspect is the tape monitor switch.
 
rBuckner said:
Any of the other switches can cause your issue. As you had sound on both speakers when driving the amps directly the speaker switches, which come after the amps, were not in doubt. Your main suspect is the tape monitor switch.
Click to expand...
Ok. Thanks! I will try that. Following the switch schematics is pretty confusing. I just got my Deoxit in a few days ago so I'm going to spray away in there and let it dry out.
 
ShortBaldGuy said:
Ok. Thanks! I will try that. Following the switch schematics is pretty confusing. I just got my Deoxit in a few days ago so I'm going to spray away in there and let it dry out.
Click to expand...
Hey, I've been in the electronics industry since 1979 and I can't follow them very well either! Not to mention all Marantz technical docs are error filled. Just don't "hose" everything down. I've seen it and it's ugly!!
 
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