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Marantz 2235B has no sound

S

sound man

Member
I just picked up a 2235B which "worked the last time it was used" about five years ago. It was stored in a plastic bag in a garage and was pretty dirty inside. I cleaned all the switches so that they seem to work, but the relay doesn't click. It powers up, the lights come on, but no click and no sound. I don't see any obvious signs of shorting anywhere. I did note that the pre out terminals seemed a little darker than the main in terminals inside the case. Didn't really look burned, just less shiny. The jumpers were missing so I used two patch cords. Is there anything that a novice can check with a dmm before I take it to someone for repair?
 
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Here is the service manual.

http://akdatabase.com/AKview/displayimage.php?album=1&pos=52

IF you doubt your ability...DO NOT TRY THIS AT HOME.

You could check the power supply voltage level.
Then check the amp adjustments.

Remove any fuses, one at a time and check them with the ohm setting on the meter. You want to see 0 ohm or a very little number. Put each fuse back before taking any more out.
 
check your tape monitor switches. I bet they are dirty. push them in and out a bunch of times..... I have had 2 Marantz receivers that seemed completely dead until I cleaned (de-oxed) all the pots and switches. if you have headphones, use those and play with the switches and listen for the channels to kick in. If it truly worked before being stored away, I have to believe that dirty switches are your problem.... good luck !!! Dan :music:
 
You don't need the pre-amp jumpers on this model. I would check the output transistors first.
 
Thank you for the guidance and the link to the manual. I checked the offset. My meter doesn't have a 1 volt setting. I used 200m setting and got readings that bounced between 00.1 and 00.2 on the speaker terminals, left and right, and the same on speaker b terminals. Should I adjust the trimmer to bring that down to zero? How do I check the output transistors?
 
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No relay click, no dc offset- the relay is the link between your speaker terminals and your amplifier board.

Measure L701 and L702 on the amplifier board, they look like a copper coil- this is the test point before the relay.
 
I measured both L701 and L702, coil to ground on the chassis. Both read zero. I want to give repairing this a try. Where do I go from here?
 
Unless I'm missing something, I only see one fuse, the one on the back of the receiver. It tests good, although the metal ends are not tight to the glass barrel. I checked the coils again, and I don't get a reading. I tried touching both ends of the coil to measure resistance and got open, so I don't think I made good contact. I'm holding the probe against the coil. I can't reach the back of the board with it attached to the heatsink. Should I loosen it and tilt the board away from the heatsink and touch the solder pad?
 
look next to the coils and there will be resistors r764 r765 .take reading from there ..
or from j715 j716 .
odd numbers are left amp . even numbers are right amp .
 
Okay, With the red red probe on J15 and black on ground I get -25.6 and on j16 I get 0. What does that tell us? I'm a bit of a noob, but I'll go until i don't feel like I can handle the job. I'll probably have to ask for clarification at times. Thanks for the help.
 
Hi BK, what do I do now then? If it makes any difference, all four transistors on the heat sink get hot. When I took the reading I measured and re-measured to be sure that I got it right.
 
That's a good clue! I suggest reading the thread on transistor testing. You'll need a meter with the diode check function. I agree with BK that one or more output transistors is likely bad.
 
Pull the pair that are causing trouble and test them. Once you have verified the pair that are bad you should be able to safely turn it on and hear sound out of the good channel. Make sure the idle current on the good channel is within spec.
 
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I had a chance to look at the outputs and have a few questions. How do I diconnect the wires? I'm sure that I don't cut them. Do I unsolder the pins at the board and leave the wires attached? I read a thread on testing diodes and transistors a while ago and meant to bookmark it but forgot to bookmark. Someone in the thread mentioned that it should become a sticky. Does anyone have a link to it?
Thanks.
 
I pulled and tested the transistors. It looks like the lower A757 transistor is bad. It gave me these readings:

red to base black to emitter 071
red to base black to collector 094

black to base red to emitter 072
black to base red to collector 093

black to emitter red to collector 022 plus sound
red to emitteer black to collector 023 plus sound

Can I get away with replacing just this one transistor, or should I replace all four to keep things even? As you can tell I never had electronics class, but I'm trying to learn. Thank you gentlemen for your assistance. When I pulled the two lower transistors, the relay clicked. Now, can anyone recommend a part number and supplier to order from?

Thank you, again.
 
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