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Marantz 3300 - Phono Stage - One channel not working

Hobie690

Hobie690

New Member
Hello,

The right channel of the phono stage on my Marantz 3300 is not working.

When I first was troubleshooting, I thought it was a turntable problem, but discovered that when swapping cables that the problem always stayed with the right channel of the 3300. The problem is on the right side regardless of whether I use Phono 1 or Phono 2.

I'm going to open it up and peek under the hood, but thought I'd post here to see if anyone could offer assistance.

Thanks!

Tim
 
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I'm not really familiar with the internals of the 3300, but with the 33 I had, the transistors plugged into sockets. Over the years there was some carbon, or corrosion build up on the legs. I pulled them, cleaned the legs of the transistors and the sockets. No more drop outs after that.
 
Hobie690 said:
Hello,

The right channel of the phono stage on my Marantz 3300 is not working.

When I first was troubleshooting, I thought it was a turntable problem, but discovered that when swapping cables that the problem always stayed with the right channel of the 3300. The problem is on the right side regardless of whether I use Phono 1 or Phono 2.

I'm going to open it up and peek under the hood, but thought I'd post here to see if anyone could offer assistance.

Thanks!

Tim
Click to expand...

Its been many many many moons since I popped the hood on a 3300. It could be something simple as a socket connection (as @Lavane noted) or could be a dirty pot, a number of issues for possible causes.

do you have access to a scope so you can trace the signal and see where it ends? or does not continue on?

the 3300 was a high feedback design. If you like marantz, the 33 was a better sounding unit.
 
Thanks for the responses! I've got a copy of the service manual and it lists a few resistors that could be open as well as some capacitors that could be open or shorted. I don't have access to a scope at the moment, but am hoping that perhaps shorts and opens can be diagnosed with a meter without removing them from the board. I also have the benefit that one channel is working so perhaps I can do some comparison metering.
 
mcgjohn said:
Its been many many many moons since I popped the hood on a 3300. It could be something simple as a socket connection (as @Lavane noted) or could be a dirty pot, a number of issues for possible causes.

do you have access to a scope so you can trace the signal and see where it ends? or does not continue on?

the 3300 was a high feedback design. If you like marantz, the 33 was a better sounding unit.
Click to expand...
From what I've read, and comments from a few people that had both, the 33 and 3300 are supposed to sound very similar. Honestly, I kind of wish I had bought the 3300 over the 33. The 33 with its dual channel boards, separate headphone amp and center channel board made it a bit of a pain to work on. It took a lot of dissassembly to restore.
 
Roger_88_K said:
Do you have a digital multimeter and something to provide a test tone with?
Click to expand...
I have a digital multimeter, but nothing to provide a test tone. I've just opened this up again to clean the contacts, and it occurred to me to wonder if a pin on the phono board has a problem?

I'm guessing that based on a lack of tools--unless I can borrow some from a friend--that I'm going to run out of trouble shooting options in a hurry!
 
Can someone please tell me how you remove the phono board if I want to try reseating it and checking components?
 
Replace the caps regardless and if the transistors are socketed then swap one for one cleaning before checking?
Diodes? Check on board for forward voltage. If good move on to the next.
A cheap Harbor Fright meter will do that.
Kind of a drive by post as I was wondering what’s going on here in the Marantz forum. I acquired a 4300 this week and it’s pretty cool. Needs some love but works.
A poor man’s signal tracer? I just posted in the Pioneer forum one I use.
 
This might help:
zebulon1 said:
You can use a meter set to ACmv and run some music through the aux input jacks. It’s a poor man’s signal tracer.
There are some pitfalls. One is the music you choose will end and you have to get use to seeing the meter responding to the input music.
You could play a 3Khz tone and use that but I find a piece with a jumping bass beat better using the meter.
Ground the black lead to chassis and the red to the back of the RCA jack connection that’s plugged into CD player set to play. Start there getting use to the meter jumping in the millivolts. You’ll get the hang of it. Start moving along the signal path hitting the channel input on the first board (Tone control?) continuing to the output pin of that board, seeing the signal jumping. Look at the good channel to compare and see what you should expect.
The volume can be turned up when looking past the volume control or it’s can be hard to see.
It takes a little practice but once you get the hang of it you’ll find it an easy quick way to look for a signal.
A scope is by far more readable and can give more info but not everyone has a scope.

Mark has another poor man’s tracer and it requires a small ceramic cap and an RCA patch cord. You essentially regurgitate the signal using the tape input with the monitor selected. The cap is to protect against any DC voltage. You would have to use the good channel for that procedure.
Click to expand...
 
@Hobie690 got a hold of me and he dropped off the 3300.

I confirmed the right channel is out on the phono section. Tuner and AUX are fine.

I popped the lid and noticed that someone has been in before me. The negative rail must have failed and someone replaced the pass transistor.

And the white lithium grease was used as contact cleaner on the phono-Aux selector switch.

Here is the phono from the 3300 service manual.
upload_2023-1-2_13-28-46.png

A quick scope check found the diff pair not passing signal and my transistor checker confirmed they were blown.
3300-q201.jpg
I subb'd in a pair of BC550c.

note no voltages are on the 3300 schematic but a quick scan of the 1200 (3300 pre + 250 power) listed expected voltages.

upload_2023-1-2_13-32-1.png

both use a +/- 13.5 Vcc ref.

Checking voltages the negative rail was running at -18.9v. The PS has the original 16v caps.

I checked the series pass transistor and found a SK3020. Goggle datasheet says this is an NPN instead of the PNP on the schematic.

upload_2023-1-2_13-37-48.png

I confirmed the tech installed a NPN with my transistor checker. Oops!

I put in a KSA1220 (overkill but I have one) and now V- is -15v. A bit closer to spec.

Replaced the 3 out of spec caps (10uF/100uF/220uF) on the phono board and the channel is working. Replaced the other 3 caps on the left channel.

Since everyone likes nudes, here are a few pics.

original PS board. you will see the past work of cutting the leads to the board and soldering them back together.

3300-ps-original.jpg


Original phono board
3300-phono-original.jpg


pic of the boards and updated PS. Astute users will notice the original 470/40 caps in the PS. Need to order them. And I removed the jumpers to the PS board.

3300.jpg

Once I get the 470/63v PS caps and check everything out, I'll let Hobie know

questions or comments are always welcome.
 
Last edited:
Rick!
Thank you so much for your detailed run through of the preamp for me. I'm grateful that this unit will be able to sing again soon!
 
Rick,
It popped into my head to wonder about those pots on the phono board. I moved on them when I was troubleshooting, so perhaps you could double check their values and operation once you do your final checks?
Thanks!
 
Hobie690 said:
Rick,
It popped into my head to wonder about those pots on the phono board. I moved on them when I was troubleshooting, so perhaps you could double check their values and operation once you do your final checks?
Click to expand...

OK. I'll see what it takes to reset those pots.
 
Wow. When I was troubleshooting prior to bringing it your way, I moved those pots up and down while trying to make sure they found their way back to the same location. When I turned it down on the left channel -- the working channel -- I could make the audio go away. Of course that had no impact on the right side because of the other problems you've already corrected. I do recall reading about that adjustment in the manual that you've posted.
 
That transistor must have been fried good. Usually bad transistors test as a diode in a similar tester I use.
 
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