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Marantz 2230 - Balance and distortion issue

Chris __R

Chris __R

Well-Known Member
Hi all,

Getting around to clean up a 2230 I acquired a few months ago.
It's in generally great shape (cosmetically, anyway) but the right channel has static and distortion - and has less volume. When the balance is turned all the way to the left, there is still faint distorted sound from the right speaker when turned up. When the balance is turned all the way to the right, there is a constant hiss in the left.

I have used deoxit on all controls. On the balance and volume pots I've done it 3 times so far since I have read here that the balance pot utilizes grounding to ground out the other channel.
I have checked for loose wires.

My initial thought were that I should check/replace the output transistors - but the balance issue makes me think twice.

Does anyone have any thoughts - or run into this before?
Thanks!
Chris
 
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Pull the pre/main jumpers on the back and use a cable to run preamp out right into amp in left, and preamp out left into amp in right.

If the problem stays in the right channel, it’s the amp section, if it moves to the left it’s the preamp.

Rob
 
Man, I hate to encourage recaps but on the 2230 I've got some of the cap leads were near corroded off and many were shot in terms of value or leakage. Power amp was worse than low level so the above test is well worth doing.
 
Robisme said:
Pull the pre/main jumpers on the back and use a cable to run preamp out right into amp in left, and preamp out left into amp in right.

If the problem stays in the right channel, it’s the amp section, if it moves to the left it’s the preamp.

Rob
Click to expand...
Thanks Rob - So the problem definitely moves from left to right when switching the cables which indicates the preamp.
I'm guessing it's one or more transistors on what the SM calls the tone amplifier board perhaps....
Conceptually, how would an issue with the preamp cause the right and left channels to co-mingle at the speaker outputs?
 
Situation i had on my 2230 some years back was static in one channel. Testing as you did I confirmed it was in the preamp, eventually found a noisy transistor on that board. Replaced them all while there, did the trick. Good luck.
 
milanomike said:
Situation i had on my 2230 some years back was static in one channel. Testing as you did I confirmed it was in the preamp, eventually found a noisy transistor on that board. Replaced them all while there, did the trick. Good luck.
Click to expand...
Thanks - that's encouraging.
However, looking at the service manual downloaded from HFE, it appears there might be a page missing, specifically for the board I might need to work on. P400.
I'll have to test my bad eyes to see if I can actually read the existing transistors...
 
Well, I fixed this longer back than I thought, but here's my thread, hope this helps. I'm an engineer, but not a EE, but the guys here are great and have helped me numerous times over the years. Here is my thread on this one.

milanomike

Thread '2230 - P400 Board Mislabeled - Need Help?'

On my 2230, I believe a transistor has gone out creating ugly noise thru the left channel. This is on the P400 board. So, I've decided to replace all 8 transistors (and caps once I verify it works), but I am not savvy enough to sort thru and determine equivalent replacements. I've read tons of threads but have not clearly identified replacements. Do the transistors need to be matched for this board?

Finally, my board appears to be mislabeled, I have attached a photo of the board, hope it shows OK. There are 2 H402's shown (on left and right with left being top in the photo) by...
  • Like
 
milanomike said:
Well, I fixed this longer back than I thought, but here's my thread, hope this helps. I'm an engineer, but not a EE, but the guys here are great and have helped me numerous times over the years. Here is my thread on this one.

milanomike

Thread '2230 - P400 Board Mislabeled - Need Help?'

On my 2230, I believe a transistor has gone out creating ugly noise thru the left channel. This is on the P400 board. So, I've decided to replace all 8 transistors (and caps once I verify it works), but I am not savvy enough to sort thru and determine equivalent replacements. I've read tons of threads but have not clearly identified replacements. Do the transistors need to be matched for this board?

Finally, my board appears to be mislabeled, I have attached a photo of the board, hope it shows OK. There are 2 H402's shown (on left and right with left being top in the photo) by...
  • Like
Click to expand...
Thanks Mike! Great thread - seems like it will be super helpful.
 
So, since I had a bunch around I replaced all the transistors on P400 with KSA992s and KSC1845s and fired up with my DBT.
Looked good so I tried it out:

No change in symptoms except the hum from the speakers seems actually louder now. Also, touching the volume knob when no music playing does seem to cause a slight change in the background noise. Didn’t notice that before but perhaps not new. Does the humming seem ground related?

Going to check voltages next.

Any suggestions would be welcome.
Thanks!
 
Chris __R said:
Hi all,

Getting around to clean up a 2230 I acquired a few months ago.
It's in generally great shape (cosmetically, anyway) but the right channel has static and distortion - and has less volume. When the balance is turned all the way to the left, there is still faint distorted sound from the right speaker when turned up. When the balance is turned all the way to the right, there is a constant hiss in the left.

I have used deoxit on all controls. On the balance and volume pots I've done it 3 times so far since I have read here that the balance pot utilizes grounding to ground out the other channel.
I have checked for loose wires.

My initial thought were that I should check/replace the output transistors - but the balance issue makes me think twice.

Does anyone have any thoughts - or run into this before?
Thanks!
Chris
Click to expand...
Hello Chris,

Do you have a DBT at hand? Trouble seems to come from power supply, or amp capacitors. If one of your output transistor was bad you would get a dead short and the DBT would light brightly. All electrolytics caps have seen better years, i think todays cap have a shelf life of 3 years.
Take a look at the big capacitors, if they have something suspisious, buldgy on top, or bottom of the caps.
 
FRANKPIETTE said:
Hello Chris,

Do you have a DBT at hand? Trouble seems to come from power supply, or amp capacitors. If one of your output transistor was bad you would get a dead short and the DBT would light brightly. All electrolytics caps have seen better years, i think todays cap have a shelf life of 3 years.
Take a look at the big capacitors, if they have something suspisious, buldgy on top, or bottom of the caps.
Click to expand...
Hi Frank - yes, I have a DBT. I powered it up with that after swapping out transistors on the preamp board. None of the caps - big or otherwise - appear problematic, but tomorrow I will be taking a closer look and test.
I recently found a thread where a bad cap on the preamp board (C401) caused loud humming in both channels. I'll be checking that area out for sure as well as the power boards.
Thanks!
 
I've taken voltage measurements on P400. I have adjusted the bias (5mvDC) and power supply voltage (35.6vDC). Either there is a service manual error or something is screwing up the voltages by a factor of 10ish at H401 and H402.
Would love any comments.

P400.jpg
 
Great - thanks Rob. Guess they forgot the decimal point in the SM. So my voltages pretty much check out. If a cap were bad, wouldn’t it throw off the voltages?
 
Robisme said:
Tough call. Can you check the signal into P400 and out of it?

Rob
Click to expand...
Hi Rob - I don't have (or know how to use) an oscilloscope. Would using a multimeter to try and measure signal magnitude work? I haven't done this before, but have read about it a bit online. Just don't know if calculating the gain this way is what the signal test is looking for in this case.
 
If you could inject a tone, say 1KHz, you could check the AC voltage at certain points comparing channels.

If no signal generator, you could play a tone on your phone.

You won’t be able to detect distortion, but you will be able to compare voltages.

Rob
 
Robisme said:
If you could inject a tone, say 1KHz, you could check the AC voltage at certain points comparing channels.

If no signal generator, you could play a tone on your phone.

You won’t be able to detect distortion, but you will be able to compare voltages.

Rob
Click to expand...
I'll download a tone generator app.
By comparing AC voltages, would this give any clearer indication of bad components more so than comparing DC voltages?
Thanks,
Chris
 
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