Marantz 2235B with high pitched noise ... - diyAudio
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Old 23rd October 2010, 06:48 PM   #1
tchiwam is offline tchiwam  Finland
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Join Date: Sep 2010
Location: Lapland, Finland
Default Marantz 2235B with high pitched noise ...

I have a strange one here ...

Found the schematics from this guy Home - IRebuildMarantz. Really nice reference but I don't agree on the list of capacitors to change ...

Anyway, I have now changed a lot of capacitors, all except the "tantal" looking ones. Readjusted the Biases to 0VDC, 35VDC rail from the PSU board and 8mVDC from the power amp. Then cleaned all the pots.

Here is the problem: High pitch noise on BOTH channels I'd say around 15 to 18kHz, really annoying.

It is there on all positions except when on Phono ! I can even run a line in in the Tape 1 Monitor and there is NO noise.

AM / FM / AUX / TAPE 2 IN all of them have the high pitch noise...

The noise was there before and after the recap.

I think I can rules out the Power amp board it has such a great sound on Phono + Tape 1 Monitor.

The tone board is probably ok too, as it is on use with the Phono switch with ou without the Tape 1 Mon.

I don't want to touch the AM and FM section...

I am now leaning on checking the phono board as if it is not used it might do something funny. But the power is permanent on that board as seen on the schematics. The outputs are disconnected... Unloaded lines make noise on the power line ?

I'll get my Osciloscope and try to get that one out. But if anyone is able to pin point me to the solution I'd be grateful.

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Old 23rd October 2010, 09:06 PM   #2
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Join Date: Mar 2010
You are on the right track. It definitely is a job for an oscilloscope. Identify the waveshape, probe around to find where its amplitude is greatest, look for a bad ground somewhere.
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Old 31st October 2010, 03:43 PM   #3
tchiwam is offline tchiwam  Finland
diyAudio Member
Join Date: Sep 2010
Location: Lapland, Finland
Default Got the devil !

One of the new cap on the phono amp missed a leg, and I also noticed a cold joint on the board. That is fixed too.

Now I have to say the AMP is running hot, I have adjusted the voltages, bias and all but no avail yet, still hot. I guess I need to change some semi conductor on the PSU like some other thread mentioned.

Sounds good and it can be really loud and clear.
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