2285 (non B) - Right Channel Rumble

[k03a05]

Hi,

New to the forum... I have a Marantz 2285 (non B) that was stored for more years than I would care to admit to. I recently put it back into use, and have DeoxIT'd all the push buttons and controls, which has eliminated all issues but one.

While playing music or simply on with no source input, you can watch the speaker cones on the right channel move in and out randomly. With no input, you can hear a low rumble, and if you turn the bass pot there is an "clunk" sound from the speaker. This does not occur in the left channel, and goes way when the speakers are turned off. Same occurs with different speakers, so the unit is at issue.

Ideas?

Can anyone point me in the direction of a someone who would have a new bass pot, P/N RD02040010 / M200KΩBX2?

Thanks in advance,

George

 

[sanjib]

Check the DC voltage at the speaker terminal of the bad channel.

 

[AE Bob]

If the woofer "pumps" in and out when you turn the bass potentiometer, you likely have a leaky capacitor in the tone circuit. Another common source of noise is the differential amplifier pair at the input of the driver board. You should try separating the preamp and main amp at the jacks on the back, and using a dual patch cord to reverse the left and right, to help locate the noise to the preamp / tone circuit or power amp section.

 

[sanjib]

Connect your iPhone directly to main in with RCA cable, before switching on the receiver, reduce the volume of your phone to minimum. Switch on the receiver and check whether you are having the rumble or not. If there is no rumble it can be from preamp board as Bob suggested and if you see the same rumble then it is from the main amp board.

 

[k03a05]

Sorry for my delay in getting back with a response - damn job...

While the right channel was rumbling, I measured a fluctuating value that ranged from 0 to 50mv. Bob's description above is what I am seeing/hearing - the cone moves in/out between detents.

I also spoke to a friend that builds tube guitar amplifiers, and when I described the issue, his answer was "leaky cap". So on that and the above, I have ordered a re-cap kit for the tone board. If it goes well, will let you know, lol

Thanks for replies, very much appreciated.

 

[rBuckner]

Most of the time when I see this it's a transistor. Sure hope it's a cap though!

 

[k03a05]

An update for all who took the time to answer and help me out…

The re-cap kit for board PE01 took a few weeks to get here, a border and customs take time, but given recent events I have not a single thing to complain about.

While I waited for the tone board re-cap kit, for “practice” I re-capped power supply board P800 using Nichicon PW caps. One original cap was deformed and another - C808 - had clearly been quite warm at some point...

Also, I had sorted out that the rumble in question was likely from the pre-amp section, as I could hear it in a powered sub connected to “Pre-Out”.

The PE01 re-cap kit arrived with Nichicon replacements for electrolytic caps, Panasonic replacements for CE05 and CE06, WIMA film replacements for the tantalums and four transistors.

I slowly replaced all of the electrolytic caps and re-installed the board. The rumble was still there, sigh. As I was a bit intimidated by the close proximity of the tantalums at CE33/34/35/36, I next replaced the four transistors and the tantalums at CE13/14. Still at rumble, damn. The next evening, a bit more determined, I replaced the four remaining tantalums. While the tools were out, I replaced all the fuse-type and bi-pin bulbs with cool white LEDs (vellum is next).

I re-installed the board, and success, no rumble! The receiver has had steady use for the last two days, and aside from music, the right channel has been silent.

Am so pleased, the receiver sounds as good as or better than it did when I bought it in 1987 when I was 15. Amusingly, at that time I was annoyed that it was all I could afford at $125…

It sounds fantastic, a sincere thanks to all!

So, with P800 and PE01 successfully re-capped, is there any reason to consider recapping PH01..?

Thanks again,

George

 

[sanjib]

I think if you have components and feel confident recap the power amp boards and other boards.

 

[Fairlane]

Do the amp boards too especially since they come right out.

The 2285 is a dream to work on.

 

[k03a05]

My intention is to definitely re-cap the amps boards as a minimum and as time permits. Am only reluctant to do so as the receiver sounds great as it is.

To close the loop a bit, here are a few pics of of what has been completed to date...


P800 Board (before/after):



PE01 Board (before/after):



New Meter Vellums (green becomes blue)



And All Put Together...

 

[rBuckner]

The series with the looks I like the very best in Marantz receivers. So glad you got the gremlin out.

If you wanted to do anything more I'd suggest the speaker relay and the D33x transistors on the power supply board.