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Jumped in BIG....found a Marantz 2500.

This reminds me eerily of a similar problem I had with an HK Citation amp a few years ago - turned out to be dead filter caps:

http://www.audiokarma.org/forums/showthread.php?t=79114

Before you pull the amp tunnel (again), check for AC voltage across both sections of the right channel filter. You shouldn't have any. More than a few volts means trouble. Compare with left channel cap for reference.
 
anderslober said:
Hey Forum'ers.......a wee spot of GOOD news!!!!!!!! Before taking the 'pig' out once again, I wiggled all the connectors to the amps..........LOW and FRIGGIN behold....R channel J701 connector was loose!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! The BUZZ is gone!

There is still a very low hum.......which you only can hear if you are standing less than 1m away from the speakers........I will put his down to the main caps rippling.
Click to expand...

No more "flapping"/bottoming out on the right channel?
 
EW...skibjr......yes, I do have another volume control, so I can test the amps. I will try it.
Regarding the flapping/bottoming out........It seems to have become much better. There is still a bit of 'flap'.....but only when 'loudness' is ON, and the volume is pretty high. Without the loudness engaged..all is normal.....the unit has been playing for a few hours this morning...................

IF I decide to do the main caps...the originals are 7200uf/100v(dual caps)...what would be a good choice?.....8200uf/100v....10000uf/100v............

I would like Nichicon's..........but any good cap will be considered.

I will do the same as matthewk in his 'scary....repair'- thread. .................

Thanks.........
 
Well how about that? I checked in today for the first time in a few months, saw an interesting 2500 thread and then I got a mention at the end!
The skills on this restoration are well beyond my skills, so you are very unlikely to have a problem doing the dual-section cap rebuild. Nice work on the 2500, what a beast it must be when you crank it up.
My 2285B is still functioning perfectly with the rebuilt caps.
 
Not to start up the thread again......just finishing touches........the 2500 has been running great. Buzz was easily fixed(Luckily!).

I have been playing the 2500 through my L50's and 901's.....It sounds awesome!

The L50's , I must say, sound the best..........

Check the photos..........disregard the 'stacking'.......just for testing and show:banana:
 
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EW...the buzz was just a loose connector to the right channel...........I just re-inserted the connector, and the buzz disappeared. The very slight hum has also gone......I think it may have had something to do with un-dried deoxit still in the unit............

The unit has been playing for a few days now.........it plays quite well. Also, I have not been able to get the fan into high-gear yet....even though I have played it quite loudly for extended periods(+1.5hours).....it runs pretty cool.

The 'under-face/chassis' looks worse in the photos than it actually is. The faceplate and knobs go on today........I will post a couple of pictures.

I can't yet figure out what I like best....jbl L50 sound or Bose 901 sound......very different sound setups, but both sound great................
 
That looks so nice! I'm happy that your hard work paid off. The Marantz 2500 is the mother load of all Marantz receivers!
 
Well......it seems that I am not fully out of the woods yet.....the tuner has started drifting a bit............it will tune stations and hold them(stereo light ON), but then start drifting in and out...........

Would it be enough to clean the tuning gang fins and the shaft? I did spray the fins with an air-duster......I did not clean the shaft though...............

Please indicate if it could be something else........thanks.

The tuner board has been fully re-capped and was working fine during my initial tests.
 
Hello forum........I am back with the 2500.....still a couple of sniggles. I have a problem with the right channel still.........when I turn up the volume there is slight crackling/distortion in the channel.......I used an sx1250 as a pre-amp to confirm that it was in the Marantz 2500 right amp section. Using the 2500 as a pre-amp (sx1250 amps) caused no crackling/distortion.

So I still have a bit of trouble-shooting to do on the right Marantz channel. Any suggestions would be great..............this was the channel that had 2 un-original output tr's.......so maybe when the originals blew, they took out something else on the board. Cant wait to take 'the pig' out again......;-)))

When I have the unit on the bench, I will also clean the tuner.....hopefully this will cure my slight drifting problem.

If anyone has had a slight crackling/distortion increase with increasing volume....please chime in. At low volume all is ok.
 
Could be any number of things. Since you mentioned the low volume hum in the right channel, your right side dual filter cap may be on it's way out. Try jumpering in some known good subs and see if your peaks clean up. The reason I'd try this first is that you can do it with out having to pull that $&@#$!! amp tunnel.

If no luck subbing out your filters, double check all of your amp boards' solder connections - especially those in the later amp stages, near your outputs - the areas of high current flow.

If all else fails, you may need to pull out your scope and start looking at waveforms along the signal line to see where you're losing symmetry. Fortunately, you have your left channel as a reference, so you should be able to isolate anomalies without too much trouble.

You have my well-wishes...and my sympathy. Good luck! :thmbsp:
 
skibjr....yes, I am suspicious of the right main (dual) capacitor..........I will do some measuring and and see what pans out. I think I may as well do Matthewk's procedure.....also for longevity.

The hum that was there, has decreased to almost nothing............

I will pull 'the pig' anyway and double-check everything...............
 
I have been measuring a lot of voltages...comparing the left channel to the right channel.........I think I may have found a problem.......the amp boards are each held in place with 6 screws.........on the left channel all 6 screws measure 88.9v......on the right channel, the 3 top screws measure 60.8v and the 3 bottom screws measure 88.9v.
So, definitely a problem on the right side..............can anyone help in this respect?
Bad resistor.......bad zener........????? OR could this be THE big cap problem??
I have staired my self blind on the schematic.........thanks.....

EDIT: measured some more voltages...........j707(right amp board) connects directly to the '-' terminal of the right dual cap....it measures 60.8v. The other terminal 'A' measures 88.9v. On the left dual cap both terminals (-, A) measure 88.9v..........so, I am guessing the right dual cap is leaky........can a tech confirm this........thanks.......

Gettin' close........
 
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