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Marantz 2500 repair help

C
dankik said:
I went thru the schematic, PCB layout, and PL. The only thing that was strange was that the schematic only shows a C812 (10uF) but the board layout and your photo show C811 & C812, but if you look at the PCB, the C812 (-) ONLY connects to C811 (+) which then connects to Q807. What doesn't make sense is when you put two capacitors in series the capacitance value is one-half. So, 10uF x 2 = 5uF??? Is there a jumper wire on the back side of the board that connects to that "island" pad?

The other thing to note is that on the schematic, C810 has its polarity wrong, the (+) should be connected to ground since it is a negative voltage. But, you have it installed correctly.

The other thing I can't see from the photo are the diodes Q810/Q811... are they facing the correct directions?
View attachment 3255377
View attachment 3255380
Click to expand...
c811 is a 10uf 400v
 
Those are probably OK with DBT. If you turn scope display Off or disconnect the HV CRT voltage connector (J804), see if the DBT light goes dim. Maybe CRT circuit is drawing current. Be careful, there will be HV on J804 pins.
 
dankik said:
Those are probably OK with DBT. If you turn scope display Off or disconnect the HV CRT voltage connector (J804), see if the DBT light goes dim. Maybe CRT circuit is drawing current. Be careful, there will be HV on J804 pins.
Click to expand...
It’s the same with j804 removed
 
Just watching the dim, it starts bright, drops quiet dim, once the first relay clicks that’s when it lights up more again and then holds that level of brightness no change in brightness with the second relay it seems.
 
quadmatrix82 said:
Just watching the dim, it starts bright, drops quiet dim, once the first relay clicks that’s when it lights up more again and then holds that level of brightness no change in brightness with the second relay it seems.
Click to expand...
Hmmm... I thought there was only one speaker relay L004. Are you sure the 2nd "click" that you hear is not the relay opening due to excessive DC on the speaker outputs?
1721576614358.png

Here is how much power you should be drawing in idle (Volume control at 0), 115W.
You are using a 150W bulb, so it probably glows pretty bright, even at idle.
Does it glow bright even when the two Main Amp boards disconnected?
1721587115444.png
This is 3X more than my 2252B draws, which is 35W at idle and I use a 60W or 100W bulb.
 
Last edited:
dankik said:
Hmmm... I thought there was only one speaker relay L004. Are you sure the 2nd "click" that you hear is not the relay opening due to excessive DC on the speaker outputs?
View attachment 3256736

Here is how much power you should be drawing in idle (Volume control at 0), 115W.
You are using a 150W bulb, so it probably glows pretty bright, even at idle.
Does it glow bright even when the two Main Amp boards disconnected?
View attachment 3256857
This is 3X more than my 2252B draws, which is 35W at idle and I use a 60W or 100W bulb.
Click to expand...
Hmm this is a good point lot of watts even at idle, the brightness seems the same with the amps connected or not I will check which relays click there is a soft start and speaker relay low dc offset so I don’t think that’s an issue
 
quadmatrix82 said:
brightness seems the same with the amps connected or not
Click to expand...
I would have thought that the bias current would be a significant contributor to DBT brightness, so disconnecting the power amps should cause the DBT to dim significantly, don't know the amp and the loading of the scope, perhaps the scope is >>(much greater) than the bias
 
mbz said:
I would have thought that the bias current would be a significant contributor to DBT brightness, so disconnecting the power amps should cause the DBT to dim significantly, don't know the amp and the loading of the scope, perhaps the scope is >>(much greater) than the bias
Click to expand...
I disconnected the amp module and scope board the brightness looks the same to me.
 
I'd be tempted to pull fuses to try and work out where all the current is going.
With power amps and scope disconnected a 100W(?) bulb should almost be dim/off???

Hopefully, the fuses are easily accessible??
Pull F801, DBT power up, brightness significantly reduced/dbt off??
Reinsert F801.
Pull F802, 803 and repeat, reinsert F802, 803.
Pull F804,5 and repeat/reinsert
Pull F806,7 repeat/reinsert
 
mbz said:
I'd be tempted to pull fuses to try and work out where all the current is going.
With power amps and scope disconnected a 100W(?) bulb should almost be dim/off???

Hopefully, the fuses are easily accessible??
Pull F801, DBT power up, brightness significantly reduced/dbt off??
Reinsert F801.
Pull F802, 803 and repeat, reinsert F802, 803.
Pull F804,5 and repeat/reinsert
Pull F806,7 repeat/reinsert
Click to expand...
I removed every fuse one at a time and the dim is the same no noticeable change between any of them
 
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quadmatrix82 said:
I removed every fuse one at a time and the dim is the same no noticeable change between any of them
Click to expand...
If you take a look at the schematic you will see for eg, pulling F804, the circuit still receives power via F805, and Q809. Plz pull the fuses in pairs as listed.
 
mbz said:
I'd be tempted to pull fuses to try and work out where all the current is going.
With power amps and scope disconnected a 100W(?) bulb should almost be dim/off???

Hopefully, the fuses are easily accessible??
Pull F801, DBT power up, brightness significantly reduced/dbt off??
Reinsert F801.
Pull F802, 803 and repeat, reinsert F802, 803.
Pull F804,5 and repeat/reinsert
Pull F806,7 repeat/reinsert
Click to expand...
Thanks for the clarity, I repeated with doing the pairs as suggested, the dim is the same brightness regardless of combination here
 
I've misunderstood that you disconnected power to the power amp boards. Appears you've disconnected connector J702 but unregulated power comes from J706,7, was this also disconnected?
 
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