Yamaha C4 resistors add

[Edu1985]

I was marking the signal elextrolitical caps when i have observed 2 resistors added in the right channel 30v +_ it seems in the place of the resistors should have been bridge wires but someone putted there these 1w resistirs.i think they are 330 ohm .in the left chnannel it has no resistors and the bridge wires are there.anyone has any idea why some9ne will add these 2 resistors because i ve checked the 30v and the voltage it s ok.it s 29.7.i also checked the dc offset and on the right channel it s around 300mv as in the left it s around 100...so not that ok here..the previous owner it seems that he replaced some caps in the turnover frec ,headphone amp,and 3 more caps next to the vr 304 pot

 

[avionic]

Those two resistors are suppose to be jumper wires. The red and white jumper wires are OEM and suppose to be there.

 

[avionic]

That board is not entirely split down the middle .

 

[Edu1985]

Yes ,the red and white are jumper wires and they are linked to the same +_ 30v i believe for the L channel.i was wondering why the guy put the resistors only on the right channel and not the other channel too.buy why have he replaced the jumper wires with those resistors in the first place??could be something is wrong on one channel?the preamp.sounds fine

 

[avionic]

That board is not entirely split down the middle .

Yes ,the red and white are jumper wires and they are linked to the same +_ 30v i believe for the L channel.

That end of the board is for both channels.

.i was wondering why the guy put the resistors only on the right channel

That end of the board is for both channels.

I have no idea why the resistors were installed. I guess thats for you to find out.

 

[avionic]

Do you know how to read a schematic and use a service manual ?

 

[Edu1985]

Oh,thank you for info!i thought by the way it s layed that the chanells have separate ps

 

[Edu1985]

I know a little bit how to read a schematic.i have already redid the dc offset

 

[Edu1985]

It could be the voltage for the phono preamp ?i hope in the near future to replace all the electrolytics.i think everything is original except those 2 resistors .the previouse owner replaced 3, 47uf capacitors next to vr 304 and the capacitors on headphones board.the 3 ones i think they have died from heat from the heatsinks next to them but anyway needs a full recap for sure!

 

[avionic]

There is only one +/- 30 volt power supply that feeds both channels.

 

[petehall347]

does the board have id numbers next to the resistors ?
from what i can see i can only guess it is 1 resistor for each channel or one for + other for -

 

[Edu1985]

Yes it is but it s splits from what i have seen on the board! it s plus minus 30 splitting and going 1.down where the 2 resistors have been placed and also 2.up where the 2 red and white wires go

 

[Edu1985]

does the board have id numbers next to the resistors ?
from what i can see i can only guess it is 1 resistor for each channel or one for + other for -

No.they have no id numbers.and they are big 1w resistors 330ohm from what i ve checked on the colour code.yes they are on plus and on minus 30v rail

 

[petehall347]

if you measure the voltages across them you can use ohms law to work out the current . i strongly suspect they are current limiters .
see if you can find them on the schematic .

 

[Edu1985]

They are not on schematic!that s what i m trying to say.they were 2 leads there and the previous owner replace them with 2 resistors!

 

[Edu1985]

Yes i think so too that are current limters too..because i ve checked for heat the transistors from that board and on the channel where are the 2 resistors they run more colder the the other channel .

 

[petehall347]

work out the currents from volts and resistance . then million dollar question is what should the circuit be drawing ..

 

[avionic]

does the board have id numbers next to the resistors ?

.. No
I have a C-4 in front of me. And I repeat those resistors don't belong there! They are suppose to be jumpers there.

 

[petehall347]

putting the confusion aside and working out why they are there i still think a good idea is first to work out the current draws .