New to me Marantz 2275 (with issues)

[xalara76]

Do you have all of your voltages coming from the power supply?

Once again, throw up some pics of your work.

getting nearly 13 volts from J806.
J804 was calibrated to 35V
P800 was recapped yesterday. I get AM now Clearly, FM is just static.

 

[xalara76]

Are you on a dim bulb tester? That could account for the difference. But basically, 0.5V shouldn't affect the function of anything. I would keep moving forward with your restoration. Just test, test, test after everything you do, preferably with a DBT.

Going to recap the right amp board today and test output transistors as well. They arent originals which leads me to suspect they may be okay ? I bought Mj15003 and mh15004 NTE Power transistors. Does it matter if 15003 or 15004 are place on top or on bottom of eachother ?

 

[xalara76]

Are you on a dim bulb tester? That could account for the difference. But basically, 0.5V shouldn't affect the function of anything. I would keep moving forward with your restoration. Just test, test, test after everything you do, preferably with a DBT.

Brakes applied on the right power amp recap... unplugged it and plugged it into left amp board connectors and its working fine ... now where to look.. preamp? Toneboard ?

 

[xalara76]

Dubbing out with headphones gives me both channels. Switched to headphones only getting left channel. Using JUMPERS now for main in and pre out inputs and volume is VERY low.

 

[Steven Tate]

That's a lot of stuff going on. Do you have one good channel out to speakers?

 

[xalara76]

That's a lot of stuff going on. Do you have one good channel out to speakers?

Yes, left channel is perfect. Tested on AUX. clear crisp sound. Right channel is dead. Used RCA’s into pre out section. Very low output and only in left channel. Plugged into main in volume is louder but still only on left channel

 

[xalara76]

That's a lot of stuff going on. Do you have one good channel out to speakers?

since when did the bridge rectifier get mounted to this center chassis point ? Very weird.. looks like someone did some sloppy work in here way back.

 

[Steven Tate]

So, if you are hooked up to speakers, and you criss-cross the RCA's from Left Pre-out to Right Main In and Right Pre Out to Left Main In. Do you still get one good channel? Is it left or right?

 

[xalara76]

So, if you are hooked up to speakers, and you criss-cross the RCA's from Left Pre-out to Right Main In and Right Pre Out to Left Main In. Do you still get one good channel? Is it left or right?

Criss crossed the main in and pre out. Only left channel is playing

 

[Steven Tate]

Criss crossed the main in and pre out. Only left channel is playing

So the good side stays the same whether criss-crossed or not? That points to bad right amp board. But....right amp board worked when you plugged it into left side? If so, time to check voltages on the amp board and see if it is getting power. Are you getting +47V at J707 and -47V at J708?

 

[xalara76]

So the good side stays the same whether criss-crossed or not? That points to bad right amp board. But....right amp board worked when you plugged it into left side? If so, time to check voltages on the amp board and see if it is getting power. Are you getting +47V at J707 and -47V at J708?

Yes, -47.3 at J708 and +47V at J707

 

[Steven Tate]

If you have mini grabber test leads and can safely check collectors of J701 and J702, looking for something in the 14V range, that would tell if the front end of the board is getting the low voltage power. If it is, time to start testing transistors, starting with the outputs.

 

[xalara76]

If you have mini grabber test leads and can safely check collectors of J701 and J702, looking for something in the 14V range, that would tell if the front end of the board is getting the low voltage power. If it is, time to start testing transistors, starting with the outputs.

J702 at -14.5 (fluctuates slightly within range)
J701 at -13.6 (fluctuates slightly within range)

 

[Steven Tate]

Good. So you are getting power everywhere. I would pull the output transistors and do the 6-way test with DMM in diode test function.
https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

 

[xalara76]

Good. So you are getting power everywhere. I would pull the output transistors and do the 6-way test with DMM in diode test function.
https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

pics for reference. Pointing fingers at power output transistors, going to remove solder and test

 

[Steven Tate]

You don't need to unsolder anything. Remove the two screws that attach each one to the heat sink, and they pull right out.

 

[Steven Tate]

Pay attention to which one goes where and save the mica insulator under it. After testing, clean the mica with alcohol and replace the thermal compound on both sides - very thin layer.

 

[xalara76]

You don't need to unsolder anything. Remove the two screws that attach each one to the heat sink, and they pull right out.

correct, sorry about that. Lets do some testing !

 

[xalara76]

Pay attention to which one goes where and save the mica insulator under it. After testing, clean the mica with alcohol and replace the thermal compound on both sides - very thin layer.

Ok top transistor shows 457
Bottom transistor shows 1
Both tested the same way negative on casing and positive on emitter

 

[Steven Tate]

One is PNP, and one is NPN. They each have their own testing regimen - outlined in the link above. You should be doing six tests on each one, but different polarities for PNP and NPN. Use the Diode Test mode on your DMM.