help with a Marantz 2250b

[jFF_Bulbo]

Hello. recently i bought a pair of 2250b. M1 and M2 for further references. Well, M1 was in poor condition, powers up and works only as preamp, doing it well, amplifier section disabled. M2 is in mint condition but only works as amplifier (i thought that was the meaning of a "made in heaven" couple... wrong). I move the pre-tone control board form M1 to M2 in order to have a complet unit working properly. For my surprise it didn't work. once installed the prep tone board in M2 the pre-out function not working, the RCA audio has to be plugged in the main in connectors instead in the auxiliar connectors also the tone controls do not work. Each board works in the unit it come from. The pre tone board in the M2 doesn´t have the BA312 chips but still working in M2. this is the reason to do the change of boards. I notice that both board have the same components except a pair of capacitors, the first capacitors in the circuits (image attached). M1 left. M2 right

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The M1 board have red caps marked as (105k 100v) and the board form M2 has gray caps with (1-250) written on them. I think these were replaced, but the M1 unit has many of this red capacitors in other circuits. I dont know how to let at least one unit working fine.
I have seen reviews and video about the manteinance process in a Marantz 2250b, and in all of them the pre tone control board and in other circuits has the capacitors in gray, just like in my M2 unit.

 

[KutzlerTrans]

these are 1uf capacitors. the 250 is the voltage. your 100v should work, being you should not see 100v there, but its wise not to go down in voltage, so if you find the 250v grey ones, put them back in. I understand them to be fairly reliable film capacitors.JMO.

If you are curious, put your volt meter across them Use the min/max feature if your volt meter has one.
I would be looking for cracked solder joints near the plug, or somewhere on that board.
Also, make sure you didn't pop a fuse.

 

[jFF_Bulbo]

these are 1uf capacitors. the 250 is the voltage. your 100v should work, being you should not see 100v there, but its wise not to go down in voltage, so if you find the 250v grey ones, put them back in. I understand them to be fairly reliable film capacitors.JMO.

If you are curious, put your volt meter across them Use the min/max feature if your volt meter has one.
I would be looking for cracked solder joints near the plug, or somewhere on that board.
Also, make sure you didn't pop a fuse.

Hello and thank you. One thing i forgot to comment is that every board works, even the board without the pre amp chips Ba312, but only works in the specific unit the board comes from. This blow my mind. Changing the complete board to the other unit makes its preamp section turns off completely. I don't have equipment to make test, i just started at electronic a few time ago. What should i do? move the Ba312 to the pre tone board to? move the capacitors to the complete tone board?

 

[KutzlerTrans]

I would make sure the female pin connectors are tight. If the tracks on the board are not the same and one uses the chip and the other does not, then, its a no brainer. Are the tracks the same with empty holes were the chip is? I am not familiar with this.

 

[jFF_Bulbo]

I would make sure the female pin connectors are tight. If the tracks on the board are not the same and one uses the chip and the other does not, then, its a no brainer. Are the tracks the same with empty holes were the chip is? I am not familiar with this.

i will check this more focused but i am -more or less- shure the circuit is the same. i'll post images about this soon.

 

[rBuckner]

I would not have taken the boards out of either myself. I'd be inclined to suggest putting back each where they came from, hoping you have the wires marked or listed by color. Then troubleshoot the issues.

 

[ikorman]

Those two grey caps were bad on my 2275. Along with some tantalum ones. My tech said he has NEVER seen this type of cap go bad before and I know, he has seen it all.

 

[jFF_Bulbo]

Those two grey caps were bad on my 2275. Along with some tantalum ones. My tech said he has NEVER seen this type of cap go bad before and I know, he has seen it all.

thank you for you advertising I didn't stop to think about the 7-pin connector. I was almost ready to change the capacitors and Ba312 chips from one to another. I am searching pics, I gave little importance to this.

 

[jFF_Bulbo]

Does anybody knows if the BA312 pream circuit and the BA3120 circuit are the same? i started a search in Mercadolibre, a page like Ebay here in Mexico. A pair of sellers have answer me for the BA312, but one of them can get for me the BA3120 circuit with relative low cost. I know the replacement is the NTE1433 but none is easy to find. Any help would be appreciated

 

[bryans12v]

I would find out what's wrong with the original tone board in M2, but that's me. Especially before modding another to work.

Then I would listen to M2 while fixing the amps in M1.

 

[jFF_Bulbo]

update. Images of the connectors. First one is the connector in the unit which came without the BA312. Second one is the connector in the unit working only as preamp. Well, i think the unit with gray caps make them work with 250v, so, when i installed the board with the red cap (100v caps) that could be too much volts, more that the 100v board can work with. Suggestions are accepted. I am almost ready to desolder the BA312 circuit to install them in the unit with gray-250v capacitors.

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[jFF_Bulbo]

update. Images of the connectors. First one is the connector in the unit which came without the BA312. Second one is the connector in the unit working only as preamp. Well, i think the unit with gray caps make them work with 250v, so, when i installed the board with the red cap (100v caps) that could be too much volts, more that the 100v board can work with. Suggestions are accepted. I am almost ready to desolder the BA312 circuit to install them in the unit with gray-250v capacitors.

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**ck. the images are of the same unit.....