MARANTZ 2230 power amp. PLEASE.help.

[Steven Tate]

Have you measured resistance across every resistor, including emitter resistors? I would test every one in circuit, and if very far out of spec, pull one leg and test again. One resistor short or open can cause what you are seeing.

 

[jFF_Bulbo]

Why are you letting things smoke with a DBT?????? That's why you use a DBT to PREVENT smoking components... 60w Incandescent bulb MAX and if it stays bright for over 2 seconds, shut it down and figure out why...

Yes. DBT is 60w incandescent. The thing here is DBT is not billiant with both boards installed, an, for my surprise, r 771 smokes......

 

[jFF_Bulbo]

I think your problem is not related to components rather in the trace of the board. I would take the schematic and follow all the connections on the back of the board and compare it with the good working other one.

Good idea!
I'll check both

 

[sanjib]

It looks like your left board is also not up to spec. If the original H757 is not bad I will suggest you put back in and follow skywatcher's advice.

 

[MarantzRefrb]

H757 should be 2 1n4148 in series. NOT a single one.

From the sub guide:
https://audiokarma.org/forums/index.php?threads/marantz-transistor-diode-sub-guide.926805/
A varistor VD1212 is (2) 1n4148 in series (phono P400), H757 is a S3016R varistor, just (1) 1n4148 in this location.

Stock:

Rebuilt:

 

[sanjib]

If you still have the original H757 I would suggest to put it back in and check.

 

[sanjib]

General suggestion in all threads regarding this varistor is to left alone if it works.

 

[MarantzRefrb]

It was suggested to me to replace H757 on a recent 2230 rebuild, with (1) 1N4448 or 4148.

Not purposely trying to disagree, just don't think this particular part replacement is the cause of OP's troubles.

 

[jFF_Bulbo]

If you still have the original H757 I would suggest to put it back in and check.

hello. yes i have it and i tried installing it... didn't work... i also installed a stabistor made by me (3x1N4148 in series) and nothing...

 

[jFF_Bulbo]

It was suggested to me to replace H757 on a recent 2230 rebuild, with (1) 1N4448 or 4148.

Not purposely trying to disagree, just don't think this particular part replacement is the cause of OP's troubles.

hello. thanks. a also think this is not the problem. A excesive current is going out from h755 emitter and finally h755 and r771 go out of bussiness with h754...
I cleaned the h755 zone and find nothin extrange more than the output transitor was K.O.... again....

 

[sanjib]

Is H005/H006 good?

 

[jFF_Bulbo]

Is H005/H006 good?

hello!!
one of them was ruined...again...

I dismounted both to compare, nothig extrage.... i cleaned the soldering in h755, r771 and h756 zone. h755-6 were bad again and the mj15024 (wich is new...) also is dead...... new pieces reintsalled... c762 (100pF) was installed again (i changed it for 150pf NP0, didn't work....

all the pieces changed....

the back of the problematic board p750

P750, front.

 

[sanjib]

Did you fix the biasing and dc offset problem with the other board that is not smoking?

 

[MarantzRefrb]

Sometimes it helps to look at the schematic:

Regarding your trimmers, do you have 100K ohms for R760, and 470 ohms for R765?

 

[jFF_Bulbo]

Did you fix the biasing and dc offset problem with the other board that is not smoking?

hello.
in the board wich not explodes... i tried bias adjustment, i only can get 20 mv rock solid between j757-j759..... for few secons the bias could be set to 10 mV, but is starts to clim quicly and finally 20 mV.

Sometimes it helps to look at the schematic:

Regarding your trimmers, do you have 100K ohms for R760, and 470 ohms for R765?

Hello,
what a usefull info!!!!!!!!!
well.
R760- 100K (104 value)
r765 1k (102 value)
as far as i see smoke on r771, i stop test. and change pieces and test again.....
once r771 get burned (or explodes) could i check this voltages????
if i pulg tue unit to 120v, r771 just explodes..... i'm sure it will happen again, beacuse i have done nothing but replace the pieces my ESR rester /multimeter say are bad. but if i can test after failures, could be a different start.....

Rectifier bridge can be bad and be the responsible for this rebeld P750????
THANK YOU A LOT!!!!!!!!!!!!!!!!!!!!!

 

[sanjib]

You can check that by measuring the voltage at the positive leg of C007 that should be around 66.5V without the amp boards plugged in.

 

[jFF_Bulbo]

You can check that by measuring the voltage at the positive leg of C007 that should be around 66.5V without the amp boards plugged in.

c007 4700uf/80v.
ov on negative (withe wire)
71v on positive (red wire)
readings with the good board installed an the rebeld not. should i disconect the "good" board?

 

[sanjib]

What are the voltages at all legs of H755 on that board?

 

[jFF_Bulbo]

What are the voltages at all legs of H755 on that board?

hello!
not measured, once smokes (or fire) is seen, i disconect the board and change the pieces... so, the next is measure voltages even if the h755-6 & r771 fail, unit plugged to 120v (not to DBT) right???

 

[sanjib]

You measured 71V on C007 positive pin on DBT with the right amp board plugged in correct? Just measure the voltages on E, C, B of H755 on the plugged in right amp board.