bigbang2400.1

[timwebb]

i bought this amp to fix. the issue was one irf1010e had a broke leg and put it into protect. but i cant get any audio from it period. i have rail pos-neg voltage and 13.8 pos and neg on the opamps. any thing im missing?

 

[Perry Babin]

Do you have rail-rail oscillation on the output transistors?

Do you have the master/slave switch set to master?

 

[timwebb]

its set to master. and just check and i have no rail-rail oscillation.

 

[Perry Babin]

Does the amp go from protect to normal operation after a few seconds?

 

[timwebb]

yes.

 

[Perry Babin]

I'd suspect one of the 3 transistors along the top edge of the driver board on the end nearest the power supply. You'll have to check for leakage as well as for open junctions.

 

[timwebb]

ok. thanks!

 

[timwebb]

one of the 1277 have a low ohm reading from the rest. also. what is the diode in zd5? i keep forgetting?

 

[timwebb]

i cant find the kta1277 transistor. i was looking at 2sa1156 to replace it

 

[Perry Babin]

I haven't checked the one on this board (which is a modified version of the more common driver board) but it's likely a 5.6vZ. It should be marked.

I'm assuming that you're referring to the one on the lower left corner of the board near the 10k resistor. On the photos I have, it appears to be a ZD6 but the silkscreening isn't very good.

 

[Perry Babin]

The 1156 may work if you can find them.

 

[timwebb]

also the junction is kinda of high on the a1837 and c4793.

 

[Perry Babin]

You have to compare the transistors with the same part numbers. If one reads off from all of the others, it may be defective. If all are high, it's likely normal.

 

[timwebb]

ok i thought i could find the 2sa1156 but no luck. any other sub?

 

[Perry Babin]

Which one failed (Q???)?

 

[timwebb]

q43 has a low ohm reading from the rest the part is kta1277

 

[Perry Babin]

I think the KSA1220A will work in that location but I'm not 100% sure. I have one that I need to repair that I could try it in but it won't be finished until the end of the week. If you don't have the 1220A, you could use an MPSW92 for testing but you'd have to swap the 2nd and 3rd legs (being careful not to let them short).

 

[timwebb]

i have to order some. i can wait.

 

[timwebb]

ok im getting 13.4 pos and neg from the regulators. when i dont have the driver card in i have about 14.8v on the pos and neg regulators. could that be my problem also the regulators are 15v.

 

[Perry Babin]

Measure the DC voltage on the regulators with the black probe on the negative speaker terminal or with the black probe on the ground terminal of the regulator on which you're measuring the voltage.