Hi all,
Got this amp. It is dead and many traces and components looking rusty. No voltage coming to pwm ic. If anybody has schematics please share. Thank you.
Got this amp. It is dead and many traces and components looking rusty. No voltage coming to pwm ic. If anybody has schematics please share. Thank you.
I have a diagram but can't post it because someone else purchased it and sent it to me so I could help them.
Q314 drives Q313 and Q313 drives voltage to the 494.
Q314 drives Q313 and Q313 drives voltage to the 494.
It's odd for Q314 to fail. What about it makes you think it's defective?
Post the DC voltage on all terminals of Q313.
Post the DC voltage on all terminals of Q313.
Because it is not reading like normal transistor.
Q313 voltages
Pin1 7.74v
Pin2 0.723v
Pin3 13.33v
It's not a normal transistor. It's a 'digital' transistor with internal resistors.
Are you sure that you have the pin numbering right?
If they're reversed, the transistor appears to be defective.
Confirm that the collector of Q314 is very near ground.
Are you sure that you have the pin numbering right?
If they're reversed, the transistor appears to be defective.
Confirm that the collector of Q314 is very near ground.
Ya I am using A1220A instead A1358 as A1358 was bad. Base is having 13.33v, collector is having 0.723v this pin is connected to 494. Emitter is having 7.74v.
The emitter should be connected to the 12v power source.
The base should be about .7v below the emitter.
The collector should be very near the emitter voltage.
Is Q313 getting hot?
The base should be about .7v below the emitter.
The collector should be very near the emitter voltage.
Is Q313 getting hot?
The Q313 was reversed. According to the print on the board the thick line suppose to be indicating back of the transistor but here it is different. Amp came from another tech who stated to the customer that he can't fix. I found few parts were bad and replaced and after correcting Q313 amp is now coming on. But there is a difference in positive and negative rail by 4~5v. And on one channel it have 0.2v dc and on another 0.35v. But amp is playing now.
Measure the rail voltage using the negative speaker terminals as the reference.
When you measure DC offset (?) did you have a load connected and did you measure directly across the two speaker terminals for that channel?
When you measure DC offset (?) did you have a load connected and did you measure directly across the two speaker terminals for that channel?