Help Rockford 1100a2

[stoke]

this is the reading from u11

U1
Pin 1: 0
Pin 2: 4
Pin 3: 0
Pin 4: 2
Pin 5: 1 .........only diff
Pin 6: 3
Pin 7: 0
Pin 8: 13
Pin 9: 0
Pin 10: 0
Pin 11: 13
Pin 12: 13
Pin 13: 4
Pin 14: 4
Pin 15: 4
Pin 16:0

 

[Perry Babin]

It's unlikely that you'd have 2 ICs fail in the same way. If you have a better meter, recheck the voltages with it.

 

[stoke]

sorry for take so long, i got some trouble with my job ..... well with the amp i Recheck with a fluke multimeter

i still have Q5,Q6,Q12 and Q13 getting hot and that speaker output side measured -3volts and make a noise when i plug the speaker on it .... the other side i dont have any sound... both side dont make any sound with audio plug it in.

U1
Pin 1: 0.004
Pin 2: 4.936
Pin 3: 0.063
Pin 4: 2.817
Pin 5: 1.492
Pin 6: 3.476
Pin 7: 0.001
Pin 8: 13.42
Pin 9: 0.111
Pin 10: 0.108
Pin 11: 13.38
Pin 12: 13.39
Pin 13: 4.949
Pin 14: 4.949
Pin 15: 4.949
Pin 16:0.001

U11
Pin 1: 1.078
Pin 2: 4.940
Pin 3: 0.074
Pin 4: 2.679
Pin 5: 1.494
Pin 6: 3.481
Pin 7: 0.00
Pin 8: 13.44
Pin 9: 0.264
Pin 10: 0.269
Pin 11: 13.45
Pin 12: 13.46
Pin 13: 4.94
Pin 14: 4.94
Pin 15: 4.94
Pin 16:0.00

 

[Perry Babin]

The channel with 3v is likely blown and causing the amp to go into protect mode. Check for shorted output transistors and open (or out-of-tolerance 0.1 ohm source resistors).

 

[stoke]

what could be the best way to do this check with out take out the transistor.

 

[Perry Babin]

Measure the resistance between the legs of the output transistors. You should not read anything near 0 ohms with any combination of probe placement on the legs of any individual transistor.

 

[stoke]

i know in that way but some times and maybe is this case you need to take out the transistor because on the circuit board you get a non 0 measured between the legs. i check twice all the transistor and no one present a measure near 0 ohms. i will take out all transistors in this channel to confirm if they are working properly

 

[Perry Babin]

Don't take them out yet.

With the amp powered up and trying to power up, measure the voltage on each output transistor, red probe on leg 1 and black probe on leg 3. Do any measure more than 3v?

 

[stoke]

hi again, after replaced R5, R19 and Q213 of left speaker channel ,, i have the right speaker channel now working and none transistor are getting hot. but im still getting -3 volts. even when i have legs 1 and 3 pulled out of all transistor on the left speaker channel

 

[Perry Babin]

Did you have precisely the same voltage when you had the outputs in the circuit?

Also... You can't replace only one output and expect the amp to be reliable. At the very least, you need to replace the other transistors in parallel with Q213. It would be better to replace all outputs in the channel.

 

[stoke]

i will check

 

[stoke]

well i found some open transistor, but i noticed -16volts on gate legs from Q211 TO Q215 and -18volt Q216 TO Q220

 

[stoke]

AND i STILL HAVE -3VOLT ON + CONNECTOR OF THE CHANNEL,
all center legs were pull it out..

 

[Perry Babin]

-3v on the positive terminal of which channel (assuming the left channel)?

When you read -18v on the gates of those transistors, did you have the outputs in the circuit?

Was this the channel with the -3v on the output?

 

[stoke]

yes is the same channel i told you before.

what do you mean about have the outputs in the circuit?

 

[Perry Babin]

Many people remove transistors and try to troubleshoot a problem with voltage readings. That won't work with the output transistors removed from the circuit.

 

[stoke]

ok. but is fine to do it just with the center leg pulled out

 

[Perry Babin]

If that was a question, no. You have to have all legs in the circuit if you're going to try to troubleshoot with voltage readings on the outputs.

 

[stoke]

AMP FIXED..... thanks just one output trasistor open

 

[Perry Babin]

One open output won't cause DC offset on the output.

How many outputs did you replace?