Power Acoustic OV1-5500D

[S Merlington]

This amp had blown outputs and blown power supply fets replaced all outputs (FB31N20D) and all power supply fets (IRFZ46N's)

This amp has one of thoose driverboards that stand up in front of the fan..

With the driverboard installed the amp will power up and draw excessive current If i remove it the amp will power up fine..

I checked every transistor and resistor off the driverboard and all test fine...


Any ideas Where to look next?

 

[Perry Babin]

Does it draw excessive before the end of the mute delay?

 

[S Merlington]

No it doesnt draw current unitl after the mute delay

 

[Perry Babin]

Does the voltage on the positive speaker terminal swing positive or negative before the end of the delay?

 

[S Merlington]

The voltage stays at 0.001 during the muting then when its at the end of the delay it swings to negative

 

[Perry Babin]

Generally when an amp draws excessive current, it's not possible to see the voltage swing on the output. What do you consider excessive current draw?

Are all of the various voltages present on the driver board connector?

 

[S Merlington]

Once the mute delay is over amps light changes from red to green and draws about 15 amps of current before the protection circuit kicks in it will repeat it over and over..


Heres the voltages i get

+IN:0.07
-IN:0.02
SG:0.01
+15:13.80
-!5:-13.22
SW:0.00
VPP:89.9
DRV:0.22
OUT:0.01
PG:0.02
DRV:-70.1
VNN:-70.2

Theese voltages are with the driverboard out

When the amp starts to draw current and cycle's the outputs with the middle leg connected to the output filter inductors get hot

 

[Perry Babin]

That sounds like the low side drivers are not working properly. Do you read 150 ohms between the emitters of Q124/5 and Q126/7?

When you checked Q124/5, did you confirm that both had two good junctions and were not leaky?