Orion HCCA 150 Pop top amp

[Perry Babin]

Is it possible that the insulator is damaged under one of those transistors?

Will the board lift out of the heatsink?

 

[JUNEBUG131]

The insulator is on underside of board ? Will check removing board now

 

[Perry Babin]

The blue silpad is the insulator. Any defect, a burr on a transistor or a metal shard under a transistor could cause a transistor to short to the heatsink.

 

[JUNEBUG131]

With the board out heatsink ,still short on 2 and 3 leg of power supply fets

 

[Perry Babin]

Have any more of the output transistors failed?

Are the solder joints broken on of the PS FETs?

 

[JUNEBUG131]

output transistors ok no shorts
Checked for broken joint on PS FETs , they are good .
I reheated the solder on the one's that looked fishy

 

[Perry Babin]

Do you have any PS FETs that read lower legs 1-2 than the rest?

 

[JUNEBUG131]

One side 1-2 leg .140 1-5 PS FETs , 1-2 leg .629 6-10 PS FETs ,

2nd side 1-2 leg .160 1-5 PS FETs , 1-2 leg .629 6-10 PS FETs

 

[JUNEBUG131]

Could the read be caused by the 2 output transistors I removed?

 

[Perry Babin]

Remove and check the driver transistors for the FETs reading low. Also check the 10 ohm resistor that's connected between the MPSA56 driver's collector and ground.

Check the drivers for leakage as well as open and shorted junctions.

 

[JUNEBUG131]

the drivers are the MPSA56 ? 10 ohm resistor are ? can you point them out . thanks

 

[JUNEBUG131]

The blue 10 ohm resistors running across the bottom of PS FETs ?

 

[Perry Babin]

See attached.

 

[JUNEBUG131]

Found 3 10 ohm resistors meter read 10.2 ohm on all 3 , just can't find the 4th the one that's by the + - studs, is it a different looking one? Here's some pictures maybe you know what to look for thanks

 

[JUNEBUG131]

The mpsA56s and mpsA06s read .668 - .679 from center leg to right and left leg . On the PS side

 

[JUNEBUG131]

Should I remove the PS FETs that read low ?

 

[JUNEBUG131]

Ok , I removed PS FET # 1 from the 1st top row, found out that's the faulty one, now all other PS FETs that were reading low now are at .638 from legs 1-2 . is that go?

 

[Perry Babin]

What does the FET you removed read, out of the circuit?

Clamp everything back down and see if it will power up without blowing the fuses.

 

[JUNEBUG131]

FET read .877 from leg 1 2-3 and sorted from leg 2-3 . Will it work without missing/removed FET ?

 

[JUNEBUG131]

How long should I leave amp on,
if it powers on ?