Orion HCCA 2100 no rail voltage.

[Chopperbuilder]

All the output transistors are new. I checked for solder bridges and found none.

I tried pulling the the fuse and amp did not power up. The fuse on the left in the photo on post #19 is the fuse that supplies power to the 494. That is also the side that the PS FET's are getting hot.

 

[Chopperbuilder]

Just checked the rectifiers with the meter set on Ohms. It appears one is bad. Going to pull it check it and replace it if needed.

 

[Chopperbuilder]

Checked it and one side is open. Do you know of a replacement for SF304A?

 

[Perry Babin]

APT30D60BCAG - Microsemi






- datasheet

?

 

[Chopperbuilder]

Was just looking at the data sheet on that one. Thank you. Is APT30D60BCTG the match to it?


When I pulled that rectifier I was expecting to see FEN30DP or FEP30DP which I happen to have one each of those on hand.

 

[Perry Babin]

The CT is the positive rectifier. Isn't the defective rectifier a negative rectifier (diodes facing out)?

The rectifier you have should work.

 

[Chopperbuilder]

Yes, it is a negative rectifier. I was asking about it's match because when dealing with components that work together in pairs I like to replace both.



Cool, I'll install what I have then.

 

[Chopperbuilder]

Couple things to mention. I am still powering the amp through a choke. With the remote not connected DC voltage at the terminal is +12.3v. With the remote connected voltage is at +7.8v. Resistor between pins 4 and 7 is still in place with DC voltage at +0.001v. Tried removing the resistor and voltage went up to +2.95v pulsating.


New rectifiers installed. Amp now powers up with even +/- rail DC voltage on both sets of rectifiers, +/-4.45v. I know it should be far more than that. PS FET's on the left side are still heating up.


I also found that there is 0v on al three legs of the voltage regulator circled in the attached photo.

 

[Perry Babin]

Check those 2 large resistors near the regulators. They look burned. The other two for the other regs also have seen better days.

 

[Chopperbuilder]

One was open and another below specs. Took me a bit to figure out what the value on one of them was as the color bands were basically unreadable. Actually from what I could make out it wasn't the right resistor. Appeared to have been replaced at some point before. The rest are in specs.



Replaced both and now have power on that voltage regulator.



Still have the problem of the PS FET's on the left side getting hot.

 

[Perry Babin]

Are both channels producing audio?

Those resistors are 5.6 ohms, the same as the other side.

Are all of the FETs (both power supplies) on one side of the heatsink heating up?

 

[Chopperbuilder]

One channel is producing only a static sound and the other channel a squealing sound.

Yes, all the FET's (both power supplies) on the one side are heating up.

 

[Perry Babin]

Are the drive signals the same on pins 9 and 10 of the 494?

Are the drive signals the same on the FETs on both sides?

 

[Chopperbuilder]

The DC voltage on pins 9 and 10 of the 494 are the same, both are also pulsating.

The DC voltage on the drive of the FETS is different from side to side, more so on the upper voltage supply.

 

[Perry Babin]

Did you scope die completely?

 

[Chopperbuilder]

I wouldn't call it dead but it is no longer is usable. I just tried it and could not get any sort of stable wave form out of it.

 

[Chopperbuilder]

Just to make certain I understood, by drive signal you were talking about the gates of the FET's, correct?

 

[Perry Babin]

The drive signal starts at the 494, throught he emitter-follower pair (A06/56) and to the gates of the FETs. It has to be checked all along that path. If it stops at some point in that path, you have to determine why.

 

[Chopperbuilder]

AS I mentioned in the beginning of this thread, I replaced all of the PS FET's, A06/56, capacitors and output transistors. Not sure what could be causing the problem...

 

[Chopperbuilder]

The 494 was bad. Replaced it and the voltage on pin 4 is at +0.090v (with no resistor between pins 4 and 7) and pins 9 and 10 are now even and stable.



Does not produce audio but the static and squealing is gone.



PS FET's still heating up.