Orion HCCA 2100 no rail voltage.

[Chopperbuilder]

Here are photos of the driver signals. Scope set at 2v/div and 20us

Both power supplies are not producing the same rail voltage. The lower supply rail voltage is +/-23.0v. Upper power supply rail voltage is +/- 4.09v.

Yes, only the one supply is heating up, the one with low rail voltage.

The hot supply is also the one with the new rectifiers.

 

[Perry Babin]

Can you easily desolder the red and black wires that connect the hot supply to the audio circuit? If so, do so. Does that significantly change the rail voltage and current draw?

Is the output polarity right on the supply that you replaced the rectifiers in?

 

[Chopperbuilder]

Two things I do have, is a really good soldering station and a really good de-soldering station.

Disconnected the red and black wires that connect the hot supply to the audio circuit. DC rail voltage on that side jumped up to +/-32.5v. Current draw across my limiter dropped from +4.57v down to +2.0v DC.

 

[Perry Babin]

That would generally indicate that the problem is in the audio circuit. Generally, the outputs are the components passing the current but if all emitter resistors read 0.000v DC. The current is going somewhere else.

Does the other channel produce clean audio now?

 

[Chopperbuilder]

Amp power light does not come on with those wires disconnected. While the output isn't as loud as should be, it does produce good clean audio out of the other channel.


Also noticed FET's are not heating up with those wires disconnected.

 

[Perry Babin]

Do you have an incandescent lamp (120v) that you could insert into the output of the power supply to limit current? A lower wattage would be better than higher.

 

[Chopperbuilder]

Yes. A 40 watt bulb was the smallest I could find. It cuts the voltage down to 6.5v DC at the amp power terminal.

 

[Perry Babin]

I should have been more clear.

You will leave the 3 parallel 6 ohm resistors in the B+ line.
You would solder the black wire between the output of the second power supply back into place.
You would insert the 120v lamp in-between the solder pad for the red wire and the red wire for the second power supply.

 

[Chopperbuilder]

I did that.

Also just found I have no voltage on any of the three legs of the voltage regulator circled in the attached photo. It is next to the one that didn't have voltage before. That is the photo I used before, with the old resistors in place.

 

[Perry Babin]

Did the 5.6 ohm resistor burn again?

 

[Chopperbuilder]

It checks good, in circuit.

 

[Perry Babin]

Bad or broken solder connection or trace? Follow the circuit back to its source of power.

Or.. is the entire rail that feeds this resistor dead/0v?

 

[Chopperbuilder]

The whole rail the feeds it was dead. One of the connections at the lamp had come loose.



Noticed that the bulb is dimly lit when I power on the amp.

 

[Chopperbuilder]

Hey Perry, I'm getting ready to take my scope to have someone look at it and see if we can't fix it. I'll be back in an hour or two


Should I pick up a lower wattage bulb while I'm out? Or is the 40 watt one good enough?

 

[Perry Babin]

The 40 appears to be OK. We just needed something to pass a limited current to the output stage.

 

[Chopperbuilder]

I believe we have the problem pin pointed down to capacitors on the power supply of the scope.

 

[Chopperbuilder]

So, back to the amp. What's next?

 

[Perry Babin]

Find the reason that it has no voltage on that resistor.

Do you have positive AND negative rail voltage on that side?

If they are uneven, what are they?

 

[Chopperbuilder]

The reason that resistor had no voltage was because the connection to the lamp had come loose.



I do have positive and negative rail DC voltage on that side +25.25 and -26.26

 

[Perry Babin]

Is the amp producing clean audio on both channels?