Hifonics XXV-Cyclops repair

[Deadly Sones]

Ok... def not have 15v on either L7815 or L7915. I followed pin 14 of the output card to 3rd leg of the L7815.

L7815 has 8.71v on pin 1, 0.002v on pin 2, 7.14v on pin 3 right now

diode check red lead on pin 1 - pins 1-2: OL, Pins 1-3: OL, Pins 2-3: .510
diode check black lead pin 1 - pins 1-2: .551, pins 1-3: .559, Pins 2-3: .920
Defective?

L7915 has 0.001v on pin 1, -9.10v on pin 2, 8.35v on pin 3

diode check red lead on pin 1 - pins 1-2: OL, pins 1-3: .986, pins 2-3: .532
diode check black on pin 1 - pins 1-2: .555, pins 1-3: .522, pins 2-3: OL

Also defective?

Could my supply be the prob? As soon as I connect remote my suppy is going from 12.56 to 8.5v at the power terminals... using the limiter...

 

[Perry Babin]

Post a couple of photos showing all areas of the board.

 

[Deadly Sones]

Some pics as requested. lmk if you'd like any others in better quality pic of a certain area.

 

[Perry Babin]

On C53 and C54, is the amplitude of the square wave signal approximately the same on both terminals of each capacitor? What is the amplitude? Post a photo of the waveform if you're not sure.

 

[Deadly Sones]

I have +5.17v on C53 + leg, and 0.000v on neg leg & 0.000v on pos leg of the C54 and -5.41v on the neg leg.

Attached is the 4 leg photos and one of my settings.

 

[Deadly Sones]

Just checking the legs again, I now have 4.95v on + leg of C53 and -5.15v on C54 neg leg. Not sure why its changing... might be my ps dipping a lil.

 

[Perry Babin]

The output from a small winding on T1 drives those capacitors. Are you sure that the power supply FETs driving T1 are being driven properly?

You should see a swing from ground to 2x the B+ voltage on the primary windings of the transformer.

 

[Deadly Sones]

No, there doesn't appear to be any swing... if I put the black prob on ground terminal and test any of the transformers I get 12.66 volts on every primary winding (no matter if I touch the pos or ground, theres power on all 3 primary) with the amp off, and drops to 8.2v as soon as I add the remote (through resistor).

The transformer feeding the 15v I get 0.000v if I use ground terminal, and 12.66v (or 8.2v) if I connect black prob to one of the primary windings. If I test black lead on the secondary center and red on the 15v I get 0.000v

 

[Perry Babin]

Do you see the 24v of swing on the primary windings of the other transformers?

If not, you may have blown FETs for the transformer that has the 15v windings.

 

[Deadly Sones]

I have the same readings for all the transformers. Where exactly should I be placing the leads?

 

[Perry Babin]

You touch the scope probe to the primary windings (set it to 10us and 10v/div). I'm assuming that the scope is grounded to the 12v power supply. If not, the scope ground will go to the amp ground. You should see the 24v of swing on the outer primary windings or the center legs of the FETs driving those windings.

 

[Deadly Sones]

I hear a small hum coming from that transformer, and I do see a swing. It changes pitch as I wiggle it.

 

[Perry Babin]

How does it compare to the other 3 transformer primary windings?

 

[Deadly Sones]

All have the same amplitude, some just start climbing at slightly different points

 

[Deadly Sones]

These are the 4 windings for the 2 transformers closest the driver card. They have the small windings for the 15v and I think 12v or some other lines (the other transformer).

The first two are from the 15v one.

 

[Perry Babin]

Touch the scope probe to pin 9 or 10 of the driver IC for the power supply with the scope set to 5v/div and post the photo.

 

[Deadly Sones]

this is what I see

 

[Perry Babin]

Is your timebase multiplier set to 10x?

If it is, set it to 1x.

 

[Deadly Sones]

Yes I did, lol.

 

[Perry Babin]

The amplitude appears to be too low. Is the scope set to 5v/div?