Orion 1200 D

[Perry Babin]

Does one end of the resistors have the same signal as pins 9 and 10?

Does the other end read 0 ohms to ground?

 

[mike49504]

Yes 1 end is 0.4 ohms to ground on both resistors and the other end of both resistors have the same signal as pins 9 and10

 

[Perry Babin]

Were the 1266s new or used?

 

[mike49504]

brand new ordered them from allied electronics

 

[Perry Babin]

They don't appear to have enough gain. Do you have any other PNP transistors that you could install?

 

[mike49504]

I have the following transistors on hand

MPSA56
MPSA06
MPSA12
C1815
A1023
2SA935
2N4403
2N4401

just to name a few that i have on hand

 

[Perry Babin]

Try the a1023s.

 

[mike49504]

I put in the 1023's still have the same issue the signal looks the same

 

[Perry Babin]

How difficult would it be to remove the power supply FETs?

If it's not too difficult, remove them to see if the signal improves.

 

[mike49504]

Heres what i get with all the power supply fets removed. The probe was on 1 end of the gate resistor.

 

[Perry Babin]

What's the waveform on pin 9/10 of the 494 look like?

 

[mike49504]

The signal looks the same on pins 9 and 10 and also looks the same on the gate resistors .

 

[Perry Babin]

I'd suggest replacing the IC if...

none of the pins of the 494 have negative voltage

pins 13 and 14 of the 494 have 5v

 

[mike49504]

Ok pins 13 and 14 have 4.98 volts on them . So i will replace the 494 .

Should i put the A1266's back in or keep the 1023's ?

 

[Perry Babin]

There's really no reason to swap the 1023s out unless you don't have many in stock.

 

[mike49504]

Switched the 494 out to a new one . Same thing the signal looks the same and i have 4.94 volts on pins 13 and 14

 

[Perry Babin]

Post the voltage on all pins of the 494.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

 

[mike49504]

1:0
2:4.94
3:0.6
4:.03
5:1.48
6:3.71
7:0
8:13.38
9:5.70
10:5.70
11:13.37
12:13.37
13:4.94
14:4.94
15:4.94
16:0

 

[Perry Babin]

Is it possible that the photo isn't clearly showing the waveform?

The 5.70v DC seems to indicate that the output is normal.

There should be a square wave with a duty cycle that's ~50%. I can't see the bottom of the square wave. Is it there or is the bottom of the square wave almost non-existent?

 

[mike49504]

Its almost non existent .