orion XTR 900/2

[scampo77]

i cant understand where my power is going i cant find it anywhere.

i have 12v on the center leg of the power supply and 12v on the torridial transformer. i also have 12v on the first leg of Q44. and the 3rd leg of Q45.

other than this i cant find < .5v anywhere else and i cant see anything else burnt any ideas?

i have 2 big caps that are 3300uF 35v and when i put my ESR meter on them they start super high around 4 and over ~1 min it drops to .07. is this normal? what does this mean?

also i replaced the transistors in the blue boxes

 

[kjf]

any output from the 494?

 

[Perry Babin]

Post the DC voltage on 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:

 

[scampo77]

all legs are 0v

 

[Perry Babin]

What is the DC voltage on the thermal switch on the bottom of the board?

 

[scampo77]

its battery voltage on both sides ~13v

 

[Perry Babin]

There is an MPSA56 with its collector connected to pin 12. Post the DC voltage on all 3 legs.

 

[scampo77]

its Q44

E - 13V
B - 13V
C - 0V

and i just changed this one a hour ago

 

[Perry Babin]

There's an MPSA06 connected to the base of the A56. Post the voltage on it.

 

[scampo77]

the A56 at location Q44 is attached to a black strip thing with 8 pins on it that i have never seen before and i dont know what it is. the base (the middle leg) is attached to this thing. i tried to draw lines showing where everything goes to

MPSA06 location Q45

E - 0
B - 0
C - 13v

i just want to make sure that according to my picture that the emitter is on the left the base in the middle and the collector is on the right

 

[Perry Babin]

That strip is a a resistor network. It's 4 independent resistors, all the same value.

It doesn't appear that you're getting remote voltage. Follow the trace from the remote terminal to the resistor network to see where it's being lost.

 

[scampo77]

is it possible that i dont have a remote power? i dont have a terminal for it. the only thing i have is "remote gain" which is a female plug like a headphone jack.

 

[Perry Babin]

You have to have remote voltage connected to the 5-pin plug for it to power up. Look on the cover to see which terminal is remote.

 

[scampo77]

ok i figured out what was going on. i applied remote power and the second i do my power supply starts getting hot.

i am getting more action at my 494 now

1- 0
2- 0
3- 0
4- 0
5- 1.5
6- 3.4
7- 0
8- 10
9- 4
10- 4
11- 9.8
12- 9.8
13- 5
14- 5
15- 0
16- 0

 

[Perry Babin]

You should have all transistors clamped tightly to the heatsink when testing, especially in situations where transistors are heating quickly.

What are you using for a power supply?

Have you checked the output transistors to see if any are shorted?

 

[scampo77]

im using a 5A 13v PSU and i have the big resistor inline in the power in.

i never manage to measure the power supply or the outputs succsesfully when they are all in place. i never trust my readings. should i start pulling it apart?

they arent getting super hot like i have seen in the past where within a second i have smoke. over about 3 mins they are getting warm. im not sure if there is a difference

 

[Perry Babin]

Shorted transistors can be found without removing them?

What value resistor are you using?

 

[scampo77]

alright ill try but it looks the same as when i have tried in the past
leg 1-3 i get 60 ohm and all the others i get around 1M ohm this is only on the outputs and i get the same for all of them. im not sure if i can "close them" with the piece of wire and these numbers are so different from testing them individually. i guess i should look for something < 5 ohm?

im using a 5A PSU

and the resistor i dont know the size but i got it according to your website.

 

[ppia600]

Also check legs 2 to 3, one or more of them will be lower than the rest if not by much. Remove the lowest then check the others again. Of course they can sometimes still be damaged even if they read ok.