What does +3v3a mean in a schematic

[srinath]

OK by process of elimination - I think -

The problem has to be in D453, r453, c465, r454, or d458uz5v1.

Why ?

I got 5.5v in pin 4, fed by the other side of the rectifier diode bridge, and that is regulated by the 7806 to 6v I believe.

The d453 etc is in the line straight off the fuse.
I will yank that out and see what it does to the voltage - or I may pull d458 first since the short is to ground.
Maybe also I need to look for a solder bridge, though the solder was all stock factory in that board.
Anyway your ideas welcome too.
Cool.
Srinath.

[srinath]

I'll pull d458 out and see if the voltage @ pin 4 gets back to 6v dc.
If not, the next one would be the r454 followed by c465.
I think one if those has shorted to ground and got the voltage out from 7806 transistor to not get to 6v.
Cool.
Srinath.

[gmphadte]

Do noy pull out any zeners from the circuit e.g. d458. U will damage the circuits.

Gajanan Phadte

[tauro0221]

Hi,
My advice is now to check for a short or a low resistance value to ground using the ohmmeter. I would check the resistance to ground at the point between R455 and C466. The D455 and D457 will isolate the reading from the transformer. Check the resistance and post the reading. D453 it is not the problem because it is follow by R453 4700 ohms resistor in series too high to loaded the PS. At this point you have to be careful because the IC451 feed voltage to the micro.

[srinath]

Tauro0221: The r455-c466 junction to ground flashed a 120 ohm or so and went back to open. Sort of like a capacitor would.

Gmphadte: How would I damage it ? from heat ? I anyway would replace it with a new one. Desoldering takes more heat than soldering.

Cool.
Srinath.

[gmphadte]

No need for replacing the zener. U will damage if u remove and power on the circuit.

If u have voltage at pin 4 (5.5V, maybe 5.8V without load) and pin 2(5.1V), then look for the other circuit where from pin 1 returns. This pin 1 will be high(some + voltage near 5V) only when the power good detection and reset circuit works, and then only the relays will remain on.

Gajanan Phadte

[tauro0221]

Hi,
That means that there are no shorts. We need to go back. Check the resistance for the IC451 output pin to ground. Remove fuse F453 and check resistance from the fuse load side to ground and from T451 pin 2 to ground. Also check resistance across capacitor C462. Post reading.

[srinath]

Tauro0221: I will get that checked tonight.

Gmphadte: I got these readings @ cp458 - Pin 1 was 0 vdc, 2 was 2.82 vdc, and 4 was like 5.5 vdc. Now I got that reading without anything connected to 458.

Ok If removing zener diode and powering up is bad, then I could replace it with a new one and try powering it up ?
Anyway I'll let you guys - Tauro in particular :-), tell me what to do, you have been great. What a learning experience this has been.

Cool.
Srinath.

[tauro0221]

Hi,
just in case one more resistance check. With the fuse F453 remove check the resistance of the transformer winding between pin 1 and 2. Post the reading.

[srinath]

OK cool.
Srinath.