Need help finding a schematic for a Quasar TV/VCR combo

[mikeydude]

Model # VV8220
Chassis # KM-201

TV stopped working (no picture, sound still worked)
I found a few burned resistors (value?), an open power resistor, and I can't
identify one other part.

I need help getting the values of the following part numbers on the PCB:
R802
R804
R1002
D851

More details:
1) The part labeled D851 has one side connected to the main power (120V),
and the other side to the degaussing coil. It is a rectangular plastic box
with two leads coming out the bottom.
When I measured it with an analog VOM, it gave the same reading with the
leads connected either way. It wasn't open or shorted.
What is this part?

2) Both 800 series resistors that are bad are connected after the bridge
rectifier and before the STR30130 voltage regulator.
Could it be just a voltage spike that caused it, or is there something else
I should look for?
(A partial schematic I drew is available via e-mail if you need a more
accurate description of the circuit. Also posted a message with schematic
attached in "alt.binaries.schematics.electronic")

Thanks in advance for any help you can give,
-Mike

 

[Jerry G.]

Try any of the parts distributors for Panasonic, or Matsuchita. These are
copyright material, and they will not give out photocopies without written
permission.

--

Jerry G.
======


Model # VV8220
Chassis # KM-201

TV stopped working (no picture, sound still worked)
I found a few burned resistors (value?), an open power resistor, and I can't
identify one other part.

I need help getting the values of the following part numbers on the PCB:
R802
R804
R1002
D851

More details:
1) The part labeled D851 has one side connected to the main power (120V),
and the other side to the degaussing coil. It is a rectangular plastic box
with two leads coming out the bottom.
When I measured it with an analog VOM, it gave the same reading with the
leads connected either way. It wasn't open or shorted.
What is this part?

2) Both 800 series resistors that are bad are connected after the bridge
rectifier and before the STR30130 voltage regulator.
Could it be just a voltage spike that caused it, or is there something else
I should look for?
(A partial schematic I drew is available via e-mail if you need a more
accurate description of the circuit. Also posted a message with schematic
attached in "alt.binaries.schematics.electronic")

Thanks in advance for any help you can give,
-Mike

 

[mikeydude]

Thanks for your reply.
I was not asking for an illegal copy of the schematic.
I will buy a schematic if that is necessary.
In reality, all I need is someone that has a schematic to help me identify a
few parts.
Everything checks out except R804 and D851

Thanks,
Mike

 

[Graham W]

Thanks for your reply.
I was not asking for an illegal copy of the schematic.
I will buy a schematic if that is necessary.
In reality, all I need is someone that has a schematic to help me
identify a few parts.
Everything checks out except R804 and D851

D851 is certainly not a diode and almost certainly not broken,
you'll be glad to hear! It is a PTC thermistor to control the de-gauss
current through the de-gauss coils. However, there are usually three
legs to this device so check again to see if there's another connection.

What are the two rectangular things you have drawn - one has RL010
in it and the other a diode symbol? Are there further circuit connections
to those two which you haven't indicated?

 

[mikeydude]

Thanks for your post.
I was concerned about D851. I'm glad to hear it is a thermistor.
I unsoldered it from the board, so I'm sure there are only two leads coming
from it.
There are some markings on it, and I remember 050K being one of them, if
that's any help.

As far as your questions:
RL010 is a relay which turns the main power on/off. (I only traced out the
leads connected to the circuit in question.)

D1001 - I'm pretty sure it is a rectifier which feeds another (lower
voltage?) circuit. It looks like a small IC with 4 legs.
The symbol I drew is from the PCB diagram. (I started to trace out the rest
of that circuit too, since the PCB had been hot there, but I didn't since
the components checked out ok).

Really then, the only ID I need now is for R804. It was too badly burned to
ID.
It looks like a 1/2 watt resistor.
R802 is also bad, but it is a power resistor - 180ohm, 3watt.

Thanks,
-Mike
(P.S. I checked out your website. We have a lot of similar interests!)

 

[Franc Zabkar]

D851 is certainly not a diode and almost certainly not broken,
you'll be glad to hear! It is a PTC thermistor to control the de-gauss
current through the de-gauss coils. However, there are usually three
legs to this device so check again to see if there's another connection.

PTCs come in 3-pin and 2-pin versions.

See http://www.wagner.net.au/Catalogue/03_02.pdf

What are the two rectangular things you have drawn - one has RL010
in it and the other a diode symbol? Are there further circuit connections
to those two which you haven't indicated?

- Franc Zabkar

 

[Franc Zabkar]

Model # VV8220
Chassis # KM-201

I need help getting the values of the following part numbers on the PCB:
R802
R804

More details:

2) Both 800 series resistors that are bad are connected after the bridge
rectifier and before the STR30130 voltage regulator.
Could it be just a voltage spike that caused it, or is there something else
I should look for?

An STR30130 datasheet is available from http://alldatasheet.com and
from http://www.nteinc.com/specs/1700to1799/NTE1776.html.

Before worrying about your resistors, I would test the regulator. Pins
2,3,4 are the B,C,E of an NPN Darlington pair. A DMM diode test should
show two diode drops between pins 2 and 3, and between pins 2 and 4.
Pins 3 and 4 should test open in one direction and as a diode in the
reverse direction. The resistances in the application circuit are R802
= 2.2 ohm, R804 = 12K.

Are you sure you have drawn R806 and R807 correctly? AFAICT, pin 1
should connect to ground.

(A partial schematic I drew is available via e-mail if you need a more
accurate description of the circuit. Also posted a message with schematic
attached in "alt.binaries.schematics.electronic")

Thanks in advance for any help you can give,
-Mike

- Franc Zabkar

 

[mikeydude]

Where to start...
First, thanks for the post and the link to the datasheets.
Second... the reply.
----------------------------------------------------------------------------
--------------------------------------------------------

The resistances in the application circuit are R802 = 2.2 ohm, R804 = 12K.

R802 is a power resistor with the value printed on it. 5.6 ohm, 3 watt.
R804 is burned and unreadable, but it has a value of 11.36k ohms, so I
replaced it with a 12k resistor after reading your post.
----------------------------------------------------------------------------
---------------------------------------------------------

Are you sure you have drawn R806 and R807 correctly? AFAICT, pin 1 should

connect to ground.

One side of R806 (220k) should connect directly to pin 2 of the regulator,
the other side of the resistor is to ground.
R807 is correctly drawn. It is a fairly low resistance (39 ohms). Pretty
sure the value is correct. The colors read: orn/wht/blk/gold/wht.
----------------------------------------------------------------------------
---------------------------------------------------------

Before worrying about your resistors, I would test the regulator. Pins
2,3,4 are the B,C,E of an NPN Darlington pair. A DMM diode test should
show two diode drops between pins 2 and 3, and between pins 2 and 4.
Pins 3 and 4 should test open in one direction and as a diode in the
reverse direction.

Testing between pins 2 & 3, it reads like a diode with the cathode on pin 3.
This seems correct from what I see in the datasheet. Shouldn't this show
up under test as a single base-collector junction?
It looks like both collectors of the Darlington pair are connected.
Testing between pins 3 & 4 also reads like a diode with the cathode on pin
3. Seems ok.
Testing between pins 2 & 4 reads like a diode, but with higher resistance.
Consistant with a two diode drop, I would think.

Appreciate the help,
-Mike

 

[Franc Zabkar]

Where to start...
First, thanks for the post and the link to the datasheets.
Second... the reply.
----------------------------------------------------------------------------
--------------------------------------------------------

R802 is a power resistor with the value printed on it. 5.6 ohm, 3 watt.
R804 is burned and unreadable, but it has a value of 11.36k ohms, so I
replaced it with a 12k resistor after reading your post.
----------------------------------------------------------------------------
---------------------------------------------------------
connect to ground.

One side of R806 (220k) should connect directly to pin 2 of the regulator,
the other side of the resistor is to ground.
R807 is correctly drawn. It is a fairly low resistance (39 ohms). Pretty
sure the value is correct. The colors read: orn/wht/blk/gold/wht.
----------------------------------------------------------------------------
---------------------------------------------------------

Testing between pins 2 & 3, it reads like a diode with the cathode on pin 3.
This seems correct from what I see in the datasheet. Shouldn't this show
up under test as a single base-collector junction?

Yes, you're right. Sorry, brain fart.

It looks like both collectors of the Darlington pair are connected.
Testing between pins 3 & 4 also reads like a diode with the cathode on pin
3. Seems ok.
Testing between pins 2 & 4 reads like a diode, but with higher resistance.
Consistant with a two diode drop, I would think.

It seems that you may be lucky and that your regulator has survived.
Perhaps R802 protected it. I'd be checking the load (HOT, FBT) for
shorts.


- Franc Zabkar

 

[mikeydude]

It seems that you may be lucky and that your regulator has survived.
Perhaps R802 protected it. I'd be checking the load (HOT, FBT) for
shorts.


- Franc Zabkar

I will check the load.

Thanks, Franc!
And thanks to all who helped!

-Mike