half a screen help

[tautech]

Have you downloaded the datasheets for the transistors in the H-Final amp?
Have you tested each transistor Hfe matches the datasheet?

I changed the transistor c838 to c945 and it still does not work.

Did you swap the leads for correct replacement?

You say :"it still does not work"
Do you mean the trace is still only half way across the display?

[kjn4685]

No I did not switch the leads. The scope does not work at all. The power led lights but there is nothing. Ok I am at fault I did not test for the hfe. Sorry how would you test in circuit or out of circuit.

[tautech]

2SC945 has a different pinout to 838.

That's why it wont work at all.

Remove transistors and test.

[kjn4685]

I have tested every transistor on that board and I got my screen back but only half a screen. Did one of the deflection plates blow. What you guys think.

[tautech]

Good. I believe the H-Final amp is OK.

We must now return to a previous post to eliminate a faulty sweep as the cause.
https://www.eevblog.com/forum/repair/have-a-screen-help/msg493043/#msg493043

Google "CRO horizontal sweep theory" for docs for greater understanding of the next step.

Can you get access to another scope ?

[kjn4685]

No I do not anyone that has one

[kjn4685]

I went to p53 in oscilloscope pdf and I did that.

[tautech]

I went to p53 in oscilloscope pdf and I did that.

In X-Y mode, where was the dot?
Did you have the Horizontal & Vertical position controls each at mid-range?

If you put a country flag in your forum profile there maybe somebody on the forum that is close to you and can help with a scope.

[kjn4685]

Yes there was spot on y and x mode. it was in the middle. It will not go any farther to left than middle.

[kjn4685]

I am back again I would like to know if I use nte 107 instead of 2sc1907 will it work. The net 107 has a vcbo of 30v CEO is 12v ebo is 3v now the 2sc1907 has vcbo is 30v CEO is 19v ceo 2 v. Can anyone help me.

[kjn4685]

here is a pic of 4 more transistors that I have a suspension might be a problem. what you guys think.
lou

[tautech]

I am back again I would like to know if I use nte 107 instead of 2sc1907 will it work. The net 107 has a vcbo of 30v CEO is 12v ebo is 3v now the 2sc1907 has vcbo is 30v CEO is 19v ceo 2 v. Can anyone help me.

Which part of the scope are they?
These transistors are not a very good match, but may be OK for test purposes.
BUT they have a different pin out !

here is a pic of 4 more transistors that I have a suspension might be a problem. what you guys think.

What Schematic # ? Which part of the scope circuit?
What are the transistor numbers so we can look at the schematic?

[kjn4685]

q658 q659 q660 q661 these are to-126

[kjn4685]

q658 2sb1109c q658 sd1109c q660 2sd1609c q661 2sb1109c This is what is in the s/m. Now on the broad is q658 c1306 q659 c3423 q660 c3423 q661 c 1306.

[tautech]

Which schematic are they shown in??

[kjn4685]

Yes you are right Tautech sorry if I spelled it wrong  . these trans are above the others they are in a group of 4 they are to-126 package but the pin outs are the same as the broad here is the pic

[kjn4685]

# 6 oscillscope pdf

[tautech]

q658 q659 q660 q661 these are to-126

Are these not on the PCB?
Have you have missed them !!!

These are the H Final output stage transistors that have been the most likely MAIN suspects from the start.

REMOVE each and test.

[tautech]

here is a pic of 4 more transistors that I have a suspension might be a problem. what you guys think.

These are the Vertical final output amp transistors and are not related to your problem.

[kjn4685]

I have pulled them and when I tested them they have no hfe. So I have to change them and order.

[tautech]

I have pulled them and when I tested them they have no hfe. So I have to change them and order.

That cannot be correct, you have "half a screen". Get the datasheets to be sure you test correctly.

q658 c1306 q659 c3423 q660 c3423 q661 c 1306.

2SC1306 Hfe 25-200, 2SC3423 hFE classification O: 80 to 160, Y: 120 to 240

[kjn4685]

When I test the transistors the shows pnp or npn then it gives the pin order like ecb then the meter shows the letter k and nothing else when testing in the hfe mode. So what does that mean.

[tautech]

When I test the transistors the shows pnp or npn then it gives the pin order like ecb then the meter shows the letter k and nothing else when testing in the hfe mode. So what does that mean.

I do not know what the K means on your tester.

Important. Read carefully.

The schematic (6) shows Q658 & Q661 as PNP and Q659 & Q660 as NPN

The 2SC3423 is NPN but TO-220 package (Q659 & Q660)
The 2SC1306 is NPN and TO-126 package (Q658 & Q661) Should be PNP

Please check part numbers again, this is very wrong.
There must be 2 PNP and 2 NPN.

We must identify these 4 transistors correctly.

Should also be the same package for all 4 transistors.

[kjn4685]

If I could get another scope does it have to be a analog or digital.The four transistors are just what the parts list shows. Any further I do not want to say or do.

[tautech]

Have you correctly identified the 4 output transistors in your scope (q658 q659 q660 q661) ?
Are they TO-220 or TO-126?