Author Topic: half a screen help  (Read 12588 times)

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Offline tautech

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Re: half a screen help
« Reply #25 on: September 10, 2014, 09:07:26 pm »
Have you downloaded the datasheets for the transistors in the H-Final amp?
Have you tested each transistor Hfe matches the datasheet?

Quote
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?
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Offline kjn4685

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Re: half a screen help
« Reply #26 on: September 10, 2014, 09:42:49 pm »
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.
« Last Edit: September 10, 2014, 09:50:44 pm by kjn4685 »
 

Offline tautech

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Re: half a screen help
« Reply #27 on: September 10, 2014, 10:01:18 pm »
Quote
2SC945 has a different pinout to 838.
That's why it wont work at all.

Remove transistors and test.
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Offline kjn4685

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Re: half a screen help
« Reply #28 on: September 11, 2014, 11:57:45 pm »
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.
 

Offline tautech

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Re: half a screen help
« Reply #29 on: September 12, 2014, 12:11:22 am »
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 ?
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Offline kjn4685

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Re: half a screen help
« Reply #30 on: September 12, 2014, 12:28:35 am »
No I do not anyone that has one
 

Offline kjn4685

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Re: half a screen help
« Reply #31 on: September 12, 2014, 12:45:43 am »
I went to p53 in oscilloscope pdf and I did that.
 

Offline tautech

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Re: half a screen help
« Reply #32 on: September 12, 2014, 01:00:18 am »
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.
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Offline kjn4685

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Re: half a screen help
« Reply #33 on: September 12, 2014, 01:18:30 am »
Yes there was spot on y and x mode. it was in the middle. It will not go any farther to left than middle.
« Last Edit: September 12, 2014, 01:23:32 am by kjn4685 »
 

Offline kjn4685

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Re: half a screen help
« Reply #34 on: September 20, 2014, 12:47:42 am »
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.
« Last Edit: September 20, 2014, 01:45:17 am by kjn4685 »
 

Offline kjn4685

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Re: half a screen help
« Reply #35 on: September 20, 2014, 03:11:19 am »
here is a pic of 4 more transistors that I have a suspension might be a problem. what you guys think.
lou
« Last Edit: September 20, 2014, 04:55:16 am by kjn4685 »
 

Offline tautech

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Re: half a screen help
« Reply #36 on: September 20, 2014, 04:35:12 am »
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?
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Offline kjn4685

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Re: half a screen help
« Reply #37 on: September 20, 2014, 04:57:12 am »
q658 q659 q660 q661 these are to-126
 

Offline kjn4685

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Re: half a screen help
« Reply #38 on: September 20, 2014, 05:07:47 am »
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.
 

Offline tautech

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Re: half a screen help
« Reply #39 on: September 20, 2014, 05:09:47 am »
Which schematic are they shown in?????
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Offline kjn4685

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Re: half a screen help
« Reply #40 on: September 20, 2014, 05:16:42 am »
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
 

Offline kjn4685

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Re: half a screen help
« Reply #41 on: September 20, 2014, 05:17:56 am »
# 6 oscillscope pdf
« Last Edit: September 20, 2014, 05:39:09 am by kjn4685 »
 

Offline tautech

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Re: half a screen help
« Reply #42 on: September 20, 2014, 09:15:30 pm »
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.
« Last Edit: September 20, 2014, 10:20:25 pm by tautech »
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Offline tautech

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Re: half a screen help
« Reply #43 on: September 20, 2014, 10:26:45 pm »
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.
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Offline kjn4685

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Re: half a screen help
« Reply #44 on: September 21, 2014, 06:17:15 pm »
I have pulled them and when I tested them they have no hfe. So I have to change them and order.
 

Offline tautech

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Re: half a screen help
« Reply #45 on: September 21, 2014, 07:25:15 pm »
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.

Quote
q658 c1306 q659 c3423 q660 c3423 q661 c 1306.

2SC1306 Hfe 25-200, 2SC3423 hFE classification O: 80 to 160, Y: 120 to 240
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Offline kjn4685

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Re: half a screen help
« Reply #46 on: September 22, 2014, 09:09:09 pm »
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.
« Last Edit: September 23, 2014, 03:03:56 am by kjn4685 »
 

Offline tautech

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Re: half a screen help
« Reply #47 on: September 23, 2014, 08:43:21 am »
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.

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Offline kjn4685

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Re: half a screen help
« Reply #48 on: September 23, 2014, 11:22:07 pm »
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.
« Last Edit: September 25, 2014, 12:46:22 am by kjn4685 »
 

Offline tautech

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Re: half a screen help
« Reply #49 on: September 25, 2014, 01:09:16 am »
Have you correctly identified the 4 output transistors in your scope (q658 q659 q660 q661) ?
Are they TO-220 or TO-126?
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