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gehrig
Joined: 16 Apr 2008
Posts: 9
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 Posted: Wed Apr 16, 2008 7:40 pm Post subject: Need some advice repairing a CRT Black & White TTL |
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I recieved an arcade with a broken monitor for free. This is really my first attempt at repairing.
Monitor: Motorola XM501-10 (CRT: Black & White). TTL
Scenario:
When powering up the monitor, all that is visible is a bright horizontal line that is in the middle of the screen. So, this seems to be a vertical deflection problem.
I did replace some caps from a kit that I recieved. No change.
Fuses are OK.
I replaced 3 transistors on the the vertical output circuit. Q10, Q11, and Q12.
My +30, +73, +150 are ok.
According to repair manual.. and using my voltage readings, it says "possible shorted driver or open oscillator transistor." Well, I replaced those still no go.
Anyone have any suggestions? Am I on the right track?
Here are my voltage tests (in red).
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kuhurdler
Joined: 28 Dec 2006
Posts: 2580
Location: Overland Park, KS
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| Posted: Thu Apr 17, 2008 5:30 am Post subject: |
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| can you tell me what all you've replaced thus far? |
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gehrig
Joined: 16 Apr 2008
Posts: 9
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| Posted: Thu Apr 17, 2008 7:48 am Post subject: |
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Sure.. thanks for the reply.
On this circuit only Q10, Q11, Q12, C38, and C36. Off the top of my head, I can't remember what other caps I replaced (on other circuits) that I replaced. But, when I get home I can check the list.
Also, I noticed last night that my 30+ is not a bit high. Which I can adjust. It is at 33.5V.
I have checked D3 Diode out of circuit with my DMM and it appears to be working fine.
Oh... and I did notice last night that the voltages were dropping very slowly at many of my test points. |
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kuhurdler
Joined: 28 Dec 2006
Posts: 2580
Location: Overland Park, KS
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| Posted: Thu Apr 17, 2008 12:26 pm Post subject: |
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| Test Q13 with the diode tester. |
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gehrig
Joined: 16 Apr 2008
Posts: 9
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| Posted: Thu Apr 17, 2008 2:02 pm Post subject: |
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I have tested it before with a diode tester. It passes the tests.
I think I really need to test the transformer tonight. |
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silv
Joined: 07 Jun 2007
Posts: 57
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| Posted: Thu Apr 17, 2008 3:41 pm Post subject: frank |
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| Did you try to resolder probably cold solders. |
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gehrig
Joined: 16 Apr 2008
Posts: 9
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| Posted: Thu Apr 17, 2008 5:52 pm Post subject: |
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I have had these issues before I touched anything. Here is an update with transformer readings:
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kuhurdler
Joined: 28 Dec 2006
Posts: 2580
Location: Overland Park, KS
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| Posted: Thu Apr 17, 2008 9:11 pm Post subject: |
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| Check C41, R81 and R66. |
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gehrig
Joined: 16 Apr 2008
Posts: 9
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| Posted: Fri Apr 18, 2008 7:40 am Post subject: |
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Will do..
What kind of resistor is R81? I am not familiar with that symbol. What is the deal with the Ohms symbol and the label "cold"?
Edit: Also, I noticed that there is 100k pot between R56 and 73+ that is not on the schematic (it is on the repair manual however). The pot is labeled vertical size. Adjusting seemed to help a lot of my test points on the left side of the circuit shown. Though, I didn't have time last night to check all of the test points. |
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kuhurdler
Joined: 28 Dec 2006
Posts: 2580
Location: Overland Park, KS
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| Posted: Fri Apr 18, 2008 10:31 am Post subject: |
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| you already have a vert size pot on the bottom side of the schematic... how odd. could you send me the repair manual? I'm starting to question the accuracy of your schematic. |
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