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Jamesp
Joined: 28 Mar 2011
Posts: 3
Location: Beaufort, SC
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| Posted: Tue May 03, 2011 6:10 pm Post subject: VNB horizontal & Vertical |
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Hello,
I have a Marquee 9500 VNB which is overdriving on the horizontal and underdriving vertical. This can be seen when an external hash pattern test signal is applied to the projector. This does follow the neck board and is not a o result of the signal from the vertical or horizontal deflection boards. This is on the 02-270340-02P VNB. Does anyone know what could cause this. I have changed out both Q12 and Q19 for a previous discrepancy and have done so again with no joy for the results. I am leaning toward Q17 since this is a replacement transistor and not the original called for in the schematic. As always I appreciate the assistance. It has been very useful in the past.
Thanks,
JP
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Tue May 03, 2011 6:23 pm Post subject: |
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has it always done this?
measure the voltages at the collectors of q21 and q17.
also look if you have the minus 5 volts at the base of the q17.
what is the type number of the q17 btw.
jantje has some vnb`s for sale in the buy and sell section.
since the mrf549 and mrf548 parts are very hard to find this is your safest bet.
_________________
1 answer always poses multiple questions.
marquee 9500ultra HD10L moome hdmi1.3 v3+ some mods.
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Jamesp
Joined: 28 Mar 2011
Posts: 3
Location: Beaufort, SC
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| Posted: Tue May 03, 2011 6:43 pm Post subject: VNB feedback |
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| dvh99 wrote: | has it always done this?
measure the voltages at the collectors of q21 and q17.
also look if you have the minus 5 volts at the base of the q17.
what is the type number of the q17 btw.
jantje has some vnb`s for sale in the buy and sell section.
since the mrf549 and mrf548 parts are very hard to find this is your safest bet. |
Thanks for the help... The 270340 board doesn't use the MRF 548 and 549 type transistors. It uses 2SA1538 and 2SA1539 for the most common Q13 and Q17 fixes. These are TO-126 package instead of the wafer style used in the older boards.
The Q17 in question is supposed to be a 2SA1539. Installed is a NTE2509 which has comparable specs but is questionable in my case. Sometimes reading the schematics and service manual do not give enough info to go off of.
I have a source still for my 549 chips. They are getting harder to find without ordering straight from China. I'll recheck the collector voltages. Thanks for the feedback.
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Tue May 03, 2011 6:57 pm Post subject: |
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beware of fake motorola mrf devices when ordering on ebay.
_________________
1 answer always poses multiple questions.
marquee 9500ultra HD10L moome hdmi1.3 v3+ some mods.
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