No more picture...power problem? (RESOLVED)

[meanbean]

In my infinite wisdom, I accidentally tripped over the wires that connects the adjuster board to the monitor board while my Hantarex Polo 33" monitor was powered on. (The adjuster board is the one that has all the trim pots for vertical/horizontal adjustments.)

[Jess--]

without the adjustment board connected the monitors sync circuit would have gone nuts.

check the horizontal output transistor (big transistor on the heatsink next to the HT transformer, usually BU508A or similar, quite often these blow when sync goes too high / low which shuts the monitor down

[Ken Layton]

Most monitors will be damaged if the remote board is not connected when the monitor is powered up.

[meanbean]

I will check your suggestion Jess--.  Do you think my problem could be with a bad flyback?  Although, it is not making any noise or sparking.  If it was bad, wouldn't  my symptoms be the same?

[Jess--]

it is more likely that the lack of control board pushed the horizontal sync beyond safe limits, this would cause too much current to be demanded. in most cases the transistor will fail before the flyback.

a failed transistor will result in NO signs of life other than the initial Degauss noise and possibly a ticking PSU (switched mode psu's tick when overloaded due to short circuit transistors)

[meanbean]

Jess-- :

[dabone]

It's a BDX53C



Heres the spec sheet on the NTE cross.

http://www.nteinc.com/specs/2300to2399/NTE2343.html


I don't think thats your hot.


Later,
dabone

[meanbean]

So, I went back to take another look after you said that dabone.

[censei]

you can purchase the original horizontal output transistor part # BU508A at www.mouser.com

[dabone]

Ok, now that you have found your hot, check to see if it's shorted first.

Later,
dabone

[meanbean]

Results from resistance test on transistors:

BDX53C:
 (+) collector to (-) emmiter: 4.55 kΩ
 (+) base to

[dabone]

Probably, but put in the original one, not the nte back in there.
(some people complain that the nte's have less quality control, and this is something I have seen in my pinball repairs)



Later,
dabone

[meanbean]

dabonoe: I will get a BU508A instead for the replacement HOT.

censei: Thanks for the info on where I can get a BU508A transistor.

I will report back my results once I have received and installed the replacement BU508A HOT. (crosses fingers)

[Jess--]

check that bu508A is the right one for your chassis, I only quoted that number as it seems the most common used by hantarex.

[SirPeale]

Results from resistance test on transistors:

BDX53C:
 (+) collector to (-) emmiter: 4.55 kΩ
 (+) base to  (-) collector: 1.745 kΩ
 (+) base to (-) emmiter: 7.3 kΩ

NTE2300:
 (+) collector to (-) emmiter:  0.5 Ω
 (+) base to  (-) collector:  305.9 Ω
 (+) base to (-) emmiter:  306.4 Ω

From these results, is it correct in stating that I would only need to replace the NTE2300 transistor?  Thanks for the help.

Why are you doing a resistance test, and not a diode test?

[meanbean]

I didn't have any diodes to perform a gain test.

[SirPeale]

I didn't have any diodes to perform a gain test.  I was under the impression that a resistance test a valid way to test a transistor.

Nope.  You want to look for the voltage drop.  A transistor is pretty much a mushed-together diode.  Let's see if I can find some docs on the matter...

http://www.kpsec.freeuk.com/components/diode.htm

[meanbean]

Thanks for the info Peale.