Re: A few WG6100 tips and tricks

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On 4/15/04 at 1:31 PM Scott Swazey wrote:

>Oh, Oh... I know this one. There is a 10 ohm resistor at the top of the
>pre driver stage that is open. I don't have a schematic so I can't tell
>you the part number. It's going to be connected to the MPSU transistors
>that feed the output stage. Ultimately, the pre driver stage is broken.

The 10 ohm resistors check out. I've even replaced them.

>So here's what happening... one side of the pre driver stage is open, so
>the output stage is biased to one side. This pushes the vectors off to
>one
>side and makes one of the the 1.5 ohm resistors really hot.
>
>Using a DVM, measure the voltage across each of the 1.5 ohm resistors in
>both AC and DC mode. you should see 5-30 volts of AC across either 1.5
>resistor, but you should see very little DC voltage across the 1.5
>resistors. On your 6100, one of the DC measurements will probably read
>greater than one volt in DC mode. Check all the resistors in the
>pre-driver stage (the MPSU transistors). In my case, all the transistors
>were fine, but one of the resistors was open.

I get less than 1v AC across both 1.5 ohm resistors. Both read less than 1v DC.

*sigh* :(

Any other suggestions before I just toss this deflection board aside and use another?

Brian

>-Scott
>
>PS The 6100 amp is a classic transcondunctance amp (Vin, Iout), so it's
>very simple to analyze. Or in the classic textbook terms: Current
>sampling, voltage mixing. :-) Extra credit: what's the correct Rload for
>testing without a yoke?
>
>-S
>
>At 09:45 PM 4/12/2004 -0400, you wrote:
>>Thanks for the tips. I happen to be juggling three repairs right now.
>>Here's a weird one for you:
>>
>>Installed both of Bob's kits (caps, transistors, extra parts) and the
>>LV2000. Turn game on, fires up, hear deflection chatter, but the spot
>>killer is on. All voltages are good. When I turn up the brightness, I get
>>a bright "rainbow" pattern on the lower half of the screen. Not vectors,
>>mind you. Just a bright horizontal rainbow effect.
>>
>>I've gone threw the FAQ and checked everything listed there. I've gone
>>over the deflection board for bad solder joints, checked and
>>quadruple-checked the chassis transistors for any kind of shorting (mind
>>you, I didn't check their output voltage), and checked all of the
>>connector/transistor socket connections for continuity.
>>
>>Any suggestions as to what I should next? Thanks for any help offered.
>>
>>Brian
>>http://www.orubin.com
>>
>>*********** REPLY SEPARATOR ***********
>>
>>On 4/12/2004 at 6:34 PM Joe wrote:
>>
>> >Just got done fixing several 6100's this week... and here's a few tips
>> >for everyone.
>> >
>> >1. Don't use NTE 10 watt 1.5 ohm resistors. You need audio grade or non
>> >inductive ones. One of these was on a board I got in and it was making
>> >wavy lines on the bottom half of the screen after all else was repaired.
>> >
>> >2. Replace ZD902 with 2 75v 1 watt zener diodes end to end. (Positive of
>> >one to negative of the other.) This will make a teepee sticking out of
>> >your board... But, guess what, NTE 150v one watt zener is several
>dollars.
>> >My fix will cost you under $.25 and last forever. The NTE part WILL
>fail.
>> >This fix was told to me by Rick Schieve. I can't take the credit.
>> >
>> >3. Use MPSU57 and MPSU07's in place of the MPSA56 and MPSA06
>> >(respectively) in the LV section. I HIGHLY recommend using the CEN-U07
>and
>> >CEN-U57 parts. They hold up just excellent - much better than the
>uniwatt
>> >packages! If you do this, again, the LV section will be bullet proof.
>This
>> >fix will cost you just a few $$$. The other upside of this is that when
>a
>> >deflection transistor fails and begins to draw too much current through
>> >the LV section, it will only blow the 15 ohm resistor. If you have an
>LV2k
>> >in there, I hope you have surface mount soldering equipment. If you
>order
>> >the transistors from me, I will throw in some free 15 ohm resistors, if
>> >you ask.
>> >
>> >4. Run your game a little bit smaller than full screen. By doing this,
>the
>> >deflection transistors won't need to work as hard. This means less heat
>> >and longer life.
>> >
>> >If you have anything to add, please do.
>> >
>> >JB
>> >
>> >
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>> >
>>
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>>
>>"We're all a bunch of spoiled brats, if you get right down to it. You
>just
>>want to buy the meat in the store, you don't want to see Bambi getting
>cut
>>up [laughs]. You want to protest fur walking around in your leather
>shoes.
>>You want to talk the environment as you drive around in your Hummer 2.
>>We're a study in contradictions, I think. The ultimate spoiled brats of
>>the world."- Uncle Eugene Jarvis, the creator of Defender, Stargate, and
>>Robotron
>>
>>
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Received on Thu Apr 15 17:41:37 2004