Re: Testing vectorbeam monitors.

HAHAHA oops! Sorry!

On Fri, Feb 1, 2013 at 12:23 PM, Pat Danis <patdanis@verizon.net> wrote:
> Grant:
>
> If you look in the introductory pages, you will see John's name mentioned in
> the acknowledgements. I think he also hosts this manual on his site.
>
> Pat
>
>
> On 2/1/2013 7:52 AM, Grant Thienemann wrote:
>>
>> This might be helpful for you!
>>
>>
>> http://www.outerworldarcade.com/arcade/cinematronics/manuals/cine_faq_v096.pdf
>>
>> -Grant
>>
>> On Fri, Feb 1, 2013 at 3:14 AM, John Robertson <pinball@telus.net> wrote:
>>>
>>> Being a bit annoyed that I have no test procedures, nor theory on how
>>> these
>>> Vectorbeam monitors work I started playing with one today that was giving
>>> me
>>> excessive current draw on the power lines. So I've been working on a test
>>> procedure using a few of my shop tools and thought others may be
>>> interested
>>> an can also expand on the process.
>>>
>>> 1) you can power up these monitors with the YOKE unplugged with little
>>> risk
>>> to damaging any output transistors - this static test allows you to
>>> service
>>> the VH section on the bench if you can provide the required +/-25VDC. I
>>> use
>>> a dual regulated power supply and limit the current to 0.2A per supply
>>> and
>>> get full HV output with a known to be good chassis.
>>>
>>> 2) the deflection circuits on these monitors are basically stereo
>>> differential transistor amplifiers so - if you unplug the LF13331 you can
>>> feed into the inputs of the two op-amps an audio signal of -50db or so @
>>> 1000hz and then be able to trace the audio signal through the two amp
>>> sections to find problems. I'm using a heathkit Audio Signal Generator
>>> for
>>> this, you can set the output signal from 0 to 100khz, and
>>> -50/40/30/20/10/0db adjustable.
>>>
>>> Need to test if the feedback resistor can be lifted and see what happens
>>> to
>>> the input differential pair, I suspect that will aid in following the
>>> audio
>>> path.
>>>
>>> Note too that if you use a current limiting power supply you can test the
>>> amps by unplugging both the 13331 AND the output transistors - with no
>>> input
>>> signal there is little risk (is any) of damaging the driver transistors,
>>> as
>>> long as you limit the current ot around 200ma max at +/- 25VDC.
>>>
>>> I'd love to find a service manual on this sort of audio amp, but hunting
>>> online today didn't lead to anything useful other than theory - and tha
>>> twas
>>> more time than I wanted to spend on troubleshooting these.
>>>
>>> I'll try and report more tomorrow as I dig further into this chassis
>>> which
>>> currently is pegging the am-meters on the -27 supply without any
>>> obviously
>>> shorted devices.
>>>
>>> John :-#)#
>>>
>>> --
>>> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
>>> (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
>>> www.flippers.com
>>> "Old pinballers never die, they just flip out"
>>>
>>>
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>>> chris@westnet.com
>>
>>
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>>
>
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Received on Fri Feb 1 13:01:51 2013