Re: Speaking of Vectorbeam/Cinematronics...

Banded end is cathode.
On Jan 18, 2011 2:26 PM, "John Robertson" <pinball@telus.net> wrote:
> John Huie wrote:
>> I've sworn off working on this one but I'm curious what those "in the
>> know" think.
>>
>> I've got a Cine monitor that works but is missing the vertical
>> deflection. I tested the deflection transistors on the heat sinks and
>> two of them were bad. Upon replacing them, it behaved exactly the
>> same way but one of those previously bad transistors heats up veeery
>> quickly. So hot that you don't want to touch it.
>>
>> If this were your monitor, what would you suspect as the cause for
>> overheating one of those transistors? I've double checked to be sure
>> it's not grounded out. I'm thinking the thing should just be sent off
>> to someone who has more background than myself but it is interesting
>> to me to hear your thoughts anyway.
>>
>> John
>>
> Hi John,
>
> Try my voltage checks that I have just posted earlier today (Tech Tips -
> Vectorbeam...). Remember to unplug the yoke for doing these tests to
> avoid damaging components.
>
> Do you understand what the Diode Test is? Rather simple - most modern
> digital multimeters have a diode test built in. The switch position
> shows a diode... The negative lead is often the anode (banded end of a
> diode) and the positive lead is then the cathode (other end) - if you
> put the meter leads across a good diode you should see something like
> 0.3xx (Germanium ) to 0.8xx volts (Silicon diodes) when the leads are
> one way and open when the leads are reversed.
>
> Power OFF!!
>
> Now if you take the leads and check a transistor you will find that if
> the leads are across the Emitter and Collector of a transistor you
> should have roughly 0.7xx V or higher (open is often the case - a meter
> reading being blank or whatever the meter shows for not connected),
> anything around 0.0xx is likely a shorted transistor. Now find the Base
> of the transistor and put the leads between the Base and Collector
> (reverse leads if no reading) - should be around 0.7xx V, and repeat for
> the Base and Emitter (roughly the same 0.7xx voltage). Sometimes you
> will have a lower reading and you may have to remove the transistor to
> see if the rest of the circuit is causing anomalous readings (small
> value resistor for example) - if it checks OK out of circuit then it is
> /probably/ OK and can be put back.
>
> Check ALL transistors and diodes for shorts or weird readings - with
> these monitors the readings should be similar between the two channels
> (X &Y deflection) comparable transistor/diodes.
>
> Or you can send the chassis off to someone to fix - I'm sure there may
> be someone close to you (I'm in Canada) that can help.
>
> 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"
>

---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Tue Jan 18 15:54:28 2011