Re: Black Widow Video Problem

By the way,

Why not buy the scope? Any working Tektronix scope is fine for our
purpose. The one thing to look for is XY mode, but most of them have
this. Having a scope changes your outlook on electronic circuits in a
magnificent way, being able to see what is going on in stead of guessing
or shotgun repairing.. It is not complicated either. For example have a
look at this videos:

http://www.youtube.com/watch?v=lAas4RUUC5U
http://www.youtube.com/watch?v=OFGm-Pel4Hg

A recommended, cheap model would be a 465 or 465B, a 45x, or the newer
(90's that is!) 22xx series. Almost all other brand cheap, old, scopes
are trash.

- Mendel

On 31-1-2012 22:29, Mendel Pearl wrote:
> You can't scope the output of the DAC pin 18 since it is a current
> DAC. The first place where you can see the signal as a voltage swing
> is at the output of the opamp directly following the DAC. This opamp
> is the I/V converter. The switches and 1495's are just to invert
> signals and correct bowing.
>
> - Mendel
>
> On 31-1-2012 22:17, Maxstang wrote:
>> Great suggestion Bill! I'll borrow a scope.. One of these days I'll
>> be needing to buy one of those! -M
>>
>> On Jan 31, 2012, at 12:48 PM, wboucher6@cogeco.ca wrote:
>>
>>> If you have a scope, you could connect it in X-Y mode right to the
>>> 6012 DAC chip outputs (pin 18) and see if the image
>>> looks okay there. If yes, then try again after the B10/E10 switches
>>> just before the 1495's. The idea here to narrow
>>> down which section to focus on.
>>>
>>> Bill Boucher
>>>
>>>>
>>>> Thanks Douglas! That's an excellent suggestion about A/B11's
>>>> output. I'd forgotten that detail…
>>>>
>>>> I checked the resistors after I switched the chip/socket at C12 and
>>>> looked at the voltages and chip activity with a
>>>> probe afterward and it looked fine. A/B11 also seems to be making
>>>> the right noises (with the probe) but I do know
>>>> from experience that they can have strange effects as they die (had
>>>> a Tempest once with a completely mirrored image
>>>> and it was the 1495. )
>>>>
>>>> The Y pot looks original. I'll meter it and see what I see. I get
>>>> what appears to be y collapse or perhaps complete
>>>> fold over if I adjust the pot too far in either direction. Within
>>>> the small range of pot movement where there's no
>>>> collapse, the Y image can be adjusted larger and smaller…if only a
>>>> little bit. -M
>>>>
>>>>
>>>> On Jan 31, 2012, at 10:30 AM, Douglas Gauck wrote:
>>>>
>>>>> It does look like a Y axis problem. My question was how the X
>>>>> correction coming out of A/B11, going into your new
>>>>> main Y axis C12 could affect the output.
>>>>> Since it's socketed, you can pull out C12 and then check all the
>>>>> resistors around it in circuit - all that voltage
>>>>> in the area could have toasted one.
>>>>> You should be able to adjust Y size from limit to limit without
>>>>> collapse. Or do you mean shrink?
>>>>>
>>>>> Since there's been prior work done on the board (and the pots are
>>>>> often abused) is it Y size the correct 10K?
>>>>>
>>>>> -Douglas
>>>>>
>>>>>
>>>>> On Jan 31, 2012, at 12:37 PM, Malcolm Mackenzie wrote:
>>>>>
>>>>>> Thanks Douglas.
>>>>>>
>>>>>> The MC1495 at C12 has been socketed and replaced by me. That
>>>>>> chip had been socketed before, but the contacts were
>>>> shorted under the socket. I replaced the socket and chip and
>>>> that's how I got the video to come up. I haven't
>>>> replaced C11 as this problem appears to be in the Y channel, but
>>>> I'll check into it.>>
>>>>>> As far as I understand the pincushion correction 1495s won't
>>>>>> cause this problem. I'll try to piggyback a new one on
>>>> them to make sure.>>
>>>>>> One added note. I've noticed that the y-size pot has only a very
>>>>>> narrow range of adjustment. Too small and I have
>>>> y collapse, too large, and y collapse. In the very middle of
>>>> adjustment the pic stretches out to as it appears in the
>>>> pictures I posted. Don't know if this helps anyone pinpoint it.
>>>> -Malcolm>>
>>>>>> --- On Tue, 1/31/12, Douglas Gauck<douglas@gauck.com> wrote:
>>>>>>
>>>>>> From: Douglas Gauck<douglas@gauck.com>
>>>>>> Subject: Re: VECTOR: Black Widow Video Problem
>>>>>> To: vectorlist@vectorlist.org
>>>>>> Date: Tuesday, January 31, 2012, 5:49 AM
>>>>>>
>>>>>> The caps are just sauce for the goose; I'd say the next likely
>>>>>> cause is one of the MC1495Ls... at C12. I'm not up
>>>> to speed on how the others (A/B11 and A/B12) providing X and Y
>>>> correction factor in.>>
>>>>>> On Jan 30, 2012, at 11:19 PM, Maxstang wrote:
>>>>>>
>>>>>>> Thanks for the reply. TL082s have been checked and one replaced
>>>>>>> with no change. Voltages are good, but I
>>>> haven't replaced the caps yet.>> >
>>>>>>> On Jan 30, 2012, at 8:09 PM, Douglas Gauck wrote:
>>>>>>>
>>>>>>>> TL082 at D10 and/or D/E12?
>>>>>>>>
>>>>>>>> Also check the +/-15v and 6.8 volt supplies, and maybe give
>>>>>>>> them new caps?
>>>>>>>>
>>>>>>>>
>>>>>>>> On Jan 30, 2012, at 8:42 PM, Malcolm MacKenzie wrote:
>>>>>>>>
>>>>>>>>> Hi all. I've been working on a dead BW board and now have it
>>>>>>>>> at least showing video, but it's still distorted.
>>>> AVG chip and socket, and vector RAM and socket are good. Anybody
>>>> seen this before? It almost looks like vertical
>>>> fold over and the image does expand and contract along the y axis.
>>>> Self test video is similarly distorted but I don't
>>>> get any reported errors other than pokey problems. Any input is
>>>> appreciated. -Malcolm>> >>>
>>>>>>>>> Photos are here:
>>>>>>>>>
>>>>>>>>> http://i122.photobucket.com/albums/o263/maxstang289/IMG_2612.jpg
>>>>>>>>>
>>>>>>>>> http://i122.photobucket.com/albums/o263/maxstang289/IMG_2611.jpg
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Received on Tue Jan 31 17:41:40 2012