Re: No Video on Lisa 2/5

Excellent news! I've let my friend know---I bet he'll be pleased to hear about it. --Tom

On Sunday, February 25, 2018 at 1:58:43 PM UTC, James Denton wrote:
>
> Hello all,
>
> I picked up a new BU406 for Q5, and tests on the new part showed expected
> results. After replacing Q5 and all of the trimpots, this Lisa has video!
>
> https://photos.app.goo.gl/fmi3IcroVgk4Pwql1
>
> This Lisa came with 3A ROMs but no screen kit video adapter, which threw
> me off initially since the dimensions were way off and there was some noise
> on the left side. After swapping out the board with one containing F ROMs,
> everything looks good!
>
> Thanks to everyone who chimed in for the assist.
>
> James
>
> On Wednesday, February 14, 2018 at 12:52:56 PM UTC-5, James Denton wrote:
>>
>> Hey Tom,
>>
>> Thought you might be interested to know that CR9 looked OK, but Q5 may be
>> problematic. The B<->E readings are near zero in both directions. The B<->C
>> readings look OK, however. There is at least one trimpot that needs to be
>> replaced (Vertical Hold). I don't have an easy way to test U1, as I don't
>> have a bench top power supply.
>>
>> Will keep you updated as this thing progresses.
>>
>> James
>>
>> On Tue, Feb 13, 2018 at 10:55 PM, James Denton <bust..._at_email.domain.hidden
>> <javascript:>> wrote:
>>
>>> Hi Jason, Tom,
>>>
>>> Thanks very much for the schematics and the advice. I’m almost done
>>> pulling the video card out and will likely wrap that up in the morning.
>>> I’ll take a look at Q5 and see if i see similar behavior. I’ll also check
>>> out the pots.
>>>
>>> Will keep you all posted. Thanks again.
>>>
>>> James
>>>
>>> On Tue, Feb 13, 2018 at 6:38 PM Tom Stepleton <step..._at_email.domain.hidden
>>> <javascript:>> wrote:
>>>
>>>> Sorry---correction, my friend told me to investigate Q5, not Q9. (Which
>>>> was fine, although you couldn't tell for sure without desoldering
>>>> it---depending on the kind of fault, a broken Q5 and a broken CR9 could
>>>> both have produced the reading we were seeing when we were testing CR9 in
>>>> circuit.)
>>>>
>>>> And just in case it wasn't clear---we investigated the diodes and
>>>> transistors in circuit but not the *board* in circuit---we had to pull
>>>> the board out of the Lisa to get access to anything :-)
>>>>
>>>> --Tom
>>>>
>>>>
>>>> On Tuesday, February 13, 2018 at 11:20:46 PM UTC, Tom Stepleton wrote:
>>>>>
>>>>> Worth noting that Bitsavers has an original Apple schematic online as
>>>>> well:
>>>>>
>>>>>
>>>>> http://bitsavers.informatik.uni-stuttgart.de/pdf/apple/lisa/hardware/050-4012-E_Video.pdf
>>>>>
>>>>> The one Jason linked to could be just as good, although I seem to
>>>>> remember some revision differences or errors on the one for the Lisa PSU.
>>>>>
>>>>> Now... just last Saturday I watched a friend---who is very well-versed
>>>>> in Apple video systems of that era---diagnose a broken Lisa video board.
>>>>>
>>>>> For this one too there was no video at all---and curiously, when we
>>>>> went to extract the video board to investigate, there was no 'pop!' from
>>>>> discharging the anode. Based on these symptoms, my friend told me to put a
>>>>> diode tester over all of the diodes on the board (in circuit---not
>>>>> extracting anything) as well as on the transistor Q9. Sure enough, CR9 had
>>>>> failed closed. Friend concluded that the IN4936 was maybe a bit underrated
>>>>> for the job.
>>>>>
>>>>> As it turned out, we had an analog board from a dead Mac that we could
>>>>> cannibalise (the diode it uses in the same role is larger in rating and in
>>>>> size), and sure enough, it worked. Maybe someday I'll have the electronics
>>>>> skills my friend has, but it'll probably be a while before I do!
>>>>>
>>>>> My friend supposed that CR9 might be a common failure point for these
>>>>> video boards---it would be interesting if you found the problem on your
>>>>> board as well.
>>>>>
>>>>> --Tom
>>>>>
>>>>> On Tuesday, February 13, 2018 at 12:49:20 PM UTC, compu_85 wrote:
>>>>>>
>>>>>> I'd start with the video card (after swapping the power supplies
>>>>>> around). If you look at the schematic you'll see the width adjustment pot
>>>>>> at the top of the board has the 28v output from the regulator on it. Begin
>>>>>> there... no B+, no picture.
>>>>>>
>>>>>> http://www.freeinfosociety.com/electronics/schemview.php?id=1424
>>>>>>
>>>>>> -J
>>>>>>
>>>>>> On Mon, Feb 12, 2018 at 11:34 PM, James Denton <bust..._at_email.domain.hidden>
>>>>>> wrote:
>>>>>>
>>>>>>> Hello all,
>>>>>>>
>>>>>>> I recently picked up a Lisa 2/5 with known memory issues that I
>>>>>>> managed to resolve relatively quickly with known-working cards. When I
>>>>>>> power up the machine, I hear the beeps that indicate all tests passed and
>>>>>>> it's waiting for a boot disk, but there's no video at all on the screen. I
>>>>>>> moved the entire card cage to my other chassis and confirmed working video
>>>>>>> output there. While I do see some slight mirroring on the left side of the
>>>>>>> screen, and the picture seems a little narrower, I believe it may be due to
>>>>>>> the 3A ROMs installed on this board.
>>>>>>>
>>>>>>> Where is a good place to begin troubleshooting the lack of video
>>>>>>> output on this Lisa? Should I simply look to recap/rebuild the analog board
>>>>>>> or is there something that can be looked at before taking that on?
>>>>>>>
>>>>>>> Thanks in advance,
>>>>>>> James
>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Jason Perkins
>>>>>> 313 355 0085
>>>>>>
>>>>> --
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