Re: Tempest twisting images...

Found the problem. Turns out the replacement XY driver board I had
left (from my parts stock) is a version P327 with the input
protection circuit. I found that this circuit was the cause of the
twisting by hooking my scope to the inputs of Q600 and Q700 and
getting the same twisting, but not at the X & Y outputs on the
motherboard. Hence something was a problem in this circuit. Replaced
the two transistors Q804 & Q805, plus two of the diodes D806 & D808
(Germanium I think) with 1N914s.

Same problem. Poked around for another 1/2 hour...

Gave up and clipped R810 & R811 - inputs to the protection circuit -
and now the picture is fine.

As Tempest originally worked without the protection circuit I am
going to leave it disabled here - I suspect this circuit simply can't
handle the patterns that Tempest throws up, or the capacitors are too
low (88ufd instead of 100ufd, within spec +10/-20% for caps.). Still
it looks great and I have to move on...

I made a MPEG of the twisting image, if anyone wants a copy let me know.

John :-#)#

At 2:13 PM -0700 6/12/06, John Robertson wrote:
>Yes, I tried tightening the pins on the sockets. Now that I think of
>it the plug feels a little un-tight. I'll check stock to see if I
>have a plug assembly with better bite. I did do the exchange power
>transistor plug with the X transistors - the Y group won't reach -
>to make sure the problem wasn't on those two. Forgot to fully test
>the Y plug!
>
>Will come back with part two tomorrow when I get back to the shop -
>currently I'm in the warehouse digging around:
>http://flippers.com/TimeTravelWarehouse.htm
>
>There are a number of vector games there folks, good time to get
>good deals...bulk buys encouraged!
>
>John :-#)#
>
>At 9:58 PM +0100 6/12/06, simon wrote:
>>John
>>I had some strange image problems with bad Deflection transistor
>>sockets, check they are good.
>>Cheers
>>Simon
>>
>>----- Original Message -----
>>From: <mailto:pinball@telus.net>John Robertson
>>To: <mailto:vectorlist@vectorlist.org>vectorlist@vectorlist.org
>>Sent: Monday, June 12, 2006 8:39 PM
>>Subject: VECTOR: Tempest twisting images...
>>
>>Ok, I'm lazy enough, but has anyone seen a situation with a Tempest
>>monitor where the picture twists (+ Y axis) upon the display of the
>>TEMPEST name for a second? Rather interesting distortion, I
>>originally thought it was Q606 (2N3716) that was having life
>>issues, but no, replacing it didn't change this distortion, then I
>>tried the driver - MPUSU57 - again not the problem.
>>
>>Understand that I've re-capped the HV (stable voltages) and
>>installed the LV2000 kit - stable +/- B voltages. Grounds are
>>excellent, tried jumper wires to double check. Game seems happy
>>otherwise, no smoke...connectors all inspected and solder built up
>>on the monitor driver board pins as usual.
>>
>>There is also a twisting wave that appears in the picture on
>>various levels - only during play, not in the attract mode -
>>curiouser and curiouser.
>>
>>I thought it had to do with the speakers as it seemed to be most
>>prominent when the sounds were very active (lots of shots,
>>explosions), so I unplugged the speakers - no change.
>>
>>Yeah, pictures will be nice, but I'm off the warehouse right now to
>>deal with other issues. Perhaps I can get them tomorrow and post
>>them somewhere.
>>
>>Archives have nothing under twist or distortion that I can find
>>relating to this...closest I found was "Tempest Boardset Barreling"
>>by Dave Langley back a few years.
>>
>>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"
>>
>>
>>No virus found in this incoming message.
>>Checked by AVG Free Edition.
>>Version: 7.1.394 / Virus Database: 268.8.3/361 - Release Date: 11/06/2006
>
>
>--
>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"

-- 
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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