Re: Tektronix 2445 Readout is no good , video included

On Nov 19, 8:57 pm, Jim Yanik <jya...@xxxxxxxxx> wrote:
"NetSpi...@xxxxxxxxx" <NetSpi...@xxxxxxxxx> wrote innews:8e0393b6-bd6b-4506-9624-7eb217148256@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:



On Nov 19, 12:33 am, Jim Yanik <jya...@xxxxxxxxx> wrote:
"NetSpi...@xxxxxxxxx" <NetSpi...@xxxxxxxxx> wrote
innews:a089d234-8202-4980-a6d9-ae53bee0e1b7@xxxxxxxxxxxxxxxxxxxxxxxxxx
m:

On Nov 17, 3:08 am, Jim Yanik <jya...@xxxxxxxxx> wrote:
"NetSpi...@xxxxxxxxx" <NetSpi...@xxxxxxxxx> wrote
innews:28ac4545-7a53-4594-83d8-910b6ccf1d63@xxxxxxxxxxxxxxxxxxxxxxx
.co m:

On Nov 16, 6:57 am, Jim Yanik <jya...@xxxxxxxxx> wrote:
"NetSpi...@xxxxxxxxx" <NetSpi...@xxxxxxxxx> wrote in
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Jim Yanik wrote:
"NetSpi...@xxxxxxxxx" <NetSpi...@xxxxxxxxx> wrote in
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http://video.yahoo.com/video/play?vid=1466538

The readout looks bad , i can see jumpy dots ,instead of
clear numbers as in the other 2445 .
i replaced those 3 47uf caps on the A5 board (control
board) , and it didn't helped .
http://img110.imageshack.us/img110/2372/image015pn5.jpg

2445 non-B scopes have separate R-O boards.
the signal from them feeds into the vertical on the main
bottom board. try swapping the readout boards.
IIRC,there's also a pot to adjust R-O crawl/jitter.
see the cal procedure in your service manual.

On "B" models,the readout is integrated to the A5 uP board.
"B" model A5 uP boards are NOT swappable with earlier
versions.

--
Jim Yanik
jyanik
at
kua.net
tried play with jitter , didn't do the trick ...

and you are right about A5 in the 2445 , the R-O is not on
this board , i just did a swap with a good 2445 A5 and got
the same jerky readout .

what component is making the problem in the R-O of the 2445 ?
caps ? or something else ?

possibly caps,or a bad hybrid on the main board.
Does it twitch in the vert or horiz direction,or both? signal
trace solid,in both V and H axes?
This may be where you have to scope every decoupled PS supply
line. could even be some of those 0.1uf DIP caps that are all
over every board.

--
Jim Yanik
jyanik
at
kua.net

trace is solid , no trace problems .

Is that a trace with a signal displayed,or just the baseline
trace? With a signal displayed,you can see any horiz jitter.
Without an input signal,you can't see any jitter in the horiz.

and one thing i noticed , when i control the read out intensity
fully CW , the R-O shifts upwards ...

I wonder if your CRT is maxed out on intensity.(grid bias)

--
Jim Yanik
jyanik
at
kua.net

Well , the read-out is good now , i replaced the power supply , and
don't have jerky read-out .
i guess power supply ain't that good .

probably marginal electrolytics,bad ESR.
often,the PS is the source of trouble appearing elsewhere.

but i got another problem with this scope , the horiz is not good
at some of time bases , some of them ok , but lets say 5u is
drifting . i did CAL 01-04 , but got LIMIT warning in the horiz
section , could not adjust as required .
something is wrong , what i'm doing wrong ?

All the parts for timing are on the sweep hybrids.try swapping the A
and B sweep hybrids,and recal.if the problem goes away on that
range/mode,then yu have a bad hybrid.

--
Jim Yanik
jyanik
at
kua.net

Well , gonna try this after i'l find new U800 (Horiz amp ) just
destroyed the one that was on the scope .

the horiz amp got nothing to do with the timing ?

do you know where i can find U800 ?

they aren't made anymore,and the only place you can get one is from another
2445/65 scope.IIRC,there was an Ebay seller who had some salvaged ones for
sale,but the price was pretty high.

--
Jim Yanik
jyanik
at
kua.net

i'l try to salvage ...

the horiz amp got nothing to do with the timing ?
.

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