Digest for sci.electronics.repair@googlegroups.com - 8 updates in 3 topics

9:47 AM Penedão
N_Cook <diverse@tcp.co.uk>: Jun 28 11:44AM +0100

I changed TO92 Q208 2N5400 for MPSA92 and no change in crowbarring.
Before wasting any more time on this I thought I'd remove the crowbar
caps, just in case both were equally bad, so nullifying swap-over test,
but only one PA had enough switch-on instability to trigger either of
the crowbars.
With hindsight these Nichicon VP(M) caps ,2.2uF 50V are much the same as
polarised 2uF 50V caps, suspiciously small.
Simple DVM-R test showed apparent charge time of a 100uF cap, so iffy.
ESR test showed reasonable ESR, but RLC test was interesting.
Initially , for both caps the same, read 1uF then over 10 seconds
dropped to .9uF and continued slowly decrreasing exponentially.
So something in the chemistry gone wrong?, presumably cooked or
something ,with only 50V rating.
Replaced with 2.2uF 250V polyester caps on the other side of the board,
cable-tied down. I know overkill but 100V ones not laying around and
plenty of space on the track side of the output pcb.
Tried 30 switch-ons and no crowbarring and repeated on the other output.
clare@snyder.on.ca: Jun 27 02:48PM -0400

On Mon, 27 Jun 2016 08:59:14 -0400, Mark F <mark53916@gmail.com>
wrote:
 
>> the glass rod.
 
>> I believe I am the only poster who gave instructions based on
>> determining first if it is a printer or scanner issue.
NOWHERE that I can find has the OP clarified whether the lines show
up is simple prints. All I have found was in "copies" and "scans"
 
A 3200 is not a flatbed - so if there are lines in the scan, they will
be from something contaminating the scan head and will run the
"length" of the paper - in the direction of motion through the
scanner. There is no other scanner failure mode that will produce any
other pattern of lines.
 
If it is a PRINT error, there can be several patterns - with different
causes - and generally the same solution.
 
If the lines are the "lenth" of the paper and present on prints as
well as copies, there is a scratch in the drum - usually but not
alwats preceded by "spots". If they are the width of the paper and
evenly spaced by about the circumference of the drum, there is a
defect line across the drum USUALLY this is not as crisp or clean or
fine a line as the other possibilities. The solution to both PRINT
issues is to replace the drum/cartridge.
 
The solution tu the scanner problem is a carefull and thorough
cleaning of the scanner element (unless someone has scratched it by
running a staple through it)
clare@snyder.on.ca: Jun 27 02:52PM -0400


By and large, current HP product is pretty well all JUNK. Some of
their pro products are reasonable quality - but by almost any measure
- over-priced. A well used 10 year old HP printer is very likely to
outlast any of their current brand new product.
Micky <NONONObobbyburns1111@gmail.com>: Jun 27 07:28PM -0400

On Mon, 27 Jun 2016 08:59:14 -0400, Mark F <mark53916@gmail.com>
wrote:
 
> with diagonal lines would show a glitch in the diagonal
> line rather than just a horizontal line across the diagonal
> line.
 
Diagonal line is an excellent idea. Easier to see that two lines
aren't in line than to measure.
 
I had a copier, printerer, scanner that I got out of the trash and I
found a broken plastic gear in it. I screwed up and glued it so that
it had one empty space about the width of a tooth. Maybe it was
smaller but it wouldn't have turned if it weren't close. But it
worked and the problem didn't seem to show in the scans I made. I
dind't have ink so I didn't print.
 
> device since the VueScan description says it supports
> HP LaserJet 3200 and doesn't specify 3200m, but I think it
> is worth a try.
 
Hey this is great. If htey ghave a universal scanner, maybe it's only
time before some hero writes a universal printer program/driver.
 
 
Stormin Mormon <cayoung61@hotmail.com>: Jun 27 08:52PM -0400

On 6/27/2016 7:28 PM, Micky wrote:
 
>>> I believe I am the only poster who gave instructions based on
>>> determining first if it is a printer or scanner issue.
 
Very wise comment.
 
--
.
Christopher A. Young
learn more about Jesus
. www.lds.org
.
.
whit3rd <whit3rd@gmail.com>: Jun 27 11:35PM -0700

On Saturday, June 25, 2016 at 9:17:53 AM UTC-7, Emran M. wrote:
> means the rollers must be vertical.
 
> Yet, the streaks are horizontal (in the opposite direction
> in which the paper physically moves down through the scanner).
 
A scratch on the toner cartridge drum would make a vertical
mark, but the edges of the aperture can also make a horizontal
defect on the drum; it might be something simple (a dust line,
removable by lifting it off with a piece of sticky tape) or it might
be a defect caused by overheating and fusing of the toner.
whit3rd <whit3rd@gmail.com>: Jun 27 11:41PM -0700

> indicate (nearly but slightly unclearly) that it does not happen when printing
> from a computer. That makes it a scanner engine problem, and rollers don't
> cause scanner quality issues (only feed isues).
 
True. One (outlier) possibility is that the scan movement is handled by a geartrain
that has gotten slopppy. More likely, the scan head has a fluorescent lamp which
has begun to get dim and flicker. Lamp replacement is usually possible, but
not always supported by manufacturer repair parts stocks.
hrhofmann@att.net: Jun 27 04:06PM -0700

An extension cord on the AC input side of the power adapter is what I have done many times over the past 50 years of using electronics with power bricks. At first, I sort of felt funny doing it, but a couple of AC extension cords save a lot of $$$ compared to buying extension cords for the load side of all those various power bricks,
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