From: doug1052365
Subject: [TekScopes] Re: 453A intensity fluctuates
To: TekScopes@...
Date: Monday, April 15, 2013, 2:17 PM

 

I tried a different capacitor for C945 - all I had handy was
a .01/4KV. No change. Spayed a little silicone into the
grid bias pot. No change. I the took apart the H.V. box,
temporarily extending the Anode Lead so I could probe the back
of the grid bias pot with the P6013A. As I was probing there
was a large spark. Maybe I pushed something too close to the
chassis, whatever happened it fixed it. Intensity is stable now.
I'm not expecting it to stay that way. I'm sure after I re-assemble
everything it will act up again. Or if I'm lucky the spark welded
a bad connection or vaporized a conductive path. I can't do anything more now that it's working. Thanks for all suggestions.

Doug

ps I found the little spool of silver solder inside.

--- In TekScopes@..., David wrote:
>
> On Mon, 15 Apr 2013 17:44:29 -0000, "doug1052365"
> wrote:
>
> >I'm trying to track down the cause of a fairly rapid intensity fluctuation in my 453A. All power supplies including -1960 and
> >12KV are stable. I see it on the CRT grid, but not on the anode
> >of CR940 and not on the Z axis amplifier output. Turning the
> >grid bias pot a little changes the overall intensity, but the fluctuation is always there.
> >
> >I conclude the pot is OK, the problem must be C945, R944-948,
> >the neon lamps or , the CRT. I've looked inside the
> >H.V. box, all connections look good, neons are not lit and
> >don't see any arcing.
> >
> >Anyone have any ideas? I'm at the point of replacing parts
> >in trial and error fashion.
> >
> >Doug
>
> And C946. Since you eliminated the z-axis amplifier output and both
> high voltage supplies, C945, C946, and R944 to R948 are all about all
> that is left.
>
> If the problem was the 12KV, then I would expect the display
> horizontal and vertical scale to change with the brightness.
>
> Maybe there is breakdown across the printed circuit board itself that
> you will be able to see in the dark. After checking for that, I would
> change the 2 capacitors and 5 resistors.
>

On Mon, 15 Apr 2013 17:44:29 -0000, "doug1052365" <dmeek@...>
wrote:

I'm trying to track down the cause of a fairly rapid intensity fluctuation in my 453A. All power supplies including -1960 and
12KV are stable. I see it on the CRT grid, but not on the anode
of CR940 and not on the Z axis amplifier output. Turning the
grid bias pot a little changes the overall intensity, but the fluctuation is always there.

I conclude the pot is OK, the problem must be C945, R944-948,
the neon lamps or <gulp>, the CRT. I've looked inside the
H.V. box, all connections look good, neons are not lit and
don't see any arcing.

Anyone have any ideas? I'm at the point of replacing parts
in trial and error fashion.

Doug

And C946. Since you eliminated the z-axis amplifier output and both
high voltage supplies, C945, C946, and R944 to R948 are all about all
that is left.

If the problem was the 12KV, then I would expect the display
horizontal and vertical scale to change with the brightness.

Maybe there is breakdown across the printed circuit board itself that
you will be able to see in the dark. After checking for that, I would
change the 2 capacitors and 5 resistors.

Magnus
I presume you mean that you use CQ to remove SMDs and you use solder when placing new components?

Dave

Sent from my iPhone

First, open it up and see if you got the transformer or switchmode version.
If you got the transformer version add a switchmode supply of 15 to 24V for
the motor cirucit (a laptop supply should work).
The transformer version will have a slowly starting tired sound when you
pull the trigger, with the SMPS the motor should immediately get up to
speed and make a much more business-like noise. Don't worry about
overvoltage on the motor, it's only on for seconds.

Take out the filter tube and have a look how far the metal tube protudes
into the filter. This should at most be flush with the black cap, there is
no sense of it sticking into the tube. It will only make it hard to pull
the filter out so curt the tube with a dremel or similar grinder.

While the filter tube is out add a small wad of wire or metal wool inside
the spring. This will catch the solder and make emptying it much easier.

Make some small kinks in the spring with pliers, some are so tightly wound
they are actually airtight and restrict flow. Don't worry the solder will
fly straight towards the end from inertia and not come out the sides.

The little black silicone washer sealing the filter tube to the metal tube
will eventually wear out (the hole gets larger) and not form a proper seal.
A short section (2mm) of silicone tubing slipped on the metal tube fixes
this.

Ideally you'd get a drill to drill out the metal tube, it eventually
accumulates burnt flux residue and solder oxide. You'll need an extra long
drill to reach through. Since extra long drills cost about as much as a new
handpiece this is optional but it's really worth it if you use the unit
much. The cleaning rods are really insufficient.

Don't wait till the tube is blocked, clean it often.

A small vacuum gauge (0 to -1 atmosphere) is really useful in diagnosing
any problem with insufficient suction.

ST

On Sat, Apr 6, 2013 at 10:24 PM, jonathanrwbrooks <
jonathan@...> wrote:

Hi Stephan,

I have bought one and would apprecaite any tips. It does seem to come with
a good few spares.

Kind regards Jonathan.

OK, and why is Bismuth bad?

I'm not just asking to waste your time, a colleague recently proposed using
it as permanent solder.
Intuitively I felt it wasn't a good idea, but don't really know why.

This isn't totally off topic by the way - low melting point solder was used
in a Tek product - the P6401 has a thermal fuse held down by some low melt
alloy.

ST


On Mon, Apr 15, 2013 at 8:17 PM, vdonisa <vdonisa@...> wrote:

Bismuth if it contains any. If so I personally would use it just to help
remove the ROHS solder then clean out the resulting concoction and do the
final soldering with standard 63/37.

--- In TekScopes@..., Stefan Trethan <stefan_trethan@>
wrote:

Do you have any more information on this?
What are the potential problems of leaving CQ in place as a solder?

ST

On Mon, Apr 15, 2013 at 5:30 PM, Dave C <davec2468@> wrote:

As Carlos said, Field's Metal is the prefered one: it has no lead.

Don't confuse ChipQuik (don't know QuickChip) with real solder. CQ is

not

a substitute for solder, it's a desoldering aid. Solder paste is

usually

used for reflow soldering of SMDs.

Dave

------------------------------------

Yahoo! Groups Links

From: doug1052365
Subject: [TekScopes] 453A intensity fluctuates
To: TekScopes@...
Date: Monday, April 15, 2013, 10:44 AM

 

I'm trying to track down the cause of a fairly rapid intensity fluctuation in my 453A. All power supplies including -1960 and
12KV are stable. I see it on the CRT grid, but not on the anode
of CR940 and not on the Z axis amplifier output. Turning the
grid bias pot a little changes the overall intensity, but the fluctuation is always there.

I conclude the pot is OK, the problem must be C945, R944-948,
the neon lamps or , the CRT. I've looked inside the
H.V. box, all connections look good, neons are not lit and
don't see any arcing.

Anyone have any ideas? I'm at the point of replacing parts
in trial and error fashion.

Doug

---
FINALLY, I did check the A and the B lights and in every combination of
switch settings I could think of the A light never went out or switched to
the B light. This is why I think you should try what Albert suggested. It
sounds like he has a 7904A in which case he would know what this switch
does.

Dennis

Try with S4488 (corner logic board A13) in the other position?
Albert

I can confirm that ChipQuick works nicely for SMD components. We are using it to rework 10-pin to 28-pin-SMD-components on multilayer PCBs, and it is a great aid for manual, easy repair work. Their flux is also good, as it is very sticky.

Do you have any more information on this?
What are the potential problems of leaving CQ in place as a solder?

ST

On Mon, Apr 15, 2013 at 5:30 PM, Dave C <davec2468@...> wrote:

As Carlos said, Field's Metal is the prefered one: it has no lead.

Don't confuse ChipQuik (don't know QuickChip) with real solder. CQ is not
a substitute for solder, it's a desoldering aid. Solder paste is usually
used for reflow soldering of SMDs.

Dave