Date   

Repair of Tek 465 coarse/fine x-position pot

Tom Gardner
 

I recently obtained a non-functional 465 that had probably
been dropped. After replacing the CRT and HV diodes it
works well except for the fine x-position pot. Looking at
the geometry and construction, that looks like it would
be a common failure point.

The coarse x-position pot worked well, but fine x-position pot
didn't work unless you pulled out on the knob while turning.
Removing the fine position pot revealed its spindle moved
freely in and out. When fully pulled out and turned, the pot wiper
turned normally, but even when slightly pushed in, the spindle
lost contact with the wiper. I suspect the scope had been rested
face-down with weight on the knob, and that had pushed
the spindle and detached it from the wiper. Irritating, irksome,
but the scope could be used without it.

Any attempt to slip the knob over the spindle failed because the
slightest friction moved the spindle in.

After a few abortive attempts, the solution is simple and
effective. Put the coarse knob on as normal, then slip a spring
over the fine-position spindle. Carefully putting the fine knob
on again still fails, but now the spring pushes the fine knob out
sufficiently that it re-engages with the wiper.

Success.


dm504a for sale

 

Hi,


I have a auto ranging DM504A multimeter that needs calibration. I reads a bit low on most ranges. I do not have calibration equipment good enough to do this calibration. The 200mv and 2000mv scales are recalibrated for dcv. Make offer to me off list at
j_massengale@...


Jerry Massengale


Re: Tektronic 466 - Storage Modes inop

 

The 5111 and 577 D1 both use bistable storage only. I've found the operation of (older) bistable storage systems mostly marginal. It is quite sensitive to temperature and periods of non-use but it does recover (mostly) after several hours under power.
The 466 has a different construction; it can benefit from being revived under power but far less so.

I have bistable storage 'scopes and several of the other types. I have always found that the non-bistable systems need far less recovery, like the 464, 466, 7613. I've seen the same differentiated behaviour in 'scopes using both systems, like the 7623A, 7633, 7834.

Bistable-only systems generally are older than the other systems, so with those, age may play a role in itself.

My 577 D1 and 5113 (bistable only, basically identical systems) need at least half an hour after being switched on to provide good storage. Scopes like the 464, 466 and 7834 just need a few minutes.

I think your 466 has a problem. Could just be a matter of voltage adjustments in the storage system.

Raymond


Re: 7854 RAM card upgrade only - any interest?

 

There's a new page <36> for a revised version of the A32 rear panel
schematic that shows the removal of the external power sockets and how that
switch is wired along with some inverters (U17 on A32) which were added.

I don't have the updated parts list for the IC type of the inverter but I'd
pretty much guess that 74ls04 or 74hc04 would do fine (though you might need
the HCT version).

If modifying an existing A32 you'd probably need to get inventive on
mounting and powering that IC.

Dave

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 10 March 2016 06:12
To: TekScopes@...
Subject: Re: [TekScopes] 7854 RAM card upgrade only - any interest?

The wiring diagram of the new Tek A28 board answers one mystery and raises
another one. First, the vacant chip sites are for 2732 ROMs, not for added
RAM.

With the other address map reserved areas you have identified and our lack
of information about the firmware, I think this means we have no practical
way to increase the RAM beyond the existing 8K words. Mystery solved, but no
new goodies. We almost certainly do not need the vacant chip sites on our
new card.


You mentioned that Tek somehow "sandwiched" the patch ROM content into the
latest ROMs along with the existing coed. This is probably not quite true.
The patch ROM and the FPLA chip act together to overlay bits of ROM code. On
the new card, merging the patched code into the base ROMs probably requires
no added space because the patches effectively replace bits of the earlier
version code. The MPU gets either the original code or a replacement overlay
depending on what the FPLA selects. The new ROMs roll the patches into the
base code, eliminating the need for overlays.


Second, and a new mystery, the new Tek memory card has no connections for
the Memory Backup / Self Test switch on the back panel of the scope. The
switch may therefore be wired into some other card (MPU?). I will look into
the old style MPU board tomorrow to see if the BAT line goes anywhere. It
does go from the rear panel connector board to both the RAM and the MPU
boards, but I don't see it in the MPU board diagram.


Cliff






------------------------------------
Posted by: test2cal@...
------------------------------------


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

Yahoo Groups Links


Looking for 067-1331-00 Sampling Head Simulator. WTB.

Egge Siert
 

Hi to All,


Looking for this Service Fixture. Some years ago USA Only Seller CHIPXS sold tenths of them for little money. But that was before I got addicted to the 11K Series. Anybody who wants to seperate from such a device?


Greetings,


Egge Siert


Re: Tektronic 466 - Storage Modes inop

Tim Phillips <tim@...>
 

from Tim P (UK)
Aha !! The manual for the 5111 storage 'scope specifies a turn-on procedure for an instrument that has not been used for a while (2 wks) or from new.
With power OFF, Upper and lower store ON, brightness MAX, power up. This "reduces the ion content in the CRT" (from the manual), wait for the screen to flood. After 5 minutes ,do a couple of Erases, then U/L Store OFF. The full story is on pp1-4 of the 5111 manual, but, of course, I don't know whether this procedure is specific to the 5000 storage scopes or even that CRT.
Tim

----- Original Message -----
From: "edbreya@... [TekScopes]" <TekScopes@...>
To: <TekScopes@...>
Sent: Thursday, March 10, 2016 3:54 AM
Subject: [TekScopes] Re: Tektronic 466 - Storage Modes inop


I don't know if this will help, but it may be a good idea to let it cook for a few hours, especially if it hasn't been run in a few years. I have a 577 D1 storage type on which the display looks awful when first turned on, in storage mode, with a big pincushion green background that can't be turned off. After running for about twenty minutes, and a few erase cycles, it blanks out nicely.

If it doesn't settle down, you may want to check and tweak the flood gun circuits. Once the basic operation is confirmed, you can check the screen and storage mesh by filling the display - just set up for a free-running sweep, and work the vertical position up and down until the whole thing is written. Ideally, it should present a uniform filled green screen. You'll see any bad spots or after-images.

Ed



Re: 7854 RAM card upgrade only - any interest?

Cliff Carrie
 

The wiring diagram of the new Tek A28 board answers one mystery and raises another one. First, the vacant chip sites are for 2732 ROMs, not for added RAM.

With the other address map reserved areas you have identified and our lack of information about the firmware, I think this means we have no practical way to increase the RAM beyond the existing 8K words. Mystery solved, but no new goodies. We almost certainly do not need the vacant chip sites on our new card.


You mentioned that Tek somehow "sandwiched" the patch ROM content into the latest ROMs along with the existing coed. This is probably not quite true. The patch ROM and the FPLA chip act together to overlay bits of ROM code. On the new card, merging the patched code into the base ROMs probably requires no added space because the patches effectively replace bits of the earlier version code. The MPU gets either the original code or a replacement overlay depending on what the FPLA selects. The new ROMs roll the patches into the base code, eliminating the need for overlays.


Second, and a new mystery, the new Tek memory card has no connections for the Memory Backup / Self Test switch on the back panel of the scope. The switch may therefore be wired into some other card (MPU?). I will look into the old style MPU board tomorrow to see if the BAT line goes anywhere. It does go from the rear panel connector board to both the RAM and the MPU boards, but I don't see it in the MPU board diagram.


Cliff


Re: MAKING EXCELLENT PCBs using toner transfer

Ed Breya
 

Haha. That reminds me of how I etched boards when I was a kid - with ferric chloride solution in a Pyrex cake pan on the electric range in the kitchen. My mother didn't appreciate it, and threatened numerous times to kill me if I ever stained her white Formica counter tops. I never did, although there was a close call once with some potassium permanganate from an experiment - if you clean up quickly, Formica is amazing stuff.

Ed


Re: MAKING EXCELLENT PCBs using toner transfer

petertech99h
 

Hi all, In the days 'BC' (before CAD) I used Red and Blue mylarlayout tapes and black adhesive IC pad shapes scaled 2X to do double sidedPCBs.  The artwork got sent out and photographed with filters to produce 2production films, 1 top, 1 bottom, black pads showed up on both films,overlapping red and blue produced black traces on both sides. In high school I did a double-sided PCB making 2 artworksover a drafted layout with layout targets just outside the board outline thenimage the board one side at a time with 2 plates of glass and the board andartworks sandwiched inside. The secret to good etching at home with ferric chloride, isto dilute it 50% with hot water and keep a small heat lamp on the tank. I putrubber grommets on the corners of the PCB to space it up high enough to etchunderneath. Place in a flat glass cassarole dish fill with just enough etchantto cover the top of the PCB, then rock the dish at the right speed to get theetchant to sweep across the length of the board!  Results where great, no pitting, uneven edges and a 5-6 minuteetch!!, rather fast! Basically you could etch a board with 1 cup of 50/50solution and it would turn green by the time you where done, very little waste. I learned this technique from a techwho in the early days made the proto boards in house. He also made a jig with aslow stepper motor and an off-center roller to lift the edge of the dish to gentlyslosh the etchant on the boards, he made it big enough to do 4 different PCBs in4 different trays at the same time!

Is anyone interested how plate-thru holes are made? or iseveryone up to speed on that?  It’s possible to do that at home too!

Lots of fun, still have my first ever double sided boardsplus a spare!

Pete

On Monday, March 7, 2016 8:13 PM, "gmt1@... [TekScopes]" <TekScopes@...> wrote:


  Hi Folks,
You can make PCB boards of the highest quality using the toner transfer method.
The secret is to use Pulsar’s Transfer Paper and Pulsar’s Green TRF Foil (both products made in the US) and
a modified laminator .Pulsar products are sold worldwide i gather.

Use Ferric chlorides etchant.
I have no connection with Pulsar (just a happy customer)

I struggled for years to make decent PCBs and this is by far the best DIY system avaliable.
You can produce boards that match Photographic methods and make very fine tracks.
All electronic enthusiast should be able to make there own PCBs and produce there own TEK

extender boards relatively cheaply.
Not a lot of info on Pulsar,on the net, for some reason but i found this excellent writeup
from a local mob here in Australia see......
http://ultrakeet.com.au/write-ups/makepcbs http://ultrakeet.com.au/write-ups/makepcbs
Regards
George








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Re: MAKING EXCELLENT PCBs using toner transfer

Jim Popwell <jpopwell@...>
 

Hi Pete,
i’d like any pointers on plated thru hole at home….
if you can point me to any sites, thanks…
jim

On Mar 9, 2016, at 7:45 PM, Peter Hildebrandt petertech99h@... [TekScopes] <TekScopes@...> wrote:

Hi all,
In the days 'BC' (before CAD) I used Red and Blue mylar layout tapes and black adhesive IC pad shapes scaled 2X to do double sided PCBs. The artwork got sent out and photographed with filters to produce 2 production films, 1 top, 1 bottom, black pads showed up on both films, overlapping red and blue produced black traces on both sides.
In high school I did a double-sided PCB making 2 artworks over a drafted layout with layout targets just outside the board outline then image the board one side at a time with 2 plates of glass and the board and artworks sandwiched inside.
Is anyone interested how plate-thru holes are made? or is everyone up to speed on that? It may be possible to do that at home too!

Lots of fun, still have the boards plus a spare!
Pete

On Tuesday, March 8, 2016 12:59 AM, "'Dennis Tillman' dennis@... <mailto:dennis@...> [TekScopes]" <TekScopes@... <mailto:TekScopes@...>> wrote:


Hi Dave,
Me too. Plus OSHPark boards are gold coated which is very unusual and very prettyl!!!.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... <mailto:TekScopes@...> [mailto:TekScopes@... <mailto:TekScopes@...>]
Sent: Monday, March 07, 2016 9:31 PM
To: TekScopes@... <mailto:TekScopes@...>
Subject: Re: [TekScopes] MAKING EXCELLENT PCBs using toner transfer

I have been very happy getting boards made by OSHpark.com <http://oshpark.com/>, who offer both two and four layer small quantity fabrication at a reasonable price.

I did buy the Pulsar kit, but only with the intention of using it for certain projects where I felt it would be more cost effective than using a fab (such as a large area board of which I only plan to make one copy).

Dave Casey

On 3/7/2016 10:34 PM, 'Dennis Tillman' dennis@... <mailto:dennis@...> [TekScopes]
wrote:

Hi George, Dave, et al,
I made my own PC Boards back in the 1960s using a variety of methods
including photolithography, toner transfer, PC layout tape, and
special ink pens. The problem with all of these methods is you can
realistically only do single sided boards.

I worked out a way to do double sided boards but I first had to design
and build a very accurate jig to hold the boards and the photomasks in
perfect alignment under hot lights for several minutes. Even with all
that, there was still no way to do plated through holes. In most cases
I was clever enough to make the connections from one side of the board
to the other by carefully choosing where the via was located so it
corresponded to where a part would be placed. Then the lead from the
part or IC did double duty by acting as a via.

If you want to do a PC Board today it seems to me that a better use of
your time would be ExpressPCB which has free software. It is a
do-it-yourself solution to PCB layout but they can handle up to 4
layer boards with vias, and they do silk screen layers on the top, and
(I think) the bottom as well. A big plus is you can learn it quickly
but it doesn't do much more than board layout. The biggest drawback is
you have to buy your boards from them and you have to buy 4 boards at
a time. Prices are reasonable. (I have no financial connection with them).

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, March 07, 2016 5:52 PM
Subject: Re: [TekScopes] MAKING EXCELLENT PCBs using toner transfer

Their website is http://www.pulsarprofx.com <http://www.pulsarprofx.com/>

Regards,

Dave Casey

On 3/7/2016 7:13 PM, gmt1@... <mailto:gmt1@...> [TekScopes] wrote:

Hi Folks,
You can make PCB boards of the highest quality using the toner
transfer method.
The secret is to use Pulsar’s Transfer Paper and Pulsar’s Green TRF
Foil (both products made in the US) and a modified laminator .Pulsar
products are sold worldwide i gather.

Use Ferric chlorides etchant.
I have no connection with Pulsar (just a happy customer)

I struggled for years to make decent PCBs and this is by far the
best DIY system avaliable.
You can produce boards that match Photographic methods and make very
fine tracks.
All electronic enthusiast should be able to make there own PCBs and
produce there own TEK

extender boards relatively cheaply.
Not a lot of info on Pulsar,on the net, for some reason but i found
this excellent writeup from a local mob here in Australia see......
http://ultrakeet.com.au/write-ups/makepcbs <http://ultrakeet.com.au/write-ups/makepcbs>
http://ultrakeet.com.au/write-ups/makepcbs <http://ultrakeet.com.au/write-ups/makepcbs>
Regards
George








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[Non-text portions of this message have been removed]

------------------------------------
Posted by: Dave Casey <dcasey@... <mailto:dcasey@...>>
------------------------------------

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

Yahoo Groups Links

[Non-text portions of this message have been removed]

------------------------------------
Posted by: Dave Casey <dcasey@... <mailto:dcasey@...>>
------------------------------------

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

Yahoo Groups Links

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453 SN: 043226 Anode Now Solid State

Joseph Rooney
 

Chasing down a gain change warmup problem, I decided to replace the 5642's in the anode with replacements I found on line. Pictures here: https://flic.kr/p/EV6GoL https://flic.kr/p/EV6GoL https://flic.kr/p/EV6GQ7 https://flic.kr/p/EV6GQ7 after replacement of 5642's with two ESJA52-10 from HVStuff.com . Didn't fix the problem, I had to order them from China, took less than a week. Found 5kv rectifiers at Halted that were just too big to be in series. https://flic.kr/p/F6Ajfn https://flic.kr/p/F6Ajfn


These are far smaller than the 152-0408-00 we routinely used at Tektronix to replace 5642's and I'm quite sure they will work in your 5642 replacement scheme.


Joe


Re: Tektronic 466 - Storage Modes inop

Ed Breya
 

I don't know if this will help, but it may be a good idea to let it cook for a few hours, especially if it hasn't been run in a few years. I have a 577 D1 storage type on which the display looks awful when first turned on, in storage mode, with a big pincushion green background that can't be turned off. After running for about twenty minutes, and a few erase cycles, it blanks out nicely.

If it doesn't settle down, you may want to check and tweak the flood gun circuits. Once the basic operation is confirmed, you can check the screen and storage mesh by filling the display - just set up for a free-running sweep, and work the vertical position up and down until the whole thing is written. Ideally, it should present a uniform filled green screen. You'll see any bad spots or after-images.

Ed


Re: MAKING EXCELLENT PCBs using toner transfer

petertech99h
 

Hi all,
In the days 'BC' (before CAD) I used Red and Blue mylar layout tapes and black adhesive IC pad shapes scaled 2X to do double sided PCBs.  The artwork got sent out and photographed with filters to produce 2 production films, 1 top, 1 bottom, black pads showed up on both films, overlapping red and blue produced black traces on both sides.
In high school I did a double-sided PCB making 2 artworks over a drafted layout with layout targets just outside the board outline then image the board one side at a time with 2 plates of glass and the board and artworks sandwiched inside.
Is anyone interested how plate-thru holes are made? or is everyone up to speed on that?  It may be possible to do that at home too!

Lots of fun, still have the boards plus a spare!
Pete

On Tuesday, March 8, 2016 12:59 AM, "'Dennis Tillman' dennis@... [TekScopes]" <TekScopes@...> wrote:


  Hi Dave,
Me too. Plus OSHPark boards are gold coated which is very unusual and very prettyl!!!.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, March 07, 2016 9:31 PM
To: TekScopes@...
Subject: Re: [TekScopes] MAKING EXCELLENT PCBs using toner transfer

I have been very happy getting boards made by OSHpark.com, who offer both two and four layer small quantity fabrication at a reasonable price.

I did buy the Pulsar kit, but only with the intention of using it for certain projects where I felt it would be more cost effective than using a fab (such as a large area board of which I only plan to make one copy).

Dave Casey

On 3/7/2016 10:34 PM, 'Dennis Tillman' dennis@... [TekScopes]
wrote:

Hi George, Dave, et al,
I made my own PC Boards back in the 1960s using a variety of methods
including photolithography, toner transfer, PC layout tape, and
special ink pens. The problem with all of these methods is you can
realistically only do single sided boards.

I worked out a way to do double sided boards but I first had to design
and build a very accurate jig to hold the boards and the photomasks in
perfect alignment under hot lights for several minutes. Even with all
that, there was still no way to do plated through holes. In most cases
I was clever enough to make the connections from one side of the board
to the other by carefully choosing where the via was located so it
corresponded to where a part would be placed. Then the lead from the
part or IC did double duty by acting as a via.

If you want to do a PC Board today it seems to me that a better use of
your time would be ExpressPCB which has free software. It is a
do-it-yourself solution to PCB layout but they can handle up to 4
layer boards with vias, and they do silk screen layers on the top, and
(I think) the bottom as well. A big plus is you can learn it quickly
but it doesn't do much more than board layout. The biggest drawback is
you have to buy your boards from them and you have to buy 4 boards at
a time. Prices are reasonable. (I have no financial connection with them).

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, March 07, 2016 5:52 PM
Subject: Re: [TekScopes] MAKING EXCELLENT PCBs using toner transfer

Their website is http://www.pulsarprofx.com

Regards,

Dave Casey

On 3/7/2016 7:13 PM, gmt1@... [TekScopes] wrote:

Hi Folks,
You can make PCB boards of the highest quality using the toner
transfer method.
The secret is to use Pulsar’s Transfer Paper and Pulsar’s Green TRF
Foil (both products made in the US) and a modified laminator .Pulsar
products are sold worldwide i gather.

Use Ferric chlorides etchant.
I have no connection with Pulsar (just a happy customer)

I struggled for years to make decent PCBs and this is by far the
best DIY system avaliable.
You can produce boards that match Photographic methods and make very
fine tracks.
All electronic enthusiast should be able to make there own PCBs and
produce there own TEK

extender boards relatively cheaply.
Not a lot of info on Pulsar,on the net, for some reason but i found
this excellent writeup from a local mob here in Australia see......
http://ultrakeet.com.au/write-ups/makepcbs
http://ultrakeet.com.au/write-ups/makepcbs
Regards
George












------------------------------------
Posted by: Dave Casey <dcasey@...>
------------------------------------

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Yahoo Groups Links

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------------------------------------
Posted by: Dave Casey <dcasey@...>
------------------------------------

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Yahoo Groups Links

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Re: 7854 Repair & Restoration

Brian Bloom
 

I'll leave it running and 'play' with my psu-shorting 485 while keeping an eye on it and periodically tapping on U50 and it's surroundings and report back....
>That sounds promising.

>For what it is worth, U50 and the basics of this vertical amplifier
>design are shared by the 7834, 7844, 7854, and 7904. There might be
>something to learn from those service manuals.

>I have taken the very similar vertical amplifier board off of my 7834
>many times. It is not difficult to do however watch out for the
>vertical deflection plate connections which are directly under the
>board. Before removing the board, shine a light between it and the
>CRT and make a note of the lead dressing. This has to be duplicated
>when you reassemble it to preserve the transient response. The wires
>are *not* soldered to the CRT pins. Instead they are soldered to
>collets which slip over the CRT pins and they can carefully be pulled
>directly off or at least that is how my 7834 is constructed.

>I ended up buying a Wiha nut driver set to work in the area around the
>CRT amplifiers.


Found it.

After hooking the jumpers back up and running it a while with the sweep, I'm able to tap on U50 (kinda hard) with a ceramic screwdriver and induce the exact fault. Beamfinder deflected to the top of the CRT.

I can also tap on it again and it goes back to normal.

So then, I guess U50's non-soldered connections just need to be cleaned to make full-time positive contact again?

If Francis couldn't get a display on the scope before, I guess that the roughness of shipping caused the connections to rub and make partial contact again. That would have led to me being able to get a display on it once I powered it up...


So then... about the CRT circuit... DS47 is supposed to have a slight glow? Isn't that chain of neons supposed to be circuit protection?

I wonder if other scopes of the 78**/79** series have the same thing going on..

I'm really curious why Francis had circled the diodes in the focus-grid dc restorer. I guess I should just ask him.


Re: Tektronic 466 - Storage Modes inop

 

On 09 Mar 2016 18:46:03 -0800, you wrote:

This is a new-to-me 466. It seems pretty much OK in non-store modes. When I pop it into variable Persistance, I still see the trace, but no storage. No effect from the View Time Storage Level, or Storage Intensity controls. Pushing Erase, blanks the trace for a second, but no flash of light, as I'd expect.

LV DC supplies all look OK.

Weirdest symptom follows: With the intensity turned all the way down, I see a few dimly lit, stationary 'spots' on the screen and a faint overall green glow.
That is normal. I have noticed faint illuminated shadows and
illuminated dots before on storage CRTs.

No experience with tinkering at storage circuits... yet....

Comments, Ideas, admonishments, etc appreciated...
After checking the general stuff like the low voltage power supply
outputs and doing a detailed visual inspection, I would consider
connectors and socketted parts like transistors and ICs.

If that does not turn up anything, then I would do the z-axis
calibration procedures followed by the storage calibration procedures.


Re: 7854 Repair & Restoration

 

On 09 Mar 2016 17:18:14 -0800, you wrote:

...

It's not R105. I've got it powered up with jumpers disconnected as you suggested. (The display is some sections of dashes)
I can adjust R105 and it operates smoothly. there's not even the slightest sign of internal damage to the pot.

However, tapping on U50 makes the trace randomly jump to the upper part of the CRT. It hasn't yet gone off the CRT, and it seems to always recover. Then again, I just powered the scope on a few minutes ago...

I'll leave it running and 'play' with my psu-shorting 485 while keeping an eye on it and periodically tapping on U50 and it's surroundings and report back....
That sounds promising.

For what it is worth, U50 and the basics of this vertical amplifier
design are shared by the 7834, 7844, 7854, and 7904. There might be
something to learn from those service manuals.

I have taken the very similar vertical amplifier board off of my 7834
many times. It is not difficult to do however watch out for the
vertical deflection plate connections which are directly under the
board. Before removing the board, shine a light between it and the
CRT and make a note of the lead dressing. This has to be duplicated
when you reassemble it to preserve the transient response. The wires
are *not* soldered to the CRT pins. Instead they are soldered to
collets which slip over the CRT pins and they can carefully be pulled
directly off or at least that is how my 7834 is constructed.

I ended up buying a Wiha nut driver set to work in the area around the
CRT amplifiers.

On 09 Mar 2016 17:31:18 -0800, you wrote:

I think it has something to do with the 'node' that's pressure-seated against the top of the can of U50. If I press beside it on the can (with a ceramic screwdriver - my spudger....), it makes the trace jump to the top of the crt every time.

I assume that the pressure bracket with connected center node is to make sure U50's case stays grounded... If that is correct, what would happen if U50's case became un-grounded?
The board layout and schematic show 12 pins and no ground on U50. The
package guide shows a pin welded to the top of the can.

Does that top lead on U50 actually go to ground?

I am hoping that the problem is an intermittently open resistor or
solder joint. Probe around U50 with your insulated spudger (I know
this device as a diddle stick) and see if you can localize the
problem.

On 09 Mar 2016 18:23:56 -0800, you wrote:

I think we may be in the wrong path with this problem. I had my head next to the CRT HV can a bit ago and heard some random mild arcing noises.
I plugged the vert board jumpers back in, took the CRT can shield off, and powered up..
Darn. And the area around U50 was such a neat solution. Maybe there
are two different problems.

Is there supposed to be a neon mildly glowing in there?? (I don't think so..)
None of the neon bulbs should be glowing during normal operation. The
specific bulb will reveal which circuit is misbehaving.

It's DS47, which is 'Focus Grid DC Restorer' circuit. From what my eyes are capable of seeing, there doesn't appear to be any change in it when I mess with the focus control.
High voltage capacitors C36 and C39 are the parts most likely to fail
and cause the neon bulbs to light. Note that the schematic is very
specific that the resistors in this area are carbon composition.

Inspect the area around the focus DC restorer with a bight light
looking for anything funny. Then try to do an inspection of this area
in darkness when the failure is occurring.

DC restorer problems can be annoying to track down. I would consider
just replacing all of the parts.

So candidates are:
the "Focus Control" circuit, diagram 13
The "Focus-Grid DC Restorer" circuit diagram 14
The focus control circuit does not have any voltages higher than +130
volts.

If horses come before zebras, then the DC restorer is where to look
first.

I haven't yet tried to figure out the circuit, but I'll do my best to narrow down the possibilities.

Remember: I noted a while back that the schematic book that came with the scope had the "Focus Grid DC Restorer" circuit circled.
Usually we have to deal with z-axis DC restorer problems so I do not
know what happens when the focus DC restorer fails.


Tektronic 466 - Storage Modes inop

Jim McIntyre
 

This is a new-to-me 466. It seems pretty much OK in non-store modes. When I pop it into variable Persistance, I still see the trace, but no storage. No effect from the View Time Storage Level, or Storage Intensity controls. Pushing Erase, blanks the trace for a second, but no flash of light, as I'd expect.


LV DC supplies all look OK.


Weirdest symptom follows: With the intensity turned all the way down, I see a few dimly lit, stationary 'spots' on the screen and a faint overall green glow.


No experience with tinkering at storage circuits... yet....


Comments, Ideas, admonishments, etc appreciated...


Re: 7854 Repair & Restoration

Brian Bloom
 

I think we may be in the wrong path with this problem. I had my head next to the CRT HV can a bit ago and heard some random mild arcing noises.
I plugged the vert board jumpers back in, took the CRT can shield off, and powered up..

Is there supposed to be a neon mildly glowing in there?? (I don't think so..)


It's DS47, which is 'Focus Grid DC Restorer' circuit. From what my eyes are capable of seeing, there doesn't appear to be any change in it when I mess with the focus control.

So candidates are:
the "Focus Control" circuit, diagram 13
The "Focus-Grid DC Restorer" circuit diagram 14

I haven't yet tried to figure out the circuit, but I'll do my best to narrow down the possibilities.

Remember: I noted a while back that the schematic book that came with the scope had the "Focus Grid DC Restorer" circuit circled.


Re: SG504 Test Method

 

I hope I did not come across as hash. I really wanted to think that a
VNA could be used to do what you were trying because it would solve a
very difficult problem.

My next post was going to include math. :)

There are performance advantages if the source and receiver are
leveled to a certain extent but in a VNA, it is more important that
their levels do not drift with time and temperature.

I think just using the Boonton by itself to verify the SG504 would be
the best way to go. You have some requirements for other applications
though.

Most users in the forum lack a power meter like your Boonton. Real
sampling oscilloscopes are more common and are what I usually
recommend if nothing better is available but they are more difficult
to use than a power meter. A sampling voltmeter like a Racal-Dana
9301A or 9303 could also be used and I suspect HP had something
similar other than a power meter.

On 09 Mar 2016 11:26:04 -0800, you wrote:

Thanks for the insight David:

I did a quick test and I don't see any VNA source changes b4 and after the SOL cal, viewing with the scope. Thus a SOL cal has no effect on the precision of the signal amplitude delivered to the DUT. The VNA rcvr must be doing all the 'corrections'.
So your understanding is correct.
What I do see (O'scope) is the VNA signal amplitude error is within 0.5dB of the amplitude required at low frequencies <100Mhz. More accurate (0.25dB) at higher frequencies 100 to 200Mhz. Scope is a 300Mhz unit so I can't check further with it.
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I'll definitely have to use the Boonton 4210-4B to assess the true amplitude across the Ghz range.
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...

Ancel


Re: 7854 Repair & Restoration

Brian Bloom
 

I think it has something to do with the 'node' that's pressure-seated against the top of the can of U50. If I press beside it on the can (with a ceramic screwdriver - my spudger....), it makes the trace jump to the top of the crt every time.

I assume that the pressure bracket with connected center node is to make sure U50's case stays grounded... If that is correct, what would happen if U50's case became un-grounded?

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