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IMHO,the operative words "but here?" express succinctly what many of us feel.

Best wishes to all,Brian g

Hello
I figure i can pop out my nvram chip and replace with a another that has the FFT option enabled.
Anyone sell these. If you have such chip in yours would you consider copying it and selling it to me.
The reason I ask it no Dos machines or nvram programmers or isa-gpib around here.

Thanks
Paba

I see it. Thank you. Very, very strange. Looks as though I will need to remove the 2 fuse holders, too, to remove the panel to access the nut holding the pot. Why in the world did Tek make that so complex and difficult? But I appreciate the assistance.

R

On Fri, Sep 25, 2020 at 02:08 AM, Richard P wrote:

I can’t say that I see a pot mounting nut on my old 453 unit. Where should I
look?

Remove the aluminum cover sideplate, mounted with two nuts accepting Allen screws (Astig and Trace Rotation) and the variable time/div knob.
Underneath, you'll find the nut holding the pot. It's mounted on a recessed part in the extrusion.

Raymond

Hello, John,

Thank you. I uploaded just now two photos...the front panel and the rear panel. I can’t say that I see a pot mounting nut on my old 453 unit. Where should I look?

Richard

Richard,
In the exploded mechanical drawing of the 453A manual there is a sub-panel behind the outer panel of the swing out section. The pot mounting nut is behind the outer panel. I assume the 453 is similar.
--John Gord

I am looking to replace a 20K pot/switch in my 453. It’s the variable on/off control for time/division, channel B, located on the side of the scope in a recessed panel. The panel swings out easily for servicing when the cabinet is removed. But I can’t figure out how the pot is mounted to the panel. Behind the knob there is...nothing. No typical retaining nut on the threaded shaft. How do I remove this pot? How is it mounted? Thanks.

Richard

Any ideas what could be causing all that ripple on the -5 line?

I did try to buy this item but after a signed contract and payment mostly silence.
Has anyone else paid for this item ? If so then this is a scam.
Please drop me a private message to confirm.

If not then this migth still be valid deal but something might have happened to 'Mark Yeager'.

Oh, the trigger pulse is a flat topped rectangular wave, looks clean both without and with the display section attached.

Hi and thanks to all, especially Harvey. I am not much further forward. I haven't gone for replacing the caps as advised by Harvey, but have managed instead to probe the power supply into the scope, and to upload a pic of what the interference looks like taken at the screen. This pulse is lessened but still present all the way around the scope. My old Trio scope shows almost nothing at all when the same probe is held against its CRT. The PSU output is clean and the trigger pulse is about 5V at the same frequency of 31.5ish kHz.

Is this info helpful to you who know so much more than I? I am out of my depth so moving very cautiously here!

FOLKS Athens TWDs are both spoken for and shipped. thanks for all the interest. I ultimately had FAR more requests than I had scopes to give away.

Charlie C

I have had a problem with a couple of 475's and 475A's caused by Q904 in the A sweep circuit. This part is specified as a 151-0190-01. The base -0190 is a 2N3904, but the -01 version is a Teledyne part in a round white ceramic package with a triangular lead pattern, rather than the black plastic TO-92 of the regular 2N3904. I don't know what the selection criteria for this part are, but it is specified as being supplied by Teledyne. (There are 9 variants of the -0190 listed in Tek documentation). I have found that these tend to be lower beta than other 2N3904's, and I have had some success using the lowest-beta part I could find in this position.

--
Bob Haas

Thanks for the info :-)

It's a low priority "nice to have" for me too.

Regards,
Dave

On Thu, Sep 24, 2020 at 05:47 PM, <tekscopegroup@...> wrote:

I just found that have among my notes that the front cover PN 200-2520-00 fits
All 22xx models.

I mostly agree: I think that the same front cover fits all 2200 models, except the 224X and 2252 models.

Raymond

I just found that have among my notes that the front cover PN 200-2520-00 fits All 22xx models.
Was trying to verify this by looking up this number in the 2213A SM, but could not find where they list the optional accessories, on page 1-1 it only says "to refer to the Accessories page at the back of this manual", no page number given. I have manual 070-4733-00 purchased ages ago from Artek 1984, Last Rev 1988.

If you look up this PN on ebay there are several covers that look correct, but are either too expensive or shipping is too high.

My target was/still is finding a cover for my 2213A, but its very low priority for now,
unless a very must buy crazy good deal comes along.

Here in my area, we have a shipping store call Go'ng Postal. I have them
boxed in bubble wrap, 3" on all sides. Then that box is inside another box
with 3" of foam or bubble wrap on all sides. He charges me anywhere from
$35 to $47 each time. It seems to vary with the same instrument. Depends
on his mood I guess - lol. It will cause the shipping charges to be more
due to dimensional shipping weight, but it's worth it.

People think you can ship them an instrument for $10. They don't realize
that it costs about $50 to properly box it. Then it may be $50-$80 on top
of that. I hear that if you insure for $2000, UPS take much better care of
it in transportation. The boxes don't get tossed as much.

Dave

Adam,

For those ini Southern California, there's a pack-and-ship company called
BoxBrothers that has a number of branches in California. My experience is
with the branches near Los Angeles. They have a "guaranteed" service. They
line all sides of the box with 2" styrofoam and they cut it so there is
little, if any, styrofoam "dust".. The item is bubble-wrapped and placed in
the opening with additional bubble or styro peanuts to fill the voids. They
wrap so the item will not move within the foam cube they create. I used
this service multiple times - my test was shipping some optical equipment.
Prisms in it were affixed with glue so my concern was that shock could
break them free. The item arrived and was fine. I subsequently used their
service for shipping space program surplus that I knew even taking as
checked baggage on a flight home was going to be problematic - it was not
at all dangerous, but on an x-ray scanner, might look to be. All of those
items arrived fine. This service was expensive, but low compared with the
cost of the items.

I did use FedEx to ship an Apollo optical unit assembly (the sextant used
in the Command Module) that belongd to a friend of mine, for auction. I
wrapped the unit itself with polyethylene foam and stretch-wrapped it in
place. FedEx then packed and shipped it. The auction house took photos for
their catalog and it was in as good condition as when I shipped it. I had
it insusred for $5000 which was a lot less than what it wound up selling
for, but it meant that FedEx was going to pack it well and handle it
equally well. The auction house told me the packing was similar to what
BoxBrothers does - the double-walled box was completely lined with 2" of
styrofoam with an extra 1" on the bottom.

Before 9/11, I had won a high-resolution graphics display system on a GSA
sale. This was a system made by Celco and was the imaging part of a film
recorder. It was used to turn digital images into film ones for the
enterainment film industry. The CRT in it was a very high-resolution one.
It had a low-persistence phosphor and a spot size of around 1 micron. This
was NOT a direct-view tube - basically one line was displayed at a time
until the entire image had been recorded on the film. It used a precison
magnetic deflection system built by Celco. If I recall correctly, the tube
was made by Litton. There was no way I was going to ship that tube, so I
boxed it up - "floated" in soft foam - and took it as a carry-on item. I
doubut I could do that today. I got it home fine, reassembled the display
part and then it sat for several years. I wanted to try to use it, but it
had no cables. Celco told me the cabling could be rebuilt (these were
pretty much custom systems) and they could do it for $5000. I wound up
selling it to R/Greenberg Associates, the folks known for generating titles
for movies. They had a system like it and wanted it for spare parts. They
came to pick it up. They told me the tube worked when they tested it. From
the same lot, I also won a Tek 556 dual-beam scope. I boxed that myself and
shipped it (quite expensive). When it arrived home, it powered up and
worked on the first try. I was worried about that dual-beam tube, it all
was OK. I think that was the heaviest Tek scope I ever shipped. My packing
method was similar to what I and others have described.

Steve

Adam,

None of 'pack and ship' places I've dealt with know how to deal with heavy delicate stuff. To them heavy generally seems to mean sturdy.

In addition to the other sources folks have mentioned, most home centers seem to carry moving boxes these days. Lowes and Home Depot have high pressure double-wall corrugated boxes.

If you pack it yourself (and I suggest you do) I would:
- Double box
- Use double-wall outer boxes for anything over 35 pounds
- Have at least 3" cushion on all six sides between inner and outer boxes.
- Put address labels on all inner boxes, and large items. Boxes get damaged and labels get stripped. Inner labels increase the chance of most of the shipment getting there. This has saved me several times.
- Put an address label inside the top flap of the outside box.
- Use extra padding/blocking for the front and back panels. I usually cut strips of corrugated and "S" curl them around controls or use small boxes to make sure the panels, controls, and the tube face are protected.
- Pack tight. Leave no air and compress the packing as much as you can get away with without damaging the outer box. Loose packing results in a guaranteed damaged box. A box damaged in transit is not a recipe for shipping success.
- Do not use "air pillows' with heavy items. If one air pillow breaks or leaks your cushion pretty much goes away. They always leak or break. Always
- Tape all the way around the box in both axes on the closed sides of the box with one continuous piece of tape and overlap the ends at least 8 inches. Use real >1.5" wide shipping tape. Use good quality tape designed for shipping that is at least 2 mil thick.
- While not essential, it's a good idea to seal all box flap edges. If the box deforms it is more likely to retain the all important packing material.
- When in doubt, overpack. Be doubtful. Extra packing doesn't add much to shipping cost (as long as it doesn't require an oversize box.)

--
Oz (in DFW) N1OZ

However.... Something is not right here as I would say you (and us) are spending too much time analyzing and speculating on this one problem. If you have a good new oscillator and have good new FFs, the circuit should just be fixed and work as it did 30 years ago.

Tony, your point is well taken and apologies for over-analyzing. It is mostly about learning and trying to understand on my part and a certain amount of confusion. However, I think I have now discovered why the crystal output was so variable. More below.

I had a quick look at the DIL packaged 50MHz oscillators available from RS Online and they are all marked TTL/CMOS compatible, from where did you get yours?

From an eBay seller.

Please don't be insulted - you haven't switched the scope input to 50 ohms have you?

Not at all. Checked just in case, but my Philips scope does warn and will not allow switching to 50Ω while a probe is connected to the channel. It was not set to 50Ω. I did realise that the FC cable was still connected up and plugged in but both scope and FC were using 1MΩ inputs. Connecting the FC does have some effect on amplitude but not quite that much.

Another long shot to try when you have the FFs and the oscillator out, ohm the trace to ground and +5 (power off) and see if there is any resistance. Should be an open circuit.

I am still hoping I can get the ICs out in one piece so as to be able to make a comparison between old and new and do a "post-mortem" as I agree with the consensus that there is likely a fault with one of them.

It might be worthwhile to repeat the oscillator output test with the load resistor connected to +5 rather than ground. The oscillator on my board appears to pull a high level down rather than drive a low level up to a TTL level. ... I had suggested much earlier that you try pulling pin 8 of the oscillator up through a resistor to +5 to see if it improves the clock level. Did you try that? Might try a 1K pull up with the scope monitoring the pin and see if you get a clock with a better TTL signal.

I did (rather embarrasingly) find a problem with the earth lead on the scope probe which caused a much reduced signal amplitude at times. I also found that when my hand was on the scope probe this also seems to reduce signal amplitude significantly. Both of these issues, while not explaining the abscence of signals on the processor (these were also checked with an LA), did contribute the variations I was seeing while testing the crystals and the resulting confusion. Having sorted that out, I re-ran the tests on both old and new crystals, first with the 1kΩ resistor then with 470Ω, 30 mins each. The new crystal has a slightly higher output (perhaps by 0.2V) without load. Both hold steady at just below 4V with a 1kΩ load resistor and about 3.8V with a 470kΩ load resistor. Neither gets warm to the touch. It seems reasonable to conclude that both crystals are good and the problem is with one of the ICs.

While repeating the tests I did also try pulling up to +5V as suggested rather than pulling down to GND with a 1kΩ resistor but that made no difference to the amplitude of the signal. It only changes the shape of the wave very slightly.

I am still waiting for the remaining parts to arrive at which point I will be able to replace the two ICs, finish re-capping (except for the large can), re-assemble and test the clock. In the meantime I have partially re-capped the board. I still need to tackle removing the two 74S112 ICs.