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I have a TDS784D where all four ceramic attenuator hybrids are cracked. I'm looking for replacements, and would like to know if any other models use compatible attenuators. Would the attenuators from a TDS744A work (even partially so I can check the rest of the scope)?

If anyone knows where I might be able to find them at a reasonable cost, I would love to hear from you. I'll take one with SPC problems since I know I can replace the relays.

Hi Robbie,

The Tek solder is flux cored so all you have to do is follow the soldering instructions in the manual.

It's not a bad idea to install connectors in the motor leads. Purists might object but I don't think there's anything wrong with it. I always install IEC mains connectors in those old scopes even though they were never heard of when the scopes were made.

If the filament of V799 tests zero ohms then it's probably OK. Just make sure it lights up when you next power it up. Pin 5 should be an open circuit to both sides of the filament.

Good luck,

Morris

--- In TekScopes@..., "dutchbosstard" <childwhereugo@> wrote:

thanks morris. I am going to try and buy the silver solder from stan's parts shop. I might also try and buy the cover clamps from there also since there is a minimum $10 order.

will I need to use flux with this tektronix silver solder, or is it already flux-cored? All the soldering I have done has always been with 60/40 flux cored solder, so I have never used flux and solder separately. If I do need to use flux, which kind should I use with this kind of solder?

As far as the fan goes, couldnt I just cut the wires and after I take it apart, soak it if necessary, and re-lube it, reconnect it back using these insulated male/female disconnect connectors from home depot? I know it would probably look tacky, but couldn't this possibly be better than having to solder/unsolder, especially if i ever need to pull the fan out again? Or do I just need to suck it up and stop being a pansy about soldering? haha.

this is what I had in mind if i were to just cut the wires:



let me know what you think, I am still going to try and buy about 15-20 feet of silver solder, in case I ever need it.

also since im not gonna be able to power on the scope until I get that fan taken care of, I did find V799, did some reading and looked up the datasheet, checked it with my multimeter and it measured zero ohms between pins 3&4 and 2&7. pin 5 is the plate, and i'm not sure if i could check it's resistance.

let me know what you think,

-Robby

--- In TekScopes@..., "Morris" <vilgotch@> wrote:

Hi again Robbie,

In answer to your questions, firstly no, you don't have to soak the bearings if you can get them turning. I have found that a lot of gunk collects there in some scopes if they were used in a dusty environment so I just like to give them a good clean. If 3-in-one works then go with it.

Tek solder would be ideal if you can get it. If it appears cheaply on ebay then so much the better.

The easiest way to check the sensing diode is to see if it lights up. Checking the filament pins with an ohmmeter will work but it should be obvious by inspection. Note that those tubes have an internal spring contact that shorts across the diode (anode to one side of filament) if and when the filament burns out. That's a fail safe mechanism to make sure the regulated heater voltage fails low.

It's good that you have the A type newer timebases. They can be a bit finicky to get going but hopefully the tunnel diodes in them are OK. We'll see once you've got through the preparatory stuff.

Let us know how you get on,

Morris


--- In TekScopes@..., "dutchbosstard" <childwhereugo@> wrote:

first I would like to say thank you for the very clear advice.

I have been slowly going through the manual since the day i got the scope, but i definitely need to read it thoroughly instead of just kind of skimming it. Yes, i did read the part in the manual about running it with all plug-ins installed. If anyone would like to know, I believe my scope may be a 1967 model, since there is a little information diagram on the bottom of the power supply that has written that it was inspected in '67. It also has the newer 21A and 22A time bases, and the vertical plugins that came with it are the type 53/54K and the type M 4 trace plugin. I do not know the name of the style of screw-in connector, not a BNC. they look like these:




can someone give me the name for those things? i guess i should be happy that the 2 probes that came with the scope have the same strange looking connector. the timebases have BNC connectors.

as far as the fans go, would it really be necessary to soak them in diesel fuel, if i happen to get em turning after disassembly? I know that electric motors and generators often use oil-lite bearings, i've never heard of the bearings losing their oil, but then again I dont know much about oil-lite other than it feels strange, looks strange, and has an interesting smell to it. However, if i cannot get the 555 fan to get turn nicely after taking it apart, i will surely follow your advice word for word.

as far as solder goes, I did indeed read where it says in the power supply to use the silver bearing solder. what I am confused on is: is this solder flux cored, or do i need to solder it with external flux (ive only ever soldered with 60/40 flux cored solder) or does this specific solder need flux? my last solder question is, should I buy this tektronix solder off of ebay?



as far as V799, the thermonic diode, I just did a little reading about it online, could i look up the datasheet to find the pins, remove it and measure the resistance of the filament to make sure its not blown that way?

thanks,

Robby


--- In TekScopes@..., "Morris" <vilgotch@> wrote:

Hi,

Let me add some comments from an experienced Tek scope (including a 555 scoposaurus) restorer to the excellent advice you have had so far:

I gather you are not experienced with vacuum tube equipment although you have worked with high voltage before. I assume you know how to be careful around gutsy power supplies, there's more than enough juice in the 555 to kill you.

At this stage you have had the scope running after a fashion so you can probably assume that the CRT is OK, you know the time delay relay works, no electrolytics have blown up, no smoke got released and the power supplies are at least producing enough to a give you a green flash. That's all very encouraging.

What I would do now is to stop and read the manual thoroughly so you become familiar with what's there, where the test points are and how the thing works. Then I would give it as thorough a clean as possible as has been discussed. The next thing to do before anything else is to get the fan working. The best way to do that is to remove it altogether which involves unsoldering the leads from the tagstrip, taking careful note of where to reconnect them. If there is no little roll of silver solder with the scope you need to go and get some - the commercially available silver bearing solder stuff is not exactly the same as the Tek solder but is preferable to ordinary 60/40 which should not be used.

Taking the fan motor apart is pretty straightforward, just make sure you record where everything goes so you can reassemble it. The bearings can be soaked in thin oil (such as 3-in-1), diesel fuel or kerosene to clean all the gunk off and then lubed with something thicker. Car engine oil is probably OK. Once it spins freely, you can put it back. Eventually you might do the same for the fan in the power supply but for now just put some oil into the oil holes on the bearings.

Once both fans are running you can run the scope again and check the LV power supply voltages at the test points. Start with the -150 which is the master reference for everything else. You don't need to measure the HV just yet but make sure the heater voltages are right. The heater supply is regulated using V799 in the power supply, a special thermal sensing diode type 2AS15A. If it's failed with an open filament then the heater voltage will be low to pretty well all the tubes in the scope. If V799's not lighting up you will need to suspend all operations until you can find a replacement (plenty available on eBay).

Incidentally I missed whether you mentioned which timebase & vertical plugins are installed. Please let us know. Don't try to run the scope without plugins.

Once you've done all that, get back to the brains trust here and I'm sure you will get excellent advice on how to proceed further.

Good Luck!!

Morris

--- In TekScopes@..., "dutchbosstard" <childwhereugo@> wrote:

so yesterday i got real brave and decided to power the scope up. the power supply had the proper 5 amp fuse, but the heater supply had an 8 amp fuse instead of the 7 amp one. i checked the fan in the power supply and i tried turning it by hand and it seemed to spin pretty well, but the larger fan in the 555 was harder to turn, and i also had to remove its dust screen since the dust screen was pressed in, preventing the fan's movement. i powered it on with all the covers off and the PSU fan came on right away, but i noticed that the 555's fan wasnt powering on. all the tubes started to glow and i heard a relay click and then i started fiddling trying to find a beam. i rotated both of the horizontal display knobs and i couldnt get a trace, but every time i turned the know, a trace would appear for a slit second. both beams did this. after the scope had teen turned on for a whole minute, i decided to shut the thing off since the fan in the 555 didnt come off. the fan in the PSU box also had originally started rotating rather slow, but kept gaining speed until after about 30 seconds it started rotating extremely fast.

now this might be a dumb question, but could I have damaged anything by powering it on with a 8amp heater supply fuse instead of the listed 7amp? and also, is there any difference between a "slo-blow" fuse and a "time-delay" fuse?

also, what should i do about the fan in the 555? should i disconnect it and try to power it up with 115v on its own?

From: lilacbarn
Subject: [TekScopes] Re: OT: Component sought
To: TekScopes@...
Date: Saturday, July 21, 2012, 10:40 PM

?

--- In TekScopes@..., "David C. Partridge" wrote:
>
> What I am looking for is something to allow a single sided PCB to be plugged into a DIL IC socket and have the tracks on the lower side.
>
> The following links look almost right, but AFAICT they can only work on a DS PCB with plated holes (I just want to use single sided 0.1" strip-board for this).
>
> <>
>
> <>
>
> I'm sure something suitable must exist ...
>
> Thanks
> Dave
>
Dave, have you got any old wire wrap IC sockets? I have used them in the past for exactly this purpose, but I have to be careful which type of DIL socket I use on the MB as the pins are square for wire wrap and bigger than a standard IC pin. I solder them to the daughter board but leave the full length of pin to push into the MB socket. It is a fixed height above the MB.
Geoff.

What I am looking for is something to allow a single sided PCB to be plugged into a DIL IC socket and have the tracks on the lower side.
<>

I am interested in getting a Tek 21GHz 494P (possibly from eBay), and

probably

will need international shipping to New Zealand. I wonder if you guys can

help

with a succinct list of issues that I need to address.

Import: I have an import license, so not too concerned about incoming
paperwork, local taxes etc.

Export: A web site indicates that 494P may possibly be subject to US

export

control, in the form of "22 CFR". Is this true ?

No, not in general. Pretty much everything exported from the US is "subject
to export control," but a Tek 494P doesn't require a license unless you are
on a list of prohibited trading partners, associated with any such
organizations or states, or if the seller has any reason to think you will
use it to develop WMDs or otherwise engage in any prohibited usage. All of
that would be just as true if the item were a toothbrush.

There are two different lists that must be checked when considering whether
something requires an export license. The CCL is the civilian/dual-use
list, and the USML is the ITAR (arms control) list. Each has to be checked
separately, as almost nothing appears on both lists. The CCL mandates
export licensing (or the use of a specific exemption) for certain signal
analyzers that work above 30 GHz, if they have RBWs of 10 MHz or higher
and/or real-time analysis bandwidth exceeding 20 MHz. None of those
conditions apply to a 494P.

The USML (22 CFR) is concerned mostly with military items. If an item is
not designed, modified, or otherwise configured for military, security, or
intelligence use, e.g. with extended temperature ranges and/or radiation
hardening, then it is generally not covered by 22 CFR. Only a few
hot-button exceptions exist, like advanced inertial measurement hardware and
night vision gear. Those will get you a visit from people with expensive
sunglasses.

Interestingly, Tektronix has a handheld spectrum analyzer (

) with a prominent warning that says it is "listed on the United States
Munitions List (USML)." I don't see how that could be the case, since it
isn't specifically designed, modified, or configured for "intelligence,
security, or military purposes," as cited in USML category XI (b). But
then, logic doesn't always prevail in these matters.

About the only remaining complication for your seller would be if that
particular 494P was part of a specific defense system, something that was
not supposed to have been released as surplus but nevertheless was. Even a
screwdriver can be considered an ITAR-controlled item, if it was part of a
contract for maintaining fighter jets or missiles. There are lots of
stories on this list from people who have had innocuous-sounding items
"recalled" by the US government, sometimes months after purchase. This can
happen at any time, but it would be the seller's problem, not yours.

Technical: expensive things that must work to spec: YIG LO, YIG

pre-selector,

CRT and mixer. Anything else to watch out for with this unit ? How good is

the

power-on-self-test of the unit ? catching CRC errors in EEPROMs is easy,

but I

am hoping for a more thorough internal loop-back of RF.

The self-test is important but it's far from comprehensive. However, 494s
are among the more reliable variants of the 49x models, so if it works, it
is a pretty safe buy. You just need to make sure the mixer and/or
attenuator haven't been fried, and unfortunately, only checking a known
signal will reveal that. There is no substitute for hooking up a cable to
the calibrator jack and verifying that the 100 MHz signal shows up near -20
dBm regardless of the attenuator or span width.

Seller: Finding a seller with decent eBay feedback and who can check the
100MHz ref level on the unit seems a minimum. I believe that the same

mixer is

used for all bands, so is this a strong enough single test of YIG

stability, and

mixer function ? Anything else that is a valuable, quick and easy test ?

Make sure the CRT is good and that the fan isn't noisy. Both are hard to
find.

You should assume you will eventually need to swap out some of the power
supply capacitors (see for more on that),
but that is nothing to be particularly afraid of.

-- john, KE5FX

For those of you that want to make one yourself the test and burn-in
socket came from WaveShare in China (sales@...). Their part number is
499-P44-10 (REV.B). The price is $27 plus $14 to mail it via USPS. I
have no affiliation with the manufacturer etc. Better pictures of the
socket than I can take can be seen at

Hi,
The following has been sort of haunting me for a while:

When I switch on my 2445B, the fan starts running at a low speed and is barely
audible. After a while, it increases its speed to what I consider its maximum.
It is quite audible by then.

For those of you that want to make one yourself the test and burn-in
socket came from WaveShare in China (sales@...). Their part number is
499-P44-10 (REV.B). The price is $27 plus $14 to mail it via USPS. I
have no affiliation with the manufacturer etc. Better pictures of the
socket than I can take can be seen at

Hi Albert,

thanks a lot; just tested the following:

I have 2 pcs. 7A22, 1 pc 7A26, 1 pc 7B53A, 1 pc 7B85.

The 7A26 in left position shows both channels ok, in centre position only CH2 (bottom middle position readout) ok, CH1 (top middle position) no readout.
7B53A and 7B85 timebases show no difference (except additional 7B85 readout bottom right).

It seems to be the problem of the backplane-connector you mentioned.

Did you read the other readout problems thread, concerning a R7903?

not yet; have not known it yet.

Max.