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Please don't shotgun replacing electrolytics, the odds are you'll do more harm than good. Some of those multilayer boards can be problematic when de-soldering components - you SO don’t want to strip a PTH.

If it works just use it.

David

That's a great suggestion, Miguel. I went the other direction many years ago to convert a 502 to work with a 492. It was a pretty quick conversion once I was able to find a suitable crystal. So Attilio has an additional option.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

You can buy a 503 change the crystal and use the nano to retune the 2nd band pass filter



-----Mensaje original-----
De: [email protected] [mailto:[email protected]] En nombre de Attilio
Enviado el: miércoles, 30 de diciembre de 2020 1:16
Para: [email protected]
Asunto: Re: [TekScopes] Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Hi Dave,
thanks Dave, I'll go read the posts of the nanovna-users group.

--Cheers
Attilio







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On Sat, Dec 26, 2020 at 03:47 PM, Nenad Filipovic wrote:

With this math someone may profit hundreds of $ for a 585 dug up out of some
old man's basement.

No not really ... unless one's reality is "reality T.V. shows." I think, most of the people doing this have a box of old, dusty, and used tubes, sitting in the basement... that will "sell on Ebay, for a bunch, a lot, of money!"... some day... or so they think. They're only dreaming. So disappointing, for them, when Ebay bills them for the ads.

Good, clean data on the 5687/6900 is available here:



Having been thru many 100s of 5687s, as seen here:



and here:



I can say that the Tung-Sol 5687 is the NOS part to use to replace the 6900. But even so they have to be tested, see the reject rate in the Excel spreadsheet.

As nearly as I can tell the Raytheon-branded 5687 was a Tung-Sol part

Bill

On Sun, Dec 27, 2020 at 08:02 AM, - wrote:

Bendix 6900

Which 500 series was the 6900 used in? (I believe 6900 a twin medium mu triode.) 6AX7/12AX7 was high mu.
Bendix was (their gone) an interesting company, involved in the aerospace industrial military supply. (A common name during WWII and the 50's, and 60s.
The 6900 was a "hardened" tube.. made to withstand high g, shock, vibration, and was supposed to be more reliable. (well ... for at least the brief time a launched missile lasted.)
Unless one is planning on launching one's class A, audio amp, into low earth orbit... one doesn't need Bendix 6900s.

An enterprising and unscrupulous person would pay for the scope, pull the tubes, sell them on eBay at a premium to the audio-nuts, use the proceeds to repopulate the scope with NOS tubes purchased at reasonable prices, and still make bank on the deal.

Just saying.

-- Jeff Dutky

I am not sure that you understand what I am trying to say,
so let me be clear:

Whenever the scrap companies I consult for see a 453/454
valued for less than $50, they tear it to bits, and it
becomes gold scrap, aluminum scrap, copper scrap, and plastic
scrap, worth something over $100.

It has nothing to do with storage space, as they don't get
stored beyond what it takes to fill a gaylord box with the
sorted remains to capacity.

I tried for a while to stem the flow, and indeed, I am
storing a pallet full of 453/454's, and I cannot do it. This
group has only one mode: Let me cherry pick your stash, for
less than the scrap value, remove any semblance of order in
your storage space, and leave you with a sore back, and a
disarrayed heap of trash.

So, as I said, if the group wants this stuff to remain in
one piece, then it better start valuing it as if it is more
than worthless trash; it is not, it is very valuable to the
scrap dealers... As scrap. They have no interest in hanging
on to it, and letting the public rummage through their space,
cherry picking the remains. Insurance won't allow it, and
high cost of warehouse space wrecks any value such cherry
picking might expose.

-Chuck Harris



Tom Lee wrote:

Thanks Roy. Lots of people out there selling tubes I guess.

On Tue, Dec 29, 2020 at 07:15 PM, John Williams wrote:

Are you thinking of some other supplier perhaps?

Stan Winston was ... ESRC Vacuum Tubes + The Tube Center + ABC Vacuum Tubes ... either of those, or all of them.

Hmm. Radio Electric Supply is owned by Dale and Roy Rogalski. I don’t know if anyone else was associated with them. I talked to them today and apparently are doing well. Are you thinking of some other supplier perhaps?

Dave,

I restored one of these earlier this year. I upped the capacitance of the condensers and used high temp. low ESR and long life ones. I restuffed the two main screw cans with 1200mfd 250V LGR types. I changed the 150000 ohm 1W bleeder across the 1200mfd condensers to 100000 ohm 5W. I wanted a faster bleeding due to additional capacitance and the resistor is runs cooler than the original since it is larger in wattage. Some of the resistors were underrated in wattage so those were increased in wattage. ALL the 9/9,1V zeners will be open in any plug-in or mainframe. Look at the schematic for these. I used the 1,3W BZXB85 types. Those are 2% tolerance. The higher power of these from the original 1/2W will not hurt. The higher power means the Z of the zener is lower. The 1mfd coupling/bypass on the rear facing board between the hypcons had high ESR so I replaced them with film types. These 1mfd condensers bypass the 9/9,1V zeners. Check the diodes in the d-c restoration circuit. Those can be leaky. The 22meg carbon resistors will very likely be high, about 30meg. I replaced mine with 1/2W 1% types. When these are high, the brightness is high then will drop as the unit warms up. I put good quality heatsink compound on the devices that have heatsinks. I did add a few TO39/5 heatsinks on some of the transistors because these did run hot. I did take all the knobs off and oiled the set screws and shafts. A steel set screw in aluminum to another metal means electrolysis making set screws hard to get out or seize. I did put in an NTC, CL70, to limit inrush current from the mains when turned on. Pull the transistors and ICs out enough to move back and forth to make sure the contact is good. I have seen ones that were "open circuit" until it/they were moved a couple of times in their sockets. I added a resistor in series with the green pilot lamp to make it last longer. I like my pilot lamps in things to be bright enough to know the piece is on while running on a lower voltage, e.g. 5V on a 47/1847 lamp, 3,5-4V on the 683 lamps Tek. used. Look out for the 151-0367-00 transistors. These likely will be bad from C to E as a diode. The ones that have a blue face will not be bad. Check the others. This number is used in a number of plug-ins and mainframes. I used KSP10BU as replacements. Someone else suggested a couple of other numbers are as good as replacements. What I said is what I have done. You do what you want with your item. No criticism or preaching is intended you must do these things. I am picky about my things and what parts I get because of my experience and research. I will never claim to be "the" expert or perfect. I am happy to see you got an item you wanted, it works and will give you the service you desire. It is nice to read of others getting what they want and getting it working again. A great sense of joy comes from making something not working to working again whatever the item is. There are many great nice people on this group that will be happy to help you and give advice. I have learned from them and am grateful to them.

Mark

Dave,

Just got a nice looking 7904A. Plugged it in with sufficient fear and
trembling, exc. for noisy controls, seemed to work OK. Got trace and sweep
and expanded sweep. Didnt put any signals into it. I did a lot of TV work
in the day, saw stuff blow up, slightly paranoid about leaving old caps
powered up so I pulled the cord.

The kicker is the 7L12 2.4 GHz spectrum analyzer and 7S12 TDR plugins. I
didnt plug them in!

Ive ordered all the electrolytic caps to do a shotgun replace. If the scope
works fine, if the plugins work, finer yet!

Any 'gotchas" inside? I read about the blue edge connectors. Any
info/advice on the plugins?

Cheers/73 Dave/

Hi Dave,
thanks Dave, I'll go read the posts of the nanovna-users group.

--Cheers
Attilio

Hi Tom,
you are a great person.
Sometimes the bureaucracy can demoralize you, you must not give up.

I think I will purchase both the nanoVNA and a noise generator to use my 7L13 while waiting to find its TR502 tracking generator.

Happy New Year
Attilio

Fellow techies,

I'm pleased to announce I've fixed the problems with the Blue Feather file library. It's back up and operating as normal.

For those who have requested the login info, please continue to use the same user/password I supplied you before. There's been no change in that regard.

Thanks for your patience.

--
---
Bruce Lane, ARS KC7GR

kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)

Hi Attilio,

If your intention was/is to make frequency-response measurements with your SA in combination with a noise source, the nanoVNA will do that all by itself; no other device needed -- the nano will present a plot of frequency response magnitude and phase. So, think of the nanoVNA as a separate instrument.

There's also a related project, the tinySA, which is in the same form factor as the nanoVNA. The tinySA can also be used as a signal generator, although a rudimentary one. As with the nanoVNA, the tinySA is very inexpensive (order of $40, depending on vendor).

I have no relationship with the designers or vendors of these products, by the way. I've just been evaluating ways to keep my lab courses going in this age of COVID-forced lockdowns and remote teaching. Shipping "real" lab equipment is impractical for many obvious reasons. But the tinySA and nanoVNA go a long way toward enabling students to do all their lab experiments at home, and with a capital outlay that my department can absorb. Ironically, my biggest challenge is to find a suitable oscilloscope of similar price/performance. Getting approval to ship soldering stations and solder turned out to be a bureaucratic nightmare ("But what if students burn down their homes, or eat the solder?"). Solving that problem proved to consume much more time and energy than any other step in the process.

I'll now go back to the bench and solder something as therapy. ;)

-- Felice anno nuovo,
Tom


--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

My only Tektronix scope is an RM45A (rack-mount 545A) and my interest in 500 series scopes is the only reason I'm here! My favorite feature of the scope is using "B intensified by A," turning the delay multiplier to select a portion of the waveform, and then switching to "A delayed by B."

I raised a 549 from the grave and it is now working well, except for the memory function. The storage board is of version 'E' (actually indicated as HE, what must stand for Hoogeveen, The Netherlands type 'E'). If someone has the documentation on this version, that would be very welcome. The problem I now have is that the upper half of the CTR does not light up when the STORE function is activated. When the INTEGRATE TRACES button is pressed, than the upper part of the screen does light up and stays like that even when when STORE is depressed. Ingrate Traces has to be pushed again to get a normal screen. Switching the connections of the UPPER and LOWER on the PCB indicates that the electronics are working fine for upper and lower.
In addition to this, no signal remains on the screen in STORE mode. TP FLOOD CATH is 112 volt (seems to be low) and can not be altered since R1185 is missing. So 2 main questions:
1) why does the upper part of the CTR not light up in STORE mode;
2) why does the memory function not work.

Any help/suggestions will be appreciated