Date   

Re: Fix or Part Out a Tek 475A

Simon
 

You can check the operation of the Z axis amplifier by looking at the waveform at TP1366 or TP1364. I would have most faith in the circuit diagram and what is marked on the transistor in the circuit unless you think someone else has been there. These are high speed switching transistors and you should be able to find equivalents from an internet search. Pinouts can vary between manufacturers. The power supply is 110 V so some may require higher Vce.
Simon


Re: Fix or Part Out a Tek 475A

 

There are a number of symptoms, which are a bit vague:

first, and most obviously, there is no response to turning the beam intensity knob; the trace stays the same brightness no matter what the knob (or pot) position. I verified that the voltage on the center tap of the beam intensity pot swings between -8V and +15V when you rotate the knob.

second, there appears to be a "ghost image" of the trace at the ground level. At first I had thought that the trace was "wrapping around" the screen, but now I suspect that I am seeing the retrace that is not being properly blanked.

third, I noticed that the A INTENS mode didn't show a clearly intensified region, but seemed to respond to the delayed B trigger correctly. Again, this points to a problem in the beam intensity amplifier.

Other than these malfunctions I have full, clear traces on the screen, and they respond to the focus adjustment. This leads me to suspect that the high voltage section is working mostly properly, and that the tube is in good condition (I've had absurdly good luck buying "for parts" scopes from eBay. Everything has powered up and shown traces on the screen. The only malfunctions have been this 475A, which is still being fully diagnosed, and a 2215A that had a blown capacitor in the horizontal position circuit. I was expecting much less functionality, and much less guilt about disassembling the non-working scopes for parts).

Also, I don't currently have a "well insulated probe" for my multi-meter (it's on the list of things to get), so I'm not willing to poke at the 1250V test points. Fortunately I don't think that the HV section is suspect, outside of the beam intensity amplifier.

As I said above (maybe while you were posting your message) I already went in and pulled each of the transistors in the beam intensity amplifier, one by one, and tested them in a component tester. Three of the transistors appeared to be bad, one acted like a short circuit, and the other two acted like fully open circuits.

When I posted my reply above, however, I had been looking at the wrong service manual (I had mistakenly opened the manual for the 475 rather than the 475A). One of the two blown transistors (Q1352) does not have a non-Tek part number specified; it is listed only as 151-0407-00 from manufacturer 80009 (Tektronix). The same part in the 475 is listed as a 2N3501, but I have no idea what help that might be.

I'm something of a novice when it comes to transistors, so I don't really know what characteristics I should be looking at, or even what most of the characteristics mean (I can make a guess, but it's not what you could call an "educated guess" other than that I know the difference between voltage, current, power, and frequency, and I have heard of most of the terms involved with transistors).


Re: Fix or Part Out a Tek 475A

Simon
 

You don’t say what the symptoms are. No trace? Not found by a press on the beam finder button? You can work on the HT section by taking off the metal screening plate (5-6 screws). If you look around the front left side, you will see test points for the cathode (-2450 V) and first grid (-2530 V). They are close to thick wires that route to the CRT socket. Measure these voltages with a meter (full scale 3000 V) using well insulated probes. You can also measure the grid-cathode voltage with a plastic multimeter; should be around -80 V and vary with intensity and and grid bias pot settings.
On switching off the scope these voltages decay fairly quickly, but it is best to be sure by briefly grounding the cathode test point. The accepted technique when probing high voltages is to always have one hand behind your back, a zap through the whole body to ground is not so bad as a zap from one arm to another.
If you have good HT, it is worth switching on the scope in a darkened room to see if you have a green glow from the front of the CRT, which would indicate that the tube is OK, but that the beam is too displaced to form a spot or trace (wrong signals on the X Y plates, in which case it is best to troubleshoot the drives to these plates. The X plates are driven by the red and green wires going through a hole in the main board in front of the HT section (position 7E on A9 board). The Y plates can be probed at the resistive T network (R497) connected to the front two Y plates. Be careful probing this part which is a little fragile and very hard to replace. The front two Y plates are connected to the back two Y plates inside the CRT. The back two Y plates are driven by the Y output custom IC amplifier U470. Mine had gone bad and the spot was deflected way off center.
If you suspect the THT circuit supplying the post deflection anode (around 15 kV), you can test it by pulling out the white plastic plug holding the fat red wire. This voltage is dangerous and takes a while to decay after switch off. TV repairmen know how to ground this by sliding a grounded flat blade under the rubber boot on the front of the CRT. You can test the THT by poking one end of an automotive ignition wire connected to a spark plug into the THT socket. If you get a good spark chances are the THT is good enough to produce a bright spot.
If the HT and THT are OK, I would check the waveform at TPs 1364 and 1366 to make sure you are getting enough voltage to unblank the beam in sync with the timebase. Reseating the transistors in this circuit may be needed.
Simon


Re: Fix or Part Out a Tek 475A

 

So I've gone ahead with trying to fix the 475A further. I examined both the block diagram of the CRT control system, and the schematic for the beam intensity and blanking amplifier. There are 7 transistors involved in the beam intensity amplifier, and I located each of them on the circuit board.

With the unit powered off and unplugged, I carefully extracted each transistor, one at at time, and ran them through my component identifier tool. I found two parts that the tool did not see as present in the test socket (I assume that these are blown open, Q1352 and Q1358), one that triggered the self-calibration function (assumed to be blown short, Q1344), and one that reads as a PNP when the parts list says in should be an NPN (Q1338, I don't know what to make of that: I've seen that the board images are occasionally wrong, but if the schematic and parts list are wrong, what can I do?).

I replaced the shorted transistor straight away (it's a bog standard 2N3906), but the others are more difficult:

Q1338 is an NPN SKA6516 according to the service manual, but the device is marked identifies as a PNP transistor, the part is printed with a Tek part# "151367 TI 877" or "TI 811" it's hard to tell from the style of the printing. I'm tempted to leave this one in place until it is proven to be a problem.
Q1352 is an NPN 2N3501 according to the service manual, but the manual also says it is "selected from 2N3501". Without knowing the selection criteria, how can I possibly replace it with a comparable part?
Q1358 is a PNP MPS3640 according to the service manual. I have looked at Newark, Arrow, Mouser, DIgiKey and JameCo for replacements, with very little success. I have found an SMD part that appears to be the same number (MMBT3640) but it's power dissipation is only a fraction of the MPS3604 in a TO92 package. I'm guessing (from an abundance of ignorance) that the headline spec is Ft of 500MHz, but I know that I would need to exceed the other specs as well (not so hard for Vcb, Vce, and Veb, but power dissipation seems to be hard to match, and I haven't really looked at collector capacitance).

I know that some of the "selected" parts are selected in groups of two or more, usually to have matching characteristics, or characteristics in some precise ratio. I don't see any indication of what that criteria would be in this case.

So, my questions are:

1. What should I do about Q1338 which seems to be a different part than what the manual specifies?
2. How do I "select" a new 2N3501 to replace the blown part?
3. How do I choose a replacement for the MPS3640 that doesn't seem to be manufactured anymore?

Thanks

-- Jeff Dutky

P.S. I have managed, thus far, to avoid getting zapped.


Re: New member - Hi everyone!

Dave Seiter
 

Welcome!  The 465 is the only portable scope I have, and was a recent acquisition that I couldn't pass up ($20!).  Not entirely true I guess, as I also have a T912 and a NLS Miniscope.  It's a great piece of gear.  I always told myself I'd stay away from the portables because I had to draw the line somewhere....
Before long, you'll thinking "where did I put the 7844 with the 7CT1N?"
-Dave (another one)

On Saturday, November 21, 2020, 06:29:06 PM PST, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Hello all,
I just joined yesterday after looking for a good forum group to connect with regarding my rekindled interest in Tektronix oscilloscopes.
My history with these scopes goes back to my Army days in the 80's. Since then I went on to get an engineering degree and have only gotten to get my hands on lab equipment on odd occasions while my "real" work consisted of sitting in front of computer screens fiddling with CAD tools. I can't say that was ever my first passion.
Currently, my first interest is the old 465 scope I used in the Army. There's just a personal synchronicity between their place in time, quality of design and construction, and gestalt that resonates with me. It's a thing that's stayed with me since I went back to school - that "real" engineering that harkens back to those "steely eyed missile men" of the 60's - the over the top thoroughness and precision I used to experience in the equipment I worked on in the Army. The 465 manual (my recent acquisition included one) is a great example. It just doesn't exist in the hurry up rush to market the tech industry has become.
Pardon my rose colored goggles.
After many years of wishing and looking hopefully at eBay I found and purchased a good deal on a working scope. I immediately fired it up and was right back in "the van" (see profile pic). Suddenly my garage bench is being turned into a electronics workstation. Just like I've always wanted.
Which brings me back to here: Now that I understand what's going on inside these things, and there are so many "parts" scopes out there, I find myself wanting to fixing them. As great as the manual is, there's just no substitute for the massive amount of knowledge out there. And that goes beyond particulars of 465 operation and repair. For example, where do I find parts!? So far I've been lucky, but I can tell some things are going to be hard to find.
I've already purchased a "parts" scope, but it's in such great physical condition that I can tell it's likely to become my real shop scope. I'm already deep into tearing it down. I has a bad B-delay time/div switch cam (already ordered NOS on eBay), a bad HV oscillator filter cap (C1419), and perhaps more. All very fixable. I'm documenting the tear down as much as I can. I haven't found any detailed instructions online so far, so I'm thinking I might write a "how to"? We'll see. I'll be glad to share if 'yall think it's a worthwhile endeavor.
In any case, I wanted to take the opportunity to say "Hi!". And Dennis suggested I introduce myself. Thanks for approving me Dennis! He also suggested I ask that 'yall fill out your bios. Please do check in on mine - a little more back-story in there. As Dennis says, he's just as guilty not having his filled out, but he noted that my having one helped him out. As he noted, this forum is full of fascinating individuals, and your backgrounds are so full of valuable experience that it's a shame to not share your wealth of knowledge with newbies like myself. I'm sure I'm just as much a quiet low key personality as the rest of 'ya. But I crack up when I look at the member directory. A bunch of pictures of myself looking back at me. I'd love to be able to peruse the bios and get to know you all.
I've blabbered on enough. Have a great evening, and I look forward to sharing and talking with you down the road.
Dave


2710 Spectrum Analyser 'Cannot count VCO, IF' error

Martin Whybrow
 

Having repaired the PSU section of my 2710, I'm now trying to deal with the other issues it has. I'm seeing the error message 'Cannot count VCO, IF'; I've checked the counter signals going into the microprocessor board and have measured the following:
J180 - 100MHz at -14dBm, bursts of approx 1us long, repeating every 12us.
J190 - 10 MHz at 0dBm
J195 - 100MHz at -8dBm changing to -4dBm regularly
Can anyone confirm whether or not these signals are what would be expected at the input to the counter, in particular the signal at P180?


Re: New member - Hi everyone!

 

Welcome to the asylum ... I mean party!

You can get full documentation (as PDFs) on most Tek scopes at either TekWiki (w1f0.com/tekwiki) or at the Boat Anchor Manual Archive (bama.edebris.com).

Here is the TekWiki page for the 465: http://w140.com/tekwiki/wiki/465
and the same at BAMA: https://bama.edebris.com/manuals/tek/465/

Careful, the TekWiki site, especially, is rocket fuel for the condition. I started out with two scopes that belonged to my father (a 475 and a 2213), that work more than well enough for my purposes (and could be made to work perfectly with the proper application of time, skill, and money). I now have half a dozen scopes, half of which are parts scopes for the 475, and two of which (a 475A and a 2215A) are completely new models that I lusted for after reading about them on TekWiki (and there is another that I am planning to buy, if I can just find a nice specimen at a reasonable price).

-- Jeff Dutky


CRT in TAS 475

Dave Brown
 

Anyone know what the Tek part no. for the CRT used in the TAS 475 is?
DaveB, NZ


Re: New member - Hi everyone!

Bill Perkins <sales@...>
 

Welcome to the rabbit hole :-) That's how it starts ...
Never mind, it's a warren long since . . .

I have a lot of scopes but the 465 is one of my favorites. Once
upon a time I only had one scope ...

Me too, see the link:

https://www.pearl-hifi.com/07_Facility_Tour/hotlink-ok/Just_Bought_Another_Tek_Scope.jpg
Paul
Bill @ PEARL, Inc.


Re: New member - Hi everyone!

Paul Amaranth
 

On Sun, Nov 22, 2020 at 02:28:42AM +0000, Dave Peterson via groups.io wrote:
I've already purchased a "parts" scope, but it's in such great physical condition that I can tell it's likely to become my real shop scope. I'm already deep into tearing it down. I has a bad B-delay time/div switch cam (already ordered NOS on eBay), a bad HV oscillator filter cap (C1419), and perhaps more. All very fixable. I'm documenting the tear down as much as I can. I haven't found any detailed instructions online so far, so I'm thinking I might write a "how to"? We'll see. I'll be glad to share if 'yall think it's a worthwhile endeavor.
Welcome to the rabbit hole :-) That's how it starts ...

I have a lot of scopes but the 465 is one of my favorites. Once upon a time I only had one scope ...

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


New member - Hi everyone!

Dave Peterson
 

Hello all,
I just joined yesterday after looking for a good forum group to connect with regarding my rekindled interest in Tektronix oscilloscopes.
My history with these scopes goes back to my Army days in the 80's. Since then I went on to get an engineering degree and have only gotten to get my hands on lab equipment on odd occasions while my "real" work consisted of sitting in front of computer screens fiddling with CAD tools. I can't say that was ever my first passion.
Currently, my first interest is the old 465 scope I used in the Army. There's just a personal synchronicity between their place in time, quality of design and construction, and gestalt that resonates with me. It's a thing that's stayed with me since I went back to school - that "real" engineering that harkens back to those "steely eyed missile men" of the 60's - the over the top thoroughness and precision I used to experience in the equipment I worked on in the Army. The 465 manual (my recent acquisition included one) is a great example. It just doesn't exist in the hurry up rush to market the tech industry has become.
Pardon my rose colored goggles.
After many years of wishing and looking hopefully at eBay I found and purchased a good deal on a working scope. I immediately fired it up and was right back in "the van" (see profile pic). Suddenly my garage bench is being turned into a electronics workstation. Just like I've always wanted.
Which brings me back to here: Now that I understand what's going on inside these things, and there are so many "parts" scopes out there, I find myself wanting to fixing them. As great as the manual is, there's just no substitute for the massive amount of knowledge out there. And that goes beyond particulars of 465 operation and repair. For example, where do I find parts!? So far I've been lucky, but I can tell some things are going to be hard to find.
I've already purchased a "parts" scope, but it's in such great physical condition that I can tell it's likely to become my real shop scope. I'm already deep into tearing it down. I has a bad B-delay time/div switch cam (already ordered NOS on eBay), a bad HV oscillator filter cap (C1419), and perhaps more. All very fixable. I'm documenting the tear down as much as I can. I haven't found any detailed instructions online so far, so I'm thinking I might write a "how to"? We'll see. I'll be glad to share if 'yall think it's a worthwhile endeavor.
In any case, I wanted to take the opportunity to say "Hi!". And Dennis suggested I introduce myself. Thanks for approving me Dennis! He also suggested I ask that 'yall fill out your bios. Please do check in on mine - a little more back-story in there. As Dennis says, he's just as guilty not having his filled out, but he noted that my having one helped him out. As he noted, this forum is full of fascinating individuals, and your backgrounds are so full of valuable experience that it's a shame to not share your wealth of knowledge with newbies like myself. I'm sure I'm just as much a quiet low key personality as the rest of 'ya. But I crack up when I look at the member directory. A bunch of pictures of myself looking back at me. I'd love to be able to peruse the bios and get to know you all.
I've blabbered on enough. Have a great evening, and I look forward to sharing and talking with you down the road.
Dave


Re: Open Filament on scope

Randy.AB9GO
 

I used to fix a rectifier tube in an old 30's radio I had in my tube
tester. It was a type I couldn't find locally so I put it in my old Simpson
tube tester and cranked the filament voltage up to 117. It was a 25 volt
filament and when you tapped the tube it would spot weld the filament back
together again. It would last a while and I would have to do it again.
With the CRT you're starting with nothing and if you totally blow the
filament you've lost nothing, so you can only win! Don't fear the
capacitor!

randy.ab9go@gmail.com


2465B cable I can't identify, what is it for?

Grayson Evans
 

I am reassembling my 2465B after PS overhaul. There is a two conductor "cable" that comes from the A4 readout board and looks like it is supposed to plug into J305 on the A3 inverter board (which is +5V). It seems to me when I took the PS out this was not connected to anything.
No manual I have been able to download has the A4 board that is in my scope, so I can't find what the cable is for. One of the manuals I have shows a small A4 board (about half the length of the PS). But the one in my scope is full length, the same size as the processor board.
Thanks for any help.
Grayson


515A-S1 Oscilloscope DC Fan Motor Question

Paul Humel
 

I recently purchased a Type 515A oscilloscope online, and noticed that it’s labelled “Type 515A-S1”. After some investigation I found that the “-S1” means that it can run on voltages of up to 800 cycles per second. And I found that in order to do this, the cooling fan is DC instead of AC. I opened mine up, and discovered that the DC fan motor has been replaced by a lightweight AC fan motor (Tektronix P/N 147-022). While I don't use 800 cps power, I’d like to keep my 515A-S1 “anatomically correct” and install the proper Tektronix DC fan motor. Does anyone have an idea of where I could find one? Thanks.


Re: Open Filament on scope

Dave Peterson
 

Please let us know how it turns out. If successful it'd be good to know what ended up working.

New to the group, and new to Tek scope refurbishing. So full of newby enthusiasm. But have a history with these things and think this might be my retirement hobby! I've been looking for a good forum/group to interact with for sharing info. This seems like a good one.

Hoping I can find shared experiences like yours, so hope to learn what happened here. I've never heard of such a thing! Repairing an open filament with a cap discharge? Yikes!

Good luck!
Dave


Re: Broken Tektronix scopes free

Dave Peterson
 

Apologies if this is a duplicate. I just joined, and may need approval from the moderator.

I'm interested in the 465s if I'm not too late. I'm in San Francisco and willing to pay shipping within the US.

What's the condition of the scopes? Good? Bad? Ugly?

Feel free to contact me directly. My email is now in my profile.

Thanks!
Dave


Re: Broken Tektronix scopes free

Dave Peterson
 

Would also like to know more about the 465s.
Condition? Nasty, ok, good?
I'm in San Francisco. Where would you be shipping from?
Thanks,
Dave


Re: Multi-section electrolytic capacitors from Hayseed

PAUL KOBY
 

I have used Hayseedhamfest for multisection caps for an HP VTVM rebuild. They make great caps.
Their only draw back is they are not inexpesive.
Paul Koby
KA5OBI


Re: Fix or Part Out a Tek 475A

Ed Breya
 

The normal way to discharge Tek CRTs with Alden connectors, is to carefully pull the CRT end of the connector out, and discharge the tip to the chassis. Problem is, this isn't always easy, because the connector halves are often stuck together pretty well - especially if one part is silicone rubber. Also, it's usually in tight quarters, with fairly short leads. First twist the halves to break the bond, then hold the outer part firmly and twist and pull the inner part just until it unsnaps, and withdraw it slowly. The real trick is to not be nervous or shaky, and accidentally let go of the CRT lead - hold steady until you can get the exposed pin to contact only an open area of chassis or shielding. If you slip and let it loose on the way out, the lead may flail around and zap your fingers, or worse, land in some nearby circuitry. Dexterity and control are crucial - like opening a bag of chips without having it suddenly shred and fling the contents everywhere. Practice makes perfect - you can eventually do it with one hand, without even looking.

Ed


Re: Multi-section electrolytic capacitors from Hayseed

John Atwood
 

FWI: Antique Electronic Supply (tubesandmore.com <http://tubesandmore.com/>) sells new manufacture twist-lock electrolytics under their “CE Manufacturing" brand. They bought the tooling and equipment from Aerovox when Aerovox shut down their line ten or fifteen years ago. The property tags on the equipment say “Mallory”, though. They do have a source for cans, tabs, phenolic bases, etched foil, etc., but I doubt they would sell them to individuals. The capacitors are a bit expensive, but they are the real deal, not restuffed cans. See:
https://www.tubesandmore.com/products/capacitors?filters=Brand%3DCE%20Manufacturing <https://www.tubesandmore.com/products/capacitors?filters=Brand=CE%20Manufacturing>

My connection: I do occasional consulting for them.

- John Atwood, WA1ICI

13141 - 13160 of 186446