John,
?? I would like to request a copy of the 453 Mod 127C Schematic.?? I still have some NTSC gear around and want to see how Tek implemented sync separation, for possible inclusion into a 453A.
??Thanks,
Denis


________________________________

Are the parts that are supposed to be blanked getting blanked?
-ls-

David Holland <david.w.holland@...> wrote:

Hello all,

I'm kind of getting around to poking at my 7854 scope.

The stored trace brightness is excessive, and the adjustment won't go
down any further. I'm reasonably certain the pot is good, since
it'll smoothy vary over what range it does have. (From "too bright",
to "cr*p, I'd better turn that down before the CRT gets burnt").
Normal display, and readout's are of a more reasonable intensity, and
have goodly range. (Readout isn't working correctly, but that's
not the problem I want to concentrate first on.)

Before I crack the covers, any suggestions of which parts of the
service manual would be most relevant to read...

thanks in advance...

David


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

Yahoo! Groups Links

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

Yahoo! Groups Links

The regulated voltages at P1896 all look fine. Note that the pin 2
voltage at 129.5 is right where it should be after you adjusted R1293
for what I assume is +55 at TP1625.

The unregulated voltages look fine to me also. The fact that they are
a little high may be do to low plug-in load. The unregulated voltages
are marked with nominal values.

Others here probably have better suggestions for working with the CRT
but I would do a sanity check of TP1635 (next to U1635) which should
be within millivolts of zero if the -3kV supply regulation is working
correctly. Then I would check TP1876 (at the bottom of schematic 11)
which is the output of the z-axis amplifier and marked 7.6 volts.

At this point if everything seems normal, I would break out the high
voltage probe and check the -3kV supply. There is a test point shown
off of pin 2 of the CRT (again at the bottom of schematic 11) but it
is not numbered.

On Mon, 09 Jul 2012 16:06:02 -0000, "keithostertag"
<keitho@...> wrote:

Thanks David. Here are my current readings after adjusting R1293/TP1625 and R1513/-50V:

At P1896:
Pin 2 (+130V): 129.5
Pin 3 (+50V): 50.0
Pin 4 (+15V): 15.07
Pin 5 (+5V): 5.02
Pin 6 (-15V): -14.98
Pin 7 (-50V): -50.0

At P1452 (red):
Pins 1&2 (-17V): -18.78
Pin 3 (+54V): 58
Pins 4&5 (+17V): 18.78
Pin 6 (-54V): -58

+5L at pin3 of P1417 (blue) = 5.06

So I still need to check some caps to resolve those high unregulated lines at P1452.

But, I've got no crt activity at all, and the above are close enough to at least have some crt, right? So I guess I need to start looking around for why I have no crt. No BF, no readout, nada. Just grat illumination.

BTW- my "Control Illumination" button on the front panel won't stay pushed in.

Thanks,
Keith Ostertag

Hello all,

I'm kind of getting around to poking at my 7854 scope.

The stored trace brightness is excessive, and the adjustment won't go
down any further. I'm reasonably certain the pot is good, since
it'll smoothy vary over what range it does have. (From "too bright",
to "cr*p, I'd better turn that down before the CRT gets burnt").
Normal display, and readout's are of a more reasonable intensity, and
have goodly range. (Readout isn't working correctly, but that's
not the problem I want to concentrate first on.)

Before I crack the covers, any suggestions of which parts of the
service manual would be most relevant to read...

thanks in advance...

David


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

Yahoo! Groups Links

Hello,

I have repaired the low voltage power supply, the problem was in a 6080 tube V737A. I have replaced this tube and voltage are ok. For future repair and check purpose, have anyone the current for each voltage ?
I have performed calibration, it seem to work well.
A strange problem appears on crt when the trace intensity increase, past the control middle point, trace thickens and glow down.
I have checked -1700V and +8300V they don't change with knob moving, control grid voltage (pin 3) change accordingly with intensity control from -1900 to -1700.

Juri

From: dutchbosstard
Subject: [TekScopes] Re: Just got a tek 555 for free, and in need of some advice!
To: TekScopes@...
Date: Monday, July 9, 2012, 3:44 AM

?

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.

Hi Robby,
??
At the present time I am working on 4 Tek 555 scopes. I have 3 of them working, 555 #4 is not working yet but will be soon.
??
As for the fans I use a drop of 3-in-ONE oil and find that it works very well. Fans must spin freely or they will not run or they will run slowly.
??
Test points for LV power supplys are on the bottom of power supply unit.
??
Because the Tek 555 is a dual beam scope, there are two -1350 HV adjustments. One for each cathode.?? The HV Anode lead that plugs into the CRT will provide about +8650 volts.
This totals out to 10KV accelerating voltage.
??
When you get your Tek 555 working,?? remember that the upper beam will only write to the upper 4 cm of the crt and the lower beam will only write to the lower 4 cm of the crt.
??
I have some spare parts for 555 scopes.?? Let me know if there is anything you need.
??
Have attached??photos of my three working 555 scopes.
??
Keith


--- On Fri, 7/6/12, dutchbosstard <childwhereugo@...> wrote:


From: dutchbosstard <childwhereugo@...>
Subject: [TekScopes] Re: Just got a tek 555 for free, and in need of some advice!
To: TekScopes@...
Date: Friday, July 6, 2012, 10:01 PM



??



awesome. so when i get it back to my house ill carefully hit it with 40 psi. im guessing that shouldnt damage any tubes as long as im careful. My air compressor is sanborn reciprocating compressor - ive never noticed any oil in the lines, only a small bit of moisture from when i drain the tank all the way. it also has a air filter on the input.

so i guess ill just utilize a dry cloth until i get the scope back to my house.

a few questions about the test points - when the time comes that i power up the scope, where are the test points for the low voltages from the power supply? are they in the PSU box? or are they somewhere inside the scope? also, when i opened up the case yesterday i found the -1350V test point for the CRT, but I was under the impression that the total accelerating voltage for the crt is 10kV. where is that test point located, and should i worry about it?

also what fuses should i see for the main fuse, and the filament fuse in the PSU box?

thanks,

Robby

--- In TekScopes@..., tubesnthings@ wrote:

Valid concerns! Set air pressure no higher than necessary, say below 40
psi.
Use caution and common sense - 40 year old dust doesn't belong in your
lungs - do it outside and wear a mask.



In a message dated 7/6/2012 1:43:15 P.M. Pacific Daylight Time,
childwhereugo@ writes:

since i have an air compressor at home, should i try blowing out all the
dust? Ive heard that you can do this to electronic equipment, but i am kinda
terrified to do this since i dont want to have anything become
unconnected, or cause anything to short out, or worse yet - damage a tube.

are these valid concerns, or am i overacting? my air compressor is usually
set to 100 PSI.

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?

John,
?? I would like to request a copy of the 453 Mod 127C Schematic.?? I still have some NTSC gear around and want to see how Tek implemented sync separation, for possible inclusion into a 453A.
??Thanks,
Denis


________________________________
From: John S <John@...>
To: TekScopes@...
Sent: Friday, March 4, 2011 9:21 AM
Subject: [TekScopes] Video triggering of 'scopes in general


??
- All the old TV standards adopted around the world have an odd numbers of lines in a "complete" picture, which is defined as a TV Frame. (25Hz Europe, c.30Hz USA)
- To conserve RF bandwidth, the signal is transmitted in sequential Fields, each of which contains half the lines (odd lines Field 1, even lines Filed 2 etc), as required to assemble the full TV Frame.
- This is known as interlace scanning, and gives rise to display artefacts such as line-twitter on strong horizontal black-white transitions.
- As the odd number of lines is clearly not divisible by 2, odd fields terminate (theoretically) half way through a line, and even fields commence similarly.
- The problem confronted by TV engineers is to get the 'scope to trigger stably (ideally) at the FRAME rate, which is half the field rate. This allows a 'scope with a good dual-time-base delayed sweep to select a particular line. (The line can be a bit dim, as the 'scope is only writing for c. 60uS in every c. 40mS).
- I have a 453 with TV triggering ( MOD127C ): Tek used to supply special graticules (which I also have) based around standardised TV test & measurement waveforms.
- broadcasters use a few of the "blank" lines in the field blanking area* to transmit the test waveforms so an entire transmission chain can be quality monitored

I can supply a copy of the MOD127C 453 handbook description to anyone who's interested.

John

* the "field blanking" lines contain synchronising pulses which are "broader" than on normal video lines, and the shift in DC level is used by the sync separators in the TV to lock the frame oscillator to field rate. They were kept free of video in order to allow the CRT scan time to return to the top of the screen without losing active picture content.

--- In mailto:TekScopes%40yahoogroups.com, Gala Dragos <gala_dragos@> wrote:

Hi!

I've worked with a TD2002B recently. It had a trigger mode named "Video". It was used to display PAL/SECAM/NTSC video signals and lines. How do I do that with Tektronix 475 or 465 ?

Thanks.