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Old 12th Aug 2019, 3:33 pm   #1
M3VUV51
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Default Tektronix 453 poorly.

Hi all.
Was using my old tek 453 today, it was working OK then all of a sudden it lost its sweep.

If I input a signal I just get a vertical line, ie no horiz sweep.

Any idea where to start looking?

Cheers, Paul M3VUV.
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Old 12th Aug 2019, 6:02 pm   #2
6AL5W-Martin
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Default Re: Tektronix 453 poorly.

hello Paul,
you have tested all switches and knobs from the time base?
Sometimes there is only a wrong switch position, by example: XY mode can do that.
greetings
Martin
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Old 12th Aug 2019, 6:05 pm   #3
M3VUV51
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Default Re: Tektronix 453 poorly.

yes there all fine,i was using it to scope a 100khz signal just fine looked away when i looked back it was just a dot!
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Old 12th Aug 2019, 9:12 pm   #4
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Default Re: Tektronix 453 poorly.

Tek453
If it was working perfectly, and then failed, without you touching or altering any controls, then clearly some part inside has failed.
As you have a vertical line, then the Y system is working.
No sweep indicates failure in X amplifier, Time base generator, or Trigger.
Probably not power supply itself, as you have the Y system operating.

So just get out your meter and check all voltages in the X-TB system.
As you don't want any TB operation or charging of capacitors, switch off the Time Base by Normal Trigger, External trigger, External Horzontal.
That will give you stable operating conditions in the X system with central spot, and you can then measure all voltages. They should be within +-10% of the manual.
Shift (X Position) will of course move the voltages in the 4 stages of the X amplifier, so that is easiest as the first check at the X plates on the tube.

Likely problems are failure of high voltage transistors, or any zener diodes.
The manual is very good for quoting typical voltages almost everywhere.
wme_bill
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Old 12th Aug 2019, 9:31 pm   #5
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Default Re: Tektronix 453 poorly.

yup,i need to digest the manual,only posted her in case something was a common point of fail ,its a job for the morning.
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Old 12th Aug 2019, 10:16 pm   #6
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Default Re: Tektronix 453 poorly.

I had a 454 which behaved like this when I bought it. The fault was the Nuvistor in the trigger circuit. Swapping it with one from one of the input amplifiers fixed it (but left the input amplifier not working).

If the 453 uses Nuvistors in the same places, which I suspect it does, then it's a quick and easy swap to try.

Chris
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Old 13th Aug 2019, 6:53 am   #7
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Default Re: Tektronix 453 poorly.

Q504 (2N964) is a high frequency Ge PNP transistor used to switch the integrator on. It needs to be Ge because it has to switch in response to the ~300mV step from the Ge tunnel diode and I needed to replace the equivalent part in a 454. The B sweep generator is almost identical so you can generally swap parts between the A and B sides for testing.

Roger
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Old 13th Aug 2019, 10:10 am   #8
M3VUV51
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Default Re: Tektronix 453 poorly.

any idea where i find q504?,ive looked but cant see it,also any idea what board etc the nuvistor are located on?,cheers m3vuv.

mine has a serial number of 100919 so assume it has fets instead of nuvistors,ive a manual from bama but sure this covers the earlear models,anyone know of one for this late serial number i can download?
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Old 13th Aug 2019, 12:12 pm   #9
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Default Re: Tektronix 453 poorly.

If you have the correct Service Manual, Q504 is on diagram 9 "A Sweep Generator". It is almost in the centre of the diagram about two thirds down from the top. It has a test-point TP504 next to it.

I can recommend that you contact Marc Christian at Telford Electronics:

telfordelectronics@btinternet.com

for manuals. Quote your serial number and Marc will usually find the correct manual. Prices are about 15 - 20 depending on the size (the 453 manual is quite substantial). I find that the original Tek paper manuals (or the newly printed ones from Artek) are much easier to use than pdf for most things.

If you really want a pdf manual, I think the 453A manual on Tekwiki (http://w140.com/tekwiki/wiki/453) is probably the one, as it doesn't use nuvistors.

Colin.
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Old 13th Aug 2019, 1:43 pm   #10
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Default Re: Tektronix 453 poorly.

Hi!

I think the correct book that most covers your instrument is the "453 Military Version Manual" TM 11–6625–1722–15 – the circuit diagrams in this are specifically annotated "453 Oscilloscope from S/N 20,000 onwards, it has FET Vertical Amplifier Input transistors as opposed to nuvistor–valves, and refers to the "Sweep Gating Generator Q504" on it's block diagram!

I don't think physical layout drawings are included in it tho' – you'll find layout drawings in TM 11–6625–1722–24P!

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Old 13th Aug 2019, 2:28 pm   #11
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Default Re: Tektronix 453 poorly.

we must be talking qbout different scopes here,,on the horiz amp/sweep board my transistors start at 600 numbers thru to 700s so far ive checked q814,q824,q834,q844,q863,q873,q894,thats what it shows on the schematic in the manual i have from bama what tallys with the parts on my board,there is no q504 on my horiz amp/sweep board!

All those transistors test OK.
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Old 13th Aug 2019, 4:14 pm   #12
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Default Re: Tektronix 453 poorly.

Do you have a second 'scope?



John
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Old 13th Aug 2019, 4:30 pm   #13
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Default Re: Tektronix 453 poorly.

Did you do the tests wme_bill suggested ? If you can move the spot horizontally in XY mode that eliminates a chunk of circuitry!

Is it a dot in the middle or on the left edge ?

dc
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Old 13th Aug 2019, 4:32 pm   #14
John_BS
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Default Re: Tektronix 453 poorly.

If your x amp is working, you should

a) have about + 48V on each X plate with the beam centred
b) be able to move the beam with the horizontal position control.

If the X amp is OK, we move to the A sweep generator, which does have 500 numbered transistors, and is not located on the top board, but underneath and beside the Y input amps.

Have you checked the main regulated supplies (+12, -12 and +75V?)

John
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Old 13th Aug 2019, 6:00 pm   #15
Craig Sawyers
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Default Re: Tektronix 453 poorly.

Those early epoxy potted transistors in the 453 are prone to failure. I had to replace a couple of them in mine. I think over time stress on the chip or bonds to the external pins fails.

But John is right, before fingering transistor failure, check the supplies first.

Craig
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Old 13th Aug 2019, 7:45 pm   #16
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Default Re: Tektronix 453 poorly.

Hi Paul,

I recently restored my early-production 453, and most of the issues were related to the nuvistors. Working on that assumption for a moment, I can tell you that V743 on the top board and V533 on the bottom board can cause the sweep to stop.

As you know that the nuvistors in the Y amps are good, (V23 & V123 on the bottom board) I suggest you use one of them to replace the two suspect ones in turn and see if you get your sweep back.

If that works for you, then good luck getting any original 8393s or indeed any 12v heater nuvistors.

All is not lost however, this is how I repaired mine.

https://www.vintage-radio.net/forum/...d.php?t=158107
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Old 13th Aug 2019, 9:30 pm   #17
John_BS
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Default Re: Tektronix 453 poorly.

Graham: He's got a later FET version so the Nuvistor tack is not relevant!



John
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Old 13th Aug 2019, 9:54 pm   #18
WME_bill
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Default Re: Tektronix 453 poorly.

Tek453. serial 100919
The manual you want is for serial 20,000 up.
All this talk of nuvistors relates to earlier versions or other models. Your version is all FET/transistor.
For Roger Evans, Q504 is a germanium ultra high speed switching: 2N964 or 2N711 or 2N705 (all Texas) or ASZ21 Mullard. I have a number of these spare, if anyone wants some. Needed for this position around most tunnel diode trigger circuits, by Tek and HP180 series.
I attach parts of the manual relating to the A timebase board layout, and a selection of the circuit diagrams. For US serial 20000 up and to Guernsey S/N 100200.
A note on the Tek suggested commercial replacements for the Tek type numbers:
FET 151-1005 = 2N4303 selected
FET 153-0570 = 2N4303 matched
2N4275 = 2N2369, 2N4122 = BFX48
Tunnel diodes 5ma TD3 or 1N3716
Other types noted on the circuit diagrams.

One other point. Try not to keep removing transistors and components generally, testing them and then refixing them. This can often create other faults. Do the voltage measurement I suggested. That will pin the problem down to a small area. Then check voltage around that area in detail. Only then actually start removing or replacing transistors or parts.

If you are still having trouble getting the manual, I hesitate as it is huge but could be persuaded to copy my version. It is nearly 2" thick, and large sheets. Try Chris5500 suggestion. Telford do a good job with supplying manuals.
wme_bill
Attached Files
File Type: pdf Tek453 part circuits.pdf (680.6 KB, 3 views)
File Type: pdf Tek453_partial A sweep board.pdf (780.9 KB, 4 views)
File Type: pdf Tek453_partial A trigger board.pdf (388.3 KB, 6 views)
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Old 13th Aug 2019, 10:02 pm   #19
M3VUV51
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Default Re: Tektronix 453 poorly.

Cheers folks, I wil keep you posted, I'm loathe to give up on this as it was given to me by a silent key. Original issue was with the Z axis when I got it I fixed that but now this.

Oh well. 73 M3VUV.
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Old 13th Aug 2019, 10:12 pm   #20
John_BS
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Default Re: Tektronix 453 poorly.

Let us know if you have another 'scope as that will influence advice given.

John

PS random thought: do you get a trace or flash if you switch to B sweep?
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