Textronix 453 oscilloscope

[Brased]

The 453A has a larger screen (8 vertical divisions instead of 6) and does use fets. It is marked as '453A Oscilloscope' (no 'Type') above the screen. This was the successor to the 453 and although I haven't checked, I suspect that there was little change from the later version 453.

I have a Guernsey built 453 with fet inputs. There are some clues as to the date of the change-over. The boards in my nuvistor version are dated 1965 while the later version has dates of '1965, 1967' and '1966, 1969'. My impression of the boards is that the redesign of the boards to accommodate fets was kept to a minimum. Tek tended to this policy as can be seen in their power supply designs. Indeed my 453A also seems to use some of the same boards as the 453.

This website may be of interest:
http://www.diyguitarist.com/TestEqui...ktronix453.htm

Edward

[Mike-repairman]

Edward, if you are around...

I have been studying some of the more unusual features of the 453 but one thing is puzzling me about the timebases.

I assume that there are two separate ones (that can be used one for each input channel) but they appear to be linked, even when you pull out the grey knob and rotate it to a different position to the main A timebase.

If I turn the grey knob to the left of the setting of the outer ring the speed stays the same; if I turn it to the right of the outer ring setting the speed again stays the same but the whole trace moves to the left of the screen, eventually disappearing.

I guess there is a way to set it up so that you can basically use it as two scopes in one with different signals in the two channels and two speeds on the timebases?

I have checked inside and the two timebase knobs do rotate the two sets of wafers independently so it's not a physical malfunction; obviously the way I am setting it up. I do realise that if the two waveforms are not time related they may not sync, but I always get the same speed on both channels.

Any ideas?

Have included the front panel image and wonder how you set your one up.

http://i7.photobucket.com/albums/y29...peSettings.jpg

Thanks,

Mike.

[ppppenguin]

The 453, like most professional 'scopes, has a delayed timebase system. A is usually main, B is delayed. (NB: If you have a 5xx Tek then it's slightly more complicated).

The A timebase is used to display signals as you would expect. The B timebase is used to strobe out a small portion of the displayed waveform. It's a bit like having a really big and flexible horizontal magnifier. The interlocked controls for the A and B timebases ensure that the B timebase runs at the same or faster speed than A.

Usual way to use this:
B sweep mode: "B starts after delay time"
Display trace using A timebase
Switch to "A inten during B"
Choose a B timebase speed a bit faster than A and adjust the brightened portion of the trace using the multiturn "delay time multiplier"
When you have the wanted bit of waveform brightened, switch to B timebase and that bit will be displayed over the whole screen.

There are other more complex ways of using the delayed timebase but on most scopes you cannot use A for one trace and B for the other. There are exceptions (I think the Tek 556 is one) but you are unlikely to come across them.

PS: Keep the sweep length set to "full" until you are familiar with delayed timebases. Likewise ignore the B timebase trigger system.

[Brased]

Hi Mike

The best advice is to look at the operating instructions part of the manual and then to play with the scope.The Tek manuals are excellent in this respect and describe things in detail with waveforms, etc. I find that things do make much more sense then. It is really worthwhile printing off this section of the manual if you are using a BAMA download.

The 556 (and 555) had true dual gun CRTs and two separate timebase plugins so would work like two independent scopes.

Edward

[Mike-repairman]

Thanks Jeffrey and Edward; it makes a lot more sense now. I was thinking of the scope as a true dual with separate timebases for separate channels, like the 556 and 555 that I played with all those years ago.

I understand the magnifying glass concept now, although the manual was a little mind boggling albeit comprehensive.

Just tried Jeffrey's instructions and it works fine, and now i fully understand what it is doing.

Thanks again,

Mike.

[ppppenguin]

Most dual trace scopes use a single electron gun with electronic switching. The Tek 551, 555 and 556 are true dual beam. Also some old Cossors and no doubt a few others. If both the X and Y plates are separate for each beam then you can have truly separate timebases for each beam.

Imagine a Tek 556 with a pair of 1A4 plug ins. Up to 8 traces, 4 on each timebase!

For TV work, dual timebases allow you to strobe a single line out of an entire field. This really needs the A timebase to have decent TV triggering and enough brightness to cope with the very low duty cycle. Using external triggering I've strobed out a few 100ns from the 8 field PAL sequence on my 2465. Best done at night with all lights off and giving your eyes time to adapt to the dark. If ever there was a job where a digital scope wins by a mile

[Mike-repairman]

Jeffrey, I haven't done any TV work for around 25 years so it won't be used for that. Think the last one I did had a wooden case. :^O
I primarily use a scope to look for distortion in valve amps which don't require a very sophisticated scope at all, but it makes a nice addition to my Telequipment D61a in the rack.
Mike.

[JHGibson]

The 453 scope switched from using nuvistors to fets after serial number 20,000. There is a lot of information about the 453 at www.reprise.com/host/scopes/
I only parted with my 453 after I aquired a 456, the 100 Mhz version. I found it priced at $40 in a surplus store. The repair tag on it said "Beyond economical repair" Always ready for a challenge, I bought it. The problem turned out to be that the power supply taps were set to 240 volts while our voltage is 120!
John.

[Mike-repairman]

Thanks for the link John,

You had a good bargain at $40.

I agree that the sync is very good on this model; I've seen most makes in the past when I worked for a surplus electronics company in the mid seventies, and some of the scopes (especially the cheaper ones) were absolutely useless on sync.

A scope that won't sync is as useless as a chocolate teapot.

I remember telephoning the service dept. for one of the cheap ones and asked them how to fix a sync fault. They were at least honest in saying that the sync function was pretty useless and that there probably wasn't a fault on the unit at all!

Mike.

[Top Cap]

Hi Mike, the advantage of a dual timebase system is the fact that you can lock the scope to a large pulse part of the waveform, where the sync will be steady. You can then home-in on the required part of the waveform that would otherwise be difficult to sync to, perhaps it is very small or changing in shape making sync rather difficult to achieve. You should be able to create a brightened area, variable in size using the B timebase knob. The multi turn delay control allows you to move this brightened area to the part of the waveform you want to look closely at. If the bright area is too narrow or wide, re-select a B setting so that the area encompasses the wanted object. Then selecting B will give you a full screen of the previously brightened area. Of course not all scopes work like this but I think yours does. It used to be handy for looking at very small amplitude bursts of HF pulses riding on low frequency pulses.
Les

[Mike-repairman]

Thanks, Les, I think I've cracked it now; and I understand the principles of what it's doing.
Mike.

[PJL]

I have the 454A which is a 150MHz version which came from a forum member and I wouldn't part with it. Rock solid triggering using tunnel diodes and bright enough for single trace at fast speeds. I previously had a 10MHz telequipment and it's like comparing a BMW with roller skates.

There's no going back once you have used a Tek...Peter

[Mike-repairman]

Agree Peter; it's certainly the best scope I've ever had, especially for the sync.
I think my first was a Cossor 1035, LOL.
Wouldn't have the energy to lift that now!
Mike.

[Top Cap]

We used to tease the HP salesman years ago when he tried to sell us some 1740's, we told him that HP should stick to what they do best i.e. sig gens and speccy analysers and leave the scopes to TEK. All founded on the fact that the TEK scopes had supreme triggering capabilities. Of course the latest digital scopes from HP, now Agilent (Who said it was an anagram for genital !) perform so much better. Incidentally, of all of the Tek scopes I handled, I only came across one failure of a tunnel diode giving poor sync symptoms.

[Mike-repairman]

Yes Top Cap, HP were very good at making Sig gens and analysers but the cost of their spares was horrendous, about £50 for a BNC lead back in the 70's if I remember correctly!
Mind you the actual units weren't cheap either.
Mike.

[ppppenguin]

The 453 was the first of a long series of classic scopes. Tek got it right with almost every single one.

453 and 454
465, 475, 485 etc
22xx series
24xx series
...and that was it for real analogue scopes from Tek.

There were also the 5000 and 7000 series mainframes with impressive performance and equally impressive prices. These were the true successors to the 500 series.

[Mike-repairman]

Apologies for resurrecting my old thread but my son found this on Youtube that shows what can be done with a 453...

http://uk.youtube.com/watch?v=6Ac1G_5N73g

Worth a look.

Mike.

[Colin]

Wow! ... Does anyone know how this is done?

[ppppenguin]

Google oscilloscope art for loads of stuff on this subject. Such as this page with loads of links:
http://blog.makezine.com/archive/200...scope_art.html

Usually done with a PC audio card driving the X and Y axes of a 'scope. Then it's just a matter of software to generate the vector graphics.

[XTC]

Originally Posted by ppppenguin

Then it's just a matter of software to generate the vector graphics.

Looks like a shed load of code to write for nothing very useful.

Good practice?

Pete.