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Old 13th Aug 2019, 10:19 pm   #21
John_BS
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Default Re: Tektronix 453 poorly.

PPS:

I've repaired about a dozen 453's and 454's, and never found failures in the sweep section. There is an issue sometimes with the trigger circuit, but I don't think that's your problem. Gently wiggling transistors in their holders is a good idea as it ensures the contacts are cleaned. Ditto the relevant pin connectors around the board carrying signals in and out.
And I meant to ask earlier: have you checked that there's no sweep at any Time-base setting? Ditto with the sweep variable control unlocked from the cal position?
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Old 13th Aug 2019, 10:22 pm   #22
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Default Re: Tektronix 453 poorly.

Bill, John,

Have we established that for sure?

Mine is 100,007 and has 6 nuvistors

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The OPs is 100,919, the jury is out
Chris (and other sources) say FET versions are higher than 20,000 so on the face of it that's wrong.

Production from the Guernsey factory where mine originated all seem to have a leading "1" and 453's from Portland Oregon appear to have a leading "0"

Did both factories produce FET 453's with S/Ns beginning with 2?
What I am suggesting is that a "2" for the most significant digit means FETs, irrespective of the number of following digits.

If you aren't sure Paul, please post an image of the top large PCB in your instrument.
Alternatively compare your board to mine:-

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Old 13th Aug 2019, 10:33 pm   #23
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Default Re: Tektronix 453 poorly.

I think we're all pretty sure. In fact the easiest "test" is to look at the panel on the side: if there are two fuse holders it's a Nuvistor model. There are other more subtle differences which I'll outline when I get around to writing a treatise on the subject! Fantastic scopes.
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Old 13th Aug 2019, 11:03 pm   #24
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Default Re: Tektronix 453 poorly.

Tek serial numbering is quite confusing due to manufacturing being spread across several countries.

See this old thread:



https://www.vintage-radio.net/forum/...eferrerid=9910
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Old 14th Aug 2019, 8:28 am   #25
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Default Re: Tektronix 453 poorly.

Here's some pics of my top board etc.
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Old 14th Aug 2019, 9:12 am   #26
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Default Re: Tektronix 453 poorly.

So where are the nuvistors located in these? I fail to see any in mine, not sure where to look TBH though!
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Old 14th Aug 2019, 9:23 am   #27
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Default Re: Tektronix 453 poorly.

Quote:
Originally Posted by John_BS View Post
PPS:

I've repaired about a dozen 453's and 454's, and never found failures in the sweep section. There is an issue sometimes with the trigger circuit, but I don't think that's your problem. Gently wiggling transistors in their holders is a good idea as it ensures the contacts are cleaned. Ditto the relevant pin connectors around the board carrying signals in and out.
And I meant to ask earlier: have you checked that there's no sweep at any Time-base setting? Ditto with the sweep variable control unlocked from the cal position?
It has no sweep on any timebase settings also with the sweep variable in both positions, all votages are within spec, transistors in the horiz amp test good, also the dot/trace does move with the horiz position control, I dont have another scope to test as sold my spare a few weeks ago.
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Old 14th Aug 2019, 10:40 am   #28
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Default Re: Tektronix 453 poorly.

I'm going to scan & post a schematic of the A sweep generator . If it's too large to post can you send me your email by PM and I'll send it that way.


Thanks for confirming the sweep status etc. Don't go looking for Nuvistors: there are none!


In the meantime could you set up the scope as Bill suggested earlier: set the Hor Display to "Ext Horiz" & turn up the brightness: you should be able to scan the dot with the horizontal pos-tion. Set to the middle of the screen and turn the brightness back down.

John
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Old 14th Aug 2019, 10:46 am   #29
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Default Re: Tektronix 453 poorly.

Here's the scan. I'd suggest you go around the board (it's the one underneath the scope with the calibrator pot core at one end) and initially measure the DC voltages on all the active pins A B C >> AA AB etc and compare with the circuit. Mine has the 7V dc on output AA and 0V on AD under these conditions.


John
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Old 14th Aug 2019, 11:52 am   #30
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Default Re: Tektronix 453 poorly.

Hi John.

I've found Q524 to be dead, it's an NPN but the issue is I can't read the number on it.

Would you have any idea so I can get a replacement?

Cheers, Paul.
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Old 14th Aug 2019, 12:31 pm   #31
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Default Re: Tektronix 453 poorly.

It's strange Q414 on the same board seems to have a hole/dimple in the side/top of it but tests OK!
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Old 14th Aug 2019, 12:36 pm   #32
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Default Re: Tektronix 453 poorly.

Quote:
Originally Posted by M3VUV51 View Post
hi john,ive found Q524 to be dead,its an npn but the issue is i cant read the number on it,would you have any idea so i can get a replacement?,cheers paul.
Let's see if I and my friend John agree....According to my manual, Q524 is Tek P/N 151-0223-00 and is a silicon transistor type 2N4275. This looks to be the commonest transistor in the 453. Q414 is the same type. Maybe some have failed before and been replaced with physically different ones?

You really ought to get yourself the correct manual, it will bring dividends in the future.

Colin.

Last edited by ColinTheAmpMan1; 14th Aug 2019 at 12:45 pm. Reason: More info.
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Old 14th Aug 2019, 12:52 pm   #33
M3VUV51
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Default Re: Tektronix 453 poorly.

Do you think a BC108 would be a suitable sub?
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Old 14th Aug 2019, 12:59 pm   #34
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Default Re: Tektronix 453 poorly.

http://bama.edebris.com/manuals/tek/453a/


It appears to be a 2N4275 and is available from a UK ebay seller for very little money.

<Edit> crossed with Colin.
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Old 14th Aug 2019, 1:31 pm   #35
M3VUV51
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Default Re: Tektronix 453 poorly.

I was looking to use something I have to try.
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Old 14th Aug 2019, 1:50 pm   #36
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Default Re: Tektronix 453 poorly.

It's silicon NPN, so try the BC108.

I know we have established beyond doubt that yours is the later FET model, I must say, given the serial numbers of yours and mine, I am very surprised.

Does your scope say "Type 453A Oscilloscope" on the front or just 453?
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Old 14th Aug 2019, 1:52 pm   #37
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Default Re: Tektronix 453 poorly.

Yea, possibly a bc108 - power / Ic look OK, not sure about Vce (40V for 2N4275)
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Old 14th Aug 2019, 2:32 pm   #38
M3VUV51
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Default Re: Tektronix 453 poorly.

Quote:
Originally Posted by rambo1152 View Post
Quote:
Originally Posted by M3VUV51 View Post
i was looking to have something i have to try.
It's silicon NPN, so try the BC108.

I know we have established beyond doubt that yours is the later FET model, I must say, given the serial numbers of yours and mine, I am very surprised.

Does your scope say "Type 453A Oscilloscope" on the front or just 453?
Mine's a 453 not the later a type, ie only has 6 screen divisions not 8 as per the later a model.
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Old 14th Aug 2019, 2:37 pm   #39
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Default Re: Tektronix 453 poorly.

Quote:
Originally Posted by dave cox View Post
Yea, possibly a bc108 - power / Ic look OK, not sure about Vce (40V for 2N4275)
google gives the vce max as 45v for the bc 108,think ill try it and see.
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Old 14th Aug 2019, 2:58 pm   #40
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Default Re: Tektronix 453 poorly.

Quote:
Originally Posted by M3VUV51 View Post
mines a 453 not the later a type,ie only has 6 screen divisions not 8 as per the later a model.
And I assume "Tektronix Guernsey Ltd., CI" between the two Y inputs?

Mine's a "453" six Y divisions and nuvistors and a very early S/N 100007
I can only assume there were only six other earlier ones that left the Guernsey factory!

50 years ago I had a Cossor 1059 with a serial number of one hundred and something.
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