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Old 8th Jul 2013, 9:40 pm   #101
davidgem1406
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Default Re: Tektronix 465B Scope - Some problems.

I have now changed 2 capacitors C4006 and C4003. They have both been replaced by electrolytics.
Before and after the changes I monitored what was on each capacitor.

For C4006 the 47uf there was 0.9V PtP @ 10Ms/Div and HF @ 0.2V (Image_Z1)
After the change was made there was no difference.

For C4003 the 10uf Tantalum there was HF up to 20mV PtP @ 50uS/Div, this I could not sync. (Image_Z2)
After the change was made there was no difference.

There was no improvement or change to the trace problem.

The 10uf used for C4003 although I have no particular reason to think it may be faulty I can not vouch for its integrity as it was removed from a redundant power supply board.

I have new capacitors on order.

Dave
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Old 8th Jul 2013, 10:05 pm   #102
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Default Re: Tektronix 465B Scope - Some problems.

I have just noticed that the power supply diagram seems to have an error
At the + of bridge CR4531 it states +150.6V. Further along the same rail it states 110V unregulated. That just can not be! unless the figure is that of an off load value. I will have to check the information given for measuring the supply voltage.
It also states for waveform 94 a DC figure of 150Vwith 100Hz sawtooth of 1.2V on top of the DC level. So we have 100Hz ripple of 1.2V

Power supply diagram attached.

Dave.
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Old 9th Jul 2013, 1:26 pm   #103
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Default Re: Tektronix 465B Scope - Some problems.

The upper "unreg 110" is a misprint (that's actually the next one down) it should be "unreg 150"

dc

PS:
C4010 looks a bit 'odd' to me, is it really 47u in series with 390K ?
What's is it doing there ?

Last edited by dave cox; 9th Jul 2013 at 1:40 pm. Reason: PS
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Old 9th Jul 2013, 2:50 pm   #104
Leon Crampin
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Default Re: Tektronix 465B Scope - Some problems.

It's 47 pF.

Leon.
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Old 9th Jul 2013, 3:09 pm   #105
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Default Re: Tektronix 465B Scope - Some problems.

Hi Dave,

Thanks for that info, now makes more sense.

Dave
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Old 1st Aug 2013, 10:20 pm   #106
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Default Re: Tektronix 465B Scope - Some problems.

Just a bit of an update here to say that the Tek is not forgotten.
For now I have had to put it to one side and do other things, I will get back to it.

I did in fact buy another CRT, there were 2 available and that went down to 1, so I decided to take that before it went elsewhere.

Dave..
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Old 2nd Aug 2013, 10:38 pm   #107
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Default Re: Tektronix 465B Scope - Some problems.

1/. Not a fault really but something that threw me until I read the service manual. Although the vertical Volts/Div switches are marked up to 50V per Div the 3 top ranges 10, 20 & 50 V/Div are not usable. The switches do not rotate any further than the 5V/Div position. I found that rather strange, why mark them up to 50V/Div? (Image 002)

Hi, It is a long time since I used one of these scopes but I think the answer to the "unusable" ranges is that when you connect a x10 probe, this is detected and the light illuminating the volts/division switch moves round so that the 5V/div now reads 50V/div, i.e. it now shows the correct overall sensitivity of the system, taking the probe attenuation into account.

Ross
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Old 3rd Aug 2013, 2:41 pm   #108
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Default Re: Tektronix 465B Scope - Some problems.

Hi Ross,

Alistair D in post #3 solved that one.
Quote:
Originally Posted by Alistair D View Post
1) Try shorting the body of the input BNC socket to the ring at its base, something will happen. The idea is that if you use an X10 probe with a shorting clip fitted the V/div markings will be correct for the probe.
I don,t have a fixed x10 probe, only switch-able, so it wont be used by me.

Regards
Dave
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Old 3rd Aug 2013, 3:14 pm   #109
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Default Re: Tektronix 465B Scope - Some problems.

Dave, I have just taken my 465b out of permanent service. The Gods have been very kind to me and given me a 485. Now that it is the reserve scope I do not mind opening it up and taking measurements if you need to do a comparison. I am on here every day so it wont take long to get back to you.

Al
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Old 3rd Aug 2013, 3:37 pm   #110
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Default Re: Tektronix 465B Scope - Some problems.

Quote:
The Gods have been very kind to me
To whom should we pray?

J
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Old 3rd Aug 2013, 3:41 pm   #111
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Default Re: Tektronix 465B Scope - Some problems.

Actually it was to Murphy V310 and Radioman. Very kind people indeed.

Al
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Old 3rd Aug 2013, 6:18 pm   #112
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Default Re: Tektronix 465B Scope - Some problems.

Switchable scope probes seem to be taking over the world. They're everywhere.

Shame is the fixed x10 probe, without the switching complication, can give lower capacitive loading on the circuit being probed and better bandwidth. x1 is relatively rarely needed, especially considering the capacitive loading, so it makes sense to usually buy x10 fixed probes and have a fixed x1 kicking around for spacial occasions.

Bandwidth in a scope is an expensive commodity, it's a pity to throw it away in the probe.

David
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Old 3rd Aug 2013, 8:24 pm   #113
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Default Re: Tektronix 465B Scope - Some problems.

Hi Al,

Thanks very much for that offer I will bear it in mind when I get back onto the Tek.

Hello David,

Well yes that is for sure the better option but the money they are asking for fixed 10x probes seems to be very high.

Dave.
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Old 31st Dec 2013, 1:04 am   #114
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Default Re: Tektronix 465B Scope - Some problems.

Hello Dave:

I am trying to fix my Tektronix 475 with a similar problem like yours.

I would like to know If you solved the failure. Was the crt?

Thank you very much in advanced.

Happy New Year !!!!!!!!

José
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Old 4th Jan 2014, 11:35 pm   #115
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Default Re: Tektronix 465B Scope - Some problems.

Hello Jose,

No sorry no more progress on the scope as yet, been involved in other things.
I will undoubtedly get back to it as I want it to be usable.

Been trying to clear up partly done projects that just been hanging around.

Ill be back!! as they say...

Happy new year also ..

Dave.
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Old 11th Jan 2014, 3:09 pm   #116
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Default Re: Tektronix 465B Scope - Some problems.

Hello Dave:

Thank you for the answer. I will be waiting your updates.

Happy 2014 !!

Kind regards,

José
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Old 13th Mar 2014, 6:04 pm   #117
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Default Re: Tektronix 465B Scope - Some problems.

At last today I have picked this up again to continue trying to solve the problem.

First I checked the power supply waveforms according to the information given in the manual. Although there were some discrepancies these did not seem to be anything to be concerned about. Waveform 94 ripple was at 1.5V instead of 1.2V and 99 was at 3.5V +1V ripple instead of 3V + 0.6V ripple.

I then disconnected the vertical and horizontal plates connecting them directly to the 55V rail. The problem remained the same. (The distorted spot)
There are 3 images given Image 1 is the best possible using focus and astig, Image 2 is the result of turning the focus pot fully anti clockwise, whilst Image 3 is fully clockwise.

My decision now is to change the CRT as I have a spare that is supposedly in good working order, we hope, unless anybody can come up with any other notions in a rather short time before I actually change the CRT.

Dave.
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Old 14th Mar 2014, 1:22 pm   #118
davidgem1406
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Default Re: Tektronix 465B Scope - Some problems.

Now I have replaced the CRT things take on a different view.

We now have a line that is in focus, looks like the original did have some problem. Wonder if another knock may put it right again

I have shown 2 pictures of the result. The first is showing the call square wave in focus, as best it can be, the second is the influence that shifting the astig and focus controls are having, not what I would have expected.

Also I would have expected to see a much finer trace that this is producing. When compared to my Telequipment D83 all in all the Tek is left wanting.
Maybe this is the way these Tek scopes are?

Anyway as far as I can tell at the moment it all seems to be working as it should. I will make some more tests at high frequencies and see how it responds.

Dave.
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Old 14th Mar 2014, 3:06 pm   #119
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Default Re: Tektronix 465B Scope - Some problems.

David, are you operating it with the cover on or off? This is a much higher bandwidth 'scope than a D83, which is only 50mhz. Make sure that the eht oscillator shield is in place and the cover on, then pull out the bandwidth limiter so its not picking up and amplifying stray rf.
Bill
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Old 14th Mar 2014, 5:41 pm   #120
davidgem1406
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Default Re: Tektronix 465B Scope - Some problems.

Hello Bill,

The EHT shield is in place but the cover is not. I will fit the cover and see if there is any change and report back.

Thanks for the reply.
Dave.
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