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Hello all,

I’ve been searching for repair information regarding a Tektronixs 465 oscilloscope and found this interesting website.
So, I just registered and like to introduce myself.

I’m Wilfred, 62 years old and living in the Netherlands.
My interests are electronics, in particular restoring the good old tube televisions and radio’s, Oldtimer cars and general technical things.

Recently I found a Tektronix 465 scope in a fairly good shape, with some issues though, but in a working condition.
The 100:1 attenuator on channel B needed replacement, capacitor C1552 as well.
Anyway, at some point I noticed that the beam was intermittent blurry due to the astigmatism.
Astigmatism could be adjusted but not within reach of the potentiometer.
It was even so that the scope reacted strange when I turned the potentiometer to one side, the illumination of the small light bulbs went too dark and also the beam disappeared.
Voltage on the grid seems to be okay, 0-110 V depending on adjustment.

I’m afraid that the picture tube has an shortage issue between grids, but like to know from the members experience if this would be he case indeed.

Thanks a lot for any reply and have a great day !

Wilfred

Get service manual.

Check all LV PS voltages.

Follow HV PS and CRT checks and service.

Most likey HV mult, high R resistors, HV transformer.

Unlikey that CRT is bad.

Jon

Hi Jon,

Thanks for your reply.
I already downloaded a manual, without it’s impossible to do any repairs.
I will check your suggestions, I also noticed that as soon as the picture is unstable in terms of astigmatism, the voltage on the grid remains the same. Also, the picture is sometimes sharp at 30V and sometimes at almost zero.

Anyway, tomorrow is another day.

Thanks,

Wilfred

Wilfred,

The astig pot could be dirty/bad by your description. The crt socket could be dirty and needs to be cleaned and reseated. R1486 is a known resistor that will be high in value. A Vishay VR37 will replace it. The 10meg, R1427 could be too high in value. There are other resistors that should be increased in wattage. Any 0367 transistors should be checked for leakage from C to E and replace with KSP10BU if any are leaky.

Being the age it is, recapping is advised. C1481 can be replaced with a film type.

The two 1,5A bridge rectifiers should be replaced with 4A.

Mark

Good morning,
Thank you all for the support, I will follow up and let you know.
Wilfred

Hello,

Some bad news, I'm afraid.
Yesterday evening everything looked all right and sharp, but at some point the picture went unstable and way out of focus, I could also hear some strange noises coming out the picture tube.
Now the EHT is missing and I can see an abnormal and too small signal in amplitude on the collector of the line output transistor Q1418. Line control looks normal, Q1418 itself doesn't show any shortcut and looks okay on the tester. + 24.4V is present on Q1418.
I looks to me that the line output transformer T1420 is defective, but it's very difficult to reach as far as I can see.
Is there any trick to test this, other then dismantle it ?

Thanks.

Wilfred

Dear Wilford, bravo for your work, very sorry for the problems ....but an old story.

Such vintage scopes are 1970s..1980s ( check serial, parts date codes). So, common that insulation, transformers high voltage are going to fail.

Our workhorse scopes since 1970s and still have a few ....Unless it was dropped or shipped roughly, the CRT is unlikely to fail, but does suffer gradually losses of cathode output

Most likely fail points...

1/ High Voltage multiplier, HV transformers
( many threads on rebuild, DIY)

2/ arcs, corona due to deterioration of cables, insulation, dust, carbon deposits over the decades at CRT Ultor to Aquadag.

3/ power supply electrolytic capacitors

thus complete restoration of 465/475/B is a project. And after you still have an old and tired scope.

Nowadays we use the 1980s..1990s Tektronix CRT Like 2465/7/B or 2236 etc.


Suggest you search both tekscopes and tekscopes2 on groups.io as well as EEVblog and general net for Tek or Tektronix 465 and 475
restoration, repair, high voltage teardown

Maybe consider to get another scope.... last version 475B was superior in several ways...look out for them at ham radio flea, Craig List, or epay....

Bon chance

Jon

Hello again,

It's been a while since I wrote and had to say goodbye to my 465 oscilloscope, but I managed to find another one and luckily without any issues.
The serial number is 109003, which is I understood one of the latest. (Not sure though)
Anyway, I did a check on the power supply voltages and the big capacitor's ripples between the plus and minus on the Elco itself:

C1512 (550uF) 79V and 300mV ripple,
C1513 (1200uF) 74V and 1V ripple,
C1542 (5500uF) 23V and 1.5V ripple,
C1552 (50009uF) .2V and 700mV ripple,
C1562 (3000uF) 12V and 1V ripple.

Any idea if this is acceptable ?

It might be wise to replace them in the future, but for now I just leave it as it is and use the oscilloscope it was made for.

Thanks again and have a lovely evening,

Wilfred

Wilfred:

All of the capacitors that you mention are part of the power supply, and
their ripple is not specified, as they are part of pre-regulator
circuitry.? Can you check the regulated DC voltages and determine if the
ripple on the DC voltage buses are within limits?? These limits should
be specified somewhere in the service manual(s) (refer to w140.com).? If
the service-manual-specified limits for ripple on the various regulated
DC buses are within limits, you should be fine.

If I am missing something here, that others are aware of, please let
me/us know!

Mike N4MWP

Hello Mike,
Thanks for your reply.

I did some checks on some regulated voltages indeed in terms of voltage level and ripple or other nasty oscillation issues and all looked clean.
However, not really structured and I can't remember the values at this moment to be honest, I only know I didn't see any unexpected things.
(I've got a second scope as well fortunately)
But, I will have a look again.

It is a very nice piece of quality equipment, must have cost a serious amount of money when it was new.
Usually my interest is low frequency spectrum like audio and video, sweeps on LPF and HPF filters, but with 100 MHz I can do a lot more I reckon.

Thanks,

Wilfred

Wilfred,

At the age of the scope, recapping is a good idea. The two 1.5A bridge rectifiers should be 4A types. These bridges are known to go bad. Increasing the capacitance is fine. If you replace tantalums, go with a higher voltage, say from 20V to 25V. There are resistors that are underrated in wattage.

Mark

Rebonjour Wilfred

Bravo for the new 465.

Since the 1970s the successors were improved, so 465B has better control, LED not incandescent etc.

Nowadays the last of the analog CRT scopes from Tektronix are great buys, 2465,2465B, 2475B, etc.

A 1990s scope has much better reliability than the 1970s you have.

Just my experience

Jon

Ok, thanks.

Is there, given the serial number (109003), any indication that some modifications are already executed factory wise ?
I will have a check of course on the components both of you mentioned.

Wilfred

Did you mean 2467B?

DaveD
KC0WJN


On Thu, Mar 13, 2025 at 10:57 Jean-Paul via groups.io <jonpaul=
[email protected]> wrote:

Rebonjour Wilfred

Bravo for the new 465.

Since the 1970s the successors were improved, so 465B has better control,
LED not incandescent etc.

Nowadays the last of the analog CRT scopes from Tektronix are great buys,
2465,2465B, 2475B, etc.

A 1990s scope has much better reliability than the 1970s you have.

Just my experience

Jon

Hi, no I meant modifications on the 465. During the years of production problems in the field can occur and as result modifications to improve the performance and reliability, quality etc.

Your serial number is odd.

All Tektronix scopes serial are form X0nnnnn

X-location of mfg, eg B Beaverton G Gurnsbery....
0 first digit is always 0
Second digit is the age, 1- oldest 5 most 6 latest

Thus a typical US number is B0503334

Jon

If that first digit of the serial number is a 7, then it was assembled in Heerenveen. A six-number serial number without a letter and beginning with 7 indicates that it was assembled in Heerenveen, Netherlands.

Are you certain that the first character of the serial number is a 1?

Serials starting with a 1 are IIRC from the Guernsey plant