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Especially looking at the start of the trace, it could simply be a matter of CRT bias adjustment. Simple to do and undo visually and no loss of calibration.

Raymond

Hello *,

is there a way to the set the probe attenuation manually on that scopes which dont't have a "Probe Functions" menu like the C or D models? If there is no digital way are there any solutions on the WWW for building my own "Tekscope" connector?

Looks like a noisy contact in the X signal path.
Is the pattern stable or intermittent?
How fast was the sweep speed you used when you took the photo?
Does it react if you fiddle with the timebase selector, or the associated X controls?
Does it react if you gently tap the PCB around the X timebase/amplifier?

I have a problem with horizontal display showing double or distorted image . It happens on both channels and I uploaded a photo in the album named :

485 Problem

If anyone has seen something similar or has any suggestion, any advice would be appreciated.

Thank you

On Wed, Jan 29, 2025 at 09:12 AM, Mr Lurpak's Electronics Rescue wrote:

added some pictures

I noticed on your picture that the large ceramic resistor has burned the board.
This is/was a common problem on these supplies. It was due to too high voltage
across the resistor when in standby mode. Most of the times the supply could be
fixed and other times the board was too damaged so the supply had to be replaced.
It is best to avoid having these scopes om standby for longer periods of time.

This document might be of help on further trouble shooting:


/H?kan

On Sun, Jan 26, 2025 at 10:14 AM, Mr Lurpak's Electronics Rescue wrote:

Does anyone have an idea of what voltage this should be?

With one end removed from the board and checked on a 576 curve tracer it has zener voltage of 17.4V

/H?kan

The 485 is not a storage 'scope. It is the successor to the 465/475 line.
The 485 is a 350 MHz 'scope, and an excellent 'scope.

The 464 is a storage 'scope.

Covers for the 485 are extremely rare. I'm looking for one myself. Covers
for 464s are probably less rare.

I purchased a 485 cover along time ago and sold the 485 with the cover.
Stupid move -I should have jept the cover. I purchased the cover by
measuring the 485 and matching those measurements to a cover I found on
evay. AFAIK, 4x5 covers did not have part numbers of other identifying
marks on them.

Original probes may he found at hamfests and ebay. PDFs of Tektronix
catalogs detailing what probes go with what 'scopes are available online,
at, for instance,



For the 485, P6056 (10x) and P6057 (100x) probes were recommended.

I own a bunch of Tektronix 'scope and meter probes. I do not own any
non-Tektronix probes for my 'scopes.

There are also 'scope/probe compatibility documents on TekWiki.

TekWiki and the KO4BB websites are good sources of information, amongst
many others.

DaveD
KC0WJN


On Wed, Jan 29, 2025 at 05:21 M M via groups.io <wa6ilq=
outlook.com@groups.io> wrote:

I have inherited both a Tek 464 scope and a Tek 485 storage scope.
I've been using Teks since 1966.

I'm looking for the plastic covers for the front panels of both.
Both came to me without probes.
Does anyone manufacture new probes that are equivalent to the originals?

I do not know the number for the 464 cover. Can anyone help?
I know the part number of the 485 cover is 200-1251-00.

I'm also looking for the feet for the 485. The number may be 200-1269 (and
an unknown suffix).
I'm not a purist, just looking for functionality.
3D printed feet would be fine as long as they were equivalent and sturdy.

Thanks in advance.

Mike Morris WA6ILQ

I have inherited both a Tek 464 scope and a Tek 485 storage scope.
I've been using Teks since 1966.

I'm looking for the plastic covers for the front panels of both.
Both came to me without probes.
Does anyone manufacture new probes that are equivalent to the originals?

I do not know the number for the 464 cover. Can anyone help?
I know the part number of the 485 cover is 200-1251-00.

I'm also looking for the feet for the 485. The number may be 200-1269 (and an unknown suffix).
I'm not a purist, just looking for functionality.
3D printed feet would be fine as long as they were equivalent and sturdy.

Thanks in advance.

Mike Morris WA6ILQ

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

added some pictures for the VR9 ZENER diode that I can't find value on as blown and no schematics.





My guess could be 6.2V or 20V? likely a 1N5243B/1N52343 based on a LeCroy schematic for a "similar" PS but not same. Any ideas?

Thank you.

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

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

Has anyone here ever adapted anything to replace Option 25? I have been searching for a long time, no luck in finding one. The only thing I've come up with it the right hand side of a TR502 with missing parts.

I've put in the folder 'TG501 2ns and 1ns spectrum' plots from the TG501 for both the 2ns and 1ns outputs. The latter is clearly faulty...

Hi Raymond,

Yes I'm using a 1GHz bandwidth scope at 5GS/s. I've also tried looking at the output on a spectrum analyser, seems the largest peak is at 800MHz with many other harmonics of 200MHz/5nS.

I am thinking you could be right, someone's maybe 'got at' this unit and tried adjusting the filter and made it worse... I'm going to make up an extender board so I can try adjusting it as per the service manual.

- Keith

BTW the pulse amplitude specs are on page 1-1 in the Service Manual. TG501’s I’ve seen easily meet those specs.

Raymond

On Tue, Jan 28, 2025 at 05:13 PM, Keith wrote:

I'm wondering if it is CR515 or something else. If I measure the amplitude
(Vpp) I see:
10nS - 1.480v
5nS - 0.820v
2nS - 0.724v
1nS - noise (10mV or less)

I'd expect the 5nS output to be similar to the 10nS (and slower) markers?

Hello Keith,
You don't mention which RTM3000 you're using. They start out at 100MHz bandwidth but from your amplitude info, I guess that's not your model...
Do you have a TG501 service manual?

I haven't experienced nor read about a failed CR515.
It has always been (one or a combination of) expecting to see the 1ns pulse on - say - a 100MHz BW 'scope, incorrect filter adjustment, not using the correct (1ns only) output of the TG501, trigger problem, bad/intermittent contacts on the PCB, leading to incorrect filter adjustment. The 1ns adjustment has a big influence. Maybe someone using the wrong 'scope has been in there before you?

I just checked one of my TG501's

On a Tek 7904/7A19 (500MHz nominal BW):
10ns 1.5V
5ns 1.1V
2ns 0.9V
1ns 50mV

On a Tek 7000/S-4 sampling 'scope (<=75ps nominal rise time):
2ns 1.05V
1ns 0.35V

If no other explanation, try filter adjustment, following the service manual. It's not difficult, *if* you have the right 'scope...

Raymond

That new meter scale looks great!

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