Topics

Tektronix 465M - only scale illumination

paronaram
 

Wile I'm trying to figure out what's going on with my 2235 horizontal sweep, I got another scope, maybe this will be easier to fix.
I have Tektronix 465M with only scale illumination and broken CH 2 Volts/Div knob.
I have heard that schematic diagram can vary from s/n to s/n
Can you help find correct schematics?
s/n 6625-01-032-6914

Thank you

Mlynch001
 

I don’t think that is the unit serial number. The TEKTRONIX serial numbers usually begins with B, followed by a series of numbers. There is a downloadable copy of the 465M manual on the TEK Wiki site.

Here is the link:

http://w140.com/tekwiki/wiki/465M

--
Michael Lynch
Dardanelle, AR

paronaram
 

Thank you, OK now I know, it's a B053102

Thanks again!

Mlynch001
 

No problem, good luck. You will find this forum full of people who are very willing to help and know a lot about this equipment. I have fixed several of these scopes, so I watch he 4xx series posts with great interest.
--
Michael Lynch
Dardanelle, AR

paronaram
 

I have no luck with this ready to recycle scopes...
This one is with no exception just is bad :)
Almost every single screw stripped, this scope was probably is Tektronix repair school or something...
Missing :
- one IC U2900 from (Horizontal assy)
- some screws

Voltages:
Right by the PT:
o o o o
+32V +5V -5V GND -- ALL Good

on the other side of this same board:
o o o o
-5V GND +5V +32V -- ALL Good

+95V - is missing all I have is +10V and I checked C582 (2.2mF 200V) is leaking it's visible without removing this cap

Is it possible by restoring this +95V will bring both Channels up?

Also what type of IC I'm missing? Can I find replacement

Any help will be greatly appreciated.

Thank you.

Michael W. Lynch
 

Probably not from a TEKTRONIX School, they would have the correct Pozi-Drive screwdriver to fit the screws. Stripped screws are typical of people using a standard Phillips driver on a Pozi-Drive Screw, these are not interchangeable.

Getting all the power rails to be relatively correct is the first and foremost requirement. However, I do not recall seeing a +95V rail on a 465M? I have a 455, which is similar and it has +32REG, +32 UNREG +15, +5 REG, -5REG, +5 UNREG and -5 UNREG.

If +95V is there and not working, then it would need to work before the scope would function.

If my quick survey of the schematic and parts list is correct, U2900 is TEK p/n 155-0124-00, a Tek-made horizontal pre-amplifier chip in a 16-pin DIP, designed by Bob Nordstrom. This part is used in many pieces of TEK Equipment of the era.
--
Michael Lynch
Dardanelle, Arkansas

n4buq
 

I have a 465M and, IIRC, there is a 95V supply that drives the HV. Mine had a bad transistor or two and would blow a fuse on that line. I may be misremembering that though...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael W. Lynch via groups.io" <mlynch003=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Wednesday, April 29, 2020 10:33:32 AM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

Probably not from a TEKTRONIX School, they would have the correct Pozi-Drive
screwdriver to fit the screws. Stripped screws are typical of people using
a standard Phillips driver on a Pozi-Drive Screw, these are not
interchangeable.

Getting all the power rails to be relatively correct is the first and
foremost requirement. However, I do not recall seeing a +95V rail on a
465M? I have a 455, which is similar and it has +32REG, +32 UNREG +15, +5
REG, -5REG, +5 UNREG and -5 UNREG.

If +95V is there and not working, then it would need to work before the scope
would function.

If my quick survey of the schematic and parts list is correct, U2900 is TEK
p/n 155-0124-00, a Tek-made horizontal pre-amplifier chip in a 16-pin DIP,
designed by Bob Nordstrom. This part is used in many pieces of TEK Equipment
of the era.
--
Michael Lynch
Dardanelle, Arkansas



n4buq
 

Looking at the schematic again, +95V doesn't drive the HV like I stated but there is indeed a +95V supply (see figure FO-9).

I also remember that F558 was blown and I think I traced that to a shorted tantalum (don't remember at the moment but possibly was C558). I also had to replace a damaged (by me, I think) inductor but don't remember if that was maybe L558 or some other inductor. At any rate, I got it fixed and it works nicely (at least it did the last time I cranked it up).

Good luck with it.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "n4buq" <n4buq@...>
To: TekScopes@groups.io
Sent: Wednesday, April 29, 2020 11:06:10 AM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

I have a 465M and, IIRC, there is a 95V supply that drives the HV. Mine had
a bad transistor or two and would blow a fuse on that line. I may be
misremembering that though...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael W. Lynch via groups.io" <mlynch003=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Wednesday, April 29, 2020 10:33:32 AM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

Probably not from a TEKTRONIX School, they would have the correct
Pozi-Drive
screwdriver to fit the screws. Stripped screws are typical of people using
a standard Phillips driver on a Pozi-Drive Screw, these are not
interchangeable.

Getting all the power rails to be relatively correct is the first and
foremost requirement. However, I do not recall seeing a +95V rail on a
465M? I have a 455, which is similar and it has +32REG, +32 UNREG +15, +5
REG, -5REG, +5 UNREG and -5 UNREG.

If +95V is there and not working, then it would need to work before the
scope
would function.

If my quick survey of the schematic and parts list is correct, U2900 is TEK
p/n 155-0124-00, a Tek-made horizontal pre-amplifier chip in a 16-pin DIP,
designed by Bob Nordstrom. This part is used in many pieces of TEK
Equipment
of the era.
--
Michael Lynch
Dardanelle, Arkansas





Michael W. Lynch
 

On Wed, Apr 29, 2020 at 11:06 AM, n4buq wrote:


I have a 465M and, IIRC, there is a 95V supply that drives the HV. Mine had a
bad transistor or two and would blow a fuse on that line. I may be
misremembering that though...

Thanks,
Barry - N4BUQ
Barry,

You are not missing a thing there and I stand corrected. I see why I missed this one on my 455 as well, the 95V is not created directly from the main power supply, so it is not shown in the power supply schematic. 95V source is found in the CRT schematic, and I never looked closely at the CRT schematic, since my 455 was not having any display issues.

I would suggest looking at the CRT schematic, circuit theory of operation and diagnosing the 95V issue from there. This 95V is also fed back to the Horizontal circuit as well, so I guess it to be essential to the instrument operation.

Thanks!
--
Michael Lynch
Dardanelle, Arkansas

paronaram
 

C582 is bad. Need to find replacement.
Is there anyone online selling TEK parts? I will need that U2900 TEK p/n 155-0124-00

<a href="https://ibb.co/mSVBrnH"><img src="https://i.ibb.co/52g9XQ5/95V.jpg" alt="95V" border="0"></a>

n4buq
 

Looking back at the posts in/around 9/3/17, C582 is one of the caps I replaced. Someone commented that C582 and C584 are common failure points and I think I replaced both while I was in there.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "paronaram" <baloyan@...>
To: TekScopes@groups.io
Sent: Wednesday, April 29, 2020 11:54:33 AM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

C582 is bad. Need to find replacement.
Is there anyone online selling TEK parts? I will need that U2900 TEK p/n
155-0124-00

<a href="https://ibb.co/mSVBrnH"><img src="https://i.ibb.co/52g9XQ5/95V.jpg"
alt="95V" border="0"></a>



satbeginner
 

Hi, that amplifier is used in several Tek scopes.
I needed o e for my 2215A, and got it at Qservice in Greece.

More info on my repair here:

https://groups.io/g/TekScopes/topic/2215a_repair_and_restoration/71585054?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,71585054

It turned out they no longer had the IC as a single part, that's why I bought a board with the chip socketed on it.

Good luck,

Leo

paronaram
 

I have donor 2235, will check if they have that IC on it

Thank you Leo

 

On Wed, Apr 29, 2020 at 08:30 PM, paronaram wrote:


I have donor 2235, will check if they have that IC on it
Both the 2235 and the 2235A use it, it's A4U760.

Raymond

paronaram
 

OK finally took the 465M bottom cover off, removed leaky cap ...
Do I need to replace it with 2.2mf 200v or let's say 10mf 200v will work too?

I also found TEK 155-0124-00 on my donor 2235, and it's not in the socket, so this will be a big job to remove this IC.
Is there any special instructions to handle this IC? Static, heat etc... I have hot air desoldering station

Thank you

satbeginner
 

Hi,

My trick to remove ic's that I do need to re-use is:

Use a good soldering iron and a solder sucker (or bread?) (Do you spell it like this?) on each pin individually;
When all pins are as clean as possible, use a pair of fine pointy pliers and wiggle each pin within the via hole, so it comes loose from the via; you will hear/feel a little "click".
You will notice which pin needs extra solder removed.
This is all done at the solder side of the board.
That way I can remove the IC to be re-used.

To remove the IC don't need anymore because it's broken:
Use a pair of really small sharp side cutters and -at the component side- cut flush to the IC each individual pin so the ic plastic body comes loose.
Now desolder each pin -one at the time- to remove it from the board.

If there is room enough, I put a quality socket first to be able to easier test in the future.

Just my 2 cents, good luck

Leo

paronaram
 

Just received replacement capacitors (use to take 3-4 days for part to come in, now it's 12)
Replaced C582 and C584 2.2uf 150V 2uf 150V replaced both with 2.2uf 250V
and voltage did not came back :(

I had 10V and now I have 13V looking for 95V

Is it possible that diode is shot? CR584 (safety diode) and CR582

Thank you

paronaram
 

Checked both diodes CR582 and CR584 (on the PCB) they both OK
T550 transformer Pin#2 to Ground 3.6Ohm. Transformer is good.
I did check some other pins to the ground and I have no voltage...
On other side of this T550 transformer I am afraid to pock around ... it has 2kV TP and 1.5kV warnings, plus my Fluke can not measure 2kV :(

Is it possible that I have dead HV multiplier ?

n4buq
 

Have you checked the AC voltage at the cathode of CR582 (as opposed to just checking the resistance of the winding)? I don't think the HV multiplier is involved with +95V.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "paronaram" <baloyan@...>
To: TekScopes@groups.io
Sent: Saturday, May 9, 2020 5:37:53 PM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

Checked both diodes CR582 and CR584 (on the PCB) they both OK
T550 transformer Pin#2 to Ground 3.6Ohm. Transformer is good.
I did check some other pins to the ground and I have no voltage...
On other side of this T550 transformer I am afraid to pock around ... it has
2kV TP and 1.5kV warnings, plus my Fluke can not measure 2kV :(

Is it possible that I have dead HV multiplier ?




n4buq
 

Also, +95V is connected to R541 so the components in/around that circuit (e.g. C543, etc.) could be a problem. According to what I'm seeing in the parts list, C543 is/was a Sprague 30D and those are known to fail at this age.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "n4buq" <n4buq@...>
To: TekScopes@groups.io
Sent: Saturday, May 9, 2020 6:15:24 PM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

Have you checked the AC voltage at the cathode of CR582 (as opposed to just
checking the resistance of the winding)? I don't think the HV multiplier is
involved with +95V.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "paronaram" <baloyan@...>
To: TekScopes@groups.io
Sent: Saturday, May 9, 2020 5:37:53 PM
Subject: Re: [TekScopes] Tektronix 465M - only scale illumination

Checked both diodes CR582 and CR584 (on the PCB) they both OK
T550 transformer Pin#2 to Ground 3.6Ohm. Transformer is good.
I did check some other pins to the ground and I have no voltage...
On other side of this T550 transformer I am afraid to pock around ... it
has
2kV TP and 1.5kV warnings, plus my Fluke can not measure 2kV :(

Is it possible that I have dead HV multiplier ?