465 Missing a Few Components


Stephen
 

On Mon, Apr 5, 2021 at 11:30 AM, Dave Peterson wrote:


Stephen,
It looks like you have Q1534 reversed with Q1546 in the close-up you have
annotated.
Tracing that middle via, the "C" (if the silk screen is even there - ouch!),
of the nearer heat sinked transistor, should go to C1542 over by CR1541. It's
the center pin of the rear-most, outer-most big PS can capacitor.
Dave
You are absolutely right. However, these 3 power transistors are the same parts anyway (MJE2801).
But Q1546 and Q1566 are “selected”,...


 

On Tue, Apr 6, 2021 at 12:34 AM, Stephen wrote:


But there is nothing there. The only number is the one I took a picture of.
The board date is 1971. There is nothing else.
Photo from SM added. Number is in same location on one of my parts donkey boards.

https://groups.io/g/TekScopes/photo/262670/0?p=Created,,,50,2,0,0

Raymond


 

On Tue, Apr 6, 2021 at 12:47 AM, Raymond Domp Frank wrote:



But there is nothing there. The only number is the one I took a picture
of.
The board date is 1971. There is nothing else.
Photo from SM added. Number is in same location on one of my parts donkey
boards.

https://groups.io/g/TekScopes/photo/262670/0?p=Created ,,,50,2,0,0
Cleverly hidden underneath the "Invert" button shaft...

Raymond


Dave Peterson
 

Thanks for the pointer Raymond.

I think this topic deserves a new and separate thread. I find the early 465 history fairly interesting. Tek was clearly interested in getting this scope out on the market, and encountered a lot of changes between early releases and later. My early service manual has a large change section at the rear, and I seem to have as many variants of vertical amp board as I do 465 scopes. With associated schematics and cal procedures.

I'll post a new message thread asking for clarification on the early 465 CRT "mesh" pin 12.

Dave

On Monday, April 5, 2021, 03:35:52 PM PDT, Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Tue, Apr  6, 2021 at 12:15 AM, Dave Peterson wrote:


BTW Raymond, I have the same book: 070-1330-00 with the same diagram. This is
the book to which I'm referring when I say the CRT does not appear to have a
mesh circuit. Thus my conclusion. Not the only discrepancy I've found between
this book and my SN177xxx.
The mesh is connected to pin 12 in the CRT socket. You can see it mentioned by its name in the CRT circuit dwg in the >=250000 SM.
The test specification of the T4650 CRT, which the 465 entry in Tekwiki links to, mentions it as Post Accelerator Grid and uses the word "mesh" on page 2. That document is from November 1972, long before the first printing 250000 SM, which is dated August 1974.

Raymond


Stephen
 

Raymond,

I finally saw it. Well hidden indeed!!!

It’s exactly the same as your picture:
670-2233- (and nothing...)

https://groups.io/g/TekScopes/photo/262670/0?p=Created,,,50,2,0,0


Stephen
 

On Mon, Apr 5, 2021 at 12:00 PM, Dave Peterson wrote:


Thanks for the pointer Raymond.

I think this topic deserves a new and separate thread. I find the early 465
history fairly interesting. Tek was clearly interested in getting this scope
out on the market, and encountered a lot of changes between early releases and
later. My early service manual has a large change section at the rear, and I
seem to have as many variants of vertical amp board as I do 465 scopes. With
associated schematics and cal procedures.

I'll post a new message thread asking for clarification on the early 465 CRT
"mesh" pin 12.

Dave
Agreed,

Did you see the B-Sweep cams I posted in the photos? How do they compare to early ones that you mentioned? Same for the grounded attenuators. A picture is also available in the folder.


Stephen
 

I finally started to electrically restore this apparently quite early 465.
The 2 pass transistors have been replaced, as well as R1549, and C1549.
Also, the 15V rail was shorted to ground because of a faulty tantalum on the horizontal amp board, but I don’t know the number. The schematic from TekWiki is not very good. It’s near impossible sometimes to make out the parts numbers.
Also, some A9 board pictures do are quite different from the one I have.
Could anyone with a legible picture send it to me offline, or post it in the photo folder, please?
Now that I’ve replaced what I could so far, I turn the unit on, and the line fuse blew instantly.
I can’t try to troubleshoot it with the documents I have available at this point.

PS: No more of the rails are shorted to ground.


Dave Peterson
 

Stephen,

I don't quite have the equipment to scan the pre SN B250000 11x17 pages, but I can take photos and look up specifics for you.

The A9 board has many board layout pages in the book. Each one highlights components from different sections: Horizontal Amp, CRT, Power Supply, etc.

Please let me know what you need and I'll upload pictures. It's kind of a run-around to take and upload pictures, so a blanket dump would take a while. My phone takes pics that are several Meg in size, so I resize them down to something more on the order of several 100k. But it takes a bit of shenanigans to do. I don't want to blow up the groups disk space.

When you say the fuse blows, are you talking about the main fuse, or F1419? F1419 is the one on the board that drives the HV transformer. Quite common that C1419 shorts and causes that. If the main fuse you're going to have to see if you can identify the short in the power rails. Do any of the power test points measure 0 ohms to ground?

As you know, some of the A9 board diagrams are already in your TekScopes photo album. Let me know what's not covered that you think will help. Same with schematic pages.

Dave

On Thursday, April 8, 2021, 01:30:26 PM PDT, Stephen <stephen.nabet@gmail.com> wrote:

I finally started to electrically restore this apparently quite early 465.
The 2 pass transistors have been replaced, as well as R1549, and C1549.
Also, the 15V rail was shorted to ground because of a faulty tantalum on the horizontal amp board, but I don’t know the number.  The schematic from TekWiki is not very good.  It’s near impossible sometimes to make out the parts numbers.
Also, some A9 board pictures do are quite different from the one I have.
Could anyone with a legible picture send it to me offline, or post it in the photo folder, please?
Now that I’ve replaced what I could so far, I turn the unit on, and the line fuse blew instantly.
I can’t try to troubleshoot it with the documents I have available at this point.

PS: No more of the rails are shorted to ground.


 

On Thu, Apr 8, 2021 at 10:30 PM, Stephen wrote:


Now that I’ve replaced what I could so far, I turn the unit on, and the line
fuse blew instantly.
I guess by line fuse you mean mains fuse. Assuming that's correct, I'd start by looking at the usual suspects for this 'scope family:
See schematic dwg 12, ckt. layout in fig. 7.21: Bridge rectifiers, buffer caps, overvoltage protection circuit (around Q1514). VR1515 being shorted is a candidate. Check with current-limited voltage across Q1514 but only for a short moment, because C1512 will be reverse-biased. Just tap the test voltage for a second or so. 10V to 20V usually makes a bad circuit trip (shorted Q1514 or VR1515).
Check by connecting current-limited DC across each of the buffer caps separately, starting from a few volts.
If no shorts observed, check individual diodes in diode bridges.
All this in-circuit but *with mains plug disconnected*.

Raymond


Stephen
 

On Thu, Apr 8, 2021 at 09:41 AM, Dave Peterson wrote:

Interleaved,

Stephen,

I don't quite have the equipment to scan the pre SN B250000 11x17 pages, but I
can take photos and look up specifics for you.
That would be awesome, thank you.

The A9 board has many board layout pages in the book. Each one highlights
components from different sections: Horizontal Amp, CRT, Power Supply, etc.
I’m sure...

Please let me know what you need and I'll upload pictures. It's kind of a
run-around to take and upload pictures, so a blanket dump would take a while.
My phone takes pics that are several Meg in size, so I resize them down to
something more on the order of several 100k. But it takes a bit of shenanigans
to do. I don't want to blow up the groups disk space.
Of course, I understand. Can you send them to me full size, privately maybe?

When you say the fuse blows, are you talking about the main fuse, or F1419?
I’m talking about the main fuse, the 0.750mA one outside the unit (the scope is set to 230V, I’m in Europe)

F1419 is the one on the board that drives the HV transformer. Quite common
that C1419 shorts and causes that.
F1419 is fine. Although C1419 was testing good, I replaced it anyways because I happened to have a brand new one just if front of me. I guess it was C1419 (can’t make out the number), the large 47uF/25V tantalum underneath the high voltage cover shield, in the corner.

If the main fuse you're going to have to
see if you can identify the short in the power rails. Do any of the power test
points measure 0 ohms to ground?
Nope... The 15V rail was shorted to ground before I even powered up the scope, and I fixed that already.
None of the low voltage test points are shorted to ground now.


As you know, some of the A9 board diagrams are already in your TekScopes photo
album. Let me know what's not covered that you think will help. Same with
schematic pages.
Yes, But I’d like, if possible, to have as much as I can with the parts labeled.
I’m posting a few pictures of my A9 board after it’s been cleaned up quite a bit.
Look at the first 3 pictures in the album to get an idea of what board version we’re talking about.
Note the lack of that big resistor between the filter caps, and the slightly different layout when compared to newer units.

https://groups.io/g/TekScopes/album?id=262670

Thanks Dave.

Dave


Stephen
 

Yes Raymond,

This is the fuse I’m talking about.
Good pieces of advice, as usual. Thank you 😊


Stephen
 

BTW, you’ll notice that I’ve replaced the 2 missing pass transistors with TIP35C’s.
I checked the pinout, ans it seems to be the same as the MJE2801.


 

On Thu, Apr 8, 2021 at 10:41 PM, Dave Peterson wrote:


If the main fuse you're going to have to see if you can identify the short in
the power rails. Do any of the power test points measure 0 ohms to ground?
Shorts in the power rails after the buffer circuits usually aren't able to cause blowing of the mains fuse.
That's why I suggested checking the circuits as in my message about half an hour ago.

Raymond


Dave Peterson
 

Systems are not working well today. I'm not getting messages until much later than they are posted, so apologies if they are out of sync.
Dave

On Thursday, April 8, 2021, 02:37:07 PM PDT, Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Thu, Apr  8, 2021 at 10:41 PM, Dave Peterson wrote:


If the main fuse you're going to have to see if you can identify the short in
the power rails. Do any of the power test points measure 0 ohms to ground?
Shorts in the power rails after the buffer circuits usually aren't able to cause blowing of the mains fuse.
That's why I suggested checking the circuits as in my message about half an hour ago.

Raymond


 

On Thu, Apr 8, 2021 at 11:19 PM, Raymond Domp Frank wrote:


If no shorts observed, check individual diodes in diode bridges.

I meant to say "If no shorts elsewhere observed, check individual diodes in diode bridges".
Since you're looking for shorts (not PN junctions) in individual diodes in the bridges, that's usually possible with the bridges in.

Raymond


Ozan
 

Hi Stephen,

The schematic from
TekWiki is not very good. It’s near impossible sometimes to make out the
parts numbers.
Did you look at the SMs at :
https://bama.edebris.com/manuals/tek/465(2)/
and
https://bama.edebris.com/manuals/tek/465/

Ozan


 

On Thu, Apr 8, 2021 at 11:19 PM, Raymond Domp Frank wrote:


Check by connecting current-limited DC across each of the buffer caps
separately, starting from a few volts.
If no shorts observed, check individual diodes in diode bridges.
All this in-circuit but *with mains plug disconnected*.

This would be a good occasion for using a variac. I remember you didn't have one a few months ago, Stephen, and didn't plan on getting one yet. "Get a variac when I can" just scored one point today...
Raymond


Stephen
 

On Thu, Apr 8, 2021 at 11:26 AM, Ozan wrote:


Hi Stephen,

The schematic from
TekWiki is not very good. It’s near impossible sometimes to make out the
parts numbers.
Did you look at the SMs at :
https://bama.edebris.com/manuals/tek/465(2)/
and
https://bama.edebris.com/manuals/tek/465/

Ozan
Much, much better! Thank you Ozan. 😊


toby@...
 

On 2021-04-08 6:41 p.m., Stephen wrote:
On Thu, Apr 8, 2021 at 11:26 AM, Ozan wrote:


Hi Stephen,

The schematic from
TekWiki is not very good. It’s near impossible sometimes to make out the
parts numbers.
Did you look at the SMs at :
https://bama.edebris.com/manuals/tek/465(2)/
and
https://bama.edebris.com/manuals/tek/465/

Ozan

And I've personally scanned a clear one, not sure if it's the right SN
range for you.

https://docs.telegraphics.com.au/Tektronix_070-1330-00_465_Oscilloscope_Service_Instruction_Manual.tif

(note, multipage tif, but most system viewers are fine with it)

I would have thought I'd uploaded this to Tekwiki.

--Toby


Much, much better! Thank you Ozan. 😊





 

On Fri, Apr 9, 2021 at 12:58 AM, <toby@telegraphics.com.au> wrote:


And I've personally scanned a clear one, not sure if it's the right SN
range for you.

https://docs.telegraphics.com.au/Tektronix_070-1330-00_465_Oscilloscope_Service_Instruction_Manual.tif

(note, multipage tif, but most system viewers are fine with it)

I would have thought I'd uploaded this to Tekwiki.
That's the same as 070-1330-00465Service.pdf on https://bama.edebris.com

Raymond