465 Missing a Few Components


Stephen
 

For about 15€ I bought this 465 for parts. Seller said it didn’t turn on at all.
I opened it up, and indeed, it definitely can’t function.
There are apparently 4 missing components in the power supply.
Can anyone confirm that the 2 missing transistors are Q1534 and Q1546? Q1546 is very hard to make out from the TekWiki schematic. The other, although not missing, seems to be Q1566.
I did locate R1549, but not the small part that appears to have been removed as well, perpendicular to it.
I think it might be a small fuse...?
https://groups.io/g/TekScopes/album?id=262670

Thanks


Dave Peterson
 

Stephen,

I think you are right that it is Q1546. My A9 boards are not labeled, but the collector traces back to CR1541 and C1542, which is Q1546.

Does this scope have either option 4 or option 7? The board diagram in the SN>250K service manual (Fig. 8-18) indicates 3 possible capacitors with the note "2 Used only with Options 4 and 7". My boards have 3 pairs empty vias at that location, but look a little different than your picture in this regard.

I do have an empty via at the trace shown in your picture. The one that travels under the fuse to CR1569. The other via at that location - between the trace via and the R1549 via just to the right of the arrow tip - is not present on my boards. I'm looking at both a pre and post SN 250K boards. So I'm at a loss as to what that might have been. The trace is apparently the -8v rail, unless it's the ground side of CR1569, for what that's worth.

What is the SN range of this scope? Is it pre or post SN 250K? Any other options or indications of variation?

Sorry I'm not more help.
Dave


Dave Peterson
 

Of course, as soon as I send that:

I was looking at the SN > 250K manual, but the SN < 250K manual indicates that this is C1549. It was moved to near the PS test points in later revisions. Right next to the +15v test point.

This must be a very early SN < 250K scope! Fun! Any chance of restoring it?

Dave


Stephen
 

Hi Dave,

It has no options I can see, and nothing is mentioned on the front panel either.
It’s a European made scope, so the serial number starts with 70xxxxx.
Actually a very early European model from the low serial number. Funny, the serial is actually xxx465!!
https://groups.io/g/TekScopes/photo/262670/0?p=Created,,,50,2,0,0

There was definitely something in that spot, if I trust the solder mark on the board below R1549...
https://groups.io/g/TekScopes/photo/262670/1?p=Created,,,50,2,0,0

C1549??


Stephen
 

The image links don’t always go to the right images...

Maybe I’ll restore it. That would be nice. Otherwise, well... It was a parts scope to begin with...
But hopefully, I’ll restore it.
I can replace the two power transistors with TIP35C (maybe all of them), and swap B and C around, I guess. They’re well overrated. I’ll replace the missing parts, and take it from there.
I don’t like seeing potentially reparable good pieces of gear go to waste.


Dave Peterson
 

That serial number just begs for restoration!

One mans junk is another's treasure. I'm turning into a treasure collector. Wink.

I guess it's up to the CRT. I think most everything else is still relatively replaceable, even across SNs. The early 465s don't have a mesh in the tube according to my SMs. I don't know if my SN<250K does or doesn't. I haven't traced that aspect yet. It does seem to be a hybrid of details from both before and after SN250K. I'm curious to see if the lack of a mesh has a noticeable effect on the trace. So far mine seems perfectly nice. Maybe it has one. What other significant differences are there between pre and post SN250K? I know the time/div knob and horizontal display markings are different: https://groups.io/g/TekScopes/photo/262237/0?p=Name,,,20,0,0,0 Otherwise I think an old scope can be restored with later parts.

That's a very cool find Stephan. I am jealous. I vote for restoration, but it's not my money (or garage space). Good luck with it!
Dave


 

On Mon, Apr 5, 2021 at 11:23 PM, Stephen wrote:


It’s a European made scope, so the serial number starts with 70xxxxx.
Actually, Tektronix had factories in three locations in Europe:
Units with serial numbers starting with 1 were made in Guernsey (Channel Islands)
Units with serial numbers starting with 2 were made in London (UK)
Units with serial numbers starting with 7 were made in Heerenveen (Netherlands)

Unfortunately, there is no way to cross-reference serial numbers between factories; each used their own serialization.

Have a look for the main board number; it should have the form of 670-xxxx-yy and is usually located near the Beam Finder switch.

Raymond


Dave Peterson
 

Uh, what? That picture link did not work. Try:

"https://groups.io/g/TekScopes/photo/262237/2?p=Name,,,20,0,0,0"

With quotes?


Stephen
 

On Mon, Apr 5, 2021 at 10:48 AM, Dave Peterson wrote:


Uh, what? That picture link did not work. Try:

"https://groups.io/g/TekScopes/photo/262237/2?p=Name,,,20,0,0,0"

With quotes?
I told you. I have that problem quite often actually... Links don’t always go to the intended picture...


 

On Mon, Apr 5, 2021 at 11:44 PM, Dave Peterson wrote:


The early 465s don't have a mesh in the tube according to my SMs.
Oh yes, they definitely do.

I don't know if my SN<250K does or doesn't.
So yes, it does. The mesh not only increases the CRT's deflection sensitivity, it unfortunately also increases the spot size. A lot of development has been done after these first efforts. Later versions of the 465 used modified CRT's, resulting in slightly sharper traces. Other improvements helped that.

Raymond


Stephen
 

On Mon, Apr 5, 2021 at 10:45 AM, Raymond Domp Frank wrote:


On Mon, Apr 5, 2021 at 11:23 PM, Stephen wrote:


It’s a European made scope, so the serial number starts with 70xxxxx.
Actually, Tektronix had factories in three locations in Europe:
Units with serial numbers starting with 1 were made in Guernsey (Channel
Islands)
Units with serial numbers starting with 2 were made in London (UK)
Units with serial numbers starting with 7 were made in Heerenveen
(Netherlands)

Unfortunately, there is no way to cross-reference serial numbers between
factories; each used their own serialization.

Have a look for the main board number; it should have the form of 670-xxxx-yy
and is usually located near the Beam Finder switch.

Raymond
Indeed. I also found that, European made models are often closer to higher serial numbers in the US.
Board serial number is GC-2773-06. That’s all there is that I can see.

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

If the link doesn’t work, scroll through the pictures.

Also, that resistor and solder joint next to it, don’t look to good. They seem to have been to hell and back...


Stephen
 

Thanks for the tip Dave.

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

Let’s see if that works.

I’m definitely going through and check all the solder joints. Some look quite cold...


 

I added a photograph of the relevant part of the Main Board (fig. 7-12 in the SM, 070-1330-00),
here:

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

When using the web interface, just make sure you include the numbers and commas at the end of the link - or use mail messages.

Raymond


Dave Peterson
 

Could you clarify Raymond?

Why does the early SM that I have, have no circuitry from the transformer nor CRT mesh pin (pin 12) in the "CRT CIRCUIT" diagram?

I'm not doubting what you say - you clearly have experience in these matters. As I noted, I haven't looked into this in detail on the scope I have (SN177xxx). What is the history? Why not in the manual if all scopes have it? I'm trying to learn these details, so you're insight is appreciated.
Dave

On Monday, April 5, 2021, 02:54:34 PM PDT, Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Mon, Apr  5, 2021 at 11:44 PM, Dave Peterson wrote:


The early 465s don't have a mesh in the tube according to my SMs.
Oh yes, they definitely do.

I don't know if my SN<250K does or doesn't.
So yes, it does. The mesh not only increases the CRT's deflection sensitivity, it unfortunately also increases the spot size. A lot of development has been done after these first efforts. Later versions of the 465 used modified CRT's, resulting in slightly sharper traces. Other improvements helped that.

Raymond


 

On Tue, Apr 6, 2021 at 12:06 AM, Raymond Domp Frank wrote:


I added a photograph of the relevant part of the Main Board (fig. 7-12 in the
SM, 070-1330-00),
here:
Much more useful (SM figure 7-21):

https://groups.io/g/TekScopes/photo/262670/4?p=Created,,,50,2,0,0


Raymond


Dave Peterson
 

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.

Oh, and I just remembered another significant mismatch between pre & post SN250K: The B-sweep switch cam is different. I have an extra early cam if anyone needs one!

Dave

On Monday, April 5, 2021, 03:06:11 PM PDT, Raymond Domp Frank <hewpatek@gmail.com> wrote:

I added a photograph of the relevant part of the Main Board (fig. 7-12 in the SM, 070-1330-00),
here:

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

When using the web interface, just make sure you include the numbers and commas at the end of the link - or use mail messages.

Raymond


 

On Tue, Apr 6, 2021 at 12:00 AM, Stephen wrote:


Indeed. I also found that, European made models are often closer to higher
serial numbers in the US.
Board serial number is GC-2773-06. That’s all there is that I can see.
The 465 was designed in the USA and first produced there. In those situations, the early foreign numbers more closely relate to later USA numbers.
The board model no. probably sits between the Beam Finder switch and the front of the 'scope. It definitely is of the form "670-xxx-yy".

Raymond


Dave Peterson
 

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

On Monday, April 5, 2021, 03:06:09 PM PDT, Stephen <stephen.nabet@gmail.com> wrote:

Thanks for the tip Dave.

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

Let’s see if that works.

I’m definitely going through and check all the solder joints.  Some look quite cold...


Stephen
 

I understand, Raymond.

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.

Also, the shield on the attenuators, do not have the long “S” shaped ground spring that connects to the case.
Instead they have 2 wires directly soldered to the board.

Pictures here:
https://groups.io/g/TekScopes/photo/262670/1?p=Created,,,50,2,0,0”

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

B-Sweep cams:
https://groups.io/g/TekScopes/photo/262670/3?p=Created,,,50,2,0,0”

Thanks for the board pictures with the labeling, Raymond. That helps a lot.


 

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