465 Missing a Few Components


 

SCMenasian wrote:

MJE2955s are more readily available on epay
No need to go to epay for MJE2955s, they are cheap and common from many retail sources: they're less than $1 each on Mouser and DigiKey. If you really want to live dangerously you can get 50 or 100 count on Amazon for under $20.

-- Jef Dutky


Stephen
 

Thank you SCM. I already replaced the ones missing in mine with TIP35C, and reversed the B E leads.
But I’m sure this info will be very valuable to someone with a similar issue.
And I still haven’t found what is causing the new short on the 15V rail. But that’s ok.


SCMenasian
 

I am in the process of replacing an MJE2901 and have found that, in addition to the 'K' part number which you mention, there is a "T" part number. The MJE2901T is a T0-220 part, while the straight MJE2901 is a T0-127 part
(the one we want). Also, The MJE2955 should be electrically compatible, as long as the module load is over a couple of mA. MJE2955s are more readily available on epay.


Stephen
 

A little follow-up on the restoration of this scope.
I’ve taken some time off from my current 2 restoration/repair projects to clear my mind a bit and do other stuff.

To recap the order of events: I had a short to ground on the 15V rail, which I discovered before powering the unit, and I had resolved this issue. That was cause by C891 being shorted (A&B Trigger Generator). L891 looked burnt and damaged, but is surprisingly reading good.
When I powered up the unit, the mains fuse blew instantly. Also, after that happened, the short to ground has come back on the 15V rail. This time it’s not C891. And I can’t seem to locate the cause.
Something else happened as well. I discovered a new short, but this time on the -8 V rail.

Regarding the mains fuse blowing, I found CR1541 to be bad, and replaced it. I also replaced all the filter caps.
As far as the short of the the -8V rail, it was due to a bad contact on the A Trigger pot. That wasn’t easy to find, as it was intermittent.

Now, if nothing else pops up, I’m left with finding where this new short on the 15V rail comes from, and I should be home free.

I’ve tested as many things as I could so far with no success.

Any lead will be most welcomed and appreciated.


Dave Peterson
 

A11 if I'm remembering correctly!

It's in the circuit boards diagram, Fig 2 in the early SM. Never seen it before!

There ya go, another SN <B250K "feature". Wow. Cool.

Thanks Stephen,
Dave

On Sunday, April 11, 2021, 03:26:07 PM PDT, Stephen <stephen.nabet@gmail.com> wrote:

For Dave, who shows quite a particular interest in this.

I have no idea why, but this allegedly “earlier” 465 has a separate “Trigger View Board”.

Picture here:
https://groups.io/g/TekScopes/photo/262670/3206043?p=Created,,,50,2,0,0


Stephen
 

For Dave, who shows quite a particular interest in this.

I have no idea why, but this allegedly “earlier” 465 has a separate “Trigger View Board”.

Picture here:
https://groups.io/g/TekScopes/photo/262670/3206043?p=Created,,,50,2,0,0


Stephen
 

On Fri, Apr 9, 2021 at 02:11 PM, Dave Peterson wrote:


Oh, yep, there you go. Disregard my last message. That's what I'm talking
about. I think this is one of the features of a pre SN B250K. I'm only
guessing based on the now two examples. I don't know where these details might
be documented.

Dave
I’m not sure they are.
Also, mine is a European made model. With my limited experience, I noticed that, given the same model, European made ones are, usually, closer to later US made ones. Probably because European factories were setup later than US ones, and modifications/upgrades had already been made. But I would assume they used older parts they had, even on more recent/upgraded units, just to not waste them. That would make sense. All companies do that. But who knows really....?

I’m wondering if the regular philips screws that hold the front bezel are original. I’ve never seen that.

PS: That power supply is not very friendly with me at the moment.
I think I have been having a thing with power supplies lately. They just don’t like me, I guess. 😂


Stephen
 

On Fri, Apr 9, 2021 at 02:07 PM, Dave Peterson wrote:


Stephen,

Compare your scopes TIME/DIV B-sweep knob and HORIZ DISPLAY A button to the
picture of my pre SN B250K. There is no "LOCK KNOBS" text on them. I'm
presuming this is a pre SN B250K feature. I don't know that that is the case,
I'm just presuming so.
Maybe... who knows...

Could it be that someone has swapped these components on yours or mine?
I highly doubt that.

My scope's condition is pretty good. A bit dirty in the usual places, but doesn't
seem to have been dismantled before.
Mine as well. Everything is stock as can be. The only person sho has bee in there was only to take a few compositions out; maybe in a attempt to repair it. Other than that, it was extremely dirty. A thick layer of soot was nearly everywhere inside. I cleaned it up pretty nicely.
The exterior was pretty much in the same condition. That thing was absolutely filthy inside and out.


Dave Peterson
 

Oh, yep, there you go. Disregard my last message. That's what I'm talking about. I think this is one of the features of a pre SN B250K. I'm only guessing based on the now two examples. I don't know where these details might be documented.

Dave

On Friday, April 9, 2021, 10:43:44 AM PDT, Stephen <stephen.nabet@gmail.com> wrote:

Dave,
Maybe this last picture will answer some of your questions:
« https://groups.io/g/TekScopes/photo/262670/3204540?p=Created,,,50,2,0,0 »


Dave Peterson
 

Stephen,

Compare your scopes TIME/DIV B-sweep knob and HORIZ DISPLAY A button to the picture of my pre SN B250K. There is no "LOCK KNOBS" text on them. I'm presuming this is a pre SN B250K feature. I don't know that that is the case, I'm just presuming so.

https://groups.io/g/TekScopes/photo/262237/3196250?p=Name,,,20,0,0,0


Could it be that someone has swapped these components on yours or mine? My scope's condition is pretty good. A bit dirty in the usual places, but doesn't seem to have been dismantled before.

Dave

On Friday, April 9, 2021, 09:08:10 AM PDT, Stephen <stephen.nabet@gmail.com> wrote:

Interleaved.

On Fri, Apr  9, 2021 at 04:06 AM, Dave Peterson wrote:

Stephen seems to be in possession of of a true early scope. Stephen, is the A5
board a discrete component or IC version?
If by IC version you mean U440, it’s there.

Does it have a surviving time/div
know without "LOCK KNOBS"?
How do you mean?  I don’t see any differences between this scope and my other 465, or my 475A, or my 465B as far as the Time/Div knob(s).

And a simple "A" HORIZ DISPLAY button?
Same as above.

What other notable differences are there on the early pre SN B250K scopes?
The only noticeable difference that I see is that the CRT bezel isn’t held by checkered and captive screws like the others, but with regular non-captive philips screws.


Feel free to ask more questions if you need to.


Dave


Stephen
 

Dave,
Maybe this last picture will answer some of your questions:
« https://groups.io/g/TekScopes/photo/262670/3204540?p=Created,,,50,2,0,0 »


Stephen
 

Interleaved.

On Fri, Apr 9, 2021 at 04:06 AM, Dave Peterson wrote:

Stephen seems to be in possession of of a true early scope. Stephen, is the A5
board a discrete component or IC version?
If by IC version you mean U440, it’s there.

Does it have a surviving time/div
know without "LOCK KNOBS"?
How do you mean? I don’t see any differences between this scope and my other 465, or my 475A, or my 465B as far as the Time/Div knob(s).

And a simple "A" HORIZ DISPLAY button?
Same as above.

What other notable differences are there on the early pre SN B250K scopes?
The only noticeable difference that I see is that the CRT bezel isn’t held by checkered and captive screws like the others, but with regular non-captive philips screws.


Feel free to ask more questions if you need to.


Dave


 

On Fri, Apr 9, 2021 at 05:06 PM, Dave Peterson wrote:


I'm curious to know how "rare" these early scopes are any more. Tek seems to
have made these early changes fairly quickly, even before the actual SN B250K.
I currently posses a B177K and it seems to mostly be made up of later
components. The A9 is late, and the A5 (vertical amp) seems to be somewhat
later: non-IC discrete components matching the change schematic, but the post
B250K four digit component numbers. It includes components on the earlier
change schematic that aren't present on the later board.
Interesting, Dave. I think you already know more about the 465's history than I, with my more general knowledge.
Please keep us informed.

Raymond


 

Interleaved


On Fri, Apr 9, 2021 at 04:39 PM, Stephen wrote:


I just think that the fact that it’s serial number 465, which is the same as
the model number, is kinda neat. Other than that, nothing special. It’s just
a serial number... 🤷‍♂️
Oh yes, I completely forgot that. Of course it's very special!


I’ll use the Variac when it’ll actually get here. In transit at the
moment. 😉
It’s not a very big one, just 5A.
Absolutely big enough for all Tek 'scope work!


Meanwhile, I’m going to power the scope with a 12VAC. That’s all I have
available at this point, along with a 24VAC one, until the Variac gets here.
That is fine, start with 12VAC.

Raymond


Dave Peterson
 

Guys,

I'm curious to know how "rare" these early scopes are any more. Tek seems to have made these early changes fairly quickly, even before the actual SN B250K. I currently posses a B177K and it seems to mostly be made up of later components. The A9 is late, and the A5 (vertical amp) seems to be somewhat later: non-IC discrete components matching the change schematic, but the post B250K four digit component numbers. It includes components on the earlier change schematic that aren't present on the later board.

And as Raymond noted, the first SN starts at B010100?

So I wonder if there are few surviving examples?

I know 465s are like the VW Beetle of oscilloscopes. But even early "split window" Bugs are pretty valuable now. It seems appropriate to try to preserve surviving examples. But I'm biased.

Stephen seems to be in possession of of a true early scope. Stephen, is the A5 board a discrete component or IC version? Does it have a surviving time/div know without "LOCK KNOBS"? And a simple "A" HORIZ DISPLAY button? What other notable differences are there on the early pre SN B250K scopes?

Dave

On Friday, April 9, 2021, 07:39:48 AM PDT, Stephen <stephen.nabet@gmail.com> wrote:

I just think that the fact that it’s serial number 465, which is the same as the model number, is kinda neat.  Other than that, nothing special.  It’s just a serial number...  🤷‍♂️

I’ll use the Variac when it’ll actually get here.  In transit at the moment.  😉
It’s not a very big one, just 5A.

Meanwhile, I’m going to power the scope with a 12VAC.  That’s all I have available at this point, along with a 24VAC one, until the Variac gets here.


Stephen
 

I just think that the fact that it’s serial number 465, which is the same as the model number, is kinda neat. Other than that, nothing special. It’s just a serial number... 🤷‍♂️

I’ll use the Variac when it’ll actually get here. In transit at the moment. 😉
It’s not a very big one, just 5A.

Meanwhile, I’m going to power the scope with a 12VAC. That’s all I have available at this point, along with a 24VAC one, until the Variac gets here.


 

On Fri, Apr 9, 2021 at 03:44 PM, Stephen wrote:


Yes, nothing to loose really (but a little time), only gain... Particularly if
it turns out to be indeed a quite early European made example with an
interesting serial number for a 465 (700465). I think it ought to be
preserved, and restored. With that in mind, I’m doing my best.

BTW, I finally got a replacement for my dead Variac.
Stephen,
The gained experience in itself is worth the effort, not much money lost if it doesn't work out.
The serial number is nothing special for a Heerenveen (NL) -produced Tek. Non-US serial numbers often are like it. Both my 7854's are Guernsey-numbers below 200.

Use your variac! Initially, forget about my earlier recommendations and start by applying your variac. Start at a voltage as low as around 6 or 10VAC and see how all unregulated voltages behave at that one setting, then the regulated ones. Should be easy and very informative first steps. One remote possibility is a defective mains transformer though...

Raymond


Stephen
 

Raymond,

I know you knew that, and that it was an honest mistake.
I just pointed this out so future people that will be eventually interested in this restoration, won’t get confused, and try to locate these parts on the A1 board.

Yes, nothing to loose really (but a little time), only gain... Particularly if it turns out to be indeed a quite early European made example with an interesting serial number for a 465 (700465). I think it ought to be preserved, and restored. With that in mind, I’m doing my best.


BTW, I finally got a replacement for my dead Variac. 😉


 

On Fri, Apr 9, 2021 at 03:08 PM, Raymond Domp Frank wrote:


Very little to use, a lot to gain.
Correction: "Very little to lose, a lot to gain".

Raymond


 

On Fri, Apr 9, 2021 at 02:01 PM, Stephen wrote:


PS: BTW, it’s the A9 board, not the A1 board.
Of course it is, Stephen. Often, the mainboard is A1 and I didn't look it up. As is so often the case, extra (and wrong) data only contributed to increased confusion. At least, one of us was awake (as was I, at 5 AM today, and up again at 10 AM).

Good luck going on with this project. Very little to use, a lot to gain.

Raymond