465 Missing a Few Components


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


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 »


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.


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
 

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


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
 

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.


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
 

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 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