Tek 466 analog storage


Paul B.
 

Hi all,

I'm really not very familiar at all with these exotic beasts. I'm powering up a 466 (early version) slowly from a variac (they used a linear supply on these) and at about one-half mains voltage I'm seeing a green glow on the screen and that's all. I would guess by time I get to full mains this glow is going to be *extremely* bright and that can't be right (the intensity control doesn't make any difference, btw). What should I expect to see when powering up a 466? It's been laying around for many years without being powered up at all. I'm not giving it any input at this stage for obvs reasons; just want to check it's not a junker before spending money on it.

cheers.


Brendan
 

On Sun, Sep 2, 2018 at 06:15 AM, Paul B. wrote:


Hi all,

I'm really not very familiar at all with these exotic beasts. I'm powering up
a 466 (early version) slowly from a variac (they used a linear supply on
these) and at about one-half mains voltage I'm seeing a green glow on the
screen and that's all. I would guess by time I get to full mains this glow is
going to be *extremely* bright and that can't be right (the intensity control
doesn't make any difference, btw). What should I expect to see when powering
up a 466? It's been laying around for many years without being powered up at
all. I'm not giving it any input at this stage for obvs reasons; just want to
check it's not a junker before spending money on it.

cheers.
I would think that using a variac a1/2 voltage would cause some oddities. Other more experienced members will weigh in im sure.


Paul B.
 

I'm perfectly sure it will cause "some oddities" - I don't dispute that. I'm just very wary about winding that variac up more when the display is already brighter than IMO it should be (although I have only my limited experience with Telequipment analog storage scopes to go by which may be of no help at all here).


Roger Evans
 

If you remove the fuse in the 15V unregulated supply to the high voltage inverter (z-axis / crt schematic) you remove both the high voltage to the CRT and the CRT filament supply so that should keep the CRT safe.

I would then power up on full line voltage and check all the low voltage supplies are within spec. If they look ok then replace the fuse, move the vertical position controls to move the beam away from the visible area, intensity to minimum, and power up again on full supply voltage, ready to turn off quickly if anything is amiss.

The manual will have instructions for the setting of the storage controls for first time use.

Roger


Paul B.
 

Many thanks for that; good idea!
I'm just a bit bamboozled by the fact that the schematic you mention shows that line from the fuse going to the primary winding of a transformer. If it's +15V unreg as stated, I can't see how this 15V DC to a transformer primary is going to give any outputs from the secondary side! Maybe I'm reading it wrong (don't have my glasses so it makes following schematics very difficult!)


Roger Evans
 

The circuitry around the high voltage transformer T1501 constitutes a power oscillator running at around 50kHz, there is feedback from the CRT cathode to Q1472 that controls the drive to the power transistor Q1486 and stabilises the cathode voltage. There is a theory of operation section in the manual.

Roger


Paul B.
 
Edited

Oh, right. That hadn't occurred to me to be honest. I've removed the 'CRT fuse' as you suggested and run the rest of the scope up to 230VAC without anything going *bang* so that's a plus, anyway. However, being realistic I don't think there's much more I can do at this stage. Only one of the PSU output voltages tallies up with the schematic (the 140V TP is reading 141V) but the rest are not within what I would describe as normal. I'm hampered by the lack of a physical, hands-on manual. The scanned copy I'm using is hard to read in places and the pages are hell to find with page/up/down buttons. On top of which what little I can see of the schematic is seriously unfamiliar circuitry to me. If you can understand that rat's nest you must be a genius, that's all I can say.
Reckon I'll just have to mothball it for a few more years until I have the time to get to grips with it with a better chance of success. :(
Many thanks indeed for your assistance, anyway.


Roger Evans
 

There is a very decent PDF manual at w140.com/tekwiki/wiki/466. For serious fault finding I print off a few pages, sometimes as two sheets stuck together, and make a note on these where to find other schematics and layout pages. It looks like all the lower voltages get their reference from the +65V that you will find just below the +140V supply on schematic <11> Power Supply and Distribution. If all of your lower voltages are off by the same fraction eg all low by 20% it could just be that the +65V is off spec and everything else is OK. If you want I can talk you through some of the stages but I am far from being an expert and you will have to wait until after our holiday!

Roger


toby@...
 

On 2018-09-03 11:16 AM, Roger Evans via Groups.Io wrote:
There is a very decent PDF manual at w140.com/tekwiki/wiki/466.

That would be the one I scanned. I took a lot of care to make sure it's
clear -- if you find any problems, let me know, I still have the
original files and paper manual.

--Toby



For serious fault finding I print off a few pages, sometimes as two
sheets stuck together, and make a note on these where to find other
schematics and layout pages. It looks like all the lower voltages get
their reference from the +65V that you will find just below the +140V
supply on schematic <11> Power Supply and Distribution. If all of your
lower voltages are off by the same fraction eg all low by 20% it could
just be that the +65V is off spec and everything else is OK. If you
want I can talk you through some of the stages but I am far from being
an expert and you will have to wait until after our holiday!

Roger




Paul B.
 

Thanks very much, Roger. You can go away on your holiday; don't worry about trying to fix this!!!


EB4APL
 

Toby,

There are three 466 manuals. If yours is the one named Tektronix 466 Service Manual (PDF, OCR) <http://w140.com/tekwiki/images/c/cc/070-1753-01.pdf>, I can improve it somewhat if you don't mind. I can number the pages to reflect the original numbering and also I can add markers to point to the pages listed in the Table of Contents. I always do that in my own equipment manuals to easy the finding of schematics and alignment instructions. It'll take quite time but I'll do it if anybody is interested.

Regards,

Ignacio, EB4APL

El 03/09/2018 a las 18:32, toby@... escribió:
On 2018-09-03 11:16 AM, Roger Evans via Groups.Io wrote:
There is a very decent PDF manual at w140.com/tekwiki/wiki/466.
That would be the one I scanned. I took a lot of care to make sure it's
clear -- if you find any problems, let me know, I still have the
original files and paper manual.

--Toby



For serious fault finding I print off a few pages, sometimes as two
sheets stuck together, and make a note on these where to find other
schematics and layout pages. It looks like all the lower voltages get
their reference from the +65V that you will find just below the +140V
supply on schematic <11> Power Supply and Distribution. If all of your
lower voltages are off by the same fraction eg all low by 20% it could
just be that the +65V is off spec and everything else is OK. If you
want I can talk you through some of the stages but I am far from being
an expert and you will have to wait until after our holiday!
Roger





toby@...
 

On 2018-09-11 10:10 AM, EB4APL wrote:
Toby,

There are three 466 manuals. If yours is the one named Tektronix 466
Service Manual (PDF, OCR)
<http://w140.com/tekwiki/images/c/cc/070-1753-01.pdf>, I can improve it
somewhat if you don't mind. I can number the pages to reflect the
original numbering and also I can add markers to point to the pages
listed in the Table of Contents. I always do that in my own equipment
manuals to easy the finding of schematics and alignment instructions.
It'll take quite time but I'll do it if anybody is interested.

Regards,

Ignacio, EB4APL
Up to you. If you can do that with zero quality loss, please submit the
new version to TekWiki (I believe you can get an editor account from Kurt).

(I don't OCR anything myself, but if I recall correctly, a friend OCR'd
my scans and then I uploaded his version, so that file you mention is
probably based on mine.)

--Toby