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My Tek 465M HV multiplier has died and I am looking to build (or possibly buy) a replacement, but am confused as to its required specs.

The HV transformer has a measured ~2.4 KV outpu (+ve) at to the HV multiplier connection - that is when disconnected from it. The service manual circuit diagram shows the U550 HV box with a X3 multiplier in it. Elsewhere I read that the CRT needs 12-15 KV and in another place I read that the multiplier is a X6. To further muddy the waters the NTE538 multiplier is quoted as a replacement but the spec sheet for that unit describes it as a tripler with an input of 12 KV and an output of 30 KV, which calculates as a "2 and a 1/2er". Though I understand why the output may be lower than X3, it implies that with a 2.4KV input the CRT anode voltage would be only 5.6KV.
Can someone resolve all this for me? Sometime before the multiplier was known to be bad I think I saw a DIY multiplier design for this application but now I can't find the link.

Any information to help bring this old soldier back to life will be appreciated.
MichaelB

On 4/11/2017 12:48 AM,
uzf5mpiuz5mvlulyya3qaoosmsr6kepcti7f2jpe@... [TekScopes] wrote:

My Tek 465M HV multiplier has died and I am looking to build (or
possibly buy) a replacement, but am confused as to its required specs.

The HV transformer has a measured ~2.4 KV outpu (+ve) at to the HV
multiplier connection - that is when disconnected from it. The service
manual circuit diagram shows the U550 HV box with a X3 multiplier in
it. Elsewhere I read that the CRT needs 12-15 KV and in another place
I read that the multiplier is a X6. To further muddy the waters the
NTE538 multiplier is quoted as a replacement but the spec sheet for
that unit describes it as a tripler with an input of 12 KV and an
output of 30 KV, which calculates as a "2 and a 1/2er". Though I
understand why the output may be lower than X3, it implies that with a
2.4KV input the CRT anode voltage would be only 5.6KV.
Can someone resolve all this for me? Sometime before the multiplier
was known to be bad I think I saw a DIY multiplier design for this
application but now I can't find the link.

Any information to help bring this old soldier back to life will be
appreciated.
MichaelB

Where are you?

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Annoyingly, Tektronix sometimes refereed to the same multiplier as
x1.5 or x3 depending on if they were referring to the peak or
peak-to-peak input voltage.

So now the question is, how exactly did you measure the transformer
output at the high voltage multiplier input?

2.4 kilovolts RMS is about 3.4 kilovolts peak or 6.8 kilovolts
peak-to-peak. The Tektronix Common Parts Design Catalog says that the
152-0635-00 high voltage multiplier used in the 465M/455 is x1.5
(peak-to-peak) which would yield about 10 kilovolts which based on the
-2 kilovolt cathode voltage, is exactly right for the12 kilovolt total
acceleration listed in the specifications.

So the 465M/455 documentation says it is a x3 multiplier and the
Tektronix Common Parts Design Catalog says it is a 1.5x multiplier. If
you know the peak to peak voltage and output voltage, then you can
figure out how many diodes are in the multiplier.

The NTE538 looks like the wrong part to me.

Michael

1) The HV-Mult ( U550) in the 465M is"basically" a tripler.

2) Make sure you are using the manual for the 465M . the circuits in the 465 and 465B are NOT exactly the same as the 465M. Much of what you may have found is for the 465 and 465B and you should likely ignore it as it does not generally pertain to the 465M / U550 unique circuit

3) A basic 3X HV multiplier is a relative simple thing to breadboard and build. The real art is in parts placement and and potting to avoid arc over and humidity

4) Unfortunately the U550 in the 465M is NOT just a simple 3X HV multiplier there are other outputs from the module . Unlike other 465/ 465B HV Mults ( simple 3 terminal 3x multipliers) CRT grid bias and other voltages are generated inside U550 . Study the schematic in the correct manual carefully. Don't have the correct manual? there is a "usable" free military/Airforce TO manual floating around for free download. Google is your friend if you can keep her hands out of your pockets

Reality check time: If the U550 is really toast, finding a parts unit with original replacement is likely your only viable alternative. If this is something you just LOVE to do and you place no real value on your time ( our your "hiding" out in the shop so mamma wont nag at you to help her plant flowers ) then study the U550 circuit in the manual closely and start playing with duplicating it ( get a good pair of safety goggles). IT is basically all R / C /CR's no "active" devices . If your time does have value then I can make the business case that a very nice $300 replacement scope is really a better deal. Also it is spring time, time to file the rust off the hooks and go fishing instead

Good luck

Dave

manuals@...

--
Dave
Manuals@...
www.ArtekManuals.com

On Tue, 11 Apr 2017 09:46:28 -0400, you wrote:

Michael

1) The HV-Mult ( U550) in the 465M is"basically" a tripler.

2) Make sure you are using the manual for the 465M . the circuits in the
465 and 465B are NOT exactly the same as the 465M. Much of what you may
have found is for the 465 and 465B and you should likely ignore it as it
does not generally pertain to the 465M / U550 unique circuit

Oh, this is a good point that I forgot to mention. The 465M is
completely different from the 465 and 465B. Maybe that explains the
NTE538 reference.

3) A basic 3X HV multiplier is a relative simple thing to breadboard and
build. The real art is in parts placement and and potting to avoid arc
over and humidity

4) Unfortunately the U550 in the 465M is NOT just a simple 3X HV
multiplier there are other outputs from the module . Unlike other 465/
465B HV Mults ( simple 3 terminal 3x multipliers) CRT grid bias and
other voltages are generated inside U550 . Study the schematic in the
correct manual carefully. Don't have the correct manual? there is a
"usable" free military/Airforce TO manual floating around for free
download. Google is your friend if you can keep her hands out of your
pockets

The free military/Airforce TO manual for the 465M is pretty horrible
but the 455 is practically identical to the 465M and its service
manual can be used for this.

Upon further investigation Dave-Hess is correct. At least as far as the
HV & CRT circuits the 465M and the 455 are part for part the same. I
did not check other boards. 455 parts donors may be easier to come by
than 465M's. ???

There are not in really good photos in either manual is U550 and potted
module or and assembly with a lid on it?

Dave

manuals@...

--
Dave
Manuals@...
www.ArtekManuals.com

Dave,
Thank you for your response. Good to hear from someone who knows these instruments. I have a free downloaded pdf copy of the service manual for the 465M. I am well aware that the 465/465B/465Ms differ.
In my manual (Rev A Sept 1980) pg 4-25 para (d) High Voltage Multiplier says Diagram 8 (FO-10) shows the high voltage multiplier. However the actual Diagram 8 is FO-9 (front) and it shows the multiplier as an empty box inside box U550. (FO-10 is circuit diagram of low voltage power supplies). Diagram 8 in my .pdf is the only one showing the CRT and surrounding HV circuitry.
This is a hobby project, so time is not an issue. I have a nice Siglent DSO scope.
But going back to the numbers and the multiplier spec. I realize part of the confusion has been my sloppy thinking (and writing). But even paying attention (now) to rms vs peak=to-peak voltages, confusion still exists (for me).
My "measured" 2.4KV voltage is a "corrected" (see following explanation) reading of the high voltage transformer output at pin 10 - with the U550 "load " disconnected, measured with my Fluke 177 DVM with a HVP-40 1000:1 probe.
The probe spec. says for 50/60 Hertz, I am of course measuring a 50 Khz maybe not very sinusoidal waveform. I make no adjustment for this.
I say corrected reading because the probe instructions do not clearly account for the meter input impedance. It suggests the meter impedance should be 10 Mohms, but the Fluke spec says the meter AC voltage input Z is >5 Mohms (>10 Mohms for DC). The HV probe resistance is described in the instruction "manual" (just one folded sheet) as approx 1000M. So I'm assuming a 1000 Mohm + 1 Mohm; 1000:1 ratio; voltage divider in the probe. When connected to the meter, the 1 Mohm and the meter input Z (I'm assuming 5 Mohm) are in parallel = 5/6 Mohm. thus meter correction factor = 6/5 = 1.2. The meter ( including the 1000:1 factor) read 2 KV, thus the corrected V = 2.4KV.
Sorry to take so long , but I want you to know where my numbers come from, and assumptions made.
The Fluke meter is true RMS so assuming the transformer output waveform is sufficiently sinusoidal the ptp V into the multiplier would be 2.4 x sqroot2 x 2 = 6.8 KV. Going into a tripler - making a theoretical 20.4 KV output - which seems scarily high. And I understand the CRT likes 14-15 kv?
Or am I doing this wrong? It's been a long time since I did this sort of stuff for a living.
Hopefully you can understand and clear up my areas of confusion and point me towards a multiplier spec. or even a specific design. In a lost link I read a hobbyist built just the tripler and mounted it on top of the U550 box, so the bias circuits etc. in the U550 were retained.
I appreciate your help.
MichaelB

On 11 Apr 2017 17:21:56 +0000, you wrote:

Dave,
Thank you for your response. Good to hear from someone who knows these instruments. I have a free downloaded pdf copy of the service manual for the 465M. I am well aware that the 465/465B/465Ms differ.
In my manual (Rev A Sept 1980) pg 4-25 para (d) High Voltage Multiplier says Diagram 8 (FO-10) shows the high voltage multiplier. However the actual Diagram 8 is FO-9 (front) and it shows the multiplier as an empty box inside box U550. (FO-10 is circuit diagram of low voltage power supplies). Diagram 8 in my .pdf is the only one showing the CRT and surrounding HV circuitry.

Unfortunately the 455/465M manual just shows a blank box for the high
voltage multiplier unlike some of the other service manuals which show
internal details.

This is a hobby project, so time is not an issue. I have a nice Siglent DSO scope.
But going back to the numbers and the multiplier spec. I realize part of the confusion has been my sloppy thinking (and writing). But even paying attention (now) to rms vs peak=to-peak voltages, confusion still exists (for me).
My "measured" 2.4KV voltage is a "corrected" (see following explanation) reading of the high voltage transformer output at pin 10 - with the U550 "load " disconnected, measured with my Fluke 177 DVM with a HVP-40 1000:1 probe.
The probe spec. says for 50/60 Hertz, I am of course measuring a 50 Khz maybe not very sinusoidal waveform. I make no adjustment for this.

That and the multimeter's AC input impedance is exactly what I was
worried about.

I say corrected reading because the probe instructions do not clearly account for the meter input impedance. It suggests the meter impedance should be 10 Mohms, but the Fluke spec says the meter AC voltage input Z is >5 Mohms (>10 Mohms for DC). The HV probe resistance is described in the instruction "manual" (just one folded sheet) as approx 1000M. So I'm assuming a 1000 Mohm + 1 Mohm; 1000:1 ratio; voltage divider in the probe. When connected to the meter, the 1 Mohm and the meter input Z (I'm assuming 5 Mohm) are in parallel = 5/6 Mohm. thus meter correction factor = 6/5 = 1.2. The meter ( including the 1000:1 factor) read 2 KV, thus the corrected V = 2.4KV.
Sorry to take so long , but I want you to know where my numbers come from, and assumptions made.

That makes things difficult but how likely was it that you measured
2.4 kilovolts RMS yields 6.8 volts peak-to-peak which is exactly what
is required for a 1.5 times multiplier to make 10 kilovolts?

I think you got the correction exactly right and lucked out that the
probe and multimeter worked well at 50 kHz. That probe is only rated
for 60 Hz operation.

Honestly I do not see how the probe worked at all.

If you want to really measure the output of the high voltage
transformer, I would get a high voltage diode and capacitor and
measure just the peak voltage using your probe to measure DC.

The Fluke meter is true RMS so assuming the transformer output waveform is sufficiently sinusoidal the ptp V into the multiplier would be 2.4 x sqroot2 x 2 = 6.8 KV. Going into a tripler - making a theoretical 20.4 KV output - which seems scarily high. And I understand the CRT likes 14-15 kv?
Or am I doing this wrong? It's been a long time since I did this sort of stuff for a living.

You have it right but the point I was making is that Tektronix was not
consistent in labeling the multiplication factors. The parts book
says it is a 1.5 times multiplier for operation with a 6.8 kilovolt
peak-to-peak input but the service manual says it is a 3 times
multiplier.

The CRT's PDA (post deflection acceleration voltage is 10 kilovolts.
Nothing I have found exactly says this but the Tektronix Common Parts
Design catalog says that the 152-0635-00 high voltage multiplier
generates 10 kilovolts and the 465M/455 specifications say that the
total acceleration voltage is 12 kilovolts which if you subtract the
-2 kilovolt cathode voltage leaves 10 kilovolts for the PDA.

Hopefully you can understand and clear up my areas of confusion and point me towards a multiplier spec. or even a specific design. In a lost link I read a hobbyist built just the tripler and mounted it on top of the U550 box, so the bias circuits etc. in the U550 were retained.
I appreciate your help.
MichaelB

There are only two options here and I think the Tektronix Common Parts
Design catalog answers which one is correct.

The transformer output is either:

1. 2.4 kilovolts RMS for 6.8 kilovolts peak-to-peak and a 1.5 times
voltage multiplier is used. This is consistent with your measurements
(how?) and the Tektronix common parts design catalog.

2. 1.2 kilovolts RMS for 3.4 kilovolts peak-to-peak and a 3 times
voltage multiplier.

Dave 2: you said,
There are only two options here and I think the Tektronix Common Parts
Design catalog answers which one is correct.

The transformer output is either:

1. 2.4 kilovolts RMS for 6.8 kilovolts peak-to-peak and a 1.5 times
voltage multiplier is used. This is consistent with your measurements
(how?) and the Tektronix common parts design catalog.

2. 1.2 kilovolts RMS for 3.4 kilovolts peak-to-peak and a 3 times
voltage multiplie

.Arrrgh !
We have two Daves in this thread? I think so, but Yahoo's way of presenting (or not) the replies creates a confusion all of its own.
I have not been even thinking about the cathode voltage. When Dave2 points out it is minus 2KV I was brought up short and i) had to go back to the circuit to verify that and ii) to determine how that was done (one little diode pointing to the left) and iii) to think about the overall total acceleration voltage, not just the anode voltage - which I had been doing. I have not seen any specification of 12 KV as the desired anode to cathode voltage or 10KV as the desire anode voltage. Where is that specified?

But referring to your reply above presenting two options:
Now I'm getting even more confused. So I need a X1.5 multiplier? Huh? They work in (nominal) integer multiples. Unless one throws away every other half cycle? How?
How many diodes? How many caps needed? Circuit diagram?
I don't know if this forum can handle diagrams - I see notes about all non-text being stripped out.
But as a source of multiplier diagrams (and an explanation for me of how they work) I'm looking at www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html
If that link's diagrams can help our conversation please refer to it.
Thanks for your valuable help
MichealB

On 11 Apr 2017 19:17:21 +0000, you wrote:

Dave 2: you said,
There are only two options here and I think the Tektronix Common Parts
Design catalog answers which one is correct.

The transformer output is either:

1. 2.4 kilovolts RMS for 6.8 kilovolts peak-to-peak and a 1.5 times
voltage multiplier is used. This is consistent with your measurements
(how?) and the Tektronix common parts design catalog.

2. 1.2 kilovolts RMS for 3.4 kilovolts peak-to-peak and a 3 times
voltage multiplie

.Arrrgh !
We have two Daves in this thread? I think so, but Yahoo's way of presenting (or not) the replies creates a confusion all of its own.

There is just one Dave. We are the Dave collective. Prepare to be
assimilated.

When I was in college, we had so many Daves in my circle of friends
and acquaintances that we numbered them.

I have not been even thinking about the cathode voltage. When Dave2 points out it is minus 2KV I was brought up short and i) had to go back to the circuit to verify that and ii) to determine how that was done (one little diode pointing to the left) and iii) to think about the overall total acceleration voltage, not just the anode voltage - which I had been doing. I have not seen any specification of 12 KV as the desired anode to cathode voltage or 10KV as the desire anode voltage. Where is that specified?

The 455/465M specifications include the total CRT acceleration
voltage. The schematic and theory sections show that the cathode
voltage is -2000 volts.

But referring to your reply above presenting two options:
Now I'm getting even more confused. So I need a X1.5 multiplier? Huh? They work in (nominal) integer multiples. Unless one throws away every other half cycle? How?

The discrepancy is because sometimes the multiplier is specified for
the peak input voltage and sometimes for the peak-to-peak input
voltage which is twice as high.

If the peak voltage is 3.33 kilovolts, then a x3 multiplier produces
10 kilovolts. If the peak-to-peak voltage is 6.66 kilovolts, then a
x1.5 multiplier produces 10 kilovolts but this is exactly the same
multiplier but specified in a different way.

Tektronix called it a x3 multiplier in the schematic but a x1.5
multiplier in their parts catalog.

How many diodes? How many caps needed? Circuit diagram?
I don't know if this forum can handle diagrams - I see notes about all non-text being stripped out.
But as a source of multiplier diagrams (and an explanation for me of how they work) I'm looking at www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html
If that link's diagrams can help our conversation please refer to it.
Thanks for your valuable help
MichealB

When I drew it out based on your corrected 6.8 kilovolt voltage
measurement, I got the same schematic as the voltage tripler circuit
shown at your link. This is consistent with the output of the high
voltage based on the schematic.

For what it is worth, I consider building a separate multiplier from
parts and adding it to the oscilloscope assuming that it can be made
to fit completely reasonable. Air wire it, coat it with corona dope,
and pot it in epoxy. You get bonus points for vacuum potting it.

This is Dave #? ( manuals)

I really dont have more to add to this (since I dont have a 455/465M)
but to ask AGAIN only for my and other's education . in the diagrams
(unlike most of the other 4xx series scope) of the 465M it shows the 3X
multiplier as part of the U550 . Most of the circuitry internal to U550
is handled as external discrete components in the other 4xx series
scopes including the 3X VM

Is U550 a "potted assembly" or can it be opened so that one could
replace JUST the 3X unit? There is a lot of other circuitry inside U550
besides the 3X multi. There do not appear to be any actual pixs of U550
in the manuals

Dave #?

manuals@...



On 4/13/2017 10:27 AM, David davidwhess@... [TekScopes] wrote:

On 11 Apr 2017 19:17:21 +0000, you wrote:

Dave 2: you said,
There are only two options here and I think the Tektronix Common Parts
Design catalog answers which one is correct.

The transformer output is either:

1. 2.4 kilovolts RMS for 6.8 kilovolts peak-to-peak and a 1.5 times
voltage multiplier is used. This is consistent with your measurements
(how?) and the Tektronix common parts design catalog.

2. 1.2 kilovolts RMS for 3.4 kilovolts peak-to-peak and a 3 times
voltage multiplie

.Arrrgh !
We have two Daves in this thread? I think so, but Yahoo's way of

presenting (or not) the replies creates a confusion all of its own.

There is just one Dave. We are the Dave collective. Prepare to be
assimilated.

When I was in college, we had so many Daves in my circle of friends
and acquaintances that we numbered them.

I have not been even thinking about the cathode voltage. When Dave2

points out it is minus 2KV I was brought up short and i) had to go
back to the circuit to verify that and ii) to determine how that was
done (one little diode pointing to the left) and iii) to think about
the overall total acceleration voltage, not just the anode voltage -
which I had been doing. I have not seen any specification of 12 KV as
the desired anode to cathode voltage or 10KV as the desire anode
voltage. Where is that specified?

The 455/465M specifications include the total CRT acceleration
voltage. The schematic and theory sections show that the cathode
voltage is -2000 volts.

But referring to your reply above presenting two options:
Now I'm getting even more confused. So I need a X1.5 multiplier?

Huh? They work in (nominal) integer multiples. Unless one throws away
every other half cycle? How?

The discrepancy is because sometimes the multiplier is specified for
the peak input voltage and sometimes for the peak-to-peak input
voltage which is twice as high.

If the peak voltage is 3.33 kilovolts, then a x3 multiplier produces
10 kilovolts. If the peak-to-peak voltage is 6.66 kilovolts, then a
x1.5 multiplier produces 10 kilovolts but this is exactly the same
multiplier but specified in a different way.

Tektronix called it a x3 multiplier in the schematic but a x1.5
multiplier in their parts catalog.

How many diodes? How many caps needed? Circuit diagram?
I don't know if this forum can handle diagrams - I see notes about

all non-text being stripped out.

But as a source of multiplier diagrams (and an explanation for me of

how they work) I'm looking at
www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html

If that link's diagrams can help our conversation please refer to it.
Thanks for your valuable help
MichealB

When I drew it out based on your corrected 6.8 kilovolt voltage
measurement, I got the same schematic as the voltage tripler circuit
shown at your link. This is consistent with the output of the high
voltage based on the schematic.

For what it is worth, I consider building a separate multiplier from
parts and adding it to the oscilloscope assuming that it can be made
to fit completely reasonable. Air wire it, coat it with corona dope,
and pot it in epoxy. You get bonus points for vacuum potting it.

--
Dave
Manuals@...
www.ArtekManuals.com

I do not have a 455/465M either but QService has photographs of
152-0635-00 showing both sides including the pins which I assume are
soldering into the printed circuit board:



And I guess the late ones used red potting and where made by Murata:

Hi.. I have a 465m with HV section blowing the fuse... Found that the 32v unreg source voltage to be 56 volts !! ..A look at the diagram show the transfo, then a bridge and a 1000 mfd cap rated at 75 vdc...Is it normal to have 56 vdc instead of 32v unreg...I find this very unusual !! Please let me know..

Unregulated voltage is higher than what us really "says". For example, the +5V unreg on my scope is around +11V, which then gets regulated to +5V. According to my service manual this is normal

For your scope, the service manual doesn't give a voltage for that, so I would recommend you check the line input settings. If those are good the 56V is probably normal.

I would also recommend checking the regulation circuit for the +32V regulated as a short there can pop the fuse. Speaking of shorts, a shirt can by anywhere on the +32V rail, so you'll have to do some power tracing.

Another question, is it blowing F558 or F736?

If it's blowing F558, it's likely a problem with the HV transformer or the transistors/diodes that drive it.

Benjamin

On Sun, Jan 12, 2025 at 04:18 PM, richard ramacieri wrote:

Hi.. I have a 465m with HV section blowing the fuse... Found that the 32v
unreg source voltage to be 56 volts !! ..A look at the diagram show the
transfo, then a bridge and a 1000 mfd cap rated at 75 vdc...Is it normal to
have 56 vdc instead of 32v unreg...I find this very unusual !! Please let me
know..

Schematic shows 52V typical with 116V supply voltage, 56V is not excessive especially if your mains voltage is a bit above 120V.
Ozan

When you look at the diagram, you observe that there is a regulation by the addition of a 1000 mfd/75wdc cap..and if it is really 56 volts, the value of the cap should be much higher..

Thank Benjamin for answering....
There is a 1000mfd/75wdc cap in the circuit, so there is a filtering (regulation) on this power supply, as I look with a scope at the waveform of the 32 v unreg, it is really 56 volts... in that case, the value of the cap should be much higher than 75volts... Well, I guess that I will have to dig on that !!
Best reguard's, By the way I usually speak french, so forgive my writing ...

It me again..I just took with a scope on the suppose 32 volts unreg.. it show 56 volts with praticaly NO ripple... What do they mean when they indicate 32 volts unreg... Do they mean really 32 vdc...and if you look at the value of the 75 vdc capacitor, this value would be ok if the applied voltage is 32 volts instead of 56 volts... What is your opinion on this...
Best reguard's
RR