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Re: Tek 651HR colour monitor

 

Thanks Michael.?

That's incredibly helpful.

Jonathan
Re: Tek 651HR colour monitor

 

Hi Jonathan,

I am processing a scan I made of the 650HR manual and I believe it has schematics and information on the 651HR, as well (which is the PAL version, correct?) I will double check. Hopefully I can finish this by tomorrow.

The 650HR manual I am working with is annoying because it has all the 650A information simply crossed out with a pen.

-Michael Bierlein

On Thu, Jan 5, 2023 at 11:25 Jonathan Robin via <drjrobin=[email protected]> wrote:
I am trying to repair one of these monitors. I cannot find a manual or schematic online. Does anyone know where I can locate a scan?

Many thanks

Jonathan

Tek 651HR colour monitor

 

I am trying to repair one of these monitors. I cannot find a manual or schematic online. Does anyone know where I can locate a scan?

Many thanks

Jonathan
Re: Powering up Tek 7704A and 7603 after several year.

 

Or one of the tantalums will smoke (happened to me for the first time in a few years a couple of days ago).? I too just plug and go.

-Dave

On Friday, December 30, 2022 at 07:49:45 AM PST, David C. Partridge <david.partridge@...> wrote:


Just plug it in and turn it on.?? The worst that can happen is you blow a fuse.

?

David

?

From: [email protected] <[email protected]> On Behalf Of Hugh Graham G1AUR
Sent: 30 December 2022 15:31
To: [email protected]
Subject: [TekScopes2] Powering up Tek 7704A and 7603 after several year.

?

Hi group can anyone advise me on a safe procedure for powering up these scopes that have remained dormant for 3-4 years? I understand SMPS are not fond of Variacs so would a lamp limiter or combination of Variac and lamp limiter be a good option?
Thanks Hugh
Re: 2465 Power Supply

 

Yes, it is not worth doing anything until you know the power supply
is rock solid.

The + and - 15V switching caps are 180uf 40V, and about 50% of those
I see, that are original, are bad. They typically measure near 0uf.

I replace all of the 180uf 40V, and the 250uf 20V caps on the inverter
board with one value: 330uf 50V. I use the best low ESR, high ripple
current 105C cap I can find... Typically United Chemi Con, but Nichicon
or Panasonic make perfectly nice caps too. I use the single value to
get a better discount out of Mouser. I used to buy a lot of caps!

I have repaired a few 2465 original model scopes that have had every
one of the filter capacitors on the power supply inverter board bad.
They are usually shrink wrapped with an orange translucent sleeve.

-Chuck Harris

On Fri, 30 Dec 2022 10:33:27 -0800 "Richard" <richard@...>
wrote:
Good news! Thanks to a couple of prompts from Chuck, I changed the
main capacitors for the ¡À15 volt supplies and the display is now rock
steady. I've left it on the bench overnight, I'll do more tests in
the morning but it seems to be time for a little celebration!

Richard
Re: 2465 Power Supply

 

Richard,

Chuck is a wonderful asset to the community.? I say he has probably forgotten more than many people know in total.? When it comes to these 24xx series, he is the man.? Glad your scope is working.?
Re: 2465 Power Supply

 

Good news! Thanks to a couple of prompts from Chuck, I changed the main capacitors for the ¡À15 volt supplies and the display is now rock steady. I've left it on the bench overnight, I'll do more tests in the morning but it seems to be time for a little celebration!

Richard
Re: 2465 Power Supply

 

I forgot to mention that I already changed the 100?F C1972 for a new Nichicon 105? capacitor.
Re: 2465 Power Supply

 

Thanks Chuck, I'll apologise for the photo - I've only just worked out how to upload photos to the site and the 'scope was facing into a corner....

I've added some more photos - the worst is the -15V unregulated which has a lot of noise, the -15V regulated is noisy but not as bad. There's a HF noise on all power lines at 100kHz or so which is expected from a switcher but I don't know what to make of the 25V p-p on the -15v unregulated line. The blue wire is a 2.5mm? (14AWG)? grounding connection.

There is evidence (see photo) of the U400 having been changed. I've used Q-service already and will again, I need a couple of voltage knobs for the 2465A.

Richard
Re: Powering up Tek 7704A and 7603 after several year.

 

Thanks for advice Chuck and David thankfully neither scope was shipped¡­I collected..carefully. I q received a lesson in that from a shipped and atrociously packed 475A which arrived with a dented case and its UK 13A plug pins bent double..
Hugh
Re: Powering up Tek 7704A and 7603 after several year.

 

¿ªÔÆÌåÓý

Just plug it in and turn it on.?? The worst that can happen is you blow a fuse.

?

David

?

From: [email protected] <[email protected]> On Behalf Of Hugh Graham G1AUR
Sent: 30 December 2022 15:31
To: [email protected]
Subject: [TekScopes2] Powering up Tek 7704A and 7603 after several year.

?

Hi group can anyone advise me on a safe procedure for powering up these scopes that have remained dormant for 3-4 years? I understand SMPS are not fond of Variacs so would a lamp limiter or combination of Variac and lamp limiter be a good option?
Thanks Hugh
Re: Powering up Tek 7704A and 7603 after several year.

 

If the scope went through shipping, I take it apart and
shake it out... Always a good idea to remove stray parts
and hardware before applying power.

Next, I check the power line range switch and line fuse.

Then, I plug it in and turn it on.

While it is running, I observe it closely, and am ready
switch it off if it makes strange noises, smells, or has
an excessively bright beam.

Generally, if something is really wrong, the fuse will
blow, and any damage was going to happen anyway.

It is really never a good idea to trust old reformed
capacitors. They will let you down sooner or later.

Anything you buy on ebay will likely have been plugged
in and turned on.... robbing you of any opportunity to
do it gently... whatever that really means.

-Chuck Harris


On Fri, 30 Dec 2022 07:30:37 -0800 "Hugh Graham G1AUR"
<phoenixsound12@...> wrote:
Hi group can anyone advise me on a safe procedure for powering up
these scopes that have remained dormant for 3-4 years? I understand
SMPS are not fond of Variacs so would a lamp limiter or combination
of Variac and lamp limiter be a good option? Thanks Hugh
Powering up Tek 7704A and 7603 after several year.

 

Hi group can anyone advise me on a safe procedure for powering up these scopes that have remained dormant for 3-4 years? I understand SMPS are not fond of Variacs so would a lamp limiter or combination of Variac and lamp limiter be a good option?
Thanks Hugh
Re: 2465 Power Supply

 

Power supply ripple can easily be measured at the power supply
test DIP socket on the mother board. To get down to the ripple
levels they specify, you must run a stiff ground between the
chassis of the scope under test, and your bench scope... at least
#18 AWG wire. The scope probe ground clips won't help.

Ripple is 60/50Hz or 120/100 Hz depending on your region. It is
tested by putting the lab scope in 5ms/div sweep, and LINE
trigger. Ripple will freeze on the screen allowing you to use
cursors to measure its true amplitude. Go for the middle of
the fuzz on the trace

Noise is typically little spiky stuff at 50 to 100KHz. Use the
Bandwidth Limiter. The noise doesn't usually matter much.

Your scope should easily meet the ripple/noise specifications.
It can be really, really bad, and still look/work pretty good.

The -15V supply is usually a big culprit in the noise department,
and most of its noise comes from the HV supply. Do check its
100uf capacitor. It is near the power connector on the HV board.

Digital photos are such an easy thing to do these days, and they
give you instant feedback on quality and composition.

Don't you think you could have made one that was a little more
useful? I like to see the screen, and the entire front of the
scope so all settings and connections are obvious.

If the scope has no inputs, and you are seeing a display like
that, you have a problem in the channel hybrid, or the transistor
array that supports the readout function. I would suggest swapping
in a known working U400 hybrid first...

(2465A, I'm looking at you!)

The channel hybrid is probably the hybrid with the highest failure
rate. The transistor arrays are probably the semiconductor part
with the highest failure rate of all. The channel switch circuit
uses two transistor arrays, and a channel switch hybrid...

The best ebay supplier of 2465 parts is Q-service in Greece.

-Chuck Harris

On Thu, 29 Dec 2022 10:44:20 -0800 "Richard" <richard@...>
wrote:
This one is a plain old 2465. I do have an A version as well, that's
working quite well, but the 300MHz one is my favourite. Unfortunately
it's not jitter - that control makes no difference (although I only
moved it about 5? either way). Looking at the display more
critically, it seem to me to be power supply ripple, possibly on the
voltages supplying the tube driver and X/Y circuits.....
Re: 2465 Power Supply

 

The photo is in "Richards 2465" album in Photos....
Re: 2465 Power Supply

 

Looking at the traces - with all four channels switched on, but the first two grounded, I get noticeable hash on the 1st trace, less on the second, less on the 3rd, and almost a clean trace on the 4th. Changing the sweep speed, I get the traces in the photo

.

Re: 2465 Power Supply

 

Ripple from the HV oscillator usually goes the other way: out of the
power supply onto the -15V power bus. To reduce the spikes there is
a 100uf electrolytic cap (C1972) right near the power connector for the
HV board. It lives a pretty hard life.

I have seen grass added to the trace on several 2465's, and if you look
carefully, it looks like vvvv|vvvv|vvvv|... and is not synchronized
with the sweep. It should go away if you make the readout go away by
centering the READOUT INTENSITY control. It should also go away if
you have only channel 3 or 4 on the screen (eg. no ch1 or ch2). If this
is the case, you may have a problem with the transistor array that
connects to the channel switch (CH5 port).

-Chuck Harris


On Thu, 29 Dec 2022 10:44:20 -0800 "Richard" <richard@...>
wrote:
This one is a plain old 2465. I do have an A version as well, that's
working quite well, but the 300MHz one is my favourite. Unfortunately
it's not jitter - that control makes no difference (although I only
moved it about 5? either way). Looking at the display more
critically, it seem to me to be power supply ripple, possibly on the
voltages supplying the tube driver and X/Y circuits.....
Re: 2465 Power Supply

 

This one is a plain old 2465. I do have an A version as well, that's working quite well, but the 300MHz one is my favourite. Unfortunately it's not jitter - that control makes no difference (although I only moved it about 5? either way). Looking at the display more critically, it seem to me to be power supply ripple, possibly on the voltages supplying the tube driver and X/Y circuits.....
Re: 2465 Power Supply

 

¿ªÔÆÌåÓý

Hi

?

I just went through the calibration on a 2465A yesterday ¨C for me a 3 Hour job on that one with all of the proper Tektronix Calibration Equipment. CAL 06 always takes some time with all of the extra equipment (Cables, adapters, Tunnel Diode Pulser, 3 attenuators, Sweep Generators, etc.), steps involved.

?

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If it is just a vanilla 2465, not an A or B (you still adjust Readout Jitter on those models too), look at page 5-8 in the Rev. March 1983 and October 1984 Service Manuals, Section 3 procedure. You adjust R618 for minimum Character Jitter.

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After Calibration it is also checked on page 5-18 in that same Service Manual Revisions step dd.

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If it is a 2465A/2465B, look at page 5-11/5-12 in the Service Manual for the Jitter Adjustment. You adjust R618 for minimum Character Jitter.

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There is also a specific Readout Jitter Centering and Gain Adjustment in the Calibration Section (CAL 07), on page 5-22 or 5-23. This test makes a row of 8¡¯s across the top Readout and a row of the Bandwidth Limit Characters (BWL), across the Bottom Readout. You adjust R2918 to Center the Readout, and R2931 to adjust the Gain of the Readout. I haven¡¯t ever entered CAL 07 independently of Calibrating an Oscilloscope starting at CAL 01, I don¡¯t know if entering it directly from the menu is advisable ¨C I think the Manual says it¡¯s okay, I haven¡¯t ever done it that way.

?

There are different Adjustments if you have the 2445A/2465A Service Manual and board. The Service Manual page is 5-22 and still has R618 for Readout Jitter, R638 for Readout Gain, R639 for Readout Centering and adds R805 for Readout Horizontal Jitter. I have never seen the other board (with the R638, R639 and R805 Potentiometers ¨C maybe that is just for the 2445A), so I haven¡¯t performed this procedure. It also has a CAL 07 procedure on page 5-20 for Readout Jitter using the same Adjustments as the other 2465A and Potentiometers

?

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So, the Readout Jitter adjustment Potentiometers are:

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R618 ¨C Minimum Jitter

R2819 ¨C Readout Centering

R2931 ¨C Readout Gain (size of Characters)

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If you are going to adjust them, you can do that without going into Calibration.

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Always mark the position of the rotor (usually White plastic), with reference to the base (usually Blue or Black plastic), I use a small fine tipped sharpie for that, take a picture with your phone, and adjust as require. If you make a mistake, go back to where they were marked and try again. A small adjustment may only be required to fix them.

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Good Luck,

Ross

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?

?

From: [email protected] <[email protected]> On Behalf Of satbeginner
Sent: Thursday, December 29, 2022 8:38 AM
To: [email protected]
Subject: Re: [TekScopes2] 2465 Power Supply

?

Hi,

Not at home at the moment, but if I remember correctly, there is a "read-out jitter" adjustment somewhere in the calibration routine.

Will check later, but it is somewhere in the service manual calibration chapter.

Leo
Re: 2465 Power Supply

 

Hi,

Not at home at the moment, but if I remember correctly, there is a "read-out jitter" adjustment somewhere in the calibration routine.

Will check later, but it is somewhere in the service manual calibration chapter.

Leo
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