Hello all,
I'll try and keep this short. When it comes to electronics I'm somewhat a newb, but not entirely. I've always been interested in it, and I've recently purchased a scope - the tek 2465 300Mhz unit. Spent some time getting familiar with it, playing around in XY mode, and then used it for some diagnostics with some inductive sensors I was having an issue with. Just when I was getting ready to pack it up from verifying the sensors the scope went a bit goofy. The display at the bottom appeared to be "compressed" to a a central blur (I could change it's intensity with the readout intensity) and my traces were a short line near the center of the screen. I powered the scope off, waited a few seconds and then powered it back on, and it now powers on, lights up all the LED's, and I get a super bright --- display at the center of the screen (unaffected by intensity adjustments etc).

So, as typical I pulled the cover and did an initial once-over. I found that on the main power supply board by the mains that 2 of the capacitors look rough (one with the outer shell opened up). If you reference this pdf regarding a 2465B, the 2nd image of the A2 PCB has the very capacitors circles in red. The lower most one in the image is the one that looks like it may have blown. I haven't pulled the board out of the scope to get a better view of it yet. The rest of the capacitors on the board are the green and brown mix as the image in the PDF shows, which leads me to believe they're still the original capacitors in the unit.

Now in researching and reading about these scopes before I purchased one, I had read that the capacitors were a common issue in them. I have no worries about un-soldering components and soldering new ones in as I've done it numerous times to revive other old equipment. (And I've read about the need to cool these scopes with a fan if you operate them with the cover off)

So sorry to drag this out, so I'll try to make this quick. For those in the know about these scopes, is there a listing/BOM for what capacitors should be purchased and replaced?

Does the 2465B use the same values/locations on their boards that I can just follow the PDF I linked?

Does my issue sound like something that the capacitors could be causing? Or is it likely more involved?

I'd be happy to provide images or video as requested if it will help.

A huge thank you for taking the time to read and/or respond!
Chris

?

Sorry all, I referenced a PDF and never pasted the link!



--- In TekScopes@..., "Chris" wrote:
>
> Hello all,
> I'll try and keep this short. When it comes to electronics I'm somewhat a newb, but not entirely. I've always been interested in it, and I've recently purchased a scope - the tek 2465 300Mhz unit. Spent some time getting familiar with it, playing around in XY mode, and then used it for some diagnostics with some inductive sensors I was having an issue with. Just when I was getting ready to pack it up from verifying the sensors the scope went a bit goofy. The display at the bottom appeared to be "compressed" to a a central blur (I could change it's intensity with the readout intensity) and my traces were a short line near the center of the screen. I powered the scope off, waited a few seconds and then powered it back on, and it now powers on, lights up all the LED's, and I get a super bright --- display at the center of the screen (unaffected by intensity adjustments etc).
>
> So, as typical I pulled the cover and did an initial once-over. I found that on the main power supply board by the mains that 2 of the capacitors look rough (one with the outer shell opened up). If you reference this pdf regarding a 2465B, the 2nd image of the A2 PCB has the very capacitors circles in red. The lower most one in the image is the one that looks like it may have blown. I haven't pulled the board out of the scope to get a better view of it yet. The rest of the capacitors on the board are the green and brown mix as the image in the PDF shows, which leads me to believe they're still the original capacitors in the unit.
>
> Now in researching and reading about these scopes before I purchased one, I had read that the capacitors were a common issue in them. I have no worries about un-soldering components and soldering new ones in as I've done it numerous times to revive other old equipment. (And I've read about the need to cool these scopes with a fan if you operate them with the cover off)
>
> So sorry to drag this out, so I'll try to make this quick. For those in the know about these scopes, is there a listing/BOM for what capacitors should be purchased and replaced?
>
> Does the 2465B use the same values/locations on their boards that I can just follow the PDF I linked?
>
> Does my issue sound like something that the capacitors could be causing? Or is it likely more involved?
>
> I'd be happy to provide images or video as requested if it will help.
>
> A huge thank you for taking the time to read and/or respond!
> Chris
>

Hello all,
I'll try and keep this short. When it comes to electronics I'm somewhat a newb, but not entirely. I've always been interested in it, and I've recently purchased a scope - the tek 2465 300Mhz unit. Spent some time getting familiar with it, playing around in XY mode, and then used it for some diagnostics with some inductive sensors I was having an issue with. Just when I was getting ready to pack it up from verifying the sensors the scope went a bit goofy. The display at the bottom appeared to be "compressed" to a a central blur (I could change it's intensity with the readout intensity) and my traces were a short line near the center of the screen. I powered the scope off, waited a few seconds and then powered it back on, and it now powers on, lights up all the LED's, and I get a super bright --- display at the center of the screen (unaffected by intensity adjustments etc).

So, as typical I pulled the cover and did an initial once-over. I found that on the main power supply board by the mains that 2 of the capacitors look rough (one with the outer shell opened up). If you reference this pdf regarding a 2465B, the 2nd image of the A2 PCB has the very capacitors circles in red. The lower most one in the image is the one that looks like it may have blown. I haven't pulled the board out of the scope to get a better view of it yet. The rest of the capacitors on the board are the green and brown mix as the image in the PDF shows, which leads me to believe they're still the original capacitors in the unit.

Now in researching and reading about these scopes before I purchased one, I had read that the capacitors were a common issue in them. I have no worries about un-soldering components and soldering new ones in as I've done it numerous times to revive other old equipment. (And I've read about the need to cool these scopes with a fan if you operate them with the cover off)

So sorry to drag this out, so I'll try to make this quick. For those in the know about these scopes, is there a listing/BOM for what capacitors should be purchased and replaced?

Does the 2465B use the same values/locations on their boards that I can just follow the PDF I linked?

Does my issue sound like something that the capacitors could be causing? Or is it likely more involved?

I'd be happy to provide images or video as requested if it will help.

A huge thank you for taking the time to read and/or respond!
Chris

Chris -

I have a spreadsheet with parts for refreshing the 2465a LVPS along with Mouser part numbers. This has worked well for my scope. After reading the Condoraudio piece and looking at this list you can decide what you want to do. You can grab the spreadsheet 2465LVPS_ReCap.xls from
or I can email it directly to you if you can get your email address to me.

Chip


--- In TekScopes@..., "Chris" wrote:

Hello all,
I'll try and keep this short. When it comes to electronics I'm somewhat a newb, but not entirely. I've always been interested in it, and I've recently purchased a scope - the tek 2465 300Mhz unit. Spent some time getting familiar with it, playing around in XY mode, and then used it for some diagnostics with some inductive sensors I was having an issue with. Just when I was getting ready to pack it up from verifying the sensors the scope went a bit goofy. The display at the bottom appeared to be "compressed" to a a central blur (I could change it's intensity with the readout intensity) and my traces were a short line near the center of the screen. I powered the scope off, waited a few seconds and then powered it back on, and it now powers on, lights up all the LED's, and I get a super bright --- display at the center of the screen (unaffected by intensity adjustments etc).

So, as typical I pulled the cover and did an initial once-over. I found that on the main power supply board by the mains that 2 of the capacitors look rough (one with the outer shell opened up). If you reference this pdf regarding a 2465B, the 2nd image of the A2 PCB has the very capacitors circles in red. The lower most one in the image is the one that looks like it may have blown. I haven't pulled the board out of the scope to get a better view of it yet. The rest of the capacitors on the board are the green and brown mix as the image in the PDF shows, which leads me to believe they're still the original capacitors in the unit.

Now in researching and reading about these scopes before I purchased one, I had read that the capacitors were a common issue in them. I have no worries about un-soldering components and soldering new ones in as I've done it numerous times to revive other old equipment. (And I've read about the need to cool these scopes with a fan if you operate them with the cover off)

So sorry to drag this out, so I'll try to make this quick. For those in the know about these scopes, is there a listing/BOM for what capacitors should be purchased and replaced?

Does the 2465B use the same values/locations on their boards that I can just follow the PDF I linked?

Does my issue sound like something that the capacitors could be causing? Or is it likely more involved?

I'd be happy to provide images or video as requested if it will help.

A huge thank you for taking the time to read and/or respond!
Chris

----- Original Message -----

From: Chris

To: TekScopes@...

Sent: Sunday, February 17, 2013 5:40 PM

Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

?

Thanks! I had actually decided to pull the board and give it a close inspection and wrote down the values, then I had placed the order. Found out when it showed up that I'd ordered the wrong frame size X2 and Y rated capacitors, so I had to place another order of the correct size (had to substitute different mfg's in as they didn't have the one the condor audio pdf listed in stock) Good learning exercise if anything. The only component I didn't replace was the CR1110, dual common-cathode Schottky rectifier.

That said, I soldered everything in, re-assembled the boards and anxiously turned it on, only to find the same problem. Doh. I tested the caps after they were out with my ESR meter that I just built and they all looked acceptable. At least I can say all the caps are new so I won't have to worry about them in the future. I couldn't test the capacitance of a good handful of them as my DMM only works up to 40 micro Farad. Time for a better tester - anyone have a recommendation for a good capacitance meter? I looked at the local radio shack (best electronics store we have around here - read that as the ONLY one..) The Extech (I think it was a model 430) is listed to only 100 micro Farad, so it would still fall short.

So to not get too drawn out, I printed off some sheets from the service manual for the 2465B's: Checking the voltages (1st commandment, thou shalt check voltages right?) I stand as follows:

+10.00v is adjusted to +10.00v
+87v line is giving me about 9.5 volts
+42.4v line is giving me about 7.4 volts
the +15 volt line is giving me 7.2 volts
Digital +5v supply is 4.98volts
Analog +5v supply is 4.58 volts (close, but a tad low and out of spec)
-5V is giving me -4.96v
-8v is -8.01v
-15v is -14.97

So there's a definite problem with the 87, 42.4 and 15 volt lines, and the 5v analog should be looked at. So I've got some more studying to do on the schematics. It looks like for the most part there's an unregulated voltage, and then the regulated voltage, so my plan of attack is to check the unregulated supply voltages first as that can help narrow it down to a supply vs regulator issue.

I got the scope hoping to get into some small circuit design and electronics repair - didn't expect the scope to be the first project. Trial by fire!

So, any tips or pointers are welcome, as well as any recommendations for a good capacitance meter. (I have the BlueESR meter, just assembled their kit this last week - works like a charm)

Thanks!
Chris

--- In TekScopes@..., "random.path" wrote:
>
> Chris -
>
> I have a spreadsheet with parts for refreshing the 2465a LVPS along with Mouser part numbers. This has worked well for my scope. After reading the Condoraudio piece and looking at this list you can decide what you want to do. You can grab the spreadsheet 2465LVPS_ReCap.xls from
> or I can email it directly to you if you can get your email address to me.
>
> Chip
>
>
> --- In TekScopes@..., "Chris" wrote:
> >
> > Hello all,
> > I'll try and keep this short. When it comes to electronics I'm somewhat a newb, but not entirely. I've always been interested in it, and I've recently purchased a scope - the tek 2465 300Mhz unit. Spent some time getting familiar with it, playing around in XY mode, and then used it for some diagnostics with some inductive sensors I was having an issue with. Just when I was getting ready to pack it up from verifying the sensors the scope went a bit goofy. The display at the bottom appeared to be "compressed" to a a central blur (I could change it's intensity with the readout intensity) and my traces were a short line near the center of the screen. I powered the scope off, waited a few seconds and then powered it back on, and it now powers on, lights up all the LED's, and I get a super bright --- display at the center of the screen (unaffected by intensity adjustments etc).
> >
> > So, as typical I pulled the cover and did an initial once-over. I found that on the main power supply board by the mains that 2 of the capacitors look rough (one with the outer shell opened up). If you reference this pdf regarding a 2465B, the 2nd image of the A2 PCB has the very capacitors circles in red. The lower most one in the image is the one that looks like it may have blown. I haven't pulled the board out of the scope to get a better view of it yet. The rest of the capacitors on the board are the green and brown mix as the image in the PDF shows, which leads me to believe they're still the original capacitors in the unit.
> >
> > Now in researching and reading about these scopes before I purchased one, I had read that the capacitors were a common issue in them. I have no worries about un-soldering components and soldering new ones in as I've done it numerous times to revive other old equipment. (And I've read about the need to cool these scopes with a fan if you operate them with the cover off)
> >
> > So sorry to drag this out, so I'll try to make this quick. For those in the know about these scopes, is there a listing/BOM for what capacitors should be purchased and replaced?
> >
> > Does the 2465B use the same values/locations on their boards that I can just follow the PDF I linked?
> >
> > Does my issue sound like something that the capacitors could be causing? Or is it likely more involved?
> >
> > I'd be happy to provide images or video as requested if it will help.
> >
> > A huge thank you for taking the time to read and/or respond!
> > Chris
> >
>

Chris -

I have a spreadsheet with parts for refreshing the 2465a LVPS along with

or I can email it

Chip


--- In TekScopes@..., "Chris" wrote:

Hello all,
I'll try and keep this short. When it comes to electronics I'm

So, as typical I pulled the cover and did an initial once-over. I found

Now in researching and reading about these scopes before I purchased

So sorry to drag this out, so I'll try to make this quick. For those in

Does the 2465B use the same values/locations on their boards that I can

Does my issue sound like something that the capacitors could be causing?

I'd be happy to provide images or video as requested if it will help.

A huge thank you for taking the time to read and/or respond!
Chris

The +87 is from a doubler and added to the +42. I would take a close look at the three 10 uF caps and all the diodes in that area. Be sure to only use fast diodes for any replacements.

Since you recapped this unit, don't overlook the fact that bad capacitors can come from the factory new. Did you measure all these voltages in the scope or on an external load?




Regards,
Tom

Chris

I am in the process of fixing a 2465 power supply too,

I had a bad capacitor C1102 that measured the correct 100 uf and did not
have a large ESR but had leaked and caused the board to become conductive
and burn.

One thing that almost got me was that on the parts layout of the A3 Board in
the manual for the SN50000 and above, the labels for C1132 and C1115 are
switched.

C1132 is the 87V unregulated supply filter capacitor
And C1115 is the +5V unregulated supply filter capacitor

That could cause a problem with the +87.

The second thing is that the manual notes say the 42V regulated supply is
dependent on the 87V regulated supply, and the +15V supply is dependent on
the +42V so your problem is likely just the 87V supply.



Good luck
John

----- Original Message -----

From: Chris

To: TekScopes@...

Sent: Sunday, February 17, 2013 8:39 PM

Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

?

All voltages measured in the scope with everything hooked up. I just got done checking the voltages pre-regulator.

At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v

And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v

Based on the unregulated values, I believe the issue must lie in the regulator portions, and since I'm getting the 97.6v pre-regulated it would seem to me the voltage doubler is working. I also double checked and verified the 10v reference voltage at the test point on the main board as well as the J121 connector that feeds the main board. (I figured this was important to double check as the regulators all are based off the 10v reference as I read it). Of course this is where I wish to learn more - I understand what the individual components do but I still somewhat struggle to see what the assembly as a whole is doing, which is why I'm trying to get into all this, so maybe my understanding is skewed. :)

At any rate, it would seem to me that with the unregulated voltages where they're at, that the issue would have to lie within the follow area:

Yes? No? I mean I have the correct voltages on the left side of those three groups, and the wrong voltages on the right side, so it would seem that's where I should look next?

Thanks for helping this newb out!

Chris

--- In TekScopes@..., "Tom Miller" wrote:
>
> The +87 is from a doubler and added to the +42. I would take a close look at the three 10 uF caps and all the diodes in that area. Be sure to only use fast diodes for any replacements.
>
> Since you recapped this unit, don't overlook the fact that bad capacitors can come from the factory new. Did you measure all these voltages in the scope or on an external load?
>
>
>
>
> Regards,
> Tom
>
>

Those unregulated supplies all look good. I would concentrate on the +87 first since all the others are dependant on it. You might check the drop across R1221, the current limit shunt. At least check the resistance.

Tom
----- Original Message -----
From: Chris
To: TekScopes@...
Sent: Sunday, February 17, 2013 8:39 PM
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.



All voltages measured in the scope with everything hooked up. I just got done checking the voltages pre-regulator.

At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v

And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v

Based on the unregulated values, I believe the issue must lie in the regulator portions, and since I'm getting the 97.6v pre-regulated it would seem to me the voltage doubler is working. I also double checked and verified the 10v reference voltage at the test point on the main board as well as the J121 connector that feeds the main board. (I figured this was important to double check as the regulators all are based off the 10v reference as I read it). Of course this is where I wish to learn more - I understand what the individual components do but I still somewhat struggle to see what the assembly as a whole is doing, which is why I'm trying to get into all this, so maybe my understanding is skewed. :)

At any rate, it would seem to me that with the unregulated voltages where they're at, that the issue would have to lie within the follow area:

Yes? No? I mean I have the correct voltages on the left side of those three groups, and the wrong voltages on the right side, so it would seem that's where I should look next?

Thanks for helping this newb out!

Chris

--- In TekScopes@..., "Tom Miller" wrote:
>
> The +87 is from a doubler and added to the +42. I would take a close look at the three 10 uF caps and all the diodes in that area. Be sure to only use fast diodes for any replacements.
>
> Since you recapped this unit, don't overlook the fact that bad capacitors can come from the factory new. Did you measure all these voltages in the scope or on an external load?
>
>
>
>
> Regards,
> Tom
>
>

The +87 is from a doubler and added to the +42. I would take a close look

Since you recapped this unit, don't overlook the fact that bad capacitors

Regards,
Tom

Chris

The problem could be in the 87V regulator

Or

Their could be a short/low Resistance some where in the load

I have a 2465B open and I measured a load resistance of 25.3K to ground on
Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from the J121 connector
unit

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Chris
Sent: Sunday, February 17, 2013 5:40 PM
To: TekScopes@...
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

All voltages measured in the scope with everything hooked up. I just got
done checking the voltages pre-regulator.

At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v

And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v

Based on the unregulated values, I believe the issue must lie in the
regulator portions, and since I'm getting the 97.6v pre-regulated it would
seem to me the voltage doubler is working. I also double checked and
verified the 10v reference voltage at the test point on the main board as
well as the J121 connector that feeds the main board. (I figured this was
important to double check as the regulators all are based off the 10v
reference as I read it). Of course this is where I wish to learn more - I
understand what the individual components do but I still somewhat struggle
to see what the assembly as a whole is doing, which is why I'm trying to get
into all this, so maybe my understanding is skewed. :)

At any rate, it would seem to me that with the unregulated voltages where
they're at, that the issue would have to lie within the follow area:


Yes? No? I mean I have the correct voltages on the left side of those three
groups, and the wrong voltages on the right side, so it would seem that's
where I should look next?

Thanks for helping this newb out!

Chris


--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:

The +87 is from a doubler and added to the +42. I would take a close look

at the three 10 uF caps and all the diodes in that area. Be sure to only use
fast diodes for any replacements.

Since you recapped this unit, don't overlook the fact that bad capacitors

can come from the factory new. Did you measure all these voltages in the
scope or on an external load?

Regards,
Tom

------------------------------------

Yahoo! Groups Links

Chris

The problem could be in the 87V regulator

Or

Their could be a short/low Resistance some where in the load

I have a 2465B open and I measured a load resistance of 25.3K to ground on
Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from

unit

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On

Of Chris
Sent: Sunday, February 17, 2013 5:40 PM
To: TekScopes@...
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

All voltages measured in the scope with everything hooked up. I just got
done checking the voltages pre-regulator.

At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v

And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v

Based on the unregulated values, I believe the issue must lie in the
regulator portions, and since I'm getting the 97.6v pre-regulated it would
seem to me the voltage doubler is working. I also double checked and
verified the 10v reference voltage at the test point on the main board as
well as the J121 connector that feeds the main board. (I figured this was
important to double check as the regulators all are based off the 10v
reference as I read it). Of course this is where I wish to learn more - I
understand what the individual components do but I still somewhat struggle
to see what the assembly as a whole is doing, which is why I'm trying to

into all this, so maybe my understanding is skewed. :)

At any rate, it would seem to me that with the unregulated voltages where
they're at, that the issue would have to lie within the follow area:


Yes? No? I mean I have the correct voltages on the left side of those

groups, and the wrong voltages on the right side, so it would seem that's
where I should look next?

Thanks for helping this newb out!

Chris


--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:

The +87 is from a doubler and added to the +42. I would take a close

at the three 10 uF caps and all the diodes in that area. Be sure to only

fast diodes for any replacements.

Since you recapped this unit, don't overlook the fact that bad

can come from the factory new. Did you measure all these voltages in the
scope or on an external load?

Regards,
Tom

------------------------------------

Yahoo! Groups Links

Chris

The CR1244 is across the B-E junction of the transistor, so in circuit it
would not measure Open like a diode out of the circuit would.

I have my board out waiting for the inverter board to dry from it's
cleaning, and I measure .706V forward (of the diode) and .581V reverse
(instead of open, which is forward for the transistor junction.)

You could measure all the voltages Q1220, Q1221, Q1222, and Q1224 E,B and C
along with U1281A pin 1, 2 and 3 CR1220 anode to see what is out of wack

John



-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Chris
Sent: Monday, February 18, 2013 8:37 PM
To: TekScopes@...
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

John,
A HUGE thank you on checking that and giving me your value! I was hoping
the short wasn't in the main board somewhere as that doesn't look like fun
to pull in the least.

I just checked the resistance from the pin 7 (blue 87v wire) on the
connector (power supply still out and on the bench) and I got a value of
25.55Kohm, so it would appear I should be OK to go at that (assuming that
powering something else up on the main board doesn't cause it to
short/overload the supply). I was testing the diodes on the power supply
and diode CR1244 is giving me 0.538V forward and 0.630v reverse. I think I
might pull it and check it out of the board later tonight after I eat etc.

Thanks for the help!
Chris

--- In TekScopes@..., "John Snyder" <Kochcal@> wrote:

Chris

The problem could be in the 87V regulator

Or

Their could be a short/low Resistance some where in the load

I have a 2465B open and I measured a load resistance of 25.3K to ground on
Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from

the J121 connector

unit

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On

Behalf

Of Chris
Sent: Sunday, February 17, 2013 5:40 PM
To: TekScopes@...
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

All voltages measured in the scope with everything hooked up. I just got
done checking the voltages pre-regulator.

At J233A I get:
pin 5 (87v unregulated) 97.6v
Pin 3 (42v unregulated) 49.0v

And at J234A I get:
pin 5 (15v unregulated) 18.94v
Pin 4 (5v unregulated) 6.64
Pin 2 (-5v unregulated) -6.92v
Pin 1 (-15v unregulated) -18.54v

Based on the unregulated values, I believe the issue must lie in the
regulator portions, and since I'm getting the 97.6v pre-regulated it would
seem to me the voltage doubler is working. I also double checked and
verified the 10v reference voltage at the test point on the main board as
well as the J121 connector that feeds the main board. (I figured this was
important to double check as the regulators all are based off the 10v
reference as I read it). Of course this is where I wish to learn more - I
understand what the individual components do but I still somewhat struggle
to see what the assembly as a whole is doing, which is why I'm trying to

get

into all this, so maybe my understanding is skewed. :)

At any rate, it would seem to me that with the unregulated voltages where
they're at, that the issue would have to lie within the follow area:


Yes? No? I mean I have the correct voltages on the left side of those

three

groups, and the wrong voltages on the right side, so it would seem that's
where I should look next?

Thanks for helping this newb out!

Chris


--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:

The +87 is from a doubler and added to the +42. I would take a close

look

at the three 10 uF caps and all the diodes in that area. Be sure to only

use

fast diodes for any replacements.

Since you recapped this unit, don't overlook the fact that bad

capacitors

can come from the factory new. Did you measure all these voltages in the
scope or on an external load?

Regards,
Tom

------------------------------------

Yahoo! Groups Links

------------------------------------

Yahoo! Groups Links

----- Original Message -----

From: Chris

To: TekScopes@...

Sent: Tuesday, February 19, 2013 4:52 AM

Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.

?

I had sent a response earlier but it didn't appear to have made it.

I checked some of the voltages on the board, but can't say I entirely know what to make of all of them (newb alert again hah)

Ok, I've got 94v on the unregulated rail
On the op-amp, pin 1 vref is 10.00v Pin 2 from the voltage divider is reading as ~1v or just under. Pin 1 is reading 15.19v.

Q1222: Emitter 8v, base is grounded of course, and 11.6v on the collector.

Q1220: (sorry, not sure which is emitter/base/collector, I'd have to look up a datasheet - more newb showing through). So looking down on the power supply as it's mounted in the chassis: 11.3v on the left pin, 94.7v on the middle pin (must be the collector) and 11.8v on the right pin.

Q1221: 94v on the collector, 11.1v on the base and 10.6v on the emitter.

I didn't measure Q1223 - hard to reach that one.

R1212: 94v on the unregulated rail side, 10.5v on the other side of it.
R1220: 94v on the unregulated rail side, 9v on the other side.

Curious how I got 15.19v on pin 1 of U1281A with a 10v ref and a 1v comparison from the voltage divider off the regulated line - looking at the datasheet it looks like it should be operating as two separate op-amps with one half regulating the 87v line and the other the 42v line, so I fired it up again and checked the voltage on all of it's pins:

pin 1: 15.57v
pin 2: 1.05v
pin 3: 10.00v
pin 4: -6.86v
pin 5: 10.00v
pin 6: 1.58v
pin 7: 15.58v
pin 8: 16.42

So thinking about it for a bit, the schematic shows a voltage of -1.53v for pin 1 (a far cry from the 15v I'm getting)which I assume is the voltage I should see when the line is regulated to 82v. And I assume then that the 16.42v is the positive power for U1281, and the -6.86v is the supply that lets it pull Q1222 low when the voltage from the voltage divider feeding pin 2 = the 10v ref from pin 3.

So I guess I learned something, but as far as using the voltages to give me an indication as to what's gone wrong I'm not sure. That will take a better man (or woman) that's more educated than I! I would have to resort to the shotgun repair method at this point - replace all the components :) (certainly not to the point of wanting to shoot the scope yet lol)

As a note, when reading these voltages they can vary a bit while checking them. Sometimes it's not uncommon to see some of the voltages vary ~0.5v it seems, so that accounts for some of the variance in the first vs 2nd measurements in areas. Earlier I was reading ~9.5v on the 87v regulated line, but tonight it was just under 9v.

Thanks!
Chris

--- In TekScopes@..., "John Snyder" wrote:
>
> Chris
>
> The CR1244 is across the B-E junction of the transistor, so in circuit it
> would not measure Open like a diode out of the circuit would.
>
> I have my board out waiting for the inverter board to dry from it's
> cleaning, and I measure .706V forward (of the diode) and .581V reverse
> (instead of open, which is forward for the transistor junction.)
>
> You could measure all the voltages Q1220, Q1221, Q1222, and Q1224 E,B and C
> along with U1281A pin 1, 2 and 3 CR1220 anode to see what is out of wack
>
> John
>
>
>
> -----Original Message-----
> From: TekScopes@... [mailto:TekScopes@...] On Behalf
> Of Chris
> Sent: Monday, February 18, 2013 8:37 PM
> To: TekScopes@...
> Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.
>
> John,
> A HUGE thank you on checking that and giving me your value! I was hoping
> the short wasn't in the main board somewhere as that doesn't look like fun
> to pull in the least.
>
> I just checked the resistance from the pin 7 (blue 87v wire) on the
> connector (power supply still out and on the bench) and I got a value of
> 25.55Kohm, so it would appear I should be OK to go at that (assuming that
> powering something else up on the main board doesn't cause it to
> short/overload the supply). I was testing the diodes on the power supply
> and diode CR1244 is giving me 0.538V forward and 0.630v reverse. I think I
> might pull it and check it out of the board later tonight after I eat etc.
>
> Thanks for the help!
> Chris
>
> --- In TekScopes@..., "John Snyder" wrote:
> >
> > Chris
> >
> > The problem could be in the 87V regulator
> >
> > Or
> >
> > Their could be a short/low Resistance some where in the load
> >
> > I have a 2465B open and I measured a load resistance of 25.3K to ground on
> > Pin 7 of J121 (87V, the blue wire) with the power supply unplugged from
> the J121 connector
> > unit
> >
> > John
> >
> > -----Original Message-----
> > From: TekScopes@... [mailto:TekScopes@...] On
> Behalf
> > Of Chris
> > Sent: Sunday, February 17, 2013 5:40 PM
> > To: TekScopes@...
> > Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.
> >
> > All voltages measured in the scope with everything hooked up. I just got
> > done checking the voltages pre-regulator.
> >
> > At J233A I get:
> > pin 5 (87v unregulated) 97.6v
> > Pin 3 (42v unregulated) 49.0v
> >
> > And at J234A I get:
> > pin 5 (15v unregulated) 18.94v
> > Pin 4 (5v unregulated) 6.64
> > Pin 2 (-5v unregulated) -6.92v
> > Pin 1 (-15v unregulated) -18.54v
> >
> > Based on the unregulated values, I believe the issue must lie in the
> > regulator portions, and since I'm getting the 97.6v pre-regulated it would
> > seem to me the voltage doubler is working. I also double checked and
> > verified the 10v reference voltage at the test point on the main board as
> > well as the J121 connector that feeds the main board. (I figured this was
> > important to double check as the regulators all are based off the 10v
> > reference as I read it). Of course this is where I wish to learn more - I
> > understand what the individual components do but I still somewhat struggle
> > to see what the assembly as a whole is doing, which is why I'm trying to
> get
> > into all this, so maybe my understanding is skewed. :)
> >
> > At any rate, it would seem to me that with the unregulated voltages where
> > they're at, that the issue would have to lie within the follow area:
> >
> >
> > Yes? No? I mean I have the correct voltages on the left side of those
> three
> > groups, and the wrong voltages on the right side, so it would seem that's
> > where I should look next?
> >
> > Thanks for helping this newb out!
> >
> > Chris
> >
> >
> > --- In TekScopes@..., "Tom Miller" wrote:
> > >
> > > The +87 is from a doubler and added to the +42. I would take a close
> look
> > at the three 10 uF caps and all the diodes in that area. Be sure to only
> use
> > fast diodes for any replacements.
> > >
> > > Since you recapped this unit, don't overlook the fact that bad
> capacitors
> > can come from the factory new. Did you measure all these voltages in the
> > scope or on an external load?
> > >
> > >
> > >
> > >
> > > Regards,
> > > Tom
> > >
> > >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>

Change Q1222. It should be full off and the collector should be up around 90 volts or so. However, Q1223 could also be pulling that line down so change it also. You could lift the collector of Q1223 and see if the supply comes up just to rule that out. Also (2), is R1212 ok? If it were open, the same issue would be there.

Tom




----- Original Message -----
From: Chris
To: TekScopes@...
Sent: Tuesday, February 19, 2013 4:52 AM
Subject: [TekScopes] Re: Tektronix 2465 capacitors etc.



I had sent a response earlier but it didn't appear to have made it.

I checked some of the voltages on the board, but can't say I entirely know what to make of all of them (newb alert again hah)

Ok, I've got 94v on the unregulated rail
On the op-amp, pin 1 vref is 10.00v Pin 2 from the voltage divider is reading as ~1v or just under. Pin 1 is reading 15.19v.

Q1222: Emitter 8v, base is grounded of course, and 11.6v on the collector.

Q1220: (sorry, not sure which is emitter/base/collector, I'd have to look up a datasheet - more newb showing through). So looking down on the power supply as it's mounted in the chassis: 11.3v on the left pin, 94.7v on the middle pin (must be the collector) and 11.8v on the right pin.

Q1221: 94v on the collector, 11.1v on the base and 10.6v on the emitter.

I didn't measure Q1223 - hard to reach that one.

R1212: 94v on the unregulated rail side, 10.5v on the other side of it.
R1220: 94v on the unregulated rail side, 9v on the other side.

Curious how I got 15.19v on pin 1 of U1281A with a 10v ref and a 1v comparison from the voltage divider off the regulated line - looking at the datasheet it looks like it should be operating as two separate op-amps with one half regulating the 87v line and the other the 42v line, so I fired it up again and checked the voltage on all of it's pins:

pin 1: 15.57v
pin 2: 1.05v
pin 3: 10.00v
pin 4: -6.86v
pin 5: 10.00v
pin 6: 1.58v
pin 7: 15.58v
pin 8: 16.42

So thinking about it for a bit, the schematic shows a voltage of -1.53v for pin 1 (a far cry from the 15v I'm getting)which I assume is the voltage I should see when the line is regulated to 82v. And I assume then that the 16.42v is the positive power for U1281, and the -6.86v is the supply that lets it pull Q1222 low when the voltage from the voltage divider feeding pin 2 = the 10v ref from pin 3.

So I guess I learned something, but as far as using the voltages to give me an indication as to what's gone wrong I'm not sure. That will take a better man (or woman) that's more educated than I! I would have to resort to the shotgun repair method at this point - replace all the components :) (certainly not to the point of wanting to shoot the scope yet lol)

As a note, when reading these voltages they can vary a bit while checking them. Sometimes it's not uncommon to see some of the voltages vary ~0.5v it seems, so that accounts for some of the variance in the first vs 2nd measurements in areas. Earlier I was reading ~9.5v on the 87v regulated line, but tonight it was just under 9v.

Thanks!
Chris