Hi all,

I have a TDS684A scope that has a problem on the CRT driver board. I've noticed that R294 is discolored. Can anyone tell me what the value of this component is? It measures 2.7K ohm, and it might be correct because I can see the color band is red-purple-????. The 3rd color band is too discolored to tell what it is. If it's red then the value is correct, but I can't tell due to the burn discoloration.

Can anybody tell me what value R294 should be?

Does anyone have schematics for these CRT driver boards? The TDS520B component service manual only has the B&W display schematic :(

Thanks,
Mike

I have a 475 scope, but pretty much a beginner in its use. I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz. My question has to do with the proper type of probe. Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe? Does the scope need protection from high power RF? I want to at least see what is going into the grids of the final amplifier tubes.

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

From: Richard

To: TekScopes@...

Sent: Sunday, February 17, 2013 11:53 PM

Subject: [TekScopes] Basic Probe Question

?

I have a 475 scope, but pretty much a beginner in its use. I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz. My question has to do with the proper type of probe. Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe? Does the scope need protection from high power RF? I want to at least see what is going into the grids of the final amplifier tubes.

Hi Walter,
Will take 6 of the hp 848x sensors at 7 dollars if that is ok with you?
Cslim

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
>
>

----- 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
>
>

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

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 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

?

I'm planning a trip up to Sphere with some hopes in mind,
using my E350 van (which has a class 4 hitch.) Sometime
before the middle of May. (I have a court case going on right
now and I need to get the little passport cards first.)

I may be able to transport equipment across the border and
ship from Portland, Oregon, where that may make more sense
than asking Sphere to ship. I don't know the details of any
of that, so whether or not I can help is more something to
work out for yourselves. The main thing I care about is being
able to cross the border without being delayed for days where
I wouldn't otherwise have a problem. I don't mind putting in
some labor just because, though. That's fine. But I've no
idea if it "makes sense." I'm just going up, is all. (And
will very much enjoy it.)

Jon

?

Hi Chuck

To be honest if I had four pallets of TEK scopes I would break them up for spares as I don't think anyone is going to buy this stuff especially the tube scopes.

The only buyers for old TEK scopes are hobbyists and collectors and those who want a realtime wide bandwidth CRT scope. Technology has moved on, scopes are digital these days with A-D converters sampling at N GHz and all in a cute little box.

I want a scope that works when I switch it on, not with a power supply that goes bzzt, bzzt, tick, tick because some cap has gone short circuit or some corroded part in a socket isn't making contact.

In short, there really isn't much of a market for old TEK scopes.
They were great in their day but not so good 30 or 40 years later.

Best regards
Chris

--- In TekScopes@..., Chuck Harris wrote:
>
> Here's the thing:
>
> I have 4 pallets of tektronix scopes taking up space in my
> warehouse. One pallet is mostly 7000 series, with a few
> 5000 series mainframes, another is a mix of 7000 and 5000
> series rack mount scopes, with a 564. The third is mostly
> 453's, 454's, and a few odd 434, 464, 465, 466, 475, and 485's.
> And the fourth has a 585A, 545A, and 535A on it... the '45
> and '35 were beautiful before the tube whores stripped them...
> but recycler's don't get the luxury of judging, they just take
> what they get.... ixed in with all of this are several large
> boxes of plugins... nothing sexy, but the usual 7B53A's, and
> 7A16, 7A26, 7D14, kind of stuff...
>
> I love cleaning, fixing, calibrating and restoring scopes
> into good working condition. I have all of the Tek specified
> gear for doing this, but judging by ebay sales, buyers don't
> seem to value that effort at all.
>
> To give you an example. I found a DOA 434 in my stash, and
> because it was so cute, I cleaned it up, fixed a power supply
> problem that stumped the original owner, replaced a tantalum
> on one of the boards, fixed a really nasty trigger problem,
> that was caused by the power supply problem, lubed all of the
> pots, cleaned and lubed the panel switches, and fan, cleaned
> the attenuator contacts, and did a complete calibration. It
> took me a week of evenings to do the work. When it was put on
> ebay, as cleaned, calibrated, and guaranteed, it got a couple
> of $15 offers, and it remains unsold... as does its twin that
> I did in hopes of a better result...
>
> At current US scrap prices, I can get $17 per pound for gold
> plated circuit boards, which is the standard price recyclers
> are giving these days... I work with a recycler, so I am very
> sure of these prices... There is easily 2 pounds of circuit
> boards in a 434 [vertical, horizontal, storage, preamps, and
> power supply are all gold plated]. The 453's and 454's have
> easily 5x more...
>
> Considering how much you folks are yipping and yapping about
> tunnel diodes, and how hard they are to find, I could have
> gotten more than $15 if I simply removed the two diodes in
> this 434, and sold them on ebay. And I would still have a
> good CRT, the aluminum from the chassis and can, the gold
> plated circuit boards, a bunch of special IC's, etc... I have
> gotten $5 just from a knob, and $15 from just selling one CRT
> filter!.... to sell.
>
> What's the answer? I keep hearing about how much you guys
> love Tektronix and their scopes, but when one sells for less
> than a tankful of gas, I have to wonder if it is all just
> dreamy nostalgia talk. When a couple of days worth of cleaning,
> repairing, and calibration is worth less than you would pay
> for a dinner out with someone you don't even like all that
> much... Where is the love?
>
> What's it to be? Do I fix them, or Do I scrap them?
>
> What shall I do with these scopes?
>
> -Chuck Harris
>

Here's the thing:

I have 4 pallets of tektronix scopes taking up space in my
warehouse. One pallet is mostly 7000 series, with a few
5000 series mainframes, another is a mix of 7000 and 5000
series rack mount scopes, with a 564. The third is mostly
453's, 454's, and a few odd 434, 464, 465, 466, 475, and 485's.
And the fourth has a 585A, 545A, and 535A on it... the '45
and '35 were beautiful before the tube whores stripped them...
but recycler's don't get the luxury of judging, they just take
what they get.... ixed in with all of this are several large
boxes of plugins... nothing sexy, but the usual 7B53A's, and
7A16, 7A26, 7D14, kind of stuff...

I love cleaning, fixing, calibrating and restoring scopes
into good working condition. I have all of the Tek specified
gear for doing this, but judging by ebay sales, buyers don't
seem to value that effort at all.

To give you an example. I found a DOA 434 in my stash, and
because it was so cute, I cleaned it up, fixed a power supply
problem that stumped the original owner, replaced a tantalum
on one of the boards, fixed a really nasty trigger problem,
that was caused by the power supply problem, lubed all of the
pots, cleaned and lubed the panel switches, and fan, cleaned
the attenuator contacts, and did a complete calibration. It
took me a week of evenings to do the work. When it was put on
ebay, as cleaned, calibrated, and guaranteed, it got a couple
of $15 offers, and it remains unsold... as does its twin that
I did in hopes of a better result...

At current US scrap prices, I can get $17 per pound for gold
plated circuit boards, which is the standard price recyclers
are giving these days... I work with a recycler, so I am very
sure of these prices... There is easily 2 pounds of circuit
boards in a 434 [vertical, horizontal, storage, preamps, and
power supply are all gold plated]. The 453's and 454's have
easily 5x more...

Considering how much you folks are yipping and yapping about
tunnel diodes, and how hard they are to find, I could have
gotten more than $15 if I simply removed the two diodes in
this 434, and sold them on ebay. And I would still have a
good CRT, the aluminum from the chassis and can, the gold
plated circuit boards, a bunch of special IC's, etc... I have
gotten $5 just from a knob, and $15 from just selling one CRT
filter!.... to sell.

What's the answer? I keep hearing about how much you guys
love Tektronix and their scopes, but when one sells for less
than a tankful of gas, I have to wonder if it is all just
dreamy nostalgia talk. When a couple of days worth of cleaning,
repairing, and calibration is worth less than you would pay
for a dinner out with someone you don't even like all that
much... Where is the love?

What's it to be? Do I fix them, or Do I scrap them?

What shall I do with these scopes?

-Chuck Harris

----- 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
> >
>