2467 no power

[ahnuts72]

Houston we have a problem!!!!!!

Was trying to probe a ramp generator I'm building and the scope just shut off and wont come back on

I wasnt probing anything at the time was looking at the schematic and went to use it and no display.

Pressed the power switch and nothing not even the fan is coming on.

Checked the fuse outside and both fuses inside all fine.

No smell or smoke nothing visually burnt,bulging or leaking.

It just turned itself off and wont come back on.

Tried probing the power connector to one of the options and no voltage at all.(well several mV but should be like +5,+15,-15)


 

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[BravoV]

Have you checked the J-119 for all voltages ? This will be a good start for trouble shootings should the power supply is acting up.

Below the J-119 location pointed by arrow where you can probe those voltages, taken from your 2467 photo.

[PaulAm]

Get a service manual, open it up and check the power supply test points.  One or more of the LV power supplies is likely dead.  Aging 24xx power supplies have issues with filter caps.  I'd start there, anyway.

[ahnuts72]

Thanks bravo ill check that as soon as I get off work.

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[BravoV]

Just words of precaution, when turned on without the enclosure, those unobtainium hybrid ICs will not have enough air circulation to cool them down and will experience overheating, trust me, you don't want those pesky chips starting to accelerate their deterioration. 

Suggesting to have a big or quite powerful fan blowing the whole board when its powered on.

[ahnuts72]

Thanks Paul I have one gotta get it printed hate trying to read a pdf.

On a side note does anyone know how yo edit post in tapatalk

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[ahnuts72]

Ok 2 pins have around 1.5 volts but its oscillating from 0 volts to 1.5

No other pins have any voltage at all.

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[Bryan]

Sounds like power supply to me. Start with the fuses. There is  also a fuse F1102 (I think) that looks like a resistor so it can be easy to miss.

Post some pics of the power supply board. We can tell if the caps are original. The power supply board probably needs recapping as well as the A5 board.  Have a look at this site.

http://www.bestelectronicarticles.com/testing-equipment/analogue-oscilloscopes/tektronix-2465b-oscilloscope-restoration-repair.html

There is a  good discussion on replacing the caps ont eh A5 board as well in this link. they are know to leak and can destroy the board.

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

[echen1024]

It's probably one of those caps. They are known for going belly-up. 

[ahnuts72]

Here are the pics of the low voltage/regulator side.

Bridge has 116 Vac in
326 Vdc out
I checked voltage on J231a going to the inverter board.
Front pin + middle=327 volts  middle pin + rear pin=163.5
All fuses good even the little buss fuse.

At least ill have an excuse to get a capacitance and esr meter.

[Bryan]

Just a comment. if you are getting no voltage on any of the J119 pins then it could be that somewhere in the scope one of the areas is drawing too much power. The power supply will limit it's power and cut off the output.

In isn't fun but you are going to have to read and read and read again the service manual on the power supply. It all looks like gobblygook but once you print it out and go over it diagnosing the supplies is fairly straight forward. Follow the flow charts on troubleshooting the power supply.You may luck out and find it's just one or two defective components

p.s. The caps on the board are original and should be replaced.

I spent a fair amount of time recapping two 2465b scopes and fixing one supply. Will offer any help you may need.

[Bryan]

Oh and if all fails

http://www.ebay.com/itm/Low-Hi-Voltage-Power-Supplies-for-Tektronix-2467B-2467-2465B-2465A-2445B-/400559718322?pt=BI_Oscilloscopes&hash=item5d43383fb2

[rf-loop]

As BravoV told.

Repeat this warning: Do not use 2465/7x long time with case open without external service fan, specially if main board free airflow is not possible (ecample if it is on the table so that main board air flow is closed! Tek service manuals tell what 2400 models it is exatly nessessary to use external fan. I have some experience of repairing and calibrating these models and I will recommend external small fan for reduce some components temperature. Specially these hybrids tempetrature may rise to danger area and as we know they are expensive and difficult to find. So, care need and why take risk about damage.

(case closed and when scope run, these airflows are carefully but some amount critically designed.)

We can see in markets lots of these failed scopes with "backed" hybrids after poor service or fan failure or just random fail. (I can not understand why Tek have missed fan (airflof) control in this kind of equipment design. It is not money question, it is imho just mistake)

[ahnuts72]

I have a 8 inch desk fan blowing on it.
I turn it off as soon as im done probing voltages.

Im trying to follow the diagnostic flow chart now.

Will the supply operate out of the chassis.

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[Orange]

This PSU is a switcher, you need to load at least the +5 volt and the + and - 12volts rails. 1 amp for the +5volts, 200 mA for the 12 volts rails

If you you don't load it the voltages are incorrect and PSU makes a lot of audible noise.

Check and replace all RIFA oil-paper caps in the mains circuit,  they will will eventually blow with a lot of nasty smoke. Also replace the secondary caps with LOW ESR types like the Panasonic FC or FM types.  Also check the protection resistors in series with the oil-paper caps. Most of the times these are also pretty burn.
Check also the twin Schottky diode mounted to the cooling chassis, I had this one failed on time. And for sure the fuse in the scope chassis :-)

[ahnuts72]

Thanks orange I saw in the service manual on making the load for the 5 volt rail nut not the 12 volt one right now the power supply makes no noise when I turn it on its just like its unplugged.

Fuse on the back was the first one I checked.

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[Bryan]

You will require loading all the output rails. Manual recommends 100 ohm 5 watt for the +-15v rails and below. I found you need less resistance for the 5vd. Remember there is two 5v outputs, one labeleld +5v and the other +5vd

For the 87v and 42v I used a 2k 5 watt resistor. i found anything less in resistance and for some reason it loads it too much and all the voltages drop. Careful not to run with no load as the supply will "whistle" and there is a few components in the current limiting section that will go up in smoke . I believe R1071 and a transistor close to it.

Once you have the supply properly loaded you can confirm if the supply is the issue and not something else on the scope that is dragging the power rails down.

Have you started working from the flow chart in the service manual.?

[ahnuts72]

Yes from what I've discovered its pointing me to the inverter board.

But I have never tried to diagnose a switcher before

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[ahnuts72]

Here are a few pics of one of the caps off of the inverter board.

Top no bulge.

Should the bottom be flat too or is this normal for the era the scope was made.(1987 by the way)

[BravoV]

Looks nice ... chubby cap ! 

I think you should stop using that scope, list down the priorities and the to do list like cap refresh (like the one I posted the document at your other 2467 thread), change the leaky or about to leak cap at the digital A5 board, backup the cal data and etc.

It will be really sad day to see this gem "IF" the bad power supply rails are affecting those unobtainium chips permanently. 

[ahnuts72]

Couldnt use it if I wanted to but Im not gonna try to trouble shoot the power supply any more until I do a recap.

Can the cal data be read in circuit I dont wanna risk damaging the ram module with solder braid or my manual solder
suckertrying to de-solder it.

Or should I just get a de-soldering gun and remove it?

[edavid]

Don't listen to the recappers, that is just voodoo.  Find and fix the real problem, don't worry about imaginary bad capacitors.  Also, you can run the scope with the case off.  It's the 2430s and 2440s that need airflow, the 2467 does not.

[Bryan]

Here are a few pics of one of the caps off of the inverter board.

Top no bulge.

Should the bottom be flat too or is this normal for the era the scope was made.(1987 by the way)

When I recapped my boards a lot of the caps looked the same. they still had a decent ESR and capacitance values. Think there was 2 or 3 that were getting clsoe to out of spec. think ti was the film capacitors actually. One way to tell if the caps are bad is put the whole lot in plastic bag. Have a sniff after a couple hours. If they smell like fish fertilizer they are leaking. As the other poster staed, replacing caps is probably not going to solve the problem unless there was some duds in critical areas of the power supply. You are going to have to follow the flow chart in the service manual and work your way through. My best guess is there is something in the inverter that is shutting the whole thing down.  You can not test the power supply out of the scope without adding load resistors. If you don't it wills tart whistling and oscillating burning up R1071.
 

[ahnuts72]

Right now the flow chart has me checking the mosfets on the inverter board.

I still have my 475a so im gonna take my time trying to fix it.

Ill prob still recap the boards though.

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[valentinc]

     I recently repaired a Tektronix 2465A, which I assume has the same power supply as the 2467... The problem was the same, it didn't start at all...

     I first changed the X capacitors... The 2 bleeder resistors across them... And then the power supply still won't start... I checked almost everything, the transistors, the filter capacitors in the secondary side (and all of them were ok... both as ESR and capacitance... Not exactly the parameters as new ones, but still, it was clear that they were not the problem... I said that I'll change them later). And with the schematic in front of me, I first looked at the starting circuit of the TL594... And almost immediatley I found that the supply voltage of the IC was much lower than it would need to start... Then after a few measurements I found the electrolytic capacitor of 100uF if I remember correctly was way out... (measured only a few hundred nF and and ESR of a few hundred ohms)... I changed that... And the power supply started fine...

      Forgot to mention, the 100uF capacitor hadn't any buldge in it...

      And as I said, the output filter capacitors must be measured first... (in my opinion), because they're not necessary bad...