Tektronix 2465B oscilloscope teardown

[BravoV]

This is my first post and am a newbie.

I am waiting for my 2465B to show up. Everything is like new, the only thing is the scale illumination is not working. Is it worth replacing? I looked in the service manual and there are not pics to help me replace it.

Should I replace the board or just leave it?

If I should replace it and pics or video that show how to do it? I searched YouTube and everywhere and can't find anything

Thanks in advance for the help!

Bill

What do you mean the board ?

Try read post #19 -> HERE, is that what are you looking for ?

The illuminator is just an incandescent lamp, which I think, can be modded to use red LED.

[MarkL]

This is my first post and am a newbie.

I am waiting for my 2465B to show up. Everything is like new, the only thing is the scale illumination is not working. Is it worth replacing? I looked in the service manual and there are not pics to help me replace it.

Should I replace the board or just leave it?

If I should replace it and pics or video that show how to do it? I searched YouTube and everywhere and can't find anything

Thanks in advance for the help!

Bill

There's no pics, but there is a step-by-step description in the service manual in section 6 near the end, "A8 - Scale Illumination Circuit Board Removal".

The bulbs are in series and it's probably a burned out bulb.  The bulb type is 7153 (T-3/4).  Sources detailed here:

  https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg842072/#msg842072

Before you go through the trouble of removing the board to replace lamps (or substitute LEDs), measure the voltage going to the board to be sure it's nothing else.

[factory]

Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available? 



David

[AMR Labs]

There must be a RIFA flu going around, saw a recent post here a couple of pages back saying the same thing. Was using my 2465B (serial +50K) today and all of the sudden POP and a lot of smoke. RIFA cap exploded and burned up 30 ohm resistor in series, even tough this scope has been on 120V line all its life, as far as I know. Saw the RIFAs where pretty crazed when I did the NVRAM/A5 caps about a year ago but figured I'll get to it eventually. Well, it got to me instead.

No other evident damage was found anywhere inside. So decided it would be a good time to finally use all those caps that I ordered months ago to do the full recap. Pulled out the power supply board sandwich and installed new caps all around (one at a time to avoid mistakes) including the main filter caps, the 4.7uF Tantalum, and the 3x 1uF NP. The only film caps I forgot to order back when where the two 2200pf 250V, one 0.01uF 250V, and one 0.056uF 250V so I'll do those next time. Also replaced both 15 ohm resistors with bigger units, and the 270K resistor.

Upon first plugin test the fan runs and all front panel lights flash once in unison and then only the green Sweep/Trig led stays on and nothing else happens. The 3 GPIB indicator are also staying lit. Not sure the Sweep/Trig Led might mean something (error code) although I looked it up in the SM and all I found is the list of indicators the scope goes through in sequence on boot, and if it stops on one that can be looked up in this list. But mine is not even going through this sequence, so not even booting. Nothing visible on screen, no trace no nothing.

Measured voltages at J119 as follows:

-15 -> -11.7v
+5D -> +4.3V
+10 -> +7.3
-5 -> -3.5V
+15 -> +10.4V
+87 -> +59.6V
+42.4 -> +28.8V
-8 -> -5.3V
+5A -> +3.3V


Needless to say all rails are low and way out of spec. Also checked voltage on the (new) main caps and got about 150V on each and around 300V total, so the primary rectifier is working and juice is getting into the supply. No sounds, no clicking, nothing heard.

Just now after pulling out the power supply again double and tipple checked that all caps are in the correct position, correct value/voltage, and correct polarity before installing the boards. All are correct. And yes, I am aware of the cap layout error in the service manual. Actually I did one cap at a time, just to be extra sure not to mix anything up.

All connectors are positively in place. There is the one going to A5 which is impossible to screw up, one with the multicolor wires under the fuse, and the all-white wires next to it, and no misaligned/missed pins. Other than that, the only other plug is a 3-wire that sends power to the GPIB board. Oh, and also checked continuity of all the pins of the stab (long pin) connectors between the two boards, as they sometimes can go intermittent if pushed the wrong way.

Anybody have any ideas/suggestions? I was reading the troubleshooting charts in the SM but wanted to first ask here in case these symptoms ring a bell and have happened before to someone else after a recap. I know there are plenty of people here that have gone through this procedure, some even more then once. Besides in order to for those charts to make sense would first need to order a couple of 20/25-watt resistors to construct a load as shown in the manual in able to run the supply outside the scope to be able to poke into it without blowing it up after shorting out something. BTW has anybody build one of those test loads? The SM only shows Tek PN for a diode and a 3.3uF cap (v?) needed.

Oh man, I was so hoping this recap would go without a hitch. I found that all the 180uF and 250uF where just staring to leak a tiny bit, so that would probably mean that now with better filtering in place I would get those sharper traces etc that many people have reported. O well... And yes what little was leaking from those caps was cleaned up, no harm at all to any traces or the board. Just a funny smell when desoldering those blue caps. All other caps looked fine but where replaced anyhow. Why not have all the fun at one time. Right, I'm having fun now.

Thanks for any input.
Alex

[AMR Labs]

And finally! Onto the power supply!
....

Moving onto the rest of the CPU, we can see the usual components of a switching power supply. Fortunately, none of the regular electrolytic capacitors look swollen or otherwise damaged, but they're going to be checked anyway, given their age, and especially given the current surge the PSU was subject to. I do see more of those problematic box caps. Those are getting replaced, period, given their history. I'm not waiting for them to fail.

Besides the RIFAs, change all those blue electrolytics, they may still look ok (not swollen, etc) but they start leaking underneath and you won't notice it until they are removed. Just went through this on my 2465B on a long overdue full recap and found both 180uF and all 250uF caps where leaking a tiny bit and obviously no longer doing their job. These are the caps that are under the most stress as they are on the switcher output so they had/have a hard life. I caught mine just about in time. As a matter of fact the same thing happened to me today that a RIFA popped (on 120VAC) and burned up the 30 ohm resistor. Lots of smoke but the main fuse did not blow so I figures it should be an easy fix as these components are ahead of the actual power supply.  But now my only problem is that after the full recap I did, my power supply is no longer starting. If interested, I posted the whole story on a separate post here in this long time thread.

[tautech]

Ya gotta thank the designers for putting 30 ohm current limiting resistors in there. 
Resistors might be toast but at least you have the traces left. 

[med6753]

There must be a RIFA flu going around, saw a recent post here a couple of pages back saying the same thing. Was using my 2465B (serial +50K) today and all of the sudden POP and a lot of smoke. RIFA cap exploded and burned up 30 ohm resistor in series, even tough this scope has been on 120V line all its life, as far as I know. Saw the RIFAs where pretty crazed when I did the NVRAM/A5 caps about a year ago but figured I'll get to it eventually. Well, it got to me instead.

No other evident damage was found anywhere inside. So decided it would be a good time to finally use all those caps that I ordered months ago to do the full recap. Pulled out the power supply board sandwich and installed new caps all around (one at a time to avoid mistakes) including the main filter caps, the 4.7uF Tantalum, and the 3x 1uF NP. The only film caps I forgot to order back when where the two 2200pf 250V, one 0.01uF 250V, and one 0.056uF 250V so I'll do those next time. Also replaced both 15 ohm resistors with bigger units, and the 270K resistor.

Upon first plugin test the fan runs and all front panel lights flash once in unison and then only the green Sweep/Trig led stays on and nothing else happens. The 3 GPIB indicator are also staying lit. Not sure the Sweep/Trig Led might mean something (error code) although I looked it up in the SM and all I found is the list of indicators the scope goes through in sequence on boot, and if it stops on one that can be looked up in this list. But mine is not even going through this sequence, so not even booting. Nothing visible on screen, no trace no nothing.

Measured voltages at J119 as follows:

-15 -> -11.7v
+5D -> +4.3V
+10 -> +7.3
-5 -> -3.5V
+15 -> +10.4V
+87 -> +59.6V
+42.4 -> +28.8V
-8 -> -5.3V
+5A -> +3.3V


Needless to say all rails are low and way out of spec. Also checked voltage on the (new) main caps and got about 150V on each and around 300V total, so the primary rectifier is working and juice is getting into the supply. No sounds, no clicking, nothing heard.

Just now after pulling out the power supply again double and tipple checked that all caps are in the correct position, correct value/voltage, and correct polarity before installing the boards. All are correct. And yes, I am aware of the cap layout error in the service manual. Actually I did one cap at a time, just to be extra sure not to mix anything up.

All connectors are positively in place. There is the one going to A5 which is impossible to screw up, one with the multicolor wires under the fuse, and the all-white wires next to it, and no misaligned/missed pins. Other than that, the only other plug is a 3-wire that sends power to the GPIB board. Oh, and also checked continuity of all the pins of the stab (long pin) connectors between the two boards, as they sometimes can go intermittent if pushed the wrong way.

Anybody have any ideas/suggestions? I was reading the troubleshooting charts in the SM but wanted to first ask here in case these symptoms ring a bell and have happened before to someone else after a recap. I know there are plenty of people here that have gone through this procedure, some even more then once. Besides in order to for those charts to make sense would first need to order a couple of 20/25-watt resistors to construct a load as shown in the manual in able to run the supply outside the scope to be able to poke into it without blowing it up after shorting out something. BTW has anybody build one of those test loads? The SM only shows Tek PN for a diode and a 3.3uF cap (v?) needed.

Oh man, I was so hoping this recap would go without a hitch. I found that all the 180uF and 250uF where just staring to leak a tiny bit, so that would probably mean that now with better filtering in place I would get those sharper traces etc that many people have reported. O well... And yes what little was leaking from those caps was cleaned up, no harm at all to any traces or the board. Just a funny smell when desoldering those blue caps. All other caps looked fine but where replaced anyhow. Why not have all the fun at one time. Right, I'm having fun now.

Thanks for any input.
Alex

They key is your +10V reference. It's at +7.3V. It originates from the unregulated +15V on the A2 board.

Here's a thought....are you sure you connected the jumpers from the AC line filter to the A2 board correctly? If you scrambled them the A2 board may think it's connected for 120V which would explain the low voltage.

[AMR Labs]

They key is your +10V reference. It's at +7.3V. It originates from the unregulated +15V on the A2 board.

Here's a thought....are you sure you connected the jumpers from the AC line filter to the A2 board correctly? If you scrambled them the A2 board may think it's connected for 120V which would explain the low voltage.

Hi Med,

I am on 120VAC mains. And yes I would be quite sure that the AC input cables from the line filter and the fuse holder are securely connected to J204 and J205 which are located further towards the top of the board in comparison to the remaining two tabs where the voltage selector switch goes. I measured about 150V (at J231A/B) across each of the new 330uF 250V main input filter caps, total a bit more than 300V, so there must be a good input connection wouldn't you say? I was close to leaving in those original Sprage's as they look pristine (still have to test them), but since I had the two new Nichicons on hand, replaced them as well.

Another thought occurred to me about the voltage selector switch not being securely connected to the lower two tabs JU206 and JU207, or the switch being open for some reason. If any of those two connections where loose (causing an open circuit) then the power supply would assume to be on 240V but only getting 120V and a similar low-volt situation like now might arise. But I just checked continuity of the voltage selector switch from the tip of the two terminals on the wires that go onto the PS and there is good continuity all the way.

I now once again have the PS outside of the scope and on the bench.

BTW did you ever need to build that test load they describe in the service manual to troubleshoot any of your your power supplies? It allows to run the PS without T1060 the primary output transformer or the switching transistors being part of the circuit by just opening a jumper (W1060) next to the transformer. But first I need to have the proper load and I don't have the specified resistors on hand.

[AMR Labs]

Ya gotta thank the designers for putting 30 ohm current limiting resistors in there. 
Resistors might be toast but at least you have the traces left. 

The resistor along with the series cap is just a damper for any incoming spikes/surges. Is known as a "snubber" circuit. In this case the resistor just allows the cap failure to happen in relative slow motion and that is why not even the main AC fuse bothers to blow. With a short in the cap the resistor will slowly hara-kiri itself, but in the end its not a very useful sacrifice, other than preventing maybe a bit louder cap pop. In other circumstances I'm sure the fuse would quickly open before any damage is done to the board traces.

[med6753]

I now once again have the PS outside of the scope and on the bench.

BTW did you ever need to build that test load they describe in the service manual to troubleshoot any of your your power supplies? It allows to run the PS without T1060 the primary output transformer or the switching transistors being part of the circuit by just opening a jumper (W1060) next to the transformer. But first I need to have the proper load and I don't have the specified resistors on hand.

No, I haven't had the need to build up an external load to run the PSU on the bench. I've re-capped two 2465's and I guess I've been lucky in that both of them powered up with no issues.

[AMR Labs]

UPDATE: I found a problem and now the power supply is working again. But I am being greeted now by a 04 11 error message which indicates a faulty cal constant checksum. Maybe the FRAM did not like the lower power supply voltages or spikes etc. When I swapped out the old NVRAM I also programmed a fresh one and put it away just in case the FRAM would not work out, plus I also have the original 1990 NVRAM which should be still ok. Guess I could just swap in that new programmed NVRAM to confirm if the error goes away, and then try to reprogram the data back into the FRAM.

What happened with the power supply? Well as said I had double/triple checked all caps, but... only against my OWN NOTES which I had taken prior to start removing and replacing caps one by one. Turns out that in the case of C1220 and C1240 I read 10uF 100V but instead wrote down 100uF 10V!! Then when it came to replace those two I grabbed a bag with two extra and somewhat different looking 100uF 25V separate from the other same value/volt caps that I was correctly using for the other spots. So I figured I had ordered those two extra ones just to "upgrade" those pesky outdated "100uF 10V" units up to 25V. Surely enough found another bag with the remaining 10uF 100V ones. I ordered these parts many months ago and lost track of some details of what was destined for which cap replacement. Live and learn from your mistakes.

Found out about the mistake after I left the power on for a few minutes and heard another pop. Upon inspection C1220 had vented its top. That 25V cap was obliviously pulling down the 87V rail. Oooops...

UPDATE 2: Happy to report that I just swapped out the FRAM for the old original 1990 NVRAM, and the error code went away. Will try to erase and reprogram the FRAM a bit later see how that goes, otherwise will just order a new one.

UPDATE3: just reprogrammed the FRAM with backup data and put it back into the scope, its once again working fine.
Time to put the cover back on.

[med6753]

Good deal on getting it sorted out.  It is so easy to mix up or install capacitors backwards. Done it myself several times but on other projects.

[AMR Labs]

Yeah I'm happy this episode is over. On the plus side I could now easily get that power supply in or out of the scope in a minute or two.
Still have to eventually replace those last 4 film caps: 2x 2200pf 250VAC, 1x 0.01uF 250V, and 1x 0.056uF 250V on the inverter board.
The 2200pf and 0.01 look like Rifas and are already showing a bit of craze.

BTW one of the 15 ohm resistors is completely open circuit, and has a small surface crack on the side.

While I was in the scope also replaced one 100uF 25V cap on the A9 HV Supply board which is said to be very important.

Some pictures included.

[BravoV]

UPDATE: I found a problem and now the power supply is working again. But I am being greeted now by a 04 11 error message which indicates a faulty cal constant checksum. Maybe the FRAM did not like the lower power supply voltages or spikes etc. When I swapped out the old NVRAM I also programmed a fresh one and put it away just in case the FRAM would not work out, plus I also have the original 1990 NVRAM which should be still ok. Guess I could just swap in that new programmed NVRAM to confirm if the error goes away, and then try to reprogram the data back into the FRAM.

1st, congratulation ! 

So the problematic one is the new FRAM which was normal before ?

If the voltage rails were the culprit, this is important reference.

Thanks for sharing your journey btw. 

[AMR Labs]

So the problematic one is the new FRAM which was normal before ?

If the voltage rails were the culprit, this is important reference.

I did not replace the FRAM, just reloaded the data from the backup file with the GQ-4X4 programmer and it was again good to go.

[factory]

Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available? 

(Attachment Link)

David

Well I asked RS and they claim the part number doesn't exist, even though you can add it to the quick order box here https://uk.rs-online.com/web/ which gives the error pictured (also provides the details they can't find).
Neither RS or Farnell in the UK can supply a 1uF non-polar capacitor (CPC only have no-name brand), so I'm left with the choice of trying to buy the Nichicon part from RS Germany or from reseller on ePay, or to use a film capacitor which I have some of.


I've already found all the other parts or equivalents at RS or Farnell for the four 24x5 scopes I have, I've chosen not to use Kemet for any of the X2/Y2 capacitors and found Farnell have the LTC-7PN lithium battery for the A5 board in the 2465B.
Also I've already got a stock of 4.7uF 35V tantalum bead capacitors for replacing the original 10V part.

The only part I've not looked for yet is the mains IEC filter unit, some people have said these can smoke too, I'm curious as to which ones can fail as I'm sure they must have used a few different brands for this part.

David

[AMR Labs]

Anyone else had problems trying to get the 1uF Bipolar capacitors (UEP1H010MDD RS part #5232678) from the list, the UK site says they are unavailable, yet other global RS sites say they are available? 
David

Well I asked RS and they claim the part number doesn't exist, even though you can add it to the quick order box here https://uk.rs-online.com/web/ which gives the error pictured (also provides the details they can't find).
Neither RS or Farnell in the UK can supply a 1uF non-polar capacitor (CPC only have no-name brand), so I'm left with the choice of trying to buy the Nichicon part from RS Germany or from reseller on ePay, or to use a film capacitor which I have some of.
.....

If it is of any help I used Mouser PN 647-UMP1H010MDD1TP for the 1uF NP caps, currently it shows 2,968 in stock.

https://www.mouser.com/ProductDetail/Nichicon/UMP1H010MDD1TP?qs=%2Fha2pyFadugmOnc%252BigsU4z5Jp%252BINWyYVLC%252B8cvmeus63yOAeljh67w%3D%3D

I have never dealt with the sources you mention, and I know you are on "the other end of the pond" but I would suggest start dealing with top tier suppliers, and there will be no more headaches.

[factory]

Thanks for the alternate part, but unfortunately RS & Farnell haven't got those either.
I've now ordered most of the parts from RS components (used to be able to buy from Allied in the US through them) and Farnell (aka Newark in the US, now both part of AVNET).
I'm going to see if I can order the 1uF NP from the German part of RS, but not tonight as it's late and looks like I need to register with them.

Also going to have a look at the IEC filter at the weekend, forgot to photo it. 

David

[AMR Labs]

David this might be a silly question to ask, but being in the UK why don't you just place your order direct at Mouser USA? It should be straight forward unless there is some detail I am not aware of. Mouser even has an European branch at https://eu.mouser.com/

[factory]

Not a silly question at all, firstly they won't sell the battery for the A5 board (restricted) so I had to use Farnell as they were the only supplier I could find for the UK, secondly I had some other parts I wanted from RS so I chose them too.

We did use Mouser & Digi-key at work a lot, but they were paying the extra for the international shipping.
The shipping for a pack of ten 1uF NP caps is four times the cost of the parts, I don't want to pay that, so unless I can find something else I want from them to meet the minimum for free shipping I won't be buying from them.

David

P.S. Hopefully most of the packages will arrive tomorrow, I'm keen to get that back-up battery replaced ASAP.

[AMR Labs]

Ok David understood and thank you for the clarification. But if what you are saying is that to bring in about $5 worth of capacitors you have to pay around $20 shipping, I think it is still manageable. A as long as it is small amounts like these I for one in the same circumstances would still go for it just to solve the situation, specially as you say if you could add in some more parts to make it worth the cost. But if the shipping numbers get out of control then I'm definitively with you. Oh and then I assume that even if you place your order through Mouser EU the parts are still shipped from the US?

In any case I hope you get your parts in soon and good luck with the scope repair/restoration, most of us here have been through it in varying degrees and almost always end up with success and the satisfaction of having restored a very nice instrument, plus the added knowledge gained in the process.

[martinr33]

A couple of notes on a 2467b repair - graticule bulbs and SRAM.

1) To replace the graticule bulbs:
      - remove the four knobs under the CRT. They just pull off. Be careful.
      - Pop the cover strip on the top edge and use a T10 to remove the screws there.
      - remove the four T10s on the bottom edge, including the two in the feet. The feet will come off, don't lose them.
      - The entire front cover now comes off, exposing the metal CRT surround.. There is a plastic shield that comes loose and is easy to lose.
      - Remove the 8 T10s holding the heavy steel CRT guard in place.
      - Lift off the plastic light bulb cover. This is a thick, shaped acrylic strip.
      - Now, you can lift up the bulb strip. It is wired into the scope, but you can work on it from here.
      - Replace the three bulbs and reassemble. Don't forget the plastic shield.

This job is pretty quick, and you don't have to pull the case.

2) Replacing the SRAM.
My experience with these parts is that they can sometimes get corrupted in handling. I like to pull all pins except ground (14) and ~CE (20). Then I pull CE, and then ground. I think this approach keeps the RAM locked off until the very last minute. Then you can dump it with your TL866 or whatever.
 
My scope has 25000 hours on it, but the display looks unblemished. I think this unit probably just sat powered on in a lab. The 267b times the display out after a few minutes, so there's no burnin. Capse are next.

These are very fine instruments. Obviously, modern digital scopes surpass them, but the 400MHz analog system is amazing.

[AMR Labs]

A couple of notes on a 2467b repair - graticule bulbs and SRAM.

1) To replace the graticule bulbs:
      - remove the four knobs under the CRT. They just pull off. Be careful.
      ........

These knobs are a two part insert and cap and sometimes they are notoriously difficult to pry off after many years of being in place. I had so far no need to remove them but  if they feel stuck and hard to pull the recommended procedure to avoid damaging them seems to be to carefully warm them up with a hot air gun. If they still won't budge then gently pry from the back of the knob using needle-nose pliers set around the shaft and slightly open just enough so each side of the pliers will fall behind on opposite sides of the knob skirt, then pull off with careful leverage against the front panel.

[factory]

Ok David understood and thank you for the clarification. But if what you are saying is that to bring in about $5 worth of capacitors you have to pay around $20 shipping, I think it is still manageable. A as long as it is small amounts like these I for one in the same circumstances would still go for it just to solve the situation, specially as you say if you could add in some more parts to make it worth the cost. But if the shipping numbers get out of control then I'm definitively with you. Oh and then I assume that even if you place your order through Mouser EU the parts are still shipped from the US?

Mouser do have a UK website too, but as far as I know there is no stock held in Europe, all the parts come from the US and I don't want to give FedEx FedAxe £12 to ship a few small low value parts, also I'd rather order parts locally (RS have free shipping on any UK order).

Anyway I solved the problem with the "findparts" advert that sometimes appears at the top of the forum, it found what I couldn't on the RS website  , a bulk pack of the 1uF non-polar capacitors, the rest will go in my spares stock. 

David

[Satbeginner]

Hi,

I have an 2467B that has that slight flickering of the intensity as well...
Recap already done, all voltages rock steady, but still.
Must be something with these MCP intensity amplifier CRT's.

None of my 2565, 2465A or 2465B's have this.

Good luck, un saludo,

Leo