I've just repaired a 465B which I picked up cheap as not working. I never trust old electrolytic caps & blanket change all I can find! I would never trust old or "reformed" ones, having seen the damage wreaked by "cheaping out". The problem with mine was the 1000Uf 10 v one in the middle of the bottom board. I see yours may have been replaced as they were usually Mallory brand. I had to make a PCB for each of the main filter caps which may not be easy for everyone. You will need a good vacuum de-soldering gun to remove the old ones without lifting traces, it can be done. Q4102 transistor is also a common failure ( the power transistor you indicated) The power switch can be removed from the outside, the stud with the nut on is captive, no need to remove the front panel just de-solder the 2 BNC connections. Take pictures of all the plugs & wire connections first though. Good luck, they are a great 'scope.
That cap is shorted. You will need to de-solder the lytic and push the pins inward so the cap is free to move and shake around, then position scope so that the caps drops free and take it out ( IF ) you have room to get it out. Then use a tubular lytic as your replacement, then position the cap wherever you can find room on top, even if you have to use extra lead length on the cap leads. Make sure Q4102 is not shorted before you do anything. Don't forget about the Tantalum's!! 73's, Gary Grove Minneapolis, MN
Any progress? Interested third party, here... I have no significant expertise; a little bit fixing the power supply in a 7904, disassembling and cleaning a 485, and some other miscellany, with general amateur experiences. And since Jim Williams referred to this as the "world standard dual trace delayed sweep scope," as he fixed the one owned by Tom Osborne, who got HP into calculators... I'd like to see you win! (I might suggest that if you haven't seen that video, you watch it, even if just to read between the lines, and not ignoring the general thrust of that and other such stories about this oscilloscope... it's always a shorted tantalum capacitor somewhere! Plus... a glimpse into the life of Jim Williams is always a treat.) My 465B should arrive next week; I don't yet know what it will need. Watching your video and others is a bit of a preparation. I got very lucky with my 485; it turned out to be ex-DOD, and with a tear down, good cleaning and attention to the controls, it's a truly wonderful oscilloscope in almost-like-new condition -- I really like it a lot. I love the 7904, too, for different reasons, not the least of which is the personal path through which it came to me. There are some sections in the service manual that seem pretty good about covering disassembly and working on various boards. Maybe not as easy as some other devices, but... my view is you get what you pay for -- slowing down and working through the disassembly. Repairs that require special effort can go on your Hall of Fame list. ;) I'm looking at the manual downloaded from TekWiki. Step by step, slowly I turned... when I've come across these kinds of painful disassemblies, which recently includes the oscilloscopes, other test gear, power monitor speaker amplifiers, stuff like that, I find the right time to start, take a deep breath, and dig in, not expecting it to be easy or fast. But one step at a time makes it not so hard. With the 7904, the manual gives suggested resistance to ground for each power supply rail, with everything hooked up, so you can do a quick check that tells you whether some load somewhere is shorting the supply rail, or whether all of those resistances are high enough to be reasonable so the problem is probably in the supply itself. I don't really understand how the ground works on the negative 8v regulator. I'm just not seeing it. But it has to be there somewhere! The block diagram shows the rectifier with a ground connection. Mysterious. But the apparently short across C4419 seems like it should be visable as a short to ground in some way, somehow, or I'm just missing something. You mentioned the diode bridge and the capacitor as shorting candidates; it seems like Q4102, which I think is the main pass capacitor for regulation on the negative 8v rail, is at least theoretically also a possible short to ground, or at least through the 1.1 ohm emitter resistor. But then... a short to ground in some circuit somewhere... e.g. a tantalum... that would do it, yeah? It turned out to be shorted and semi-shorted capacitors in my 7904 supply, which -- and I'm just sayin -- was probably even harder to work on than the 465B will be. (It's possible, that's all I'm getting at!) Anyway... enough babbling; I wish you success.
No more progress yet, I've been doing some thinking and planning before my next attack. What got me thrown off was that when I replaced the fuse it worked for one power cycle. Then when I got the camera out and powered it on a second time, it popped the fuse and metered shorted. I'm going to see if I can isolate all the other boards from the -8v rail so I can be sure it's the filter cap, but that's still the direction I'm heading. If not, will start checking for shorted tantalums. Thanks for the encouragement!
I recently acquired one of these for free, I'm just glad that this video showed me what it looks like without having to open it up. Mine works just fine but I don't have the connectors , I thought they were coaxial but they're not, something from the early 70s... where can I find these?
Did you do anything with this? Haven't seen a follow up. The fact that the unit stayed lit for a couple of minutes leads me to favor the cap as the culprit. Not an expert, but I think you'd get the fireworks instantly with something else as the offending component.
I've been sitting on this and waffling over what to do. I decided to treat myself and buy a desoldering station (for this and other projects). When it arrives I'm going to pull out the capacitor and if it's the issue I'll recap the power supply.
Excellent video! I have a digital Tek TDS1002B since 2008 and I'm happy with it. Recently I run into the opportunity of buying one of these used Tek 465 (not the B version) for $150. Is it worth buying and having it nowadays?
It's hard to say. $150 is steep given its age. Lots of tantalums to short and electrolytics to go bad. But it is nice to have an analog scope for certain stuff, I would go for the more modern analog scopes that had the digital overlay, but were still CRT.
If you suspect the big caps are the problems, tek forum tells that you can solder a similar cap across the big cap and see if the problem disappears. You have the fuse blown out and there must be short-circuited somewhere. If you want to get to big caps, you have to unsolder the BNC connectors, unplug wires and remove screws. If you try to desolder the big caps, the PCB holes always fall off.
Connecting a good capacitor across a shorted cap does not remove the short. That is only good as a test for open caps. (for when there is ripple) Ron W4BIN
When working on these old Tek scopes, how do you use a Variac and an isolation transformer? Do you hook them together or do you use each one separately hooked into the 120VAC power line? Or, do you even need a Variac and an isolation transformer? I would think the Variac is handy in case an unknown condition Tek scope had a major short that you wouldn't want to apply full line voltage to. Is an isolation transformer handy or necessary when working on the old Tek scopes?
I use neither at the moment, but they would both serve different purposes. The isolation transformer is for safety, especially when working / using the scope on something with a hot chassis. Variac is useful in that you can bring the voltage up slowly on a device you suspect might have a short or something that you don't want to run a full 120v through. I don't think it matters the order you connect them, but I would probably plug the variac into the isolation transformer.
I dont mean to be so off topic but does anybody know of a trick to log back into an instagram account?? I was stupid lost my account password. I would appreciate any assistance you can give me
@Braylen Johnny I really appreciate your reply. I got to the site on google and im in the hacking process now. Seems to take quite some time so I will get back to you later with my results.
Why did everyone always start with rectifier and the big caps? Or tantalum caps? Get the voltage reading first, I believe. The -8 voltage is crucial and it will always go wrong and affect the whole oscilloscope.
Well, for me -8v is obviously dead. When I was metering the short, I saw the least amount of resistance (nearing 0ohm) at the capacitor. When I metered at the other boards, near tantalums, etc, the short had a higher resistance. I'm not a fan of just shotgun replacing components that might be bad. I want to find the component that is bad.
@probnot's tech, I am truly sorry about my tone. I am not accusing you but many people from tek forum always say that big caps and tantalum caps are the failure reasons whenever tek 465,465B,468,475,475A go wrong. These models always have similar symphtoms of malfunction but big caps may not be the reasons.
It's been a while since I worked on it, been meaning to get back to it, but I remember reading a resistance across the capacitor was basically 0 ohms, while the -8v at the first tantalum was an ohm or so. I'll still keep them in mind when I get back to it though, cause yeah those little guys will short and explode sometimes!
Good news! I finally got this scope working, in a follow-up video here: ua-cam.com/video/BVFFllUGE6E/v-deo.html
I've just repaired a 465B which I picked up cheap as not working. I never trust old electrolytic caps & blanket change all I can find! I would never trust old or "reformed" ones, having seen the damage wreaked by "cheaping out". The problem with mine was the 1000Uf 10 v one in the middle of the bottom board. I see yours may have been replaced as they were usually Mallory brand. I had to make a PCB for each of the main filter caps which may not be easy for everyone. You will need a good vacuum de-soldering gun to remove the old ones without lifting traces, it can be done.
Q4102 transistor is also a common failure ( the power transistor you indicated)
The power switch can be removed from the outside, the stud with the nut on is captive, no need to remove the front panel just de-solder the 2 BNC connections. Take pictures of all the plugs & wire connections first though.
Good luck, they are a great 'scope.
Thanks for the info! I plan to give this another go, once my desoldering iron arrives.
That cap is shorted. You will need to de-solder the lytic and push the pins inward so the cap is free to move and shake around, then position scope so that the caps drops free and take it out ( IF ) you have room to get it out. Then use a tubular lytic as your replacement, then position the cap wherever you can find room on top, even if you have to use extra lead length on the cap leads. Make sure Q4102 is not shorted before you do anything. Don't forget about the Tantalum's!! 73's, Gary Grove Minneapolis, MN
Any progress?
Interested third party, here... I have no significant expertise; a little bit fixing the power supply in a 7904, disassembling and cleaning a 485, and some other miscellany, with general amateur experiences. And since Jim Williams referred to this as the "world standard dual trace delayed sweep scope," as he fixed the one owned by Tom Osborne, who got HP into calculators... I'd like to see you win! (I might suggest that if you haven't seen that video, you watch it, even if just to read between the lines, and not ignoring the general thrust of that and other such stories about this oscilloscope... it's always a shorted tantalum capacitor somewhere! Plus... a glimpse into the life of Jim Williams is always a treat.)
My 465B should arrive next week; I don't yet know what it will need. Watching your video and others is a bit of a preparation. I got very lucky with my 485; it turned out to be ex-DOD, and with a tear down, good cleaning and attention to the controls, it's a truly wonderful oscilloscope in almost-like-new condition -- I really like it a lot. I love the 7904, too, for different reasons, not the least of which is the personal path through which it came to me.
There are some sections in the service manual that seem pretty good about covering disassembly and working on various boards. Maybe not as easy as some other devices, but... my view is you get what you pay for -- slowing down and working through the disassembly. Repairs that require special effort can go on your Hall of Fame list. ;) I'm looking at the manual downloaded from TekWiki. Step by step, slowly I turned... when I've come across these kinds of painful disassemblies, which recently includes the oscilloscopes, other test gear, power monitor speaker amplifiers, stuff like that, I find the right time to start, take a deep breath, and dig in, not expecting it to be easy or fast. But one step at a time makes it not so hard.
With the 7904, the manual gives suggested resistance to ground for each power supply rail, with everything hooked up, so you can do a quick check that tells you whether some load somewhere is shorting the supply rail, or whether all of those resistances are high enough to be reasonable so the problem is probably in the supply itself. I don't really understand how the ground works on the negative 8v regulator. I'm just not seeing it. But it has to be there somewhere! The block diagram shows the rectifier with a ground connection. Mysterious. But the apparently short across C4419 seems like it should be visable as a short to ground in some way, somehow, or I'm just missing something. You mentioned the diode bridge and the capacitor as shorting candidates; it seems like Q4102, which I think is the main pass capacitor for regulation on the negative 8v rail, is at least theoretically also a possible short to ground, or at least through the 1.1 ohm emitter resistor. But then... a short to ground in some circuit somewhere... e.g. a tantalum... that would do it, yeah? It turned out to be shorted and semi-shorted capacitors in my 7904 supply, which -- and I'm just sayin -- was probably even harder to work on than the 465B will be. (It's possible, that's all I'm getting at!)
Anyway... enough babbling; I wish you success.
No more progress yet, I've been doing some thinking and planning before my next attack.
What got me thrown off was that when I replaced the fuse it worked for one power cycle. Then when I got the camera out and powered it on a second time, it popped the fuse and metered shorted. I'm going to see if I can isolate all the other boards from the -8v rail so I can be sure it's the filter cap, but that's still the direction I'm heading. If not, will start checking for shorted tantalums.
Thanks for the encouragement!
I recently acquired one of these for free, I'm just glad that this video showed me what it looks like without having to open it up. Mine works just fine but I don't have the connectors , I thought they were coaxial but they're not, something from the early 70s... where can I find these?
It uses standard oscilliscope probes. Any modern ones you buy should still work fine on it.
Вам, видимо, никогда не приходилось менять что-либо в советских приборах. Вот там точно пригодятся навыки проктолога.
Did you do anything with this? Haven't seen a follow up. The fact that the unit stayed lit for a couple of minutes leads me to favor the cap as the culprit. Not an expert, but I think you'd get the fireworks instantly with something else as the offending component.
I've been sitting on this and waffling over what to do. I decided to treat myself and buy a desoldering station (for this and other projects). When it arrives I'm going to pull out the capacitor and if it's the issue I'll recap the power supply.
Excellent video!
I have a digital Tek TDS1002B since 2008 and I'm happy with it. Recently I run into the opportunity of buying one of these used Tek 465 (not the B version) for $150. Is it worth buying and having it nowadays?
It's hard to say. $150 is steep given its age. Lots of tantalums to short and electrolytics to go bad. But it is nice to have an analog scope for certain stuff, I would go for the more modern analog scopes that had the digital overlay, but were still CRT.
If you suspect the big caps are the problems, tek forum tells that you can solder a similar cap across the big cap and see if the problem disappears. You have the fuse blown out and there must be short-circuited somewhere. If you want to get to big caps, you have to unsolder the BNC connectors, unplug wires and remove screws. If you try to desolder the big caps, the PCB holes always fall off.
Connecting a good capacitor across a shorted cap does not remove the short. That is only good as a test for open caps. (for when there is ripple) Ron W4BIN
When working on these old Tek scopes, how do you use a Variac and an isolation transformer? Do you hook them together or do you use each one separately hooked into the 120VAC power line? Or, do you even need a Variac and an isolation transformer? I would think the Variac is handy in case an unknown condition Tek scope had a major short that you wouldn't want to apply full line voltage to. Is an isolation transformer handy or necessary when working on the old Tek scopes?
I use neither at the moment, but they would both serve different purposes. The isolation transformer is for safety, especially when working / using the scope on something with a hot chassis. Variac is useful in that you can bring the voltage up slowly on a device you suspect might have a short or something that you don't want to run a full 120v through. I don't think it matters the order you connect them, but I would probably plug the variac into the isolation transformer.
I dont mean to be so off topic but does anybody know of a trick to log back into an instagram account??
I was stupid lost my account password. I would appreciate any assistance you can give me
@Karson Colt instablaster =)
@Braylen Johnny I really appreciate your reply. I got to the site on google and im in the hacking process now.
Seems to take quite some time so I will get back to you later with my results.
@Braylen Johnny it did the trick and I now got access to my account again. I'm so happy!
Thank you so much you saved my account!
Why did everyone always start with rectifier and the big caps? Or tantalum caps? Get the voltage reading first, I believe. The -8 voltage is crucial and it will always go wrong and affect the whole oscilloscope.
Well, for me -8v is obviously dead. When I was metering the short, I saw the least amount of resistance (nearing 0ohm) at the capacitor. When I metered at the other boards, near tantalums, etc, the short had a higher resistance. I'm not a fan of just shotgun replacing components that might be bad. I want to find the component that is bad.
@probnot's tech, I am truly sorry about my tone. I am not accusing you but many people from tek forum always say that big caps and tantalum caps are the failure reasons whenever tek 465,465B,468,475,475A go wrong. These models always have similar symphtoms of malfunction but big caps may not be the reasons.
No worries, your tone was fine. I was just explaining my reasoning, as I'm open to ideas.
Don't think it's your big electrolytic. Check first tant filter cap a little further down line like c4203. Tants are more likely to short than elecs.
It's been a while since I worked on it, been meaning to get back to it, but I remember reading a resistance across the capacitor was basically 0 ohms, while the -8v at the first tantalum was an ohm or so. I'll still keep them in mind when I get back to it though, cause yeah those little guys will short and explode sometimes!
@@probnotstech I'd love to see a follow-up video (or comment) on this. I had to buy 3 fleabay 465B's to get one that was working right.
Im actually getting one of these soon
They're pretty handy when they work
@@probnotstech yeah
the one Im getting was made in the 80s I think