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Dave saved this classic from the dumpster, a HP 1740A 100MHz dual channel analog oscillocope from the mid 1970's.
It wasn't supposed to be working so this is a look at the problem, a mini teardown, and some basic PSU troubleshooting.
Update: Even after 4 hours it still doesn't fail with the covers off. So likely to be some sort of thermal issue as suspected.
Forum: www.eevblog.com/forum/blog/eev...
Original HP Journal article on the HP1740A:
www.hpl.hp.com/hpjournal/pdfs/...
Acknowledgments
The 1 740A design group was led by Stan Lang until the start of pilot production when he transferred to another project. The design team included Jim Garner, mechanical design including the vertical
attenuator switch, Eldon Cornish, who designed the horizontal section, and Van Harrison who designed the CRT circuits, power supplies, and gate amplifier.
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Пікірлер: 298

@youbecha64 8 жыл бұрын

That is the most realistic type of troubleshooting...the kind where it won't fail while you watch it.

@EEVblog 8 жыл бұрын

+youbecha64 Yup, if I had a dollar for every time it's happened...

@EETechs 8 жыл бұрын

+EEVblog You need to get a variac and set it to the line voltage as shown on your picture to verify that the line voltage drop did not cause those output voltages to dip.

@pepper669 8 жыл бұрын

+youbecha64 In demoing, I call this the negative demo effect.

@colejohnson66 5 жыл бұрын

In programming, a bug that doesn’t appear when you try to debug is called a Heisenberg

@GoldSrc_ 8 жыл бұрын

What's not to love about analog oscilloscopes, that phosphor glow is just beautiful. You have to fix this one Dave. Also, I laughed when you said "reboot it" lol.

@michaelhawthorne8696 8 жыл бұрын

I can't believe your timing with uploading this video Dave. Last week I dragged out of mothballs from the back of the factory where I work the very same CRO. It had been sitting there for 15 years or so. It was put there long before I was employed there. It wasn't wrapped up or protected in any way so everything looked crusty, rust on the BNC's dirty to look at. It past the PAT so I turned it on. Boy was it ill, Problems with the main Time Base, Vertical problems. Not quite like what you were getting Dave but felt it would need a lot of work to put it right. The traces would initially jump around even if you breathed on the control knobs. After awhile things started to settle a bit but never really stabilised. I attached a spectrum analyser to it, an SA450B which was also dragged out of mothballs and it produced a reasonable trace. It was rather unstable though and was inconsistent if you changed a Time Base setting. The general condition and the time needed to sort it out were prohibitive, It unfortunately had to make an appointment to see it's maker. Judging by how old it was, it will probably meet them too. lol Nice video though, thanks for that.

@ebayscopeman 7 жыл бұрын

HI Dave, I have a mint one of these that my best friend and TE aficionado Ken Eastep left me in his will. I was with him when he ordered and took delivery of it from HP in the late 70's. I always wondered if his wife knew what he paid for it (you could buy most of a new car for the price of a 1740A). The 1740A was designed to compete with the Tektronix 465. Somewhere I even have the HP shipping box. A great scope. Now that you have it working check the risetime of the scope using a fast rise source. Chances are by now it is marginal. Fix this by massaging the coaxial delay line. The plastisizer in the jacket of the coax reacts with the silver and causes issues. Moving it around will cure this ill. On your bridge rectifier failure I had one of them fail in the +8V supply of a Tek 475 in exactly the same fashion, so though rare now I know of two!! Great job on a classic analog scope! How about that flood gun scale illumination! Worked great for Polaroid pictures. P.S. Kenny would have loved your teardowns, repairs and videos and also would be right up to speed with current electronics development. He was born 30 years too soon!

@KennethScharf 8 жыл бұрын

I have two TEK's, a 454, and a 465. The 465 I got off Ebay from a seller that professionally reconditions them. IIRC I paid under $400 for that one. I've had my 454 for 30 years now, I bought it from a former employer who was auctioning off outdated test equipment to the employees. I paid under $250 for it at time, and they threw in a viewing hood, several probes, and a scope cart!

@pepe6666 7 жыл бұрын

this is a great video. i like how even when ya dont fix it, its still an adventure learning. what a ripper piece of equipment.

@dhpbear2 6 жыл бұрын

28:30 - David, you continue to amaze. I love the 5-DVM setup!

@PeterWalkerHP16c 4 жыл бұрын

5:41 ... that folks is why HP went from three guys in a garage to a loved and trusted, massive multinational instrument company.

@AndyHullMcPenguin 8 жыл бұрын

1st golden rule, measure voltages, 2nd golden rule, clean the switches. 3rd golden rule suspect the capacitors.

@AndyHullMcPenguin 8 жыл бұрын

+Andrew Hull .. and start with the PSU power plug and those inter-board connectors.

@garydevlin6327 4 жыл бұрын

recently found your vlog, I used to have 1 of these on my bench back at Marconi when I worked in service and cal, also repaired and cald many a hp unit among others, keep up the grt work, really enjoy your channel.

@brainndamage 8 жыл бұрын

Well, I don't know if you can see it, but it seems that all the rails are deriving their reference fron the +15V rail, so anything wrong with the 15V rail would logically effect all of them. The +15V is the only one deriving its own reference (U1 pins 3 and 4)

@brainndamage 8 жыл бұрын

So it's likely either something loading down the +15 or the power supply itself. I'd start by measuring the current draw on it, also disconnecting its filter cap and temporarily connecting a new one in, just so you eliminate it as a problem. I've once replaced a sprague with intermittent internal shorts. And look out for tantalums.

@UniqueDesignsInc 8 жыл бұрын

Another common failure with the 1700 series is the gold interconnect headers that connect the various boards. They commonly develop hairline cracks and what looks like oxidation around the gold plaited pins, where they contact the solder. I have had positive results when the old solder is removed and the pins are cleaned, then re-soldered with new solder. The horizontal time-base pcb's flex a little when changing the time-base setting and this may be why it's more common on them. Most of the IC's are standard TTL parts with the exception of the (2) Horizontal ASIC's (Gold Plated), (2) White Ceramic ASIC's, one near the CRT and one on the bottom PCB under the vertical calibration shield. One other common chip prone to fail is the 14 pin DIP chip on the Focus/Intensity/Beam Finder PCB, (HP 1821-0002) which is a CA3045 Transistor Array.

@dsmbaby 8 жыл бұрын

I absolutely share your enthusiasm for that exemplary operating manual! I wish I had something that thorough for the Lecroy scope I've been playing with lately.

@rusty- 8 жыл бұрын

I love these diagnostic videos Dave

@stonent 8 жыл бұрын

I noticed the reset light blanked out when the scope glitched and then started flickering when you had the crap jumping all over the place.

@Fractal2D 8 жыл бұрын

At 33:00 when you started to apply the heat gun to the electronics, I noticed that when you were focusing on the big long caps the black multi-meter started to dip constantly. When you pointed the heat gun away from them the black multi-meter began to rise again. I would suggest applying more heat to that area and see how low it goes and to hopefully (or not) break it again.

@EEVblog 8 жыл бұрын

+DiFractal Didn't notice that, will have to have a look, thanks.

@MrCapacitator 8 жыл бұрын

+DiFractal A couple of hundred millivolts only on a 120V line is nothing to worry about.

@ernststavroblofeld1961 8 жыл бұрын

+EEVblog 1970s technology is nice, but when are you going to make the next Samsung LCD TV repair video and nail down that bloody fault?

@stonent 8 жыл бұрын

+MrCapacitator Yeah, but if he continues to heat and it continues to drop down, something else may reach a drop out point.

@kyoudaiken 8 жыл бұрын

+Ernst Stavro Blofeld That Samsung is busted. Like most Samsungs.

@gjsmo 8 жыл бұрын

I HAVE ONE OF THESE!! This is my first scope and as a matter of fact the only working one I have. I love this thing! Wish I could afford a digital scope but I have to settle with my school's equipment if I need that capability. Still a great piece of hardware for analyzing the signals I work with. So great to see a piece of equipment I own on the channel.

@BinjKomisar11 8 жыл бұрын

Awesome video. I bought that same scope with a spare scope for parts for $70 Canadian about 8 months ago, it works great and I love it as well... Looking forward to seeing how you problem solve and deduce that sick puppy into a healthy puppy... Thanks for taking the time to make and share the vid. Thanks for all your videos, they are truly great.

@TheEPROM9 8 жыл бұрын

Looks like one you will have to come back to. Love vintage test gear.

@4IN14094 8 жыл бұрын

The manual!! It is like an old style Aircraft Maintenance Manual!(believe it or not we still have those as a backup for old aircraft.)

@martinda7446 2 жыл бұрын

Just looking back through Dave's remarkable treasure of KZfaq videos... Noticed I commented six years ago.. I just had to say I had one of these and as I looked again was struck by how beautiful this thing was. Hope Dave still has it, or it went to a good home.

@barrybogart5436 2 жыл бұрын

I just bought one today! Haven't put a funtion gen on it yet. Glad Dave worked on one.

@Oj10101 8 жыл бұрын

That scope is honeetly the most beautiful piece of engineering I have ever laid eyes upon.

@khurai111 8 жыл бұрын

That's pretty quality material for a 70's device. Metal Film resistors!!

@Kryoclasm 8 жыл бұрын

+MichaelKingsfordGray That must be why the manual looks spot on to USAF tech manuals that I used back in the day. You could have only basic electrical and mechanical knowledge; read that kind of manual and know %85 of what the engineers that designed it knew. Not only were great for working on the equipment, duh, but they also helped you learn new concepts technology on the way!

@omniyambot9876 2 жыл бұрын

@@Kryoclasm whoahh can you give an example link? That's interesting

@TKomoski 8 жыл бұрын

Looks like a vertical deflection problem, when you adjusted the trace position the vertical collapsed. You might want to look at the vertical output stage with the two wires going to the deflection plates. Your right with the case off it can cool, and operate normally. You might want to tack on a thermal probe and put the case back on and watch the temp. From what they say on the net, the vertical seems to be a common fault. Maybe apply some new thermal paste and that might do the trick. Worth a shot Dave ...

@suzesiviter6083 6 жыл бұрын

The scope has been in Australia so long the electrons are running backwards.

@solidstate90 7 жыл бұрын

THANK GOD FOR THIS VIDEO I JUST GOT A 1740A FOR 5$, TYPED IT INTO KZfaq HOPING DAVE HAD A VIDEO ON THIS BEAST

@mscir Жыл бұрын

LOL I just got one for $10 and some yard work, and it works! Got here same as you. Great guy Dave.

@sbalogh53 8 жыл бұрын

HP 1740A CRO from a dumpster? Bloody hell. You have one mighty fine dumpster in your locality. Mine only has old fish bones and other rubbish of the same type.

@Falcrist 8 жыл бұрын

Quite interesting! Did you notice that not only did all of those rails drop at the same time, they dropped by *THE EXACT SAME PROPORTION*? Every single rail you measured changed by (-20.76±0.1)%. Unless the mains flickered (and I didn't see the lights dim), I don't see how they could all drop by the exact same amount unless they all reference one of the rails. Find that rail, and you'll find the problem quickly I'll wager.

@UniqueDesignsInc 8 жыл бұрын

+Falcrist There all referenced to the 15v rail, that makes troubleshooting a problem sometimes.

@alecjahn 7 жыл бұрын

I'm curious to know, was that display bezel that same color from the factory or has it aged to that color?

@InsideOfMyOwnMind 7 жыл бұрын

I have two of these. one had a bad multiplier and the other had a bad ch 1 gain selector. So they became a box of spares and one bobby dazzler as well. I absolutely love this piece.

@MrDoneboy 4 жыл бұрын

Dave is the best at scoping it out!

@basspig 3 жыл бұрын

I bought mine new with H13 option in 1982 for 3800 dollars us. Sadly, the vertical hybrids failed and are unavailable.

@Igbon5 8 жыл бұрын

I think you got the operative words right. Wow. And beautiful.

@Maxxarcade 8 жыл бұрын

This is very similar to my 1725A. Mine was very dirty inside from being used in a garage though. I had to use De-Oxit on all of the controls, both internal and external, and also re-solder several of the header pins that connect the boards together. I also use an HP X-Y monitor from the same era. That one had a problem with a couple of the small round bridge rectifiers getting flaky.

@earx23 8 жыл бұрын

just awesome how detailed the manuals were back then. makers expected their wares to last forever! :)

@woodlandor 7 жыл бұрын

Picked one of these up for $40 a few years back. In excellent shape and works like it did 40 years ago. On/Off switch is a little dodgy at times due to wear. Not a fancy digital scope, but pretty advanced for its time.

@AdrianHiggins83 8 жыл бұрын

anyone want to recommend a inductance meter ? I bought a Model DM-9023-G thinking it was a lcr but it's a fail. thanks.

@rickshabin 8 жыл бұрын

I used these scopes in 2 workshops for 15 years in the 70s and 80s and they were extremely reliable.I liked them so much that I bought one 20 years ago and it is still working in my garage. Always start with the simple things when fault finding.Always re-solder those joints even if they look good because you can't always see the microscopic cracks. It is a crime to throw away a scope such as this.

@Murphistic 8 жыл бұрын

That problem reminds me the issue with my old crusty AT&T monitor made in 1994. Vertical positioning failed, so I only saw a thin bright horizontal line instead of picture. Fortunately, I could repair it with resoldering the joints, which lead to the main coil on the tube.

@HA7DN 3 жыл бұрын

This thing is a beauty. I'm trying to restore a 25 meg scope from ~ the same era, but from the eastern block (Hungary), and that is... Only a few PCBs, miles of wiring (all white), super-hard to access parts - but at least the documentation is kinda good. I highly respect those engineers who designed your HP for the care, and also the ones who designed this hungarian scope, because they could tame chaos itself...

@built2last31 8 жыл бұрын

mr carlson's lab blows eevblog out of the water i love mr carlson! he explains everything clearly and fixes everything he gets!!! i suggest adding him to your youtube lineup

@GoldSrc_ 8 жыл бұрын

+Joe Schmoe You can't really compare them, they both deal with different beasts, I'm sure mr carlson has also times when he can't fix stuff, but we don't get to see those, I could be wrong though.

@omfgbunder2008 8 жыл бұрын

@13:20 is that flashover from the crt gun to the flyback mesh screen?

@cheeto4493 8 жыл бұрын

Hey, that looks almost like my 1741A except mine has storage capabilities. I agree with you on the font on the knobs, very hard to read the decimal point. I ended up using a marker to bold them. Mine just has a problem with the intensity pot being touchy. Glad to see you with an Analog scope.

@SimpsonM35A2 8 жыл бұрын

I own a HP 1741A. didnt come with the manual so thats my next step to do repairs on it. seems like it wants to work but some contacts are dirty and some caps have started to leak.

@PeterBrockie 8 жыл бұрын

It kinda looks like the trace going to the diode at 27:35 might be cracked at the base of the socketed can. Could just be the angle though.

@gamerpaddy 8 жыл бұрын

how about using your thermal camera if you think its a head problem?

@Rickmakes 8 жыл бұрын

That's what I was thinking. Maybe the camera could narrow down the places he might target with the heat gun.

@EEVblog 8 жыл бұрын

+gamerpaddy Because you could be chasing countless red herrings.

@Borednesss 8 жыл бұрын

+EEVblog They would be orangish-white herrings =P

@fleuroman 8 жыл бұрын

no probes in whilst testing voltages? did you get it to fail after time with the sample on a probe?

@Starphot 8 жыл бұрын

I have the older 1710A 150MHz. I replaced the horizontal output chip on one of the channels with more discreet components. DTL logic. I still use it. Good find! I had a Tektronics 555 Quad channel with different input modules on my bench in the US Navy and a surplus one in one of the repair shops I worked for. I used a few HP oscilloscopes in my career.

@DaveCurran 8 жыл бұрын

Bad contact on the mains voltage selector, thereby dropping all secondary voltages at the same time? Or is there a common reference for all the rails (or just the the 5V rail being used as a reference for all the others), so when it drops, everything falls proportionally?

@EEVblog 8 жыл бұрын

+Dave Curran Yes, primary side was my first thought and plan of attack in the 2nd video I have half shot. I won't spoil anything...

@ethanpoole3443 8 жыл бұрын

The way it was cutting in and out, is there any chance that there is thermal protection on the voltage regulators or power supply (perhaps sensing a common shared heatsink), or even a common current sense circuit on a shared rail (such as ground) momentarily shutting things down when the total current exceeds a programmed limit? In the case of current sensing, a capacitor is often used to average out brief switching surges, but if the capacitor dries out then it may no longer properly hold off reacting to a brief switching surge that is otherwise within acceptable limits. Just some quick initial thoughts.

@TheManLab7 8 жыл бұрын

The inside of that scope is beautiful and so is the manual :)

@pnmbain 8 жыл бұрын

Great scope! I the 1742A in immaculate condition. Even came with the manual! Want to get a nice compact digital one, but this is fun to use and I have a big soft spot for the old analogue screens... Besides, haven't found much that I really NEEDED a digital one for yet.

@ele4853 8 жыл бұрын

Hello Dave! It was a trip to go through your adventure on fixing this scope. Thank you so much for posting that. I just got one myself. Unfortunately I think I have a dead vertical control, as I turned on the trace pops up I adjusted the horizontal when I tried to adjust the vertical, nothing happens, both channels dead... :-( any tip please?

@madinatore 8 жыл бұрын

Don't get fooled, those are high tech Mega Farad caps!

@TsMarinov 8 жыл бұрын

Hi Dave, I had similar HP scope with similar issue. Mine had multimeter on top with 7-segment display, the meter can be used for time measurements on the signal itself or as normal meter with external leads. Anyway, mine also had this exact issue with the power supply rails. Sadly I did find what is the problem, because it occurrence rarely, but I remember that all supply rails are referenced from the +15V rail. So if the +15V rail is overloaded and the current limit kicks in, not only the +15V rail collapses but all rails are collapsing. The problem can be overload on the +15V rail or in the PSU itself. I didn't figure it out, but may be you will have better luck. I hope this helps. Cheers!

@userPrehistoricman 8 жыл бұрын

+Tsvetan Marinov That's good info, he can focus on the boards which use +15V.

@GadgetReviewVideos 8 жыл бұрын

And out of all the comments, you had the most useful information that lead to the issue. Or at least explained why all the rails dropped together about the same percentage. Good work.

@brig.4398 8 жыл бұрын

I've seen dozens of these lately on ebay for sale, one problem is the time div switch. HP put some lubricate grease inside them at the factory. after several years it dries up and switch gets sticky. The switch has to be taken apart and cleaned.

@alejandrosobrero60 8 жыл бұрын

Hi Dave ! I've got a HP1715 200Mhz the same panel and chassis than 1740, i buyed it 4 years ago , and after cleaning all electromechanical parts it's working OK , but the multi PCBs switches of time base are a pain in the a** , once a year or so, i have to realign the knobs axis with the rotary switches and clean the contacs of the connectors between 3 daughters and mother board. Mine got PCB edge contacts, i've see that yours have a very better plastic connector between boards. TIP: Power supply is almost the same in both scopes and in the service manual says that the +15V regulator serves as reference to al other voltages in the low voltage PSU. i hope this helps.

@mcconkeyb 8 жыл бұрын

What about a winding short in the mains transformer?

@ianetalbot 8 жыл бұрын

It must have been the southern hemisphere compensation chip that had blown. Once you turned it upside-down, it worked perfectly

@RyanRockey 8 жыл бұрын

Was your flash on when you took the photo? Could the LED flash of the phone camera cause some sort of reset like xenon flash does to the Raspberry Pi?

@EEVblog 8 жыл бұрын

+Rockey Nope, hardly ever use my flash.

@drkastenbrot 8 жыл бұрын

Theres no way an LED, even below .5 watts, could cause such an issue in a well shielded oscilloscope. The LED runs at about 3 volts, a xenon at ~300 volts i think.

@smitcher 8 жыл бұрын

+EEVblog darn, see your response now... very weird that you captured the voltage dip then...

@FXGreggan. 8 жыл бұрын

Whenever you see old Sprague capacitors you should automatically assume they are bad - because they always are :)

@cboyamg 8 жыл бұрын

i was given a hp 1710b, it works without issues. is it worth anything?

@JohnSmith-lb3ge 8 жыл бұрын

Could the low voltage be causing one or more of the voltage regulators to become unstable and oscillate? I've had this problem at work with some LED indicator panels, we make a 12 volt and a 24 volt version the difference being that the 24 volt version has a 7012 12 volt regulator, now I got lazy one day and decided to test a 24 volt board with a 12 volt power supply (basically a laptop brick with alligator clips) because I had one on my bench (it was a preliminary test not a QC test) I figgered even with the dropout voltage there would still be 9 or so volts, enough to light the LED's. It worked for a short time but the reg got super hot and the thermal cut out cut in, this happend several times before I worked out the reg was getting hot and cutting out, I tried it with a 24 volt supply and it worked fine, no heat no nothing, I'm guessing with 12 volt supply that the combination of the oscillation and the capacitance and/or inductance between the reg and the supply must have boosted the voltage somehow causing the regulator to run hot

@JaySmith-cd1ln 6 жыл бұрын

Hell yeah two part movie length repair video :)

@seany1986 7 жыл бұрын

Awesome video! I calibrate Oscilloscopes! Well, it's one of the many things I test and calibrate. Nothing this old but I've worked on many HP and Agilent products. :)

@100fcab 8 жыл бұрын

In this case would wrapping it in cellophane( clear plastic ) be appropriate here to trap in the heat.

@call5sam 6 жыл бұрын

How would you go about calibrating this oscope?

@ghydda 8 жыл бұрын

Well Dave's got 5 DMMs hooked up, but I counted 6 bridge rectifiers on the schematic... What feeds of the sixth?

@shana_dmr 8 жыл бұрын

You got the prototype of "Tennis for two" video game with lightning storm simulation option package, nice! :)

@supersat 8 жыл бұрын

Dodgy mains voltage selection switch?

@SDsailor7 6 жыл бұрын

I don't know how to use a o'scope but I want to learn, can someone recommend a good video here on YT or a book? Thank You

@3Havoc 8 жыл бұрын

I picked one them up recently nice scope but I need to clean it up and fix the pannels a nice scope!

@UniqueDesignsInc 8 жыл бұрын

The small round 1A rectifiers were a common failure on these, they intermittently short and pull the transformer voltages down. I've repaired 20 - 30 of the 1700 series scopes over the years and many odd failure problems were caused by the rectifiers. The problem will happen more with the unit closed up due to the heat not getting out. I ended up adding heatsinks on top of the newly installed rectifiers to keep them cooler and haven't had any more problems since.

@danielmelendrez1616 5 жыл бұрын

"A couple" of multimeters....

@mbaker335 8 жыл бұрын

From the photo the voltages all fell to about 80% of their normal values. This has to be transformer primary side and or the transformer itself. Maybe solder in test wires taken out of a closed case so monitoring can carry on whilst the unit warms up. Transformers can get very smelly if distressed. Beautiful bit of kit. RIP. HP.

@PeterWalkerHP16c 8 жыл бұрын

The HP Way. Make a contribution to science, technology and society with innovative and quality products *_:... that are worth more to the customer than it costs us to make."_* Dave Packard.

@robmckennie4203 8 жыл бұрын

I have a bwd 521 scope (one of my prized possessions, 100mhz, true dual trace, a million knobs on the front panel, love it.) that must be at least 30 years old, and has a few of these issues, hopefully this video will help equip me to fix it.

@pelor92 8 жыл бұрын

For what is worth the 122V rail was dropping when he heated the regulators, and as soon as he lifted the "heat gun" from them it started rising again, it was slow (ten mV at a time) but steady and repetable, so maybe... we have also to consider the thermal inertia of the heat sink, it's obvious that a problem to the LDO's/regulation transistors can't be caused by 30 seconds of 100°C heat gun since the shear mass of the heatsink is sucking so much heat away from the active devices

@GeorgeTsiros 8 жыл бұрын

24:15 that 1820-1518 ic it's ceramic, right? supposedly mil-spec, but i don't see the little triangle.

@qoaa 8 жыл бұрын

that manual was printed 1 month before I was born. I was born in September 1976. a "Bicentennial" baby :-P

@nobytes2 6 жыл бұрын

Fiske Brothers Refining are still in business they are now Lubriplate Lubricants the oldest lubricant manufacturer in the USA.

@alecjahn 7 жыл бұрын

Gosh, that's a BEAUTIFUL scope (aesthetically speaking). I like my Hameg but... Dang, I gotta get my hands on an old HP at some point.

@gripper021164 8 жыл бұрын

'Dry as a dead dingo's donga'.LMAO ......Gotta love the Australian vernacular. lol.....Great vids dude, very interesting and informative......Best Regards from UK....

@shodanxx 8 жыл бұрын

Don't give up !

@KennethScharf 8 жыл бұрын

Please follow up with another video when you actually fix this! Hate to say this, but maybe you have an issue with the power transformer? Maybe an intermittent short in one of the windings? (Blow your heat gun on the tranny!) A short in ANY of the windings of a transformer will be reflected in the others! This DOES seem like a thermal effect, especially since it ain't showing up with the covers off and the thing inverted! Build yourself a heat chamber (wrap a thermal blanket around the thing!) and see what happens. When I was working at Digital Equipment in the 70's I had a board that would always fail in my lab, but it worked fine across town at another facility. I kept bringing the assembly back there to trouble shoot an they always gave it a clean bill of health. Then I realized that their lab was warmer than mine, we had real good A/C in ours. So I blew a heat gun on the board while it was plugged into an extender card and it started working! The cold spray made it fail! Turned out to be a bad I/C with an inverse thermal problem.

@necessaryevil8615 8 жыл бұрын

Isn't vintage electronics something to look at! By the way, jealous on your multimeter collection, Dave!

@lucasmun1066 8 жыл бұрын

thanks Dave. I bought Tektronix 455 for $50 us dollar to learn but i couldn't fight out what that Verneir knob did. I guess I have ways to go with electronics!

@TinkerbatTech 8 жыл бұрын

Hell, Dave. I think this is the same series of scope I was using back in the early '80s. It would work for about 15 mins, then start acting goofy. Power LED was flickering like this one. Turned out to be a cracked 1A bridge rectifier, on the side that wasn't visible. One of those small round ones. I see you've got about a half dozen of those in there. When it got warm, it would partially fail. Just something that might help? Keep on slugging! At the time, it was a really nice scope! Stu Oh, another P.S. Those stupid connectors that they used to connect the pwr tranny to the board are notoriously flaky as they age, especially with a decent amount of current thru it. (Remember having to cut those out of about 40 power supplies, and soldering the tranny right in. All issues went away. Even worse, 70's pinball machines used them for all the lighting. What a mess! stu.

@tubical71 8 жыл бұрын

If you plan a looong term use of this.....always remember these silver mica capacitors/condensers....they´re known to be very cool stuff, but they´re also known for the "silver mica desease" where the silver just dissapears from the foil, leaving just the foil formed a new insulation....Old sophisticated tube stuff suffer from this sort of grown error a lot as these SMCs are used a lot inside them...

@LEDtest 8 жыл бұрын

Did you take the photo with flash? Not that I think there will be bare die components in that thing, but maybe something else, that could be sensitive to the light in some way. It just sounds like too much of a coincidence...

@TheEternalHermit 8 жыл бұрын

Hey can you make a video on how to solder a cpu, I want to know how Ahmed (the boy with the clock) did it.

@imscuba 8 жыл бұрын

Just a few thoughts. When the fault happened, 4 things were different, only one of which was mentioned ( the lid off) The other 3: A)It was upsidown, B)There was no signal being fed into the Device, C) any tension of the Mains cord was reversed due to its orientation. All rails dropped @ same time.. any corosion on that mains plug/filter? Lose Ground Lug? I duno.. im just tossin out ideas.

@Globeglider 3 жыл бұрын

Just pick one these up, 1741A with the storage feature. But both my verniers are not functioning like yours! Fun times...

@pvc988 8 жыл бұрын

I suspect that mains transformer is dying (intermittent connection on the primary side). That would also explain that smell your friend was talking about.

@browntown52 5 ай бұрын

Lubriplate is still in business, the name is at least. No 105 engine assembly grease is a standard for mechanics.

@RossDuClair 7 жыл бұрын

Dave: I generally appreciate the trouble shooting videos you produce. On this one, you trouble shot using five DMM's. Yes, of course, you were demonstrating a problem with the power supply. Most troubleshooters are lucky to have two DMM's. May I suggest, troubleshooting on a level that does not rely on the sophisticated equipment you have on your bench?

@GrayOlson 3 жыл бұрын

7:20 "WOOOW look at this, FANTASTIC bedtime reading!" hahaha

@DarkFire515 8 жыл бұрын

Surprised it did anything at all after 35 years! Beautiful build quality, and that manual! They don't make them like this any more... As an aside, I wonder how much that cost back in 1980? Probably the equivalent of several houses :-)

@ethanpoole3443 8 жыл бұрын

At 26:43, the way they have spaced those two wires is very reminiscent of ladder line, so perhaps a balanced transmission line?

@UniqueDesignsInc 8 жыл бұрын

+Ethan Poole it is, that's the vertical differential signal from the vertical amplifiers.

@smitcher 8 жыл бұрын

Dave, did you use the flash when you took the picture?

@smitcher 8 жыл бұрын

Hoping you still have it setup and can test my photoelectric effect theory before you dismantle. Some of those chips look like the could have exposed silicon that could let in the light and possibly drag down a rail...

@EEVblog 8 жыл бұрын

+smitcher No, it's not that, and no I don't use flash on my phone.

@Alex-je6od 8 жыл бұрын

I still have the mil-spec version of that one (AN/USM-339)... Those plastic knobs are *extremely* brittle... be gentle on them, they *will* break with use.