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- เผยแพร่เมื่อ 6 ก.ย. 2020
- In this video, we look at a very old trash pulled Fluke 77 Rev L PCB. This meter uses spark gaps rather than MOVs or GDTs for it's primary clamps.
Also discussed are possible causes of high voltage, low energy transients.
Feel free to join the thread:
www.eevblog.com/forum/testgear...
An old video explaining the transients I apply:
• Programmable Transient...
The data for the meters I have tested may be found here: docs.google.com/spreadsheets/...
Answers to Frequently Asked Questions may be found here: docs.google.com/document/d/1g... - วิทยาศาสตร์และเทคโนโลยี
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That old meter did better than I expected, thanks for testing. But dont toss it, there are many collectors like me who would use it for spares at least.
I would have liked to have ran every function +/- like I normally do. Still it's a pretty good indication that the meter even as old as it is, is more robust than a lot of the ones I have looked at.
Glad to see you're okay Joe. Stay safe.
Thanks
Thank You for the video Joe!
Another great video ! That battery trick with the net adapter , learned again something new !
I have a fluke 77 that I bought back 79 new. after fixing it I still use it now,it a good meter.
Used displays for these arent made anymore, you should find one of the many folks wanting one to fix their meter, JMO.
There was a person who once wrote me asking for some parts out of one of the meters I tested. I took the time to pull the parts, package them up and ship them off free of charge to help them out. That person could not even offer a simple thank you. After this, all the meters hit the recycle bin.
The grill starter!
Although it'll probably survive that....no Uni-T lettering on this one 😁
interesting to actually see the spark gaps work
Good idea. I think we can do that.
thanks for the info and video, nice,.
She's boiling like a tea kettle, Captain. She'll not take anymore!!!
Please replace the resistor. That 77 needs to be whole.
I may replace it in order to run it through the ESD tests. If I could find a decent case, I would life cycle that rotary switch.
Thank you Joe! Trust all is well with you sir. Still have my original 77 and paid a small fortune for it sometime in the early 80's. It's good to know they can take some abuse. FWIW, mine has 3200 counts.. wonder why they didn't just make it 4000?
Hello Cliff. Good to hear you're still with us. If I had to guess, the count may have been set by the cost of the custom IC. That's something you may need to ask the original design team, if any of them are still around. There was that retired Fluke designer on Dave's site. They may be able to provide you with some accurate information on the history.
This meter, just having that little bit of protection is a huge step up from my first Fluke.
Thank you for posting this video. I was curious if the input protection in the 77 (1st generation?) was good or not. I have a 77iii that is in need of repair but not from transits. I damaged the meter trying to re-flow the U1 chip. Fluke doesn't have a replacement for it. Anyway, you also answered one of my questions with this test: how well does a spark gap compare to MOVs or GDT. Also, I would not want to have a meter near a natural gas plant trying to take measurements that have spark gap protection.
I would imagine that the electricians that work in areas like that are provided only intrinsically safe test equipment. Fluke offers so products like this. Even the fuses are sealed. Yes, an open spark gap like this would seem like a very bad idea for some applications.
Hi Joe, ever thought about a video on surge protectors? Like how to build a decent one, what kind of characteristics a high quality one should have, and testing some to destruction with your transient generator?
I have been asked about this a few times but I never understand why. I blame a lack of education but it's hard to say. Why do you feel that running an AC line surge protector on this generator would be meaningful?
Here is a good link for you to read. www.eevblog.com/forum/testgear/seanb_s-usb-charger-transient-tests/
I’ll read the thread, ok thanks Joe. Perhaps my question is more general, like what kind of tests could be done on surge protectors? But as you say, I lack education. Just curious. Thanks for your content btw.
@@cthoadmin7458 If you take the time to read that thread, I think we talk about some of the standards that are used. Read it, then let me know if you have any questions.
I think these are great meters, 70 series. I didn't like to see one on the electric chair, but good to learn from the test. They can endure a quite some abuse, and stay true for a long time. I would always trust these 30+ years old meters then the cheap "fancy" meaningless 6 digits behind the decimal point...
If your buying a 6 place beyond the decimal, most likely the amount you spend was far more than this meter, and it sits on the bench. That GMW Ultra was about as close as I show, 300k count, and current prices are about $1000.
Hello Joe! Thank's for testing this old meter, many people still use them today. What is your opinion about these old wafer range switches they use compared to the newer pcb trace ones? Any advantages or disadvantages perhaps? Price would be a disadvantage for sure I have seen new ones with different arrangement but same format for about 10 USD. Maybe an advantage (or disadvantage) is that particles from wear are not stuck on a flat surface and can be brushed away more efficient by rotating the switch? A life cycle switch test if you feel that it would be worth it? Anyway thank's for sharing and looking forward to the next video! Stay safe!
It's a good question on the switch life. I remember similar switches being used in the tuners of old TV sets and requiring constant service. This particular switch has been in service for many years and I am not sure what we could learn from running it compared with something that was NOS. If I had the case with the knob, detent spring and such, I would run it. But having the wafer free float as it is, with no support, I think would bias the data too much to be of any use. If I could find one of these meters in better condition, I would run it. I'll keep my eyes on the lookout.
@@joesmith-je3tq Fingers crossed for a bargain or a donation. The last hand held Flukes to use this type of switch where the 77 IV (later revisions changed to modern type when they started using the same main board as the 170 series) the 87 III which usually has the modern type switch but the very first revisions have the wafer type (I own one example) and the rugged and old 25 and 27 launched in 84 or 85 which remained in production until mid 2000's. Thank you for taking time to reply :-)
@@joesmith-je3tq at my workplace in january we do our anual multimeter check in case on of our fluke 77 fails i send it to you for testing this way i got mine but its to much in use to be tortured like this ;)
@@nickhetzer2744 I've had people write me about still using the Fluke 8000A at work. Some still use old analog meters. So take good care of yours.
@@joesmith-je3tq wow i didnt expected an replie but they get taken god care but they wont get repairde if they fail they are either trased or i took one home to repair also we shouldnt use them anymore we work with 600vDC at up too 400A there you need a bit more modern meter
7:14 Maybe a stupid question, but i see a ferrite bead arround the coax of the high voltage probe, why is it that there are no ferrite beads arround a normal x10 or x10/x100 probe? Does it have to do that the high voltage probe is only 500Khz rated ?
That particular high voltage probe is homemade. BW is more in the 20MHz range, not 500KHz. I've made a series of videos showing the construction and design of it. It's not uncommon to see people use Ferrite on standard scope probes. Please watch the following: th-cam.com/video/2vzvWUqUtb8/w-d-xo.html
Good question BTW.
@@joesmith-je3tq , thank you for the quick reply. I had seen that particular video before ;-)
For a while now i'm working on a like i call it, a "Poorman's passive differential probe). It's a probe for doing mains referenced measurements, and doesn't need a battery or external powersupply to work, because it's complete passive and doesn't contain OP-Amps like a normal differential probe has. At the moment i can already measure mains voltage (240V / 50Hz) and up to 600V DC (Electrophoresis powersupply) and can swap both testleads and have very accurate readings, the next step is to see how much the bandwith wil be. In a simulation program, i can reach above 500Mhz and still get accurate results, but a simulation program lives in a ideal world :-)
Ps: i have also seen your video's about your high voltage probe, but missed the fact that it has higher bandwith then 500Khz (seen a lot probe videos the last months). Grtz from Belgium.
@@BjornV78 I attempted to demonstrate the basic design of an active differential probe. The common mode and input voltages were fairly low. The fastest one was no where near your 500MHz. Look forward to seeing what you came up with.
@@joesmith-je3tq , above 500Mhz is what my design showed in the simulation program. But we all know, that a simulation and the real world are not the same.
If i reach 500Khz or maybe 1Mhz in real conditions, i'm more then happy. I want to use this probe for doing measurements on Switched-mode power supplies.
I used to do the transient (shock) experiment/Prank on other student and teachers (I was 13 and stupid-er !!!) . I use to ask them to hold the ens of the coils for me so I could attach the 6 or 9V battery terminal and while they holding the coils, I removed the battery and they get a small shock!!! they screamed and jumped because of the surprise and shock and they try to explain they really got a shock from 9 or 6-volt batteries. and I show them by touching the battery on my skin, that you can NOT get a shock... and I tell them maybe you eating too much salt with your food and that makes you more conductive than normal. DONT DO That it could potentially send someone to CARDIAC ARREST!!!
theres many folks out there looking for repair parts for flukes especially obsolete displays that would love to have that meter youre going to destroy
Interesting I read the comments here and saw 2 of yours about the displays. What's up with these displays? These can't go bad unless you split apart the LCD, which I doubt will ever happen. Maybe you talk about the displays looking faded. If that's the case, you need a new sheet of polarizing film. That's how LCDs work. If that film is damaged, usually by heat, the polarization doesn't work properly and you don't see the digits. You can find polarizing film in any LCD monitor and repair 50 of these. lol
Wow!
Like taking an 1972 Porsche 911 and hammering it with a sledgehammer to see if its pedestrian safe.. :( I have a mint Fluke 77 and repair vintage Flukes. I was pretty sad watching this.
I've seen a lot of dumb car comments over the years. I assume the people that make them know nothing about the topic and that is something that they can relate to. But because you want to talk about cars, this would be more like finding a rusted out (battery leaked) old dodge frame with an engine but no chassis (no case) at the automotive salvage yard, dragging it home and then starting the engine after adding a battery and fuses. If seeing an old meter like this get put through the paces before it goes back into the dumpster makes you sad, it's a bad channel for you.
very informative about the transients. Would replacing the spark gaps with a MOV or GDT improve the robustness? i own a fluke 23 and like it a lot, i think it comes from the same era.
It would take a lot more testing to answer that. Normally I would test every function with both positive and negative transients and functional test the meter between each voltage setting. I had no plan on adding any of this data to my spreadsheet and deviated from my normal procedure. It is very possible that had this meter been set to one of the other functions that it could have been damaged at a much lower level. It's also possible that the grill starter or my ESD gun could damage it. One thing I am certain about is that this Fluke is far more robust than the very first one I bought, the 8000A.