#52 Shop Talk Sencore CS61 - Amscope- Fluke 8520A update

Random shop talk:
gokarters.com/s...

[@cliffjones7868]

I have that unit and have a problem only on measuring AC because of a error. However the rest is working. Now if you do finish up that unit, you will get a lot more useful Meter, after my reading the users manual if found a delightful internal program, it can measure tolerances. You feed in the upper and lower limits and you can have it show a display of Pass or Fail. I have tried it with resistors and it works. So I intend on going through my thousands of electronic parts and toss the out of tolerance ones. I also have a Fluke 45 and a Fluke 8840A/AF And one of them has the same style feature like the fluke 8520A, I haven't gone and read both manuals but maybe both will act similar as far as tolerance testing. I was also told to make sure to re-seat the I.C.s and clean out any accumulated dust and I might be able to get the AC portion to function, but if not, replacing caps may be the final solution.

[@karlfell3768]

I have just repaired an old Racal sig gen. Over 90 tants replaced in total. Many had failed and taken out active component, one actually failed on the opposite board to the one I was working on, it went with one hell of a bang. That was when I decided to replace all I could see. I hate the little critters, just change the whole lot as preventative maintenance. Karl.

[@TheRadioShop]

+Karl Fell I hear that Karl. They do cause a lo of issues when they fail. And then with 40 plus volts on them surly cannot be good. Good job on fixing that Racal. Thanks for sharing.

[@Budro4764]

Is there another video on this one ??? The Fluke meter I mean ...... Glad ya'll made the storm safe. My buddy in Ayden came out great for both the storms ..........

[@Cavemaaaan]

Good Work so far, but I think I saw something that you missed in this and the last video on the Fluke 8520A - go to 8:39 in this video and look at the brown burn-spots on C237, C239 and C241. Those are failing if not shorted already. Those brown spots are not normal. You are definitely correct in what you say about Tantalum caps - they do fail at will and they do short and cause havoc :) I'm still trying to repair my IFR FM/AM-1500 from Tantalum havoc a few years back in the Generate Output Amplifier....not pretty hihi, Dan/KD8SSS

[@TheRadioShop]

Good eye. You are the first to notice that. Yes those are on their way to failure. They do check in spec but must be replaced. One of them already failed shorted and has been replaced.

[@Sloxx701]

Man I hate those old dipped tantalums, they're all friggin time bombs. Great video.

[@TheRadioShop]

Thank you, yes those things can go off in an instant and take other parts out.

[@cliffjones7868]

I have that 8020A and it works except for the option for measuring AC. So I will look at that. Now the good news about the rest there is a sequential self test that helps, it will even test all of the display functions and test all the buttons. Also it has a set of programs that can be available to the user from the keyboard , the one I like is there is a pass/fail measurement function. So you get a bunch of new resistors, you can set up the percent of tolerance, whether its standard such as 1/2% or 1% or 5% or 7-1/2% or what you deem is required . I believe this was intended for factory inspections on lots of parts measurement. You don't have to calculate by reading the value, just watch the pass/fail display on the screen. But when I order a batch of resistors I can sort the good ones from the bad easily. I would set up a couple of alligator clips on a board wired to test leads.

[@1903A3shooter]

WELL after watching both videos from 2 years ago now its time for bed and I only hope I can sleep knot knowing the results on the 8520a

[@TheRadioShop]

I have it on the bench in the house, this thing is going to drive me crazy!

[@jameslucas6589]

I am glued to this repair, and channel. I have the exact model as this Fluke but no issues ....yet. So I will go through it as well with the Tants. Did you post another update? I just found your channel and you are an amazing guy. Thank you for your sharing of your knowledge. You are an excellent teacher; very down to earth and practical.

[@TheRadioShop]

Hi James. Glad you like the content. I have not gotten back to this unit yet. So many projects and costumer stuff in here and time is always a problem. I have all the caps changed and the problem still there. So have to troubleshoot the logic now. Thanks for the kind words.

[@Wes8761]

@@TheRadioShop Hey there! Did you ever solve this repair? I have the EXACT same issue, EXACT same resistors blown....

[@jemasons]

Great vid...tantalums are a small sacrifice for the accuracy of the instrument...send us more!

[@TheRadioShop]

Thank Bill and will do.

[@RiRiCake]

Very much enjoyed your "RANT' thanks

[@TheRadioShop]

Thank you

[@saturn5tony]

Fluke = Quality = Awesome! Thanks for sharing Buddy.

[@TheRadioShop]

+saturn5tony That's right, and you are welcome my friend.

[@GrandsonofKong]

Getting it tracked down...look forward to more updates. I've got a bunch of late 80's/early 90's gear loaded with these dip tantalum caps...oh my. Most of it seems to be working just fine now.

[@TheRadioShop]

+GrandsonofKong That's the scary part "working just fine now" lol. Yep, getting the main issues eliminated one step at a time.

[@dennisqwertyuiop]

Nice visit I also like my sencore its the 80 mh model SC3080 works great nice light idea

[@TheRadioShop]

+DENNIS N Sencore is decent quality. Always has been in my eyes. Thanks Dennis.

[@mikesradiorepair]

Time to load up the shotgun, dump a handfull of tantalum caps down the barrel and blast it. Get it over with and you won't have to worry about it for a few decades. I had to laugh when you said how many tantalum caps you changed in the last 6 months. I look down at my tantalum recycle box and figure I did about 3 pounds of them in the last year on top of about 5-6 gallons of aluminium electrolytic's. Cap manufactures love me. I have gotten to the point I don't even turn on anything over 30 years old before I change the caps. Found I was wasting to much time troubleshooting only to find a bad cap was at fault. Has drastically cut down on diagnostic time. Mike

[@TheRadioShop]

+MikesRadioRepair LOl, Yeah I bet you go through a lot of those beast. Most of the stuff I have worked on in the last year only has a few tants in them. But I have also gotten very selective on what I work on now. But I agree. Anything with age I re-cap all electrolytic for good measure and find it resolves a lot of problems. I had buckets of them lol.

[@mikesradiorepair]

+The Radio Shop If you start doing a lot if tantalums don't throw them away. There is a big market for scrap tantalum. Their worth several dollars a pound, just takes a boat load of them to make up a pound. :) I recycle everything, gold plated parts, aluminum electrolytics, tantalum electrolytic, silver mica (big money) and even cut off copper leads from the above parts.

[@TheRadioShop]

+MikesRadioRepair Great idea Mike. Going to get a load out of them from this repair hehe.

[@boldford]

@@TheRadioShop Also recycles the planet's resources.

[@TRXLab]

Again great video Buddy! I like this premium brands always worth to fix. I would also swap out all caps but I would use aluminium electrolytics instead of tantalum. Even the newest types are still critical...T don't like them. Can't wait until the meter is fixed.. Take care my friend 73

[@TheRadioShop]

+TRXBench Thanks Peter. Yes they could be swapped for electrolytic. But would may have to keep some precision. Will study the circuit more. It should be a good meter when fixed. As always thanks for stopping in my friend, 73

[@giuliocoslovich]

Hello After I have replaced all the tantalium and the electrolytics caps except for the 22000uF one, the instrument worked perfectly. I have the 010 option on it so I could dump the 3 eeproms inside of it as it should be only it...

[@TheRadioShop]

Great job!!! I knew the tantalums will fix the issues. I still need to make up an order and get them for mine. Just have had no time. I would defiantly dump those 3 proms. Never know when you need a back up.Big thumbs up

[@wilsonri]

Great video as always Buddy. I learn a lot from watching these. Thanks. I wonder if those 6.5's all came from the manufacturer bad? Maybe you can get away with only changing them.

[@TheRadioShop]

+wilsonri Thanks for the nice comments. Well, we do have to look at it like this. This meter was manufactured in the mid 80's. The tantalums they used are 30 to 35 volt caps. The circuit has 27-28 volts on it. Close to their max operating voltage. When the power rail issue came up and failed it was feeding 40 volts to the 27 volt rail. Which sent this to all components on that rail. Safest way to prevent further issues is replace them all.

[@TheRangerDale]

yes Buddy part 1 I too thoght things going well then the bucket got a hole in it Part 2 lol Yep seems best pull the Tantalum capacitors before they Blow a IC out, those e-Proms Might be hard to get , mainly programmed..Enjoy the Flick like I was right with you all the way, guessing what to do nextlol lol 73's Buddy Tks for the good Effort.

[@TheRadioShop]

Thanks Dale. Yes those tants can be a pain when they go. Got all new ones to install now. I am going to try and read the proms just in case. Appreciate the comments. 73 Buddy

[@TheRangerDale]

Yes Buddy smart Idea on copy eproms, so many of those units about needing E-Proms , and good backup for you.yes 73's buddy

[@MrMac5150]

Thumbs up.

[@TheRadioShop]

+MrMac5150 Thanks MyMac

[@charlesw318]

when is the next video coming out can't wait to see it you do great work and how you do your work thanks for the help.

[@TheRadioShop]

Charles, thanks for the kind words. I have already started shooting more video on this one. If all goes well I should have another part on it out soon.

[@darylynn621]

SC 61 was made for ppl. That had to work for their money$🐴.wish I could find parts for the black ends of the probes. ? I only had 1 problem in 35 yrs, a very rare chip that reads the probe voltage for the Digital VM display died took 10 yrs to find it. 20$ min order from sencore was was 40$ in the beginning. I keep looking for another one cheap

[@denverjohnson9826]

Any idea on where to get a schematic for this scope?

[@TheRadioShop]

Yep those probes are real expensive. I like to find a new set for mine. I know those chips are hard to find. Thanks for sharing.

[@TheRadioShop]

just type it in google.

[@denverjohnson9826]

I tried Google and all I come up with is the owners manual and no schematic. The problem I'm having with the scope is the only thing I can get on the screen is what looks like what you would get when you would push the beam finder button.

[@darylynn621]

@@denverjohnson9826 I got one but loathe to part with it? For obvious reasons. Where on the world are you . Schematic It's to big to print well it would cost too much here bouts.

[@markwhi1]

I bought an Amscope a few years ago and assumed that I had just lost those stupid screws when I was unboxing it, but now I suspect they just didn't ship them. Really frustrating.

[@TheRadioShop]

Agreed. I cannot understand them shipping the screws loose/ That would be ridiculous. So my take is they did not ship them at all.

[@douro20]

If those tantalum electrolytics are giving you trouble I'd replace them with OS-CON or POSCAP.

[@TheRadioShop]

That will work :)

[@stevec5000]

I had a Sencore SC61 once and really liked it but it stopped working after just a few years. The problem seemed to be hundreds of bad connections between the boards that are connected using tin plated pins that tend to corrode and become intermittent. I'm not sure how that can be fixed though.

[@TheRadioShop]

Yes I am afraid mine are starting to do the same. I am going to try and re-plate them and see how that goes.

[@stevec5000]

I've been using a Tek 485 and 7633 but they just aren't as useful as the SC61. However I recently got a Hantek 200MHz 2 Channel Digital Storage Oscilloscope from Circuit Specialists that has a lot more features than the Sencore. I don't know how they do it but Circuit Specialists sells them cheaper than you can get from Ebay sellers in China and they had a sale so I picked one up for just $249!

[@chessapk5034]

Hey Buddy, great video. Did you ever fix the fluke? Anyway, I had a sencore sc61 too. It was nice but honestly the internal design was trash. It developed too many wonky problems so I ended up parting it out and finding for cheap a modern mid to late 1980s Heath aka Philips scope that does what I need it to do. Never missed the Sencore since. I think the sc61 is very overrated although I agree that the frequency measurement was super convenient. I seldom need a scope anyway and when I do, it's never a high bandwidth situation. Take care.

[@grounded1943]

What is the model number of the amscope

[@giuliocoslovich]

Hello The tantalium caps are: 1x 0,22u 35V 16x 1u 35V 10% 3x 2,2u 20V 4x 4,7u 50V 8x 6,8u 35V 5x 10u 10V 4x 10u 15V 4x 10u 20V 8x 22u 15V 2x 22u 35V 3x 39u 6V The electrolytics are: 2x 330u 100V 2x 470u 50V 1x 10000u 16V 1x 22000u 16V with screw terminals 1) Could it be possible to replace the tantalium caps with electrolytics or not (pro and cons)? 2) If I don't find them with the voltage shown above could I buy them with a greater voltage? No problem, right? I have to look on schematic to be sure but it seems that few of them have the same maximum voltage of the one on the place they're installed. 3) I watched on Mouser for the replacements and tantalium 10% cost less than 20% so I'm going to buy all 10% (same family so all other specs are the same). Nothing to worry also here, right?

[@TheRadioShop]

Great job on the parts list for the caps. Now for the questions.1) You can replace all the tantalums with electrolytics. When tants go bad they short circuit. This causes other components to fail hard. The reason tantalums are used is for precision. Specially in timing and phase lock loop circuits.2) keep the value the same. Raising the working voltage is fine. I have replaced 200 volt caps with 400 volt caps. Most modern day caps with higher voltage ratings are smaller than the old caps.3) I would also. 10% will be fine. Sounds like you are on the right track.

[@MichaelLloyd]

Great video. I really enjoyed it. 73 NE5U Mike

[@TheRadioShop]

Thank you Mike, glad you liked it.

[@giuliocoslovich]

Hello I bought a 8520A on eBay as is and it has the same resitor burnt and the same two tantalium capacitor shorted that are replaced in this and in the previous video. Should it be like a bug? I didn't powered it on. I'm removing all the tantalium caps to replace them and I think also to replace the 5 electrolytics of the power supply on the board without the transformer.

[@TheRadioShop]

Don't really think it is a bug. Probably failed due to operator induce the wrong voltage into the inputs or faulty tantalums. You can pull the jumpers on the power supply outputs and test voltages. If all the voltages check ok then start reinserting jumpers to each sections and see what you get. you can monitor the positive and minus 27 volts while doing so. Please let us know what you find.

[@giuliocoslovich]

Thanks for the quick reply. I'll try. But before I change all the tantalium caps and the resistor. For electrolytics I need an ESR meter...

[@TheRadioShop]

This is a good idea. Always nice to have an ESR meter to check the health of your caps. There are many types to choose from but you probably know that. I have several and use a cheap one more than others.

[@DeeegerD]

I really like your channel - however, the one thing that annoys me is you don't finish projects or don't record the finish. Just hunted for the conclusion to this 8520A and nothing :(

[@TheRadioShop]

Thank for your feedback. It is important to me. No, this unit has not been finished. There is a few pieces and parts I need to finish the job. I do not script my videos. What you see is what I see for the first time. By doing it like this we never know how it will end. Plus customers equipment has taking the lead over my projects.

[@docholliday3150]

That is just how it goes. I get a piece in and get excited, find out it needs a ton of work, order parts, fix that which leads to finding new faults and more parts. Like he said, it is a Rabbit Hole. Sometimes you have to step back and new stuff keeps coming. Even if the 8520A is never finished, I learned a lot about tants, trouble shooting and shorts and it didn't cost me a penny. Try not to be annoyed. It isn't healthy. Best, Doc

[@grantfullen9559]

Good video Buddy :) What printer do u use to print that big ?

[@TheRadioShop]

Soory Grant, been so busy with work here. It was printed with an HP 5000 laser jet.

[@darylynn621]

Too big to scan