Electronics Restoration - Eico 950B MAGIC EYE TUBE Resistance-Capacitance-Comparator Bridge Tester
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- čas přidán 30. 10. 2021
- In this video, we'll repair and test a late 1950s vintage piece of electronics test equipment. This is an Eico 950B. It tests electrolytic capacitors, mica, poly, or paper "signal" capacitors, and it also tests resistors, and will allow comparisons via a bridge circuit between two components with the use of a Magic Eye tube. We'll recap it and test all the resistors for drift and then we'll discuss in depth how it works, and test some vintage capacitors to see how well various vintage cap types have held up.
#Electronics #Restoration #Repair
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I remember this beast. We had one in our high school electronics class. that was back in 74, 75 and 76. It sucks getting old man. Thanks
So Sorry to hear about your wonderful grandmothers passing. I too was close to my grandmother. It's like loosing an angel. You posting brought back many fond memories. Bless you in your time of loss, your a great guy. My condolences to you and yours.
Really nice piece of gear. I adore old test gear, and I adore those magic eye tubes even more!
I am now obsessed with magic eye tubes, thank you for that.
Hey Brad, my Dad would have been really proud of you. He was a hands-on civilian electrical engineer with the Navy for about 30 years. He built all kinds of test gear.
Sounds like a cool guy.
@@TheGuitologist He was, but I couldn't fully admit it, until after he was gone.
@@rbarker1706 This is the human condition, man. We have no idea what we have until it's gone. And everyone we know goes away in the end. It's beauty and tragedy all wrapped up together. God is great and His wrath is terrible. God bless us all. And God bless your dad.
Hi Brad, thanks for the video! I got one of these brand new old stock sealed in the original box from an electronics store that was closing down. I also got an eico VTVM in kit form NOS at the same time. One thing to be careful of on the 950B: when you test a cap at high voltage, don't turn the voltage knob down too fast. The cap actually discharges through the pot. If you turn it down too fast, it will dump the voltage through the pot and burn it out. It's really hard to find a replacement. This was apparently more of a problem with the 950A, but I had the pot fail on the 950B as well. The power factor test is similar to an ESR test. The lower the power factor percentage, the lower the ESR. I think this only works on the two highest capacitance ranges, so it's good for testing power supply filter caps. I still use my 950B. Great piece of test gear. Thanks for sharing!
I saw your video after I uploaded this one. You did a great job. I still need to go back in and fix a couple things on this one.
Wow, that manual really is fantastic. Seeing the explanation and schematic of the bridge with the "power factor" pot in the circuit made the whole power factor thing click. I've just done the same thing- pulled down the ol' Sprague Tel-Ohmike TO-5 after much time spent upon a closet shelf. Just rebuilt the whole thing, hand-rolled the critical cap values, and replaced the flaky main pot with a new one from Mouser, but it's well-shy of the 7.5k called for in the schematic so I've added some trim pots on each side. It's getting there. One thing it's doing perfectly is measuring sub-10pF caps, which I think is a pretty cool party trick. These things really can't be beat for the leakage test, though.
I love the amps, but I really love seeing these more obscure tube devices. Also Eico is probably one of my favorite companies from back then. Just beautiful engineering.
Cool tester. Eico made some great gear back in the day. Enjoyed the walk through with the manual. THANKS Brad!
NOTE: There is a capacitor rated at 525VDC in this device. There is a reading of -520V on the schematic I initially misread as -320V. The transformer actually has 560V potential across it in total, so I made a mistake using 450V caps. A better solution is to use two 22uf 300V+ caps in series, which I will go back and do. That will give you well in excess of the spec the schematic calls for on the 525V cap. Sorry for any confusion.
Your electronic repairs remind me of in the early 60's my dad building a Heath Kit Volt, Ohm, Tach and Dwell Meter. I learned a bunch of cuss words, some Norwegian ones too.
Cool stuff brad! Love old test equiptment
I really didn't like the look of that stuff that was crumbling away from that lead in that older clip. I'm sure you're very careful, but after losing my old man through exposure to asbestos [and he didn't know when or where he'd been exposed to it] and they used it extensively in older gear of all descriptions. Mesothelioma is a particularly nasty way to die, so please take extra care.
That's a GREAT cap tester! I have one, can't be without it!
This is awesome Brad! I have one of these and the Heathkit IT-11. Fantastic units!
Love seeing these type of restoration videos from you 👍🎸 best to you man
Glad you like them.
Proper nice tactile test gear. Really cool video Brad 👍
This is so cool
IMHO, one of your better videos Brad. I would check the voltage coming at the capacitor in High Voltage situations. These circuits were designed when the voltage was around 110v, so the when you place the switch on 400v, I'd bet the voltage is higher. I know I get around 127 volts at the wall here in Florida.
Interesting testing the old parts with the equipment that they came from.
That magic eye tube is so cool
I have one of these on the shelf waiting to be serviced. This will help, thanks a lot =)
Thanks Dude I've got this very tester & need to give mine a TUNE-UP
Very nice
oh my, I think my dad had one of those...looks very familiar... He got Electrical Engineering degree in the '60s and built a lot of his equipment from kits... Had a huge Oscilloscope too and a multimeter the size of a lunch box. I sure wish we saved that stuff.
You should build the Mr. Carlson's Lab low voltage cap tester. He claims that it's highly accurate and can test for bad caps at lower voltage. I have seen it working and it appears to really be good.
I was exactly 4 years old when this was made, as it was made on my birthday.. TRW means Thompson, Ramo, and Wooldridge.
Mr Carlson has some very informative vids on on these old testers and warns of the dangers of their use and their failings remember to DISCHARGE Electrolytics? Nice video Dude. thanks.
Sorry I missed the live Brad, was set to go then passed out from the COVID. Gonna check it out now.
Hey, nice one! I've got a RLC meter with a X/N comparator mode and now I know the use case for it :)
Sometimes you need a matched pair of resistors / caps (e.g. when making a high end stereo amp, a phase inverter circuit etc.) and this is where it comes in handy.
Remember, you are putting big voltage in those . Good ones will charge up . Discharge them .
Good reminder. Perhaps I didn't make this explicit enough for others, in hindsight.
In “comparator” mode, you could even check inductors if you have a known good inductor, since it’s comparing the reactive impedance at 60 Hz. So if you have an audio output transformer that you know is good, you could compare it (the primary) with a “supposed” replacement, though the operating frequency will probably limit it to inductors no smaller than a few mH, I suspect. 🙂
This is an amazingly excellent suggestion. I had not though of that.
Actually your chair sound is cool !
It don't bothers me @ all !👍
Yep, Eico DID make kits. I had an Eico FM receiver kit my father built. ( I unbuilt it...)
Nice to see ya' got that R/C bridge workin' well.
Congrats Dad.... Go team Redish...!
nice piece of equipment... it will come in handy... like I say "old school or no school"
Woo Hoo like number 174! Nice job Brad.
about your chair, brad: if you get some kind of office chair, spring for some aftermarket wheels for it, there are now rollerblade-style wheels that are made to replace the crappy little plastic casters on most office chairs. they've made a world of difference on mine! my chairs roll around so much easier and the whole chair is much more comfortable. a set of 5 can be found on amazon for ~20 bones, or 30ish bucks at lowes. well worth the extra money!
Finally a cap leakage tester operating on proper voltages rather than the 9V on the LCR-T4 component tester from Banggood.
Just don't let Terry from D-Lab come close to the tester, he might turn it into a guitar amp :-)
You might want to test your cap leak test voltage output from the tester. Make sure after changing some of the caps inside that what the dial is showing is close to the actual output.
i have been in the process of trying to add a taste of distortion on one channel of my Bantam Bass amp. it is from the early 80's. My brother gave this to me many years ago, and I have tried everything to make this sound like some of your mods to a type of marshall. I would send it to you for a mod of your choice, if you would take it on. I used to co own a tv and video (vcr) shop with my older brother in the 70`s. I have created a pretty good schematic of what i've done and it works kind of but bleeds from the non modified bass channel to the normal modded channel and the middle and bass tone controls don`t seem to do much. Also the distortion sounds more like a big muff on seditives. I really love watching you and hjave done much stuiding on the tube amp designing but it is just so much different than adding non polar caps to speakers to change the frequencies. anyway, I had asked Uncle Doug, which he is a pretty smart guy, but doesnt do the kind of mods you do, and I appreciate your videos and have watch every one more than once. Could I please at least send you my schematic and when you have a moment take a look and give me a little insight. Or I could send you a pix, and maybe you could use it on you channel. Sorry to carry on........ it`s been a month of watching, swapping (with a decade box and resistance box), soldering and all that, and this is my last hope. Thanks so much for all your informative CZcams videos. Mark Bruno
Great Video Brad.
Very simple circuit that old 58 machine.
How does the newer digital circuit compare to the 58 in terms of simplicity?
You could also wire two 4.7 uF/160V electrolytics in inverse-series (i.e. with either the two “+” leads tied together, or the two “-“ leads), and get a (roughly) 2.35 uF/320V rating. Good enough, especially for tube gear. 🙂
I always watch the estate sales and auctions for this kind of gear. Ones that Don't meet all the test specs I want usually sell easily, so there's minimal risk to me.
What component is the Green Magic Eyes? The Green Magic Eye is an special LCR network because it has that Wide Black Window that opens and closes to know if the capacitor is leaking or not.
So which came first: the capacitor or the capacitor tester?
thats pretty cool!
what do you know about the green poly caps in 70s marshall amps? i have them in mine and im wondering if i need to check/replace them
No experience having to change any. But admittedly, experience is limited.
C2, C3 &C4 are precision capacitors. C4, in particular is AKA a reference capacitor. This is is basis for the capacitance measurement. I'm guessing if you don't have a precision device here, you measurements will suffer.
Cool, but where`s the interview with Gordon and the Boaz 1 demo??
There's about 3 hours of footage with 3 different cameras. The editing on that video will be an odyssey.
@@TheGuitologist thanks for the update.
@@TheGuitologist Thanks, can`t wait to see this guitar in action.
now whats happened? never a dull moment eh? I get it
That line capacitor should be a Y-rated cap.
That is technically correct, yes. I don't have any of those onhand, so I'm using a self-healing polyester cap at 600V. I will only be using this device on a bench with isolation transformer. If I get some of those caps in later, I'll install one.
Brad! I have a question about a 2018 Les Paul. I bought just the body and neck and installed the electronics myself. Bridge is grounded, ive shielded the entire inside cavities with copper, and have tried multiple different pickups. It squeals uncontrollably like the pups have gone microphonic. I cannot for the life of me figure out whats wrong with this thing. Ive also taken pups that squeal and put them in a different guitar to make sure it wasn’t the pups. Ive went with the traditional 50’s style and the Seymour Duncan style and doesn’t make a difference…. I really dont know what would be causing this other than a curse. Ive also re bought new Gibson pots 3 times and was very careful not to heat them up too hot. 🤯
I notice you use CRC Contact Cleaner in the green can. What is the difference of that and the blue can? Does it clean better?
It looks like the blue can is labeled "QD" for Quick Drying. I have not looked at the MSDS sheet to see what the difference in formula is. Not sure. I use the green can because a few years back I got a deal on a whole case of the stuff. I think I still have a couple cans left of it.
@@TheGuitologist Thanks I thought maybe you were using the green can because it was better.
Really cool, but why would you use this over a modern tester that just gives you an LCD readout?
You use one of these testers because it can test the capacitor at the voltage it’s used at. A capacitor might be fine at a low-voltage (such as is used in the small digital component testers) but it will fail at its circuit operating voltage. You saw when he tested for leakage… Some of the capacitors looked fine at the very low voltage ranges, but when he cranked the voltage up towards the rated voltage, they failed.
That capacitor might work fine in a transistor circuit at 5 to 15 V, but run it at 150 V, and the leakage is so high it’s closer to a resistor than a capacitor.
That’s why these testers are so useful.
On a curious side note, I've been meaning to ask why your merch doesn't have Voltage represented by the letter E?
if the chair is perfectly good, but just a bit squeaky. then I would locate were it's coming from and either put a little grease on it or some tightening up.?
Lol never noticed the chair 🪑
Magic Ei
Can you recreate Brian May’s diki box?
Hey Brad, Friendly reminder to make sure monetization is on for all your older videos, Cuz with this CZcams ad blocker war, they are really pushing the ads. so far 8 minutes of watch time, they pushed 3 ads to me, so make sure you're getting your fair share from them MF.
Thanks. Sorry for that many ads.
👍✌😎
Brad, dude. The champ handle, is finished. I need an address.
This is one of the “unsafe” models since you can easily leave hundreds of volts in the cap being tested when you remove it from the tester. The “safe” models have a momentary switch that guarantees the cap is discharged before you remove it. Mr. Carlson stresses this feature often. All my brown turd caps test perfect as yours did.
All you need to do is turn the voltage down to zero before removing the cap on this one.
@@TheGuitologist yes but imho if you put a momentary button it is bullet proof, just to be sure if you forget to dial back the voltage . Cheers from Uruguay.
@@andresbide Could also connect a wire to the chassis and install a 3-prong cord and touch a grounded probe to the positive lead before touching. It's a good reminder to respect the potential charge.
Hey Brad, do you need a new nice pocket knife? I'd love to send you something if you give me some kind of idea of what style of knife, blade shape, steel type, brand, etc. that you like. Let me know, i have a lot of brand new knives in my collection if you want one.
2 weeks, man
I just don't get the love of the 'Gibson' bumblebee caps because they are absolutely garbage when they get old. Your better off with a standard orange drop but I'll take a bag full of them just to sell for daft money on ebay to people with more money than sense.
Hey Brad. Oil your chair! :)
Believe me, I've tried.
Just goes to show that bumblebombs arent even good as resistors xD
Hey, European on my boots!
KUL
Biden capacitors . no bodys home
Unimpressive and confusing...sorry.
Just a word of advice. When you test leakage and you turn it quickly back to 0 on the voltage pot, you’re discharging all the voltage to the tiny wire in the voltage pot. If you slowly turn it and give it time to dissipate all the heat that voltage pot will last much longer. Thanks for the video.
Good advice. I didn’t think of that.