Fixing a Power Feed and How They Work!
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- Опубліковано 24 вер 2021
- This episode on Blondihacks, I show how a power feed works while I fix mine! Exclusive videos, drawings, models & plans available on Patreon!
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Hey everyone! As many noted below, what I called a “smoothing cap” on the micro switches is actually a metal oxide varistor. However I was correct about its application- to suppress transients from the switches.
**sniff** **sniff** They grow up so quickly! (In the best Dave Jones impression you can imagine!) Lol
U so clever
hahaha
"An impressive exercise in cost-cutting" - Great way to describe the nature of the electronics on that device!
Did you two coordinate power feed weekend?
@@rpavlik1 I was wondering the same thing, having watched one... and then the other pops up! ...both videos by total UA-cam legends too!
Quinn is one smart cookie...Have fun over at Metal Bash with the guys,, Wish we could go, but work has piled up and pay's the bill's :)>.
@@bearsrodshop7067 Yes, Quinn is not only smart - she explains her thoughts and process with unusual clarity, and finds ways to keep it fun! I'm sure it will be a great weekend. Maybe you can make it to the next one!
I’m impressed by the breadth of you technical knowledge Quinn. Having your understanding of electronics in your bag of tricks is great, good for you. Thanks for the explanation and congratulations on making a working “pig’s ear” out one that didn’t. Cheers, Will
I love the BOLTR style video. Especially the explanation of the circuit. Definitely would watch more of these.
It is so refreshing to see an informative video from someone very knowledgeable that does not rely gimmicks or a a running diatribe of expletives.
Perhaps the contamination on the carbon disk was the lubricating grease used on the entire assembly? There used to be electrically insulating grease used in components like that. I would enjoy watching your re-design and modification of the control circuit.
Yup, I remember those dimmer circuits. With an SCR, it's a half wave dimmer that can only reach half power for AC devices. There is an old trick of using the SCR to short the output of a bridge rectifier, and putting the load in series with the hot AC lead to that rectifier to get a full wave AC control from the SCR, they did that before Triacs were a thing. The Neon bulb fires at a known point (around 90v) on the AC slope, and an RC circuit in series with it varies the exact point in relation to the incoming AC so you get somewhere between 0 and 180 degrees of conduction angle, sorta PWM modulation of the power line, that controls a load. BTW, those neon bulbs age and their firing point moves, which can cause issues with the circuit. (maybe that's why it's been getting worse. New bulb?) Also the Neon bulb's firing point varies with light, so the circuit will work differently when the bulb is shielded from outside light (so it's interesting that they tried to use it as a power indicator!) As you pointed out, the bulb can be replaced with a proper diac diode (sorta kinda two zeners back to back in series, cathode to cathode or anode to anode).
You probably could find a replacement potentiometer that would electrically work, but with a shorter shaft. Then you could drill and tap the shaft and an extension shaft, and then insert a headless screw (threaded rod) with lock tight to extend the shaft. Simple machining problem!
16:50 I've fixed lots of old pots in a similar way, but I bend the brass springs so the wipers contacts a less worn track of carbon. Excellent sleuthing there.
AvE on speed dial! Made my day!
Hi Quinn, I have a 230 volt version of this drive. There is not a no volt release switch so the drive will restart after a power failure even if the mill spindle does not. I also did not like the 230 volt supply being directly switched by the table travel limit switches which are close to any cutting fluid used. I built a control unit with an integral NVR switch, a 230 to 24 volt transformer and three 24 volt ac relays. This is fed it with 230 volts from the mill main supply switch and is also interlocked it with the mill NVR stop/start control switches. By including a 230 to 24 volt transformer I reduced the switching voltage on the table travel switches to a safe value. With some thoughtful design this extra control box can be disconnected and the various cables easily relinked to put the set up back to your configuration. BobUK.
How does one even know all that stuff ?
I‘m seriously even more impressed with your electronics knowledge than with your Maschinist excellence - which is very impressive in its own right! 👏🏻👏🏻👏🏻👏🏻👏🏻👏🏻👏🏻👏🏻
You might enjoy the electronics projects on her blog, her homebrew computer and arcade pinball machine are both pretty epic
@@rescdsk Already on it.
Thanks a lot 😃
I recently had my ASONG AS-235 apart---a similar unit. The trace to R5 welded itself out of existence and left a smoking resistor in its wake. Some notes: The pot (RV24YN 78S B501) is available but mostly the 20S version, which has a shorter stem. The custom one is 78mm long and not available to the public. There's a CRC contact cleaner and Deoxit D5 is a favorite with electronics repair people---usually no disassembly required for pots. I traced the circuit and found that the neon bulb is strictly an indicator. Mine may be different from yours but I think the neon bulb is a way to avoid having any low-voltage section on the board but have a little light anyway. Neon is probably the best choice, if the voltage is set, because it is relatively low power and heat compared to the alternatives. It looks like the SCR is getting triggered by an RC network. The trigger circuit is directly between the gate and cathode and charges from the half-rectified mains (after it's taken a detour though the stator windings). The time constant is set by the resistance of R4 in combination with the zener-pot-R2-C2 circuit. I think that subcircuit kicks it the way an diac would. Not sure about that. ANYWAY, I tried to figure out R5 from stills of your video but just couldn't do it. Thanks for the video. It always makes me feel less insane when I see someone else doing similar things.
Proper old school electronics there. Brought back memories. Noisy pots used to be the bane of my life!
If you have room to do it, putting a zip tie through/around a spring will keep it from springing-spronging into your face.
Dear Blondihacks! Thank you for your video! I had a problem with my Chinese 'Bridgeport' which has the same cross feed drive. It kept going slower and slower until it eventually died!! I stripped the drive down but because of your examination I managed to save time trying to get the variable resistor out! I removed its cover and rotated it a number of times blowing it out clean with compressed air! 😊 Thank you!
Amazing explanation. I really love your in-depth way of going in to the smaller things which also counts, all your videos are like that which is phenomenal. Thank you for your time and effort keep up the good work and keep well.
I really enjoyed this. Looks like many of my "I've never done this, but maybe I can fix it if I can get it apart, but regardless, I'm learning something new." I'm impressed by your electronics knowledge.
Thanks for the video. Circuit looks like a half-wave SCR phase controller GE SCR Manual ca. 1970. Possibly no EEs were harmed (or even employed) in the many revisions of that PCB over the decades. The blue disks are not capacitors- they are MOVs (metal-oxide varistors) to help reduce arcing. They "wear out" eventually and tend to fail short.
Even Sprocket knows you're not really fixing things unless you have bits left over the first time you put it back together.
The traditional watchmaking apprenticeship involves being given five watches and being told to take them all apart and put them all back together. When you can do that and build a sixth watch from the left over parts you have passed. If all the watches work you have passed with honours:-)
Indeed, in several shops where I worked, we called that "cost reduction."
My boss from our old machine shop added a large amount of odd parts to this new "plane o mill" that was being assembled by our Metal Fitters dept. Very funny when they couldn't work out where all the odd parts went. We had painted some of the parts to match exact colour of the new machine.
My experiences of repairing things like this tell me that I will be back into it sooner rather than later. Cleaning pots is only a temporary fix, they will never be as good as when new. However buying a replacement but with a shorter shaft will be an exercise in making a longer shaft to suit.
That may indeed be next
@@Blondihacks And now you cheated by just getting a new mill with a new powerfeed ..
I have a new ALSGS table actuator for 230VAC. Type ALB-310SX
In it, the neon lamp is only used as a power-ON control in the switch. The forward and reverse microswitches reverse the field of the motor. The potentiometer gets a half-wave as a constant voltage and controls a tyristor that limits the rotor voltage of the motor.
There is no trigger diode or DIAC built in. The speed is the same in both directions.
Yay!! It's Blondihacks time! (Sorry I was late, I got caught up rebuilding the headliner in my mom's jeep)
Great video! I loved the AvE style tear down / inspection and the TOT-esque rebuild music. Thanks for sharing
The neon lamp should make no difference to the direction, the two microswitches should normally be used to reverse the polarity going to the DC motor after the SCR circuit. The difference in power in one direction is more likely to be in the motor or else something mechanical.
Oh my god what a punish just to get at a faulty Pot. Kudos to you Quinn for persevering.
17:32 .. this is where a classic analog multimeter shines ;)
Great job! I'm impressed, but then again I've never doubted you!
You have the nack of making everything look easy 😃could the speed difference be anything to do with how the motor brushes bed in.
17:15 One of todays equivalents is Servisol super 10 switch cleaning lubricant. Magic stuff, it cures the scratchy pots/sliders on amps and mixers etc.
I’ve had good luck with some of the products from DeoxIt. Pretty easy to get a hold of too.
CRC also makes a contact cleaner which is not expensive, probably similar to the RS stuff, and available at Quinn's local Canadian Tire.
@@LenPopp I don't think there are very many Canadian Tire stores in California :)
@@Steve_R their loss
Caig Labs Deoxit D5 in the spray can would be the replacement for the old radio shack contact cleaner. It's a miracle for anything with contacts that get intermittent. From audio equipment with dirty pots and jacks to that maglite that won't work unless you whack it against the table, it cleans contact surfaces and keeps them from getting dirty again for a long time.
I rebuild a lot of old radios. Deoxit is the best thing to use to clean contacts. Love your videos.
I know you've said in the past that you think electronics projects are better in blog form, but I thoroughly enjoyed this video! I'd love to see more electronics from you too.
Good one Quinn. My Bridgeport II power downfeed speed controller has lost it’s mojo.
I’M GOIN IN😂😂 Thanks for the motivation.
I have that old Radio Shack Micronta multimeter. 20+ years and still going strong! One year it was left alone and the batteries all let out their innards into the compartment. A quick wipe with damp paper towels and its back in action.
Electrical talk usually goes so far over my head they can see it from the ISS, so well done for getting at least some of it
into my tiny brain . Looking forward to seeing more .
I'm impressed as usual. You are a smarty! I have to think you own an analog multimeter which would have been better at showing inconsistencies in the potentiometer.
8:00 The lightpipe might not be just to provide an indicator. Neons sometimes don't light in total darkness and need some ambient light to start the strike.
Good point!
Right, I've seen that effect on power strips that have a neon indicator lamp that is old... maybe replacing that neon bulb would be the fix!
Some have a taste of radioactive gas in the neon to help ignition. Maybe 2 or 3 axial lead diacs in series would work.
It wouldn't be engineering if your workaround didn't require another workaround.
Great video, analysis and further comments. Thank you for teaching me.
CRC brand "QD Electronic Contact Cleaner". Napa Auto Parts is one of many places you can get it. or find the hobby chain where Radio Shack is supposed to re-emerge, according to Dan Maloney as stated on Hackaday:
According to the ARRL website and major media reports, up to 50 of the 147 US locations of HobbyTown, the brick-and-mortar retailer of RC and other hobby supplies, will soon host a “RadioShack Express” outlet. Each outlet will be up to 500 square feet of retail space devoted to electronic components that would be of use to HobbyTown’s core customer base, as well as other merchandise and services.
YAY, I will finally be able to get that missing channel 18 transmit crystal for my 1970s CB Radio!
This is great Mrs. Hacks! I had to rip apart mine last year and replace the board. (One of the resistors had fried so badly that I couldn’t identity it). I tried fiddling around with getting some of the other parts off as well but didn’t make nearly as much progress as you. Mine has a similar problem where it won’t travel at slower speeds. So, I’ll add cleaning my pot to my list of to-dos.
Loving your videos.
I've watched this video about 5 times now. My power feed as totally packed up. Thanks for the dicetion
Had a similar problem with my mill. I added a 200 ohm resister. to the 'A' pin on the resistor (I think,- it was a while ago and I have forgotten ) and it runs so much better at the low speed end where I use it most. It now runs smoother at these speeds and also has better control, by needing more twist of the knob to get the RPM to change.
Good idea!
A good electronic contact cleaner was "Tuner Wash," for cleaning the manual UHF and
VHF rotary channel selector switches. It worked well on relay contacts, automotive ignition points, and similar, too. IDK if they still make it, but if anyone runs across it, it's good stuff.
Be careful with TV tuner cleaner, it often contains a light grease to lubricate the mechanical contacts. A better choice might be De-Oxit, which cleans but doesn't lubricate.
Thank you very much for this video. I have one of these drives on my Taiwanese mill and although it's still working well after 14 years you never know when it will need surgery. The only trouble I've had with it has been perished rubber boots on the main switch and push button. I replaced them with rubberized material cut from fingertips of cheap work gloves, held in place wit hot melt glue.
The over greasing is to prevent corrosion while products languish in distribution in the high humidity of Guangzhou and Shenzhen ports.
I thought I was the only one who still has that old Micronta meter in (mostly) working order.
40 years and counting on that thing. It just keeps going
This video demonstrates in the BEST way possible that GOOD engineers design things to be easily disassembled and NOT assembled, a lesson taught to me as a student engineer almost 50 years ago by a genius designer. If it disassembles easily AND modularly it makes maintenance that much easier and assembly (& re-assembly) becomes a piece of cake.
Example: that RIDICULOUSLY long pot spindle shows that the bean counters weren't as smart as they thought!
1. It's almost certainly a non-standard, custom design, possibly made exclusively for the manufacturer.
2. As such it would be substantially more expensive than a standard, off the shelf unit available from countless manufacturers.
3. Trickier and more complex assembly operation overall
4. OBVIOUSLY the designer had NEVER seen inside old radios since the CORRECT solution is a VERY simple one, and often used in old radio sets ... A 'D' shaft coupler or extension rod! Doh! That way, ONLY the two bolts for the bracket would have needed removing, the shaft coupler disconnected and bingo the whole sub-assembly gets removed.
Just buying a standard 'D' shaft pot, available from multiple sources (or use a round shaft and a minute on the grinder!) fixes the issue properly!
Excellent video on how to repair something tricky but otherwise simple.
Knipex Pliers Wrenches 😍😍 my faves!
Now I want to see you rebuild this thing. Dunno how practical that would actually be, though.
I might be inclined to replace it with a servo or stepper instead.
I learned years ago that you can clean electrical contacts by dragging a dollar bill between the two faces of the contacts. The fibers in the bill are mildly abrasive and can help remove contamination.
Hi Quinn,
It is the nature of DC and AC brush/commutated motors to run at different speeds in in one direction. It has to do with the compromise position of the brushes to achieve the best torque at a desired speed and direction. For symmetrical speed the brushes can be rotated about the commutater with a constant field position. Not possible with the way your motor is built. Really enjoy the videos, keep them coming.
I agree, and you can get the same asymmetry with a permanent magnet motor if the field and brushes are misaligned. I don't think it has anything to do with the neon, as the 'dimmer' circuit will see the same polarity all the time. Assuming a series-wound motor, the reversing is almost certainly done by swapping the direction of the field winding (or brush/commutator) with the two microswitches.
@@mikerudin8261 exactly right. Her motor is probably a parallel wound motor as it needs torque not speed. Series wound motors are typically used in vacuum cleaners and other machines where the load is firmly attached at all times as they can exceed safe speeds if unloaded. A parallel wound motor will not reach destructive speeds as the back EMF will limit the speed unlike its series wound counterpart and can still be bidirectional with field reversal. Still. The speed control circuitry is pretty cheesy, I would have used a constant current field variable voltage setup personally. That would give a more constant torque curve across the range of speed.
Chinese products spend a lot of time at sea on their trip to North America. The excessive grease is there for corrosion protection.
The grease they use also stinks. I call it "Eau De Harbor Freight".
Shenzhen #5!
Thanks for the timely reminder about contact cleaner it's just what I needed to give new life to my 35-year-old guitar 🎸🎶
I have one of these. In the UK they are sold with a separate transformer box to drop our 240 volt mains power to 120 volt to run them. I have a manual for mine with a drawing, and could email you a copy if you wish. I knew it was a thyristor with a neon lamp type circuit as the manual has a circuit diagram. Great work and excellent presentation as ever.
Yeah, I built some controllers like that, around 1972. Not touched on SCR's after that since now we have much better parts and can embed a small cpu for total control. Thanks for sharing.
Quinn, enjoying your videos.! My first comment though. I know about electricity but not electronics... Down to earth description and explanations of the power feed. By the way, with 53 yrs machining experience I'm impressed with your work habits and attention to details. Thanks for your time and sharing! 👍😎
So cool to have an electronics video related to machine tools! ❤
Maybe an external ten turn pot. Nice to see there are people out there that aren't afraid of component level repair.
Late to the party, but DeoxIT sounds very similar to the old Radio Shack spray you're using. You don't even need to open up the pot, just squirt it in! I've used it a bunch for restoring old amps
A good modern equivalent of that Radio Shack contact cleaner is probably DeoxIT. I use it constantly.
Was surprised you didn't order the DIAC while you were browsing, Good job on this.
Yay! Finally incorporating electronics on your channel! More. Please!
I am glad you opened that up. I have some of those and always wondered what was inside. All of the adjustment is all on one end on mine. After a half turn you don't get much speed change at all.
That potentiometer looks very much like the potentiometer that was used to set the flaps position in my friends ultralight airplane 😅 It was also not linear at all and the flaps worked in about the same way as your power feed 😂. It was almost impossible to find a replacement pot but after weeks of googling and searching on ebay suddenly a guy in israel appeared and sold the exact same pot on ebay so we ordered three of them. The guy sent them and the package bounced back three times because he didn’t fill out the correct export forms, but on the fourth try the package got through, the pot was installed and the plane still flies this day. 😃👍🏻
Quin I went back and rewatched this video yesterday because I accidently plugged mine into 220-volts and it is a 110-volt unit, I am writing just to say thanks for pointing out that is a regular power feed in it bolted to the horizontal adapter. I have 2 of the regular units so I should be able to make a swap. When I bought mine, I paid in excess of $400 usd from PM. The ones I got from Vevor are the same units rebranded. Also, I have found repair parts for mine are not too hard or too expensive. I am going to take it apart and hopefully it just smoked the breaker, but I will not know until i do the autopsy. Anyway, thanks for the detail you provided.
Radio shack contact cleaner is amazing. I think i have also used up my can that is 10+ years old.
I have found 3 good alternatives for cleaning electronic contacts.
1. Isopropanol alcohol, 90+% is better for electronics. 70 can be used but takes longer to evaporate. clean with canned air
2. Electro Klene by Stoner, this is alcohol based, evaporates with no residue
3. Deoxit red & gold. this will leave a residue, but it cleans and restores electric connections. especially gold plated ones. It does leave a reside that you have to clean off with alcohol.
I believe the smoothing cap across the switches is actually a MOVs to reduce arcing when the switch opens. Try replacing the neon bulb with an NE2. All electronics has them 5 for $1.00. If you can get them to ship first class mail it should only be a dollar or less for shipping.
The newer neons tend to not be made as well as the old ones. Fran Blanche has an old clock with neons that needed replacing (they were run at fairly high current), so she got some new ones only to find that they started to degrade in just a few days of use!
Wow. You really know your electronics! Nice work.
Entertaining and informative as always. Keep up the good work!
I love this video! Please do more electronics explainers like this; you are so good at articulating your problem solving and though process that I learned a lot from this video.
Enjoyed this episode. Thanks Quinn.
Yep couple others saw that 400v MOV across that pot. Plumbers silicon grease for faucets will restore that damped spin on those pot shafts for everybody's fyi.
Your channel is really great. Many thanks for all those hours you put into it.
Cant wait for the new board to be made ;)
Fabulous video, a great delight and motivator to tackle stuff that challenges in so many different directions. Thanks for sharing!
It's nice to see come electronics on the channel too. An analog multimeter is handy to have around for testing pots.
Your overall knowledge of everything is amazing, yet another great video, thank you.
Good job and explanation as usual. I have found that an analog meter tends to reveal intermittent connects better than a digital meter. I too have a vintage can of RS tuner cleaner which might only be a temporary solution inn your case. When this pot acts up again, you could investigate the possibility of cutting the shaft off and making a coupler for connecting to a replacement short shaft pot. It might not be bad idea to also replace the neon indicator lamp.
I understood very little of that, and was fascinated! Clearly I need to watch more of your videos :)
Very interesting to see it disassembled and reassembled. Cheers from Australia
The pots need cleaning from time to time. I have yet to meet some that runs correctly for longer than few years without asking to be cleaned up.
The Neon won't affect the directional difference, the whole electronics is actually operating the same way in both directions, so it can not cause the asymmetry you are observing.
On top of that (found this only after reverse engineering the circuit) the Neon actually has nothing in common with the regulator itself, it is really just a power indicator, nothing else. The circuit itself is not that much a light dimmer, but rather a kitchen mixer regulator. The pot generates a variable reference voltage (which represents the required speed), which then the thyristor compares with the EMF generated by the spinning motor. If the motor spins slower, the EMF is lower and so the thyristor turns ON sooner, passing more power to the motor. When it speeds up so the EMF gets above the reference, the thyristor shuts off, waiting the motor to slow back down.
The direction switching is done by swapping the polarity of the armature brushes. So the asymmetry could be only in the motor itself, or in the gearing. It uses slanted gears, which tend to axially pull one gear up and the other down, so may cause them to shift in the bearing so get different friction. Or the motor shaft may have shifted axially, causing the brushes to run on an oxidized part of the comutator or get different field interaction with the stator. So cleaning all the bearings and lubricating them with a fresh grease may help there, if the mechanical resistance is the problem. Otherwise it won't hurt and it would be just a more extensive maintenance. Otherwise the motor asymmetry itself us a design thing, so you will have to live with it.
Blimey that is an absurdly large reduction for a single stage gearbox.
Really useful stuff. Examination component level 👍👍
My grandfather taught me the expression "it wasn't expensive enough" when something was clearly a bit too cheaply made, or built to a budget not a specification and you are very much giving the idea that this device fits that category.
Excellent and fun video. Very close to a repair café type situation. Can't wait for those to open up again. Things never go back together first try 😂
Been a huge fan of your channel, keep up the great content :)
Well done Quinn,you’re really clever.👍👍
Neon bulbs are totally symmetrical bipolar device. Diacs are a bIpolar device intended to trigger Triacs. If I understand this correctly the motor direction is determined by the polarity which is controlled by the microswitches so the electronics does not know which way the motor is connected. So I would not suspect the drive electronics to behave differently for different directions. Driving a brush motor with half wave DC is certainly a minimalistic approach but probably enough for this simple job.
They are not symmetrical, and change over time.
Your range of knowledge is remarkable.
Great fix and video!!
Impressive understanding of electronic circuits 👍👍👍.
Good ol’ contact cleaner. Fixes about everything electrical.
I've worked on a few of these frustrating and scary repair projects, where you have to disassemble 90% of something to get at what you suspect is the problem part. :-) You also _hope_ your memory is good enough to remember how all of the screws and clips and springs go back together. And, you hope you don't accidentally break some little plastic tab or other feature which would render the entire device scrap. :-) I was getting nervous when you were prying apart that potentiometer, hoping that a bunch of little plastic fragments didn't fall out of it. But, in the end, you succeeded! Bravo!
A few years ago I decided my mill/drill needed a power feed, but the available units wouldn't work because my TWS isn't a standard Rong-Fu clone, so I built my own using a gear motor. Works well, but no fast traverse (yet). The best thing was it was almost free because I already had a number of motors with different speed/torque ranges. The hole for the neon bulb may actually be a port to let light into the bulb, as most neons fire more reliably when in a lit environment. That's why some neon bulbs contain a small amount of radioactive material- it makes them fire reliably regardless of ambient light. (but I'm sure you knew that..)
"Reassembly is the reverse of disassembly."
Hah, maybe in your perfect world. But it NEVER works that way anywhere else, as almost anybody who's ever taken anything apart will tell testify under oath. As a child I suffered several beatings before learning this reality. Now I sit here stunned with your engineering and technical competence. AVE, eat your heart out!
Enjoyed ! Thanks Quinn...
Loved the explanation - thank you!
Cool! Let us know if you ever replace that neon bulb.
I've never been inside one of these, although I've used many in my day. Very interesting, clearly good electronics experience, I've worked electronics almost sixty years, never ran across the use of a neon light instead of a diac. I learn something new every day! Thanks.
Great video Quinn !
You sure know your Electronics! I am impressed, you have many talents!👍🏼👍🏼😊
I paused the video and tried to reverse engineer the circuit... and I was puzzling, I saw that 10W toaster oven, err, ceramic wire-wound resistor, and I've seen neon bulbs in oscillators, and even incandescent bulbs to balance in-rush current, but I wondered how that would play into a motor control, I hadn't yet connected the dots, my brain didn't go to "dimmers" but once you said it I was "Ah HA!" that's right!!! Now it makes sense!!! And I was very happy to hear you talking about some power switching electronics: triacs, diacs, and SCRs, I know of about them, but I don't work with them (I do mostly digital and op amps)... Still, just hearing about them again took me back to my days in college electronics courses in semiconductors. Thanks for the electronics "refresher" of sorts... Cheers!