Flyback Swap
 

I know this isn't really about TV's, but I was hoping I could get everyone's advice on doing an FBT swap for an old iMac I have. It's the first model ever released, quality-built in the US, and they would be near-indestructible if it wasn't for a glaring design flaw: the placement of the FBT. Instead of being placed next to the tube, the chassis is mounted vertically next to the tube and the flyback hangs over the tube, making it run extremely hot. About 3-4 years after the iMac had been released, reports of iMacs with dead FBT's started circulating the internet, and now that these machines are considered vintage, It's a well-known fact that they are notorius for having bad Flybacks (they overheat, the insulation on the wires inside melts, and they short). I've got a Revision A iMac, manufactured September 1998. It's in great shape except for the FBT, after it's been on for 10-30 minutes, the screens starts flickering every few minutes and you hear a quick zap from inside. It bugs me when I use it to know that it's only a matter of time before the FBT completely shorts and the iMac refuses to start up (the classic symptom of a dead FBT). I have found a replacement fly (LG #: 6174Z-1003G) online for $30 and a page with detailed instructions on doing the swap (http://www.macopz.com/columns/imacrepair/) and feel fairly confident about doing the swap, the only part that gets me is discharging the tube. Basically stick an insulated screwdriver under the cap, and make sure the screwdriver is connected to ground, right? When I google it, all I get is idiots saying "zomg teh flyback is very dangerous why risk ur life over sum old computer go buy a new one flybacks can kill u". I know it's not true, but I just wanted to check with the pros. Can you guys tell me how to do it? Also, a lot of websites recommend connecting the screwdriver to the ground pin of the power connector on the iMac itself, so when the CRT discharges all that current goes to the ground on the chassis, and to do it without having the iMac plugged in.... wouldn't that screw everything up? Well anyway if this doesn't belong here, please feel free to delete. Thanks!

I always discharge CRT's by placing about a 1 megohm resistor in series with the HV anode and the CRT ground strap. Just connect one end of the resistor to a good insulated screwdriver and the other end of the resistor to ground. Slide the screwdriver under the anode cap. You may have to do this several times to completely discharge the CRT.

http://www.repairfaq.org/sam/crtfaq.htm#crtsdc

This should help. If not that article, then something on that site should help you.

I just use a "clip lead" (a wire with alligator clips on each end) with one end on the chassis (make sure you pick a part that is connected to the CRT ground, or just clip to the CRT's ground strap/connection) and the other end on the screwdriver shaft. Yes, obviously an insulated-handle screwdriver. :) I slide the screwdriver tip under the HV cap until it touches the metal clip. I also use the same grounded-screwdriver assembly to go ahead then and unclip the HV cap from the CRT. Once you did the discharge, it should be OK to lift the edge of the rubber/plastic cap to see how to unclip the wire. Once you have unclipped it, do not touch the anode terminal of the CRT, as it will "self-recharge" to some degree. Discharge/ground it again just before you reinstall the HV wire again after your repair.

I should also point out that a charged CRT, especially on a small tube as in an Imac, probably does not have nearly enough capacity to "kill anyone". I got zapped from a plugged-in and live HV cable on a 23" B&W monitor chassis once. It felt like I got hit by a truck, but it was not fatal. HOWEVER... Do not take this comment to mean in any way that such an activity is safe at all, and do not try this (touching a live flyback output) at home, or at work either for that matter!

The HV is probably as high as 25kv, but probably less (15" screen, right?) This of course is extremely low current, in mA's so likely just a big surprise but not death. Can NEVER be too careful, however.

iMac's were extremely nice when they were first introduced, and like most pc monitors, the fly is the first thing to go. Sucks that many get trashed as a whole because the monitor breaks down. Good luck.

You don't have to worry about the HV as long as you discharge it like people said. I've repaired a lot of imacs and getting to the flyback is by far the hardest part.

So, imacs are becoming collectable? I still see these being recycled regularly. I lost interest when their value dropped below what it cost to ship them.

If you don't have wired alligator clips you can use two long screwdrivers instead, just put the flat one under the anode and the other on the CRT ground, then touch the two together. Hold the two screwdrivers together for 15 seconds then put them out...

Thanks everyone, I feel a lot more confident about doing the swap now. I fired up the iMac today and the tube is very bright and colorful, it's a little soft but when running at 640x480 it looks pretty good (I use this machine for old games, and most them run best at 640x480). The tube is surprisingly an LG, I was under the impression that they made junk but this tube has been through a lot (the iMac belonged to a graphics studio for 6 years) and it's held up pretty well. I'll order the FBT on Sunday and let you guys know how it goes. Just two things: Where is the ground strap on the CRT, and does LG make junk? I bought a DVD drive from them that was DOA but how good are they in terms of Tubes? Also, has the quality changed since their GoldStar days?

I dunno if LG makes junk per se. Not enough experience with the brand.

You might want to seriously check out that link I posted. repairfaq.com goes into great detail about CRT and other electronics repairs.

@MRX37: I forgot to mention in my last post, I've read the repairfaq at least twice, it taught me a ton about CRT's, great resource, it's been a while since I read it though I'll probably read through it again tonight.

A really weird habit I have (that started after I read that repairfaq, which in turn sparked my curiousity about CRTs) is that I can't seem to stop drawing picture tubes on my Geometry notes. The teacher will start droning on about theorems and it just happens. First I draw the shape of the tube, then the yoke, then the neck board, then the flyback suction cup, then the chassis under the tube... happens in English class and French too...

Ah. Seems like you got CRT's on the brain, kinda like the guy in Eric H's avatar.

The ground strap will either be some sort of spring or a band of braided wire that makes contact with the aquadag coating on the tube. There will be a wire soldered to this spring or braided wire that connects to the CRT neck board, the chassis, or both.

I used to draw San Francisco cable cars on my notes in school, and now I live near there...

The "ground strap" would refer to any bare wire or metal bracket(s) that make contact with the coated back surface of the CRT, and other metal that those items are connected to.

The company that is now LG has "made junk" at one time or another, as have many other big electronics companies. Their old stuff from the Goldstar days was mostly mediocre at best, as was much of the electronics from Japan at one time, and Japanese cars as well... We all know what happened later. LG is now a leader in many fields (such as ATSC digital TV, which they bought along with the rest of Zenith), and so is Samsung, for example. Samsung was a low-end Korean company at one time (though they made a cool part-tube CB radio called the Dak in the 1980's), and now their LCD panels are the best in the industry.

So when I discharge the tube to the ground strap, should the iMac be plugged in?

No, the device should be unplugged from the AC outlet.

The purpose for the CRT ground is to prevent the tube from building up a charge and arcing. There is a strong chance this arcing will cause serious damage to the chassis; especially in the form of blowing semiconductors.

I see exactly what you mean. On a crappy Gateway CRT I have, the bell of the tube builds up a static charge (you can feel it), I guess the ground strap isn't doing its job. Well thanks everyone, it may be up to two weeks before I receive the flyback so this thread might die for a while, but once I do the swap I will upload pics + results.

EDIT: I should probably add, by "Gateway CRT" I mean a computer monitor I have laying around. It's only 5 years old and was my main monitor for three years, the tube is already starting to show signs of wear (dim and bad convergence at the edges) and it's experiencing vertical foldover. Coincidentally, it's Chinese-made.

Absolutely not... Never have anything plugged in when you are going to replace parts! :eek:

Regarding discharging the CRT to "ground", you are concerned with ground relative to the CRT itself, that is, its own chassis. True ground, as in the electrical wiring system, is not necessary.

The quality of Apple's monitors really seemed to die when LG started making them. I scrapped a 17" studio monitor (the one with the awful 3 pronged base, Mitsubshi CRT, LG chassis) today. I've lost count of how many of those I've seen with bad flybacks.

I've got a few iMacs with bad flybacks. I ran one in a different case for a while after installing the missing ADB connector so I could use my old extended keyboard.

The 20 year old Sony made monitor that came with my Mac II is still going.

True, although I'm using an origianl 22" cinema display LCD that was also made by LG. It's 8 years old and still looks great. It was the largest LCD in production when it was made.

At least they didn't go with Samsung's wonderful CRTs that died after a couple o fyears. They were the only CRTs I've ever seen where emission on all 3 guns fell completely to zero. It took a while to figure out on the first one I saw.

Interesting. I've had many Samsung CRT's and they haven't gone bad on me. Usually the rest of the monitor failed before the Samsung CRT did.

The worst Samsung CRT I've seen is 7 years old, and it had the Windows taskbar burnt into the bottom of the screen. Other then that it's still decently bright.

Those little 13" Sony-made Apple monitors are unbelievable, I've seen a few and they are the brightest, most colorful displays I have ever seen, I'm hoping to run across one soon. Also I never knew the Apple three-prong base monitors had an LG chassis (although I knew about the Mits tube). I always thought those monitors had an unbelievably good picture and I'm always looking out for one.

I have to admit that I don't care for the iMac very much. I used to use a computer lab that was full of them.

They came with a game called "Bugdom". This game ran slow even in low graphics mode. This is a game that came bundled with the syetem and when there were too many ants on the screen, the game would run like a slide show.

They also generated a LOT of heat! So much infact that the computer lab room slowly grew warmer throughout the day. Keep in mind that this was a large room with about 10 iMacs in it.

Also, we had the type with the slot loading CD ROM drive. One of the drives failed, and the whole thing had to be taken apart to rescue the CD.

Holy crap do these things run hot! It warmed up the corner of my room where my desk is after 2 hours of use. Funny you should mention Bugdom, that's what I was playing on it.

I'm quite fond of the original iMac (although I hate Apple's recent junk), "we" go way back. In second grade, computers fascinated me. I had a crappy old Power Mac 60Mhz at home that I loved, I would actually read the manuals that came with it over and over, back to back, whenever I was bored. I had no internet, and only 5 games on that computer, but I was 8, what did I care? Computers were magical boxes to me back then, and I didn't really care about how they worked, just about using them. I would always take short quizzes about books I read on the Macs at school, I accumulated points for every quiz and at the end of the year I got to spend them all "buying" prizes, the program was called Accelerated Reading.

They had us take the quizzes on some old Power Macs (similar to what I had at home), and I was in there daily. One day, I walked in and saw a brand new iMac Bondi Blue in place of a Power Mac they had replaced. It was so cool!! It was see-through! I remember pointing at it and asking the librarian "What's that?" They told me it was a new computer and that they liked it because the keyboard was black and it didn't get dirty very easily.

After that day, I started reading more books just to spend time on that cool new iMac. I started begging my parents for one, even literally dreaming of having an iMac. I was as obsessed with it as much as any second grader could be obsessed with anything. Soon, the entire library and eventually the entire school upgraded to iMacs, I remember staring at the one on the on the teacher's desk and dreaming of some day having my own, reading two books a day (they were short) just so I could take more quizzes on my beloved iMac.

Eventually, I started telling the librarian that I needed to take quizzes, sitting on the iMac that faced across from her so she couldn't see the screen, and quitting out of Accelerated Reading and just clicking on all the menus and opening the control panels, and for some reason opening the CD drive and pushing it back in fascinated me. For two years I asked my parents for an iMac, "It's just ten 100-dollar bills" I remember saying..... I never did get my iMac, eventually I forgot about it when they got me a Windows machine in 5th grade.

A few months ago, I bought this particular iMac off someone on Craigstlist, it's the original Bondi Blue mac, just like the first one I ever used, the one I pointed at and asked "What's that?", the one I stared at every time we went to Sears.... So I guess you could say the original iMac is pretty significant to me, not the particular one I have but the original iMac in general. I did end up getting that iMac I wanted so badly.... Just 9 years too late and in need of a new FBT.

I feel old now. We had Apple IIs for most of the time I was in school. Pentium Is were high end when I was a senior in HS.

One thing I liked about macs was the Simpletext program. (text to speech)

I'd type in <><><><><><><><><><><><><> and it would say "less is then greater then less then greater then less then greater then less then greater then less then greater then less then greater then less then greater then less........." and the voice would get lower and lower.

I graduated HS in '95 and most of the computers in use were IBM PC Jr's and those little IBM's that had the monitor, disk drive, and CPU all built in the same case. They were outdated even in '95; but, they were still in use. I remember our class getting the lecture from our 7th grade computer science teacher telling us that the IBM PC Jr's. were obsolete and parts were not available; so, we must take care of them.

The first Macs that I spent any real time with were the Mac Plus and Mac Classics at school. At the time I wasn't really that interested in them. The Apple ][e room was much more fun. They were considered outdated by most of the staff and other students, so you never had to wait for a machine (there were always queues for the Macs), had better games and you could gain admin rights over the ][e side of the network without anyone noticing. Messing with other users provided hours of fun for a 12 year old and the staff just assumed things weren't working right because they were "the old computers". Not long after I left that school they got rid of the ][es. I wish I had known about it. I would have liked to own "my" ][e, #9 with 3 disk drives and the only color monitor in the room.

My first Mac was a Mac Plus that had been dropped cracking the neck of the CRT. I replaced it with a green CRT from an old Compaq portable. It worked, but it looked really weird.

In the late 90s various companies started dumping a lot of Macs on the used market. They were sold cheaply at the PC-centric swap meets and I quickly acquired a collection of 68k and early PPC machines. I'll always have a soft spot for the LC475. I was impressed by what that little machine could do after I upgraded it with a 33MHz CPU, 36MB RAM and an ethernet card.

The iMacs didn't impress me as much as the older machines. Eventually one of the later models will come my way, but so far my upgraded 7500 runs OS X better than my Rev C iMac.

Yeah, Rev A-D iMacs are slower than the old G3 Power Macs even though the Power Macs had slower CPU's, the bus was faster on the Power Mac. I really wish Apple hadn't been so proprietary, I want to get an old Power Mac 7100/80 (PPC) on my network but it needs some funky adapter to get online through ethernet... on the other hand, I can pick up an NIC for $5 at Fry's and pop it into any random old PC and it'll work.

I guess it's what makes Apple, Apple. Do you like their new stuff though? I think they're too occupied with the iPod/iPhone, they're not all about computers anymore like they used to be.

Apple switched to Intel x86 CPU's so I consider Macs to be just another type of PC now. They can even run Windows now.

If you can't beat em, join em I guess.

I do find it ironic that after years of Mac vs PC wars, the new Macs are a direct descendant of the original IBM PC.

I find it even more ironic that Apple still shows their Mac vs PC commercials, implying that PC's are more complex and inefficent, etc etc etc. Yet, their newest Macs are just another PC. The only differences being proprietary hardware (Kinda like Dell or HP/Compaq) and a price that's twice as much as other PC's

Even better: OS/X had been secretly running on x86 hardware for several years before they switched their Macs over.

This is turning into the Mac thread. :)

Actually the 7500 has a 50MHz bus where the Rev A-D iMacs have a 66MHz bus. The problem I had running OS X on the iMac was simply a lack of RAM. The Rev A-D iMacs have a RAM limit of 384MB, but getting there is difficult as they are very fussy about what SO-DIMMs will work. I could never find a combination of the SO-DIMMs I had that would give me more than 160MB. Even my 6100/66 managed 264MB with standard SIMMs (not that it would ever run OS X even with the 240MHz G3 card in it).

I found that while OS X will run with less it needs 512MB RAM to be comfortable. With 512MB of RAM and a 350MHz G3 card in the 7500 it ran OS X well enough to be a usable machine for most day to day applications, certainly better than a 350MHz Pentium II box trying to run Windows XP.

The ethernet connector on a 6100/7100/8100 is an AAUI connector. While finding an AAUI transceiver in the average computer store is almost impossible there are usually a few on ebay for around $10. The alternatives are to use a NUBUS ethernet card or hardwire a transceiver to the motherboard, but that's too much effort to save $10.

I've no interest in iPhones (I'd still use my old brick phone if I could, fancy phones do nothing for me) or iPods. I doubt I'll get to play with an Intel based Mac for a few years yet. I like getting my gear for nothing or almost nothing too much to buy new gear. This is a lot easier with PC stuff though. Pentium 4 class PCs are regularly dumped, but I doubt anyone will be throwing out their G5 or Intel Macs for a while yet.

Hmm, well I remember reading somewhere that Power Mac G3's had a faster bus. There's 96MB of RAM in my iMac, nowhere near enough to use OS X, and the CD drive is extremely picky about what it will and won't read, I can't even install Linux on it so if I *ahem* acquire a copy of OS X the drive won't even read it (only reads original, pressed CD's). I put an ad on Craigslist offering $10 for a broken iMac, hoping I would get a better one (I have the Rev. A, I'd love a Rev. C/D or at least a B for the better graphics) that I could swap the FBT on, but no dice.

I run OSX86 on my main PC (sometimes), and it wouldn't run very smoothly until I put 1GB of RAM into my PC, I'm sure if my processor had SSE3 then 512MB would have been enough. When it comes to my favorite OS, nothing has beat Vista yet. I know Vista is supposed to be terrible, but it's working out great for me (on my 5-year-old PC). I did need a new graphics card and more RAM for it to run well, but that's not bad for a 2002 Pentium 4. I only had to spend about $90, I don't count the cost of Vista because I get it free (taking a Computer Networking class at my local college, that makes me count as a college student I can get Vista free). Feels as fast as XP, and I like the shiny Aero graphics, I can't stand Linux. Ubuntu (and it's variants), Fedora, PCLOS, Mandriva, I've tried and hate them all because it's all beta and it keeps breaking, just when everything is running nicely, an update comes along and breaks something, Linux is fun for messing around on spare PC's but I don't want it on my main machine. I can never get my ATI card running smoothly, and only PCLOS has been able to support dual monitors. PCLOS was the best of them all, but I don't like KDE.

Something I'm interested in doing is using the iMac as my main PC, some people have done it with old 68k Macs and if you have patience it's not bad. The only thing holding me back is a good web browser for OS9, Internet Explorer can't properly display a lot of modern sites.

Well, this thread has gone completely off topic. I'm ordering the Flyback tomorrow from here: http://www.bluestar-online.com/6174Z...174z-1003g.htm

I just ordered the Flyback, hopefully if I can find a better Rev A-D iMac it'll happen before the flyback arrives, otherwise I'll be putting it into my Rev. A

I think you'll be able to use low density 256MB SO-DIMMs in a rev A imac. These are easy to spot because they have 8 RAM chips on each side instead of 4. My thinkpad requires these and won't work with the more common ones with 4 chips per side. That should get you to 512MB.

Speaking of Vista, not too long ago I tried installing it on a 400MHz PII and it worked. It needs 512MB to install, but it will run in 224. I maxed it out with 768 MB and it was usable. I even managed to install the XP drivers for the built in ATI Rage pro graphics. It wasn't noticeably worse than XP once I turned off all the fancy graphics. I suspect that it would run on a PI, but I don't have one to try it with.

Eh, Vista is where I draw the line, at least for the time being.

It's too intrusive, too resource hogging unless you go through it and turn off all the needless eye candy, too expensive, and I'm starting to really distrust Microsoft's updates. (Never turned on automatic updates until it foced me to, and even then, I refuse to let it install anything. I update manually. Even then it sneaked something onto my PC from what I heard in the news...)

I'm going to stick with XP pro until M$ forces its obsolescence. After that, I may make the leap to a flavor of Linux.

While we're on the subject of Operating Systems, is there a decent alternative to Internet Explorer on OS 9? The only modern browser seems to be iCab, and it's terrible. I would just use IE but a lot of websites don't render properly on it. I never really sat down and used the iMac too much, but I'm typing from it right now and it makes an OK computer! Definitely useable, I've got iTunes playing internet radio and I'm browsing the web from IE. One thing though, the screen regulation is pretty bad, as I scroll down web pages and scroll past bright/dark items, the screen bulges on the right as they scroll down. Will the new Flyback help?

The G3 Powermacs do have a 66MHz bus. The 7500 came out before the G3 and originally came with a 100MHz PPC 601, but the CPU is on a card and can easily be upgraded. I ran a Sonnet 350MHz G3 card in it and installed OS X using Xpostfacto. Sonnet now make a 1GHz G3 card that will run in it. They also make a 600MHz upgrade card for the Rev A-D iMacs. If you don't mind spending more money on the iMac than it's worth it's something to look at. With a 600MHz G3 and 512MB RAM it should run OS X (at least the earlier versions anyway) well.

I do like the classic Mac OS, but the lack of a relatively current web browser is a problem for day to day use. When I was using the 7500 more regularly I generally booted into OS X for any web based stuff. There is WaMCom which is a backport of Mozilla to the classic Mac OS. I haven't tried it myself yet and it hasn't been updated for ages, but it may be an option.

Poor regulation can also be caused by bad capacitors. There have usually been a least a couple of obviously bad capacitors in most of the LG monitors I have scrapped, but I haven't seen that many iMac chassis to know if they follow the same trend. The lack of ventilation in the iMac case may make the problem worse as heat kills capacitors.

If you see any that are bulging or leaking change them. The ones that look okay can also be bad, but you will need an ESR meter to check them. Some prefer to swap out all suspect capacitor as preventative maintenance.

I'm not looking forward to Vista, but it will probably be a long time before I have to deal with it. I run Windows 2000 on most of my PCs. I'm used to running my machines as lean as possible so I find XP be a bit sluggish in comparision and some of it's "features" too intrusive. I can't imagine that Vista will be better and it may be what eventually gets me to switch over to Linux.

I've lost some interest this stuff over past couple of years. The rabid tweaker in me is slowly dying. Gone are the days when spending hours perfecting every aspect of a system was fun and the end result was a joy to use. Wrestling with an XP installation has become an unpleasant chore where near enough is good enough. I guess this says less about operating systems than it does about me. I feel like I'm old and I miss the "good old days".

You'd be suprised as to how well OS X runs on older hardware. I use a G3 "Pismo" Powerbook (400Mhz, 384MB RAM) and a G4 Tower "AGP Video" (450MHZ, 768MB RAM) and the current version of OS X (10.4.10) runs great.

I've use iCab on older systems, and it does have its quirks and issues, but at least it's still being updated. The backport of Mozilla sounds interesting, i'll have to check that out.