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   egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:38 JST egregious philbin

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   I'd be remiss if I didn't mention this fantastic service manual. This monitor is a relic of a bygone era, where things were built to last, and built to be repaired.

   Block diagram. Theory of operation for every major circuit. Clearly drawn and printed schematic diagrams. Oscilloscope waveforms. Photo of the PCB with all the components indicated. The PCB has positions and polarity screened on the top and bottom.

   It's just lovely to see the amount of care put into this. It's why this is still working, 43 years after it rolled off the line.

   If I ruled the world, I'd require everything to have this level of documentation and repairability.

   https://arcarc.xmission.com/PDF_Monitors/Motorola%20M5000%20&%20M7000.pdf

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:40 JST egregious philbin

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     In this case, I stuck the chassis back on the shelf, and a couple bolts to hold it in place, and tightened down nothing else.

     And it worked perfectly the first time, and the flicker is gone.

     (The monitor is B&W, the colors are from an overlay that sits on top of the monitor and gives different areas different tinting -- very common on B&W video games.)

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:41 JST egregious philbin

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     After all that's done, it's time to test.

     Composite video is backwards compatible with B&W video, so it's very possible to bench test these with anything that can provide that -- a raspi, DVD player, whatever.

     But, this is a 23" monitor, and I don't want to pull the tube out to bench test it, so I stuck the chassis back in the cabinet.

     I'm not generally superstitious, but I am a believer in Murphy's law. The upshot here is that I never completely reassemble something I've worked on until I know it works. If you completely reassemble something without testing... well, it won't *always* not work, but it's been my experience that they are less likely to work and require you to disassemble all the stuff you just put together.

     So I don't do that.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:42 JST egregious philbin

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     Of the four can grounds, two don't connect to anything else on the PCB, and the other two connect chassis grounds, which there's no other path through.

     Folks who do nice restorations will pry open the can, scrape out all the gunk, and stick the new caps inside, so it looks 100% original.

     I do not care this much. I stuck the positive leads of the caps in the right place, and the negatives wherever they fit, which meant two leads ended up sharing the same through-hole.

     Then I used a bit of scrap wire to connect up all four negative leads.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:43 JST egregious philbin

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     One final wrinkle on this -- which I took no photos of -- is the multivalued cap. These are cans which contain multiple capacitors.

     They were very common from the 1940s up until the 1970s. They're sort of like a multi-tap transformer -- there's one cap with the largest value, and the smaller values are derived by sticking a lead into the roll. They had to be custom manufactured. Nobody does this anymore, so you have to replace them with (usually) three or four individual caps.

     The can on this one has four caps in it, and eight leads total. Four negative, which tie together and all connect to ground, and four positive.

     And on this chassis, they used opposite sides of the can to route the chassis ground. ugh.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:44 JST egregious philbin

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     Once all the caps are in the board, stop and double-check everything. For every new cap you installed:

     Is the orientation correct?

     Is the value correct for that position? Compare the kit's list (if you have one) with the manual's. Sometimes the kits have errors.

     Is the orientation correct? Yes, check it again. You *really* don't want any put in backwards.

     If everything looks good, solder them all in.

     Then, trim the excess lead sticking out the bottom of the PCB. While you do that, make sure you didn't miss any when you were soldering.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:45 JST egregious philbin

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     So, check this out! I've never seen this before, but this axial cap has some kind of printing error, and is not correctly indicating the negative lead. The light blue strip should point to it.

     Don't fret! The negative side of an axial capacitor is always the one where you can see metal.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:46 JST egregious philbin

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     Here's those caps in the board. The legs get folded over so it stays in place while you continue working.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:47 JST egregious philbin

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     Stick the new capacitor in. If this is an axial cap, orient it so the polarity and uF/voltage values are visible, not underneath it. Dress the leads so it doesn't fall out of the PCB. Don't solder it; move to the next. Do this for every cap, so you have a PCB full of loose rattley parts in what you hope are the right positions and orientations.

     Here are two caps -- upper is the original, lower is the replacement. Both are 47uF 50v, so the new one is the correct part. Into the board it goes.

     Modern caps tend to be much smaller than vintage ones.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:48 JST egregious philbin

     in reply to

     The job here is replacing all the electrolytic capacitors. The approach I've found that works best for me is breaking things up into three phases:

     Desolder *one* capacitor, paying attention to its orientation -- most caps are polarized, and putting them in backwards is a bad time.

     Double-check the orientation against the PCB. Nice PCBs will have one or both of the + and - positions labeled. Crappy PCBs don't. The worst PCBs (like the Electrohome G07) have screening errors that direct you to put the cap in backwards.

     Grab the new cap and compare it to the old one. You're looking for identical capacitance here, and equal or greater voltage. Older electronics used caps in values that are no longer made, so be extra careful if you're working on one of those.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:49 JST egregious philbin

     in reply to

     Rule #3 of electronics: trust nothing and nobody. Don't trust the person who told you what they think is wrong with a thing. Don't trust previous repair work. Don't trust the instructions for your kit. Don't trust the manual.

     Pull together all the information you can, and use your judgement. Then double-check. Then check again.

     You might think that with three different sources of information -- say, the original hardware, the manual for that hardware, and the instructions for the cap kit -- they'd all agree, or at least 2/3 of them would, right?

     Well. Not always.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:50 JST egregious philbin

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     Here's the chassis on the bench. I've never worked on an M7000 before, but this is pretty typical for the era. For years, TVs were built much like radios -- wired point-to-point on a metal chassis pan. Over the years, the pan shrank, then vanished. This is right on the cusp of that era.

     Left side is a big transformer, guessing this is a step-down -- the manual says it needs an isolation transformer, which was very common for monitors of the era.

     Middle-right of the PCB is the high-voltage transformer, aka the flyback. Big metal canister is a multivalue B+ filter capacitor, part of the power supply.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:50 JST egregious philbin

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     Okay, getting into the recapping. This is using a preassembled kit. You can buy them for many vintage electronic devices, because we haven't figured out how to make ones that don't fail yet. So they fail, constantly.

     The kit comes with a sheet saying which caps are what. Some nice ones label the caps themselves, or stick them in tape with labels on it. This one just has a printout with the values and positions, and you have to figure out where they go.

     Rule of electronics repair #2: Go slow. Slow and works when you're done beats fast and broken every time.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:51 JST egregious philbin

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     B&Ws have a semi-standard 12-position Amp 0.84" connector which supplies both power and video; and on some configurations of some models, outputs +5v to power other stuff. (not pictured)

     The chassis is mounted on an angled wood shelf, and held in with four carriage bolts, which have washers and nuts on the underside. I like to replace the nuts with wingnuts, since it makes future servicing much easier.

     The washers tend to stick to the underside of the wood, since they compress into it when the nuts get torqued down. Remove these! They love nothing more than to fall down into the bottom of the cabinet and land on your power supply, usually across two different fuses.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:52 JST egregious philbin

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     Pro tip: IPA will clean up all kinds of degrading rubber! This has been super useful to know, both for arcade games and not.

     Oh yeah, I guess I should tag this junk, even though I continue to dislike hashtags.

     #arcade #crt #monitor #repair #retro

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:52 JST egregious philbin

     in reply to

     Next step is to disconnect everything. Most monitors have the yoke hooked up with a single four-position connector. This one has four individual push-on connectors.

     Rule #1 of working on electronics: take lots of pictures, lest you forget how things went together. Take as many as you think you need, then take a few more. You'll thank yourself for it.

     If you swap the positions of these wires, the image will display mirrored, or upside-down. But if you mix the X and Y axes, you'll smoke components on the chassis, and maybe the yoke itself.

     Take photos.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:54 JST egregious philbin

     in reply to

     Okay, time to tackle this M7000.

     First thing you'll notice is this seeping gunk by the anode. In the 1970s and early 80s, they made these out of some kind of rubberized plastic material. It breaks down over the years and gets all sticky and awful.

     Lots of people see this and think the tube is leaking or something. It's not, just the rubber breaking down. After discharging the tube, you can clean it up with isopropyl alcohol.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:55 JST egregious philbin

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     Got Mario Bros and Gyruss set up.

     Got Space Encounters and the MVS-4-25 v1 cab inside using the ramp. Woudn't have minded a spotter on the MVS tbh, but I got it done okay.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:55 JST egregious philbin

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     Several of my B&W games have some monitor funkiness I need to fix. Space Encounters had a bit of flicker happening after a few hours running.

     Didn't have a key to the upper back door, but I save any keys I come across and have a ring with several dozen on it, one of which opened it right up.

     And... Yep, original caps in here, date code 8052, so somebody spent Christmas week 1980 manufacturing this monitor. It's almost as old as me, and nearly as tired to boot.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:57 JST egregious philbin

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     Most of the games I have in this place are "cabaret" cabinets, which are much smaller & lighter than the regular upright. I can muscle those in without issue.

     But now that I'm into uprights a bit more (mostly because cabarets I don't already own are few and far between), I either need a helper or a ramp.

     Especially when it comes to the real big bois, like my Neo-Geo.

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     egregious philbin (ieure@retro.social)'s status on Tuesday, 28-Nov-2023 12:06:58 JST egregious philbin

     Dad helped me build this platform and ramp system this afternoon, which makes it easy enough to move games in and out on my own. Spent $13 on some 2x8" for the base, everything else was scrap. The big wood bookcase-like thing left in my garage at the new place got deconstructed and reused for the ramp.