@Michael O Callaghan that hows ya learn. or at least how i did. Right now im working on a NES console that someone lifted 80% of the traces on cuz they didnt know what they were doing. I told them i could probably fix, but now they know not how to do it lol
My first 12” black and white tv had a white dot minutes after turning off... My parents knew this so when I heard steps on the stairs I was already to late 😂
@@Wewewea Turning brightness to 0/zero is the correct way to say it. But saying "turning brightness too 0/zero" makes no sense. Google, Bing and Duck Duck Go agree with me. Just like saying "I'm going to work/going to correct you/going to turn my volume to 0/zero" am I wrong?
Excuse my language, but holy fucking shit. My dad has a older model PET 2001 where the bright spot has bothered him for the last 15-20 years. When mentioning it, its all he ever talks about and how he could never get it fixed. I'm going to "borrow" his PET '01 and apply these fixes as a Christmas present. Thank you so, so much Adrian! Greetings from Norway!
The thing is, while he's trouble shooting, he's not an engineer, he's learning along the way. We are picking up, what he's putting down. He tries, isn't afraid, and this is working out well for him and the rest of us.
Just did the mod of changing R2 2k2 to 470R in series with 8.2 zener on a 3032 PET. The rest of the components are already at the correct values. The annoying spot has gone. Thank you Adrian and Frank!
I can't express how much I enjoyed this video. I really appreciate your perseverance. It was an amazing journey. Thank you for taking us through it step by step.
Thrilling as a sports match! I was actually shouting out loud "Ohh nooo!" when the capacitor didn't fully fix it. Great to see you getting to the bottom of this. Well done!
Funny enough, the entire time of it not being fixed (at this stage I mean) I was screaming in my head - get to a cap dude! I was for sure that once he did, it was a done deal. hahaha
I don’t know how but Adrian suddenly got me interested in a pesky spot in a ‘70s machine that I never really cared for. Love you Adrian for making such engaging content and providing so many hours of great entertainment! Keep up the great content!
This is very interesting - I have a 2001-8 with chicklet keyboard and tape which I've had since 1979 (well, my dad bought it but I commandeered it!) and needs refurbing someday. I'll keep a note of this video for when its time comes (which hopefully will be 2021!) I remember back in '85 when I last used it I would get a faint spot a few seconds after turning it off (only really visible in a darkened room) that lasted for a minute or two. Since its been unused for ~35 years its going to need a complete refurb and I will put in the mod and check the 33v Zener! Great channel Adrian, I found you through one of your earlier PET videos. Theres not a huge amount on RU-vid with these PETs, most of the attention these days is on the later more glamourous machines, but I learnt to code on my (*cough* Dads) PET and the skills it taught me have been good to me in my working life. On another note, are you trying to collect ALL the SIM RAM in the world? :D Say Hi to Rammy for me!
I own both a chiclet 2001 (1st revision analog board) and a 2001-N (2nd revision analog board). After applying the spot fixes according to your video, the 2001-N has been spot-free for a year now. I can't draw a conclusion on the chiclet 2001 yet as I only got it properly running a few days ago, but so far the fix seems to do its job very well.
Adrian, I would strongly suggest replacing ALL the electrolytics. As you noted, the ESR of those caps are pretty bad. They are after all 50 years old. Heat and age are not doing them any favors.
Fascinating. I wasn't sure that you were going to find the solution to this problem. But then again, who am I kidding -- great job -- and process duly noted. I have two PETs yet to be tended to and I will be sure to remember this great solution. 👍
That model with the chicklet keyboard and built-in cassette drive was where I first saw the "Hunt The Wumpus" game. I recorded the tunnel connections onto paper and wrote my own version of the game using just that information along with the knowledge that there were exactly two pits and exactly two caves with bats. 😄 Anyway, grats on fixing the problem.
Hi Adrian, thanks a lot for all this amazing content you upload. I’m 20 years old, I’ve never seen, used or even heard of any of the devices you show in your videos but somehow I can’t get my eyes away from the screen from the moment they begin to the moment they end! It never happened to me before, I guess that’s what happens when you find a genuinely interesting and talented youtuber.
Hi @Adrian's Digital Basement, another great video, I love problem solving videos, it is nice to know I am not the only one that has to spend ages fixing issues like this, looking forward to the next one. 👍
It's funny that as this came up in my feed I am working on editing my video about fixing an IBM 5154. So, I have something very relevant to watch while I wait for rendering to happen. Thanks!
Great work Adrian! I can imagine how much work it was to fix this. Sometimes things are looking so simple in the videos, like it took 10 Minutes to fix it, but sometimes you have to try it again and again and it actually takes months. I know it too good :) Thumbs up!
Never had so much fun watching a spot .We need this to a be yearly event , spot watching 2021.I'm kidding of course , great vid . I hope you and your viewers have a great year in 2021
I love this troubleshooting adventure and great investigation and explanation. Personally I'm lazy and would have just lived with it as I've never seen an original PET with any burn-in from 'the spot', and I actually find it kind of charming, like some ancient TVs that did this when I was a kid. I have a next-gen PET, a 2001 (3032) "Professional Computer" and it does not suffer from the spot though.
23:39 I had a Mitsubishi TV from the 1973 with that instant-on feature. It did run the heater at reduced voltage so didn't cause any significant tube life issue. The TV got scrapped a few years ago, just because no-one wanted it, but it still worked! 33:12 I've never thought to keep a dead parts bin. Mine would be very full indeed by now, mostly of smelly electrolytic capacitors.
The "dot" is residual charge left behind somewhere and released (discharged) into the monitor, the trick would be to find the part of the circuit that is responsible for fast discharge after the monitor has been turned off. The voltage affects the X/Y positioning of the beam, so... technically that could be a thing too.
I love watching the methodical way you troubleshoot these problems, Adrian! It's great to share a part of the satisfaction once these tricky bugs are sqaushed. Great work as always!
That was great, one of the best troubleshooting vids I've seen. I'm old enough to have, in a previous life, to have been CRT TV repairman. This brought back memories.
unrelated, but one of my family's last TVs lasted about 12 years, until we replaced it with a flat panel we got from a family member, we replaced it because it was taking upwards of 2 minutes to warm up, when usually it only takes about 10-30 seconds. it was a zenith i believe. I think that's very good life for being turned on for at least 14 hours a day for 12 years, and knowing my dad, we probably got it used so add that on top.
15:27 - the differences are down to yours catering to the home/personal market the loan one catering to the professional market, the green screen was considered to reduce eye fatigue, the keyboard also was a better design (IIRC they where hall effect switches rather than the traditional mechanical ones)
My parents used to admonish me for watching too much Tv as a child (40+ years ago)......."You would watch the dot" they would say....now i know what they meant !!
Wish I could give you 10,000 likes! Congratulations. What a quest :D Nice job to all involved but Adrian your persistence is what solved this. I find this type of content so satisfying it's like defeating a boss at the end of a 200hr game.
4.4K likes, 43 dislikes, yep I think that sums up how enjoyable this series is. I'm very much an electronics newbie though I used to build computers to pay my way through Uni in the 90s. This would be beyond me but I've learnt a lot. Thank you.
Congratulations on this particular video. It is clearly perceived the large amount of work behind. Researching, exchanging impressions with colleagues or mounting / dismounting the monitors with which you have done the tests.
Hahaha, I love it... using a desoldering station till solder. The irony and upright frankness about doing so. That settles it, Im sending a Christmas present.
It took me until 33:50 when you mentioned 47 microfarad for C22 to actually realize that it was 47. Earlier in the video when you applied the actual fix, I was thinking 4.7 the whole time. I made a comment trying to correct what I saw and heard but deleted it as you are correct in your video throughout. I am glad for you and enjoy!
Nice to see you figured it out in the end! First thing I noticed that was different was the flyback transformer design, as you mentioned, but I just guessed that perhaps Commodore had a different manufacturer for the later ones.
So youtube commentators noticed the spot on your monitor, which is perfectly normal for the crt's of the era, but they don't know about it because back then their parents were in elementary school. They told you that this is indicative of a fault and your CRT will explode. This is not true and they told you that either to have a laugh at your expense or to boost their paper-thin ego and pretend they know something about something. And now we have 2 very entertaining videos, and you spent month trying to fix a non-issue and finally fixed it.
I wonder if that zener is really bad. It may not be. As you said, all semiconductors tend to leak when hot. Just because that diode was leaky when hot, does not mean it has failed. Just changing the dropping resistor may have fixed the issue. Pro tip: When trying fixes, try to change only one variable at a time. If you change two parts, and the problem is fixed, which part was actually bad? Potentially none. The resistor was obviously fine, the zener may have had issues, but now we'll never know. I would have changed the resistor first (too small a dropping resistor is a n00b mistake, commodore), and tested. But swapping the zener out certainly did no harm, so there is that.
Hey Adrian, I haven't seen anyone commenting this nor heard it in your video or description (unless I missed it), so since you seemed not really ticked off at the higher value, here is a quick tip with capacitors, if they read above their rated µF value, especially that much higher, you can be sure the capacitor is bad and needs replacement, only way it can be an overachiever is by leaking electrically, aka, it's getting shorted, taking longer to discharge, appearing to have a greater capacity than it should. Hopefully this little tip can help you diagnose things a little faster and with more confidence! This might save you from a magic smoke show some day hah. Cheers, -Noma
Im always in awe of the efforts and time you devote for such a noble goal of maintening those pieces of history, kudos sir keep them coming, always very enjoyable. ( and kudos to the wifey too for enabling you for our enjoyement xD )
Hi. All modern CRTs (I mean transistor or IC driven) had circuitry preventing those kind of spots to happen. And those circuitries always were connected to the first grid of CRT. In other words if you ever face that kind of issue - first thing to do is to check parameters of components connected to the 1st grid :)
You were very brave to turn it off with the heater voltage still on. I know the cathode has about 5 to 10 seconds of thermal retention. Quite a lot of spot supresion circuits rely on the fact the cathode will be cool enough after this time, oe the EHT has bled away. I noticed the spot was a lot brighter when you powered the heater from your bench PSU.
ADRIAN!!!! Im in So California. its cold and dry today....I reached over to my laptop to move the screen..an ZAAAPPP!! (static discharge) at 22:03 I thought I touched the flyback on your video!!!! I can't stop laughing....!!
