Commodore 1084 CRT monitors: bad flybacks and blooming
ฝัง
- เผยแพร่เมื่อ 2 ก.ค. 2024
- Taking a look at a poorly Commodore 1084 that has the flyback squeal of death. Also we check out some blooming issues with the 1084S-P1. Catch part 2 here • Commodore 1084S-P CRT ...
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0:00 Intro
0:40 Disassembly
3:02 Don't try this at home
4:33 Discharge
8:07 Desoldering
12:00 Damn blooming
14:18 Danger high voltage
19:05 Dammit
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Thanks for watching! - เกม
I had the same problem. I just bought another flyback transformer and it worked again.
Another Great video as you always do!!! I really love your CRT video's.
good to know, thanks. i have three 1084's
I have an Amstrad CRT which was making a noise like that. I somehow learned to repair my 8-bit microcomputers myself (also by watching your channel), but am terrified by the thought that I should attempt to fix the CRT so I brought it to a retired CRT repair guy (couldn't find a non-retired one who would be willing to take a look). Was told it was the flyback (along with a burning resistor) and that there was no chance of me getting a replacement one. Luckily I was able to source a replacement flyback made by HR Diemen on eBay. The repair guy installed it but then the monitor's X-ray protection mechanism started to kick in, shutting the monitor down after about a second. So there was still something wrong with it, probably something not too complicated. However, my repair guy gave up on the monitor. I think I will eventually need to attempt the repair myself, but am still building up courage and the necessary knowledge.
Yeah that's a tricky one, could be the replacement flyback also has an issue and is tripping the x-ray protection, or it could be something in the x-ray protection circuit itself. If you have the schematics available they usually indicate the x-ray circuit. Sometimes you can spot it by looking at the pins coming from the flyback, one of them should have a couple of diodes facing towards each other (cathode to cathode) with a capacitor in between going to ground, but this isn't always the case.
Anyway, I hope you figure it out and feel free to throw me any questions you have
@@TheRetroChannel I have the schematics and I can see the protection circuit there. It really is a matter of me taking the CRT apart and figuring out which part is bad. But I must overcome my fear of getting electrocuted first. So I am watching CRT repair videos in the mean time :-) Do you remember the first time you tried something like that?
Sure do, and I was shit scared. You'll become comfortable with it after a while. Start with just unplugging it and opening it up, and looking around. You can safely touch the CRT itself, just don't stick your fingers under the anode cap. Grab a multimeter and probe a couple of the larger caps to see if there's any voltage stored. More than likely the caps would have discharged themselves long ago.
Once you're ready, grab a plastic handle flat blade screwdriver and clip a lead to the metal part of the screwdriver and the other end to the ground strap or one of the ears of the CRT. The lead itself doesn't need to be thick as although there could be high voltage, it will be very little current, even just after powering it off. As long as the lead doesn't have broken insulation and you have a solid connection to the screwdriver and CRT ground there's nothing to worry about. Slide the screwdriver tip under the anode cap until you feel it touch the anode clips, if you're lucky you may hear a tiny click, but more than likely it will make no noise if it's been powered off for a while.
Again once you're satisfied that there's no high voltage stored in the CRT, have a go at removing the anode. Peel back the rubber cap with your fingers and have a look underneath. Most will have some kind of clip to hold the anode in place that needs to be squeezed inwards. Do that and remove the anode lead. Take a look at the anode connector on the CRT, you'll see it's just a shallow hole. Then have a go at reconnecting the anode lead, it should clip back into place and feel solid.
That should help you feel a bit more comfortable working inside the CRT, at least when it's unplugged. The real fun starts when you want to do adjustments like geometry and convergence, those really need to be done with the CRT powered on
I recently repaired an Amstrad CTM640 monitor that was making the same noise. But it wasn't from the flyback it came from the power supply transformer. The monitor had originally failed from a blown power supply section ie diodes that then obviously blew other components. The flyback looked in good cosmetic shape so I was suspicious it had failed. Mine had a blown Schottky diode near the flyback and the two voltage regulators had gone also. Replaced these components and it now works perfectly.
My impression over here in Europe is that regarding sourcing replacement flybacks is that HR Diemen products are the only available brand. Having said that they are not being produced any more and it could well be that they will all be sold at some point and no longer available in online shops. I tried to find a flyback for a Commodore 1802 (HR 7458) (luckily I don't really need it) and didn't find anything anywhere. Asking a shop that listed it they told me they are out of stock. Luckily HR 7506 seems still to be available (NOS).
The Goerge Costanza effect
Bloom is definitely a flyback issue. The flyback doesn't only just produce voltage for the CRT, There's also secondary coils for generating some of the other voltages to run the board. Poorly designed flybacks can have worse bloom then others. It's a sign of poor voltage regulation. A bright screen causes the voltage to sag/change which is what causes the screen size to change. I believe the voltage for the deflection yoke is one thing that is powered by the flyback too so that's where the bloom is actually happening I believe.
Most CRT TVs and low end monitors have it to some degree. Higher end stuff like computer monitors tend to have much better voltage regulation and some even use components out side of the flyback to generate some of the voltages so the screen is much more stable on those. ;)
Hmm that's interesting, I didn't think about looking at what the yoke is doing. Initially I thought it was an issue with the B+ voltage to the flyback, but it seems pretty solid, only varying by about 0.16% (124.8V to 125V) between full brightness and black.
I got a JVC DTV 1700CG with this blooming issue. I checked the high voltage and it sits at 24.7Kv. It doesn't fluctuate too much as in the bad one in this video though. Around .2kv at most. Is this still a bad flyback? This is a high end monitor but with 37k hours.
@@ramiq7932 I have a 1910CG with the same issue did you find a solution to yours?
@@carlocgc seems most DTVs end up having this issue sooner or later. I assume the flyback just ages badly. Only solution is to calibrate your DTV and make sure your peak white isn't too high to minimize the blooming/breathing that happens. How many hours on your tube?
VERY interesting video mate, even if you didn't repair anything, we always learn...
The repair will definitely come in part 2
I think the replacement flybacks are very poor quality. I own a Magnavox 1CM1352 and installed the HR7533 from Donberg...it lasted just shy of 2 years. It seemed sketchy from the beginning as the pins are thin wires bent to match the original shape. Now I bought one on eBay from a guy in Germany and it's totally different. Thick straight pins that fit the board, different color and different focus/brightness adjustments. Hopefully this one is from a different manufacturer and lasts longer.
Do you have the German eBay sellers name please?
Blooming is 'usually' caused by bad B+ voltage regulation. Can either be due to a failing voltage regulator or a bad flyback as well. It's a bit of a crap shoot but in my experience, it's usually the regulator as opposed to the flyback. I would measure your B+ voltage when the blooming is occurring and see if it's changing as opposed to the high voltage. If so, I would suspect the regulator. Although...focus drift is absolutely a flyback issue. So like I said, it's a crap shoot. Just my opinion based on my experience.
Good point. I eventually figured it out in this sort of follow up video th-cam.com/video/7z6T64Elm-s/w-d-xo.htmlsi=eE7o2oKjJJuMZyDQ
Well, looking at that fault you're calling bloom, (we used to call ballooning 40 years ago... lol) I would say you have a beam current limiter issue, maybe incompatibility to replacement lopt.
Check adjustment of bcl set up as to makers manual...
THANK YOU for this comment. This makes sense, digging thru my CRT repair manuals now.
That's strange, mine 1084s p1 with HR Diemen flyback replacement had no such problems i.e no blooming.
It sounds like a washing machine spinning down when you power it off.
Enjoyed the video. I always like the monitor tuneup type stuff. Were Commodore monitors popular in Australia? Judging by their high prices on eBay here I'm guessing they were kinda rare here or most have died leaving them rare. I'd like to get one. I'm sure it would look much better than composite on a CRT TV or through a retrotink.
I guess for our much smaller population you could consider them somewhat common. But a tested and working one will still run you about $400AUD on eBay
I'm curious why you warn people about the shock they could get poking around inside a crt but you don't tell people how to discharge it first...?
Still has its front control cover!
Hah, yeah very rare these days. Wish my own 1084 had one 😄
True, but without the Commodore logo they just look like they're missing something. And yeah, TH-cam is shit when it comes to spam filtering, I have all the spam settings turned off and it will still nuke anything with a link 😒
Did anybody figured out were to buy a flyback replacement for 1084s-D2? Mine still works, it has a bit washed image but the smell of statics or something, is so nasty I cant work on it for more than half na our.
Don't know about the D2, have you tried putting in just the part numbers from the flyback into hrdiemens "original reference" search? Sounds like you do have a high voltage leak. Have you tried running it in a dark room with the rear cover off to see if you spot any arcing? Just don't get too close because if there is high voltage leaking outside the flyback, if could target you
Dönberg Electronics Ltd. Ranafast - Co. Donegal - Ireland