Absolutely beautiful fix of that power supply, that made me smile for sure! Many would've just tossed it after finding out something like that was dead, I bet.
The power supply upgrade is awesome, that's the kind of thing we only dreamed of back then. So cool to see you repair and improve their design. Love the brass stand offs. What is the red threadlocker you used, is it just red Locktite?
Nice video Tony. Very good analysis. Most step down transformers have a thermal fuse inside the casing. I can't remember whether the fuse is on the primary or the secondary but it might be worth checking before you scrap it.
Thank you! I did open that transformer after the video and I was able to revive it by just reflow the solder joints between the mains wires and the winding! But I had to cut the external shield - but it works! It’s in my spare parts bin! Thanks again!
Great video as always. Just a quick note: at 29:20, since you are dealing with AC power, by multiplying V*I you are measuring the apparent power, not the real power. PFC was not a thing at the time, and very likely this device has a very low power factor: this is probably part of the reason why the DC power you measure at 32:55 is way lower than 29 W. The power supply section will definitely waste some power, but judging from the schematics at 30:35 I would say only about 8-10 W; the rest of the 16 W descrepancy is probably caused by the difference between real and apparent power.
Thank you, I appreciate that! I noticed that while the transformer output 16VAC, I only had 18V DC after the diodes. Am I mistaken or I should have read 21.2V DC instead? I thought that that meant that those diodes were pretty inefficient, I forgot to measure the voltage drop. Could that explain the amount of power lost in the circuit? The overall consumption of the original monitor with the picture you see at the end is 26W, the modded one is 16W. Considering the Delta is not 100% efficient, it looks that the original design was using a bit more than 10W. Thanks for watching and for your feedback!
When discharging the CRT you should discharge it to the outer coating of the CRT (Aquadag) this is usually but not always connected to chassis, it either has a metal tab or a wire braid, the metal tab is usually connected to chassis. The braid if connected direct to chassis then OK but sometimes it has a resistor and capacitor to the chassis and a direct connection to the CRT socket board. The keystone can be adjusted if the electronics does not support it by altering the square magnets around the outside of the scan coil, mark before moving as they affect pin cushion also. Setting the geometry with the magnets is an art form and takes a while to learn. I was also surprised you did not open the old transformer as it is unusual for a secondary to go open, so maybe the connection between the winding and the flexible external cable has broken.
About discharging, you are totally right, I should have been more clear. In my case the tube tabs are directly screwed to the chassis so it should be ok but I should have mentioned that indeed. I hope it's clear enough. I did play with the magnets at the end of the video, I see what they do but half of them are really not accessible so I decided to just live with that distortion. I did open the old transformer - after the video was made and... Well, I'll share at some point, watch this space! That said it's a destructive process for the external metal ring which is tightly wrapped around the metal case. Besides that I managed to open it (and close it back) nicely. Thanks for watching and for the feedback!
I think I missed something. Did you test selected capacitor from the first monitor? I'm writing this while watching so maybe this will be clear in a moment.
That's a good question and I don't know the answer. It's not just the solder, there are no PCB traces there. I suppose it's a part of the regulator which is not required for the project.
Equivalent Series Resistance. A real world capacitor will show some resistance as well, not just capacitance. Usually a good capacitor will show low ESR. High ESR is normal for very low values; otherwise it indicates a failing/failed capacitor. For a 1000uF 25V capacitor you can expect a 0.14Ohm ESR. That capacitor read 0.17Ohm so it's totally fine :)
Absolutely beautiful fix of that power supply, that made me smile for sure! Many would've just tossed it after finding out something like that was dead, I bet.
Thank you! It would have been a sacrilege! I even fixed the original PSU later on! :) But I like the modded CRT now! Thanks for watching!
The solution with SMPS is so elegant! Congrats!
Thank you!
Well fettled and that modern unit is neat, it's final fittings look splendid.👍👍
Thank you Laurence! Indeed I was really not happy with the plastic stands, it looked patched up! Thanks for watching!
BRAVO! I liked this video! I really liked the switching power supply substitution for the bad transformer! Great work!
Thanks, that was a nice mod! I have another one to do very soon - no mod though!
Excellent video Tony! No wonder why your channel is growing so fast. Thanks for the mention
Thank you Sir! Your channel is growing as fast :)
A great job and another monitor not going to landfill. Win win
Thank you!
Complimenti Antonio.
Grazie egregio!
Woh, i really like your explanation and the deep dive into electronics.
Thank you, I'm glad you enjoyed it!
The power supply upgrade is awesome, that's the kind of thing we only dreamed of back then. So cool to see you repair and improve their design. Love the brass stand offs. What is the red threadlocker you used, is it just red Locktite?
it's... nail polish! :D Thanks for your kind words, it was indeed a very enjoyable project!
Nice video Tony. Very good analysis. Most step down transformers have a thermal fuse inside the casing. I can't remember whether the fuse is on the primary or the secondary but it might be worth checking before you scrap it.
Thank you! I did open that transformer after the video and I was able to revive it by just reflow the solder joints between the mains wires and the winding! But I had to cut the external shield - but it works! It’s in my spare parts bin! Thanks again!
Great video with an ingenious solution.
Thank you Ted!
Well done!!!
Thank you!
Great video as always. Just a quick note: at 29:20, since you are dealing with AC power, by multiplying V*I you are measuring the apparent power, not the real power. PFC was not a thing at the time, and very likely this device has a very low power factor: this is probably part of the reason why the DC power you measure at 32:55 is way lower than 29 W.
The power supply section will definitely waste some power, but judging from the schematics at 30:35 I would say only about 8-10 W; the rest of the 16 W descrepancy is probably caused by the difference between real and apparent power.
Thank you, I appreciate that! I noticed that while the transformer output 16VAC, I only had 18V DC after the diodes. Am I mistaken or I should have read 21.2V DC instead? I thought that that meant that those diodes were pretty inefficient, I forgot to measure the voltage drop. Could that explain the amount of power lost in the circuit?
The overall consumption of the original monitor with the picture you see at the end is 26W, the modded one is 16W. Considering the Delta is not 100% efficient, it looks that the original design was using a bit more than 10W. Thanks for watching and for your feedback!
Great video. Very evolved in my opinion.👍
Thank you!
Very nice! ❤👏
Thank you!
Amazing repair, i don't like the rifa replacement but the PSU replacement is better and a great solution
eheh, I don't blame you! Well, it's going to be a problem for when I'm 75yo I guess :D Thanks for watching!
@@tony359 thank you for the amazing CRT content and tech, i like a lot keep going! I fix CRT too but he don't work on YT
When discharging the CRT you should discharge it to the outer coating of the CRT (Aquadag) this is usually but not always connected to chassis, it either has a metal tab or a wire braid, the metal tab is usually connected to chassis. The braid if connected direct to chassis then OK but sometimes it has a resistor and capacitor to the chassis and a direct connection to the CRT socket board.
The keystone can be adjusted if the electronics does not support it by altering the square magnets around the outside of the scan coil, mark before moving as they affect pin cushion also.
Setting the geometry with the magnets is an art form and takes a while to learn.
I was also surprised you did not open the old transformer as it is unusual for a secondary to go open, so maybe the connection between the winding and the flexible external cable has broken.
About discharging, you are totally right, I should have been more clear. In my case the tube tabs are directly screwed to the chassis so it should be ok but I should have mentioned that indeed. I hope it's clear enough. I did play with the magnets at the end of the video, I see what they do but half of them are really not accessible so I decided to just live with that distortion.
I did open the old transformer - after the video was made and... Well, I'll share at some point, watch this space! That said it's a destructive process for the external metal ring which is tightly wrapped around the metal case. Besides that I managed to open it (and close it back) nicely. Thanks for watching and for the feedback!
@@tony359 I do love your video's, my background is as a repair tech in a CRT monitor manufacturer from 1978 until 2000 when it closed.
A proper CRT expert then, amazing! Thank you for your kind words!
really interesting video
Thank you!
awesome video, as always :)
Thank you!
I think I missed something. Did you test selected capacitor from the first monitor? I'm writing this while watching so maybe this will be clear in a moment.
Yes, 11:02 :)
@@tony359 Sorry, I was watching this in the park and I think I got distracted... Don't ask ;)
Park is nice :)
why did some of the legs on IC 701 not have any solder on them ?
That's a good question and I don't know the answer. It's not just the solder, there are no PCB traces there. I suppose it's a part of the regulator which is not required for the project.
Tvs keyboard or patch on monitor
Shall do.
what does ESR stand for ?
Equivalent Series Resistance. A real world capacitor will show some resistance as well, not just capacitance. Usually a good capacitor will show low ESR. High ESR is normal for very low values; otherwise it indicates a failing/failed capacitor. For a 1000uF 25V capacitor you can expect a 0.14Ohm ESR. That capacitor read 0.17Ohm so it's totally fine :)