M1212 with LC575 flyback?

[petey293]

Hello hivemind!

I'm working on getting a M1212 monitor fixed up - seems to work well except that the flyback transformer makes a god awful screech. I want so badly to use it with my Quadra 605 but I can't stand being in the same room...

I've tried coating parts of the flyback in RTV to dampen the vibrations, and tried strategically wedging toothpicks against it to try and couple the vibration to other parts, both without success. I might have even made it worse!

I've got an LC575 analog board in the parts bin that worked well when it was pulled. Could I stick the flyback from the LC575 onto my M1212?

Flyback part numbers are different, but the 2 monitors use the same CRT, same resolution, same video timings, probably same anode voltage?

 

[Byrd]

That sounds really dodgy (yeah same goes with the toothpicks), maybe the 575 has the same flyback transformer you can switch over. Alternately find a rough M1212 and use your existing monitor as donor for plastics and CRT.

 

[petey293]

That sounds really dodgy (yeah same goes with the toothpicks), maybe the 575 has the same flyback transformer you can switch over. Alternately find a rough M1212 and use your existing monitor as donor for plastics and CRT.

That's the hope, my M1212 is in nice shape aside from the flyback, I'd like to pull the flyback out of my parts LC575 and install it into the M1212.

The only thing giving me pause is the part numbers are different. Just curious if anyone here has attempted this swap before. Getting a donor m1212 isn't a bad idea but I've seen lots of complaints about the whiny flyback - I'd hate to roll the dice and end up with the same problem... If the LC575 flyback works, it might be a decent way to get some extra life out of these monitors

 

[Callan]

Hate to be the barer of bad news. It's not possible. Unless those two monitor pcbs were exactly the same I wouldn't even think about trying it. Flybacks don't just supply high voltage (although it is their main purpose). Depending on the flyback they have multiple windings supplying grid and heater voltages too. Not to mention they sometimes house the focus and screen potentiometers. They're an integral part of the circuit design. unless you have the exact part # flyback or can confirm the part you have is a cross reference to the original part # I wouldn't do it. You'll have way harder problems to solve, besides finding a flyback if you do.

 

[petey293]

Hate to be the barer of bad news. It's not possible. Unless those two monitor pcbs were exactly the same I wouldn't even think about trying it. Flybacks don't just supply high voltage (although it is their main purpose). Depending on the flyback they have multiple windings supplying grid and heater voltages too. Not to mention they sometimes house the focus and screen potentiometers. They're an integral part of the circuit design. unless you have the exact part # flyback or can confirm the part you have is a cross reference to the original part # I wouldn't do it. You'll have way harder problems to solve, besides finding a flyback if you do.

Understood, I was hoping since the CRT was the same part no. on both displays, the filament, screen and anode voltages would be the same. Hard to say for sure of course. Design looks very similar between the 2 chassis.

Focus and screen pots are located on the monitor PCB here.

 

[Callan]

It's not the output voltages that are the issue. The problem is that the monitors main pcb is dependent on that flyback being correct to produce those voltages.. For example... The first (and easiest thing to determine) are the flyback pinouts the same? Then, you get into the real issues. The input /output windings on the flyback could be totally different. What gauge wire did the manufacturer use for the windings. What type of insulation did they use? What type of core? The spacing between windings? All these things change the characteristics of that flyback.
That's why it's super important to get the same flyback, or one that was designed specifically for that monitor.

 

[petey293]

I had a quick peek at the LC575 horizontal section comparing it against the M1212, so far it looks identical, even the component designators are the same. With the same video timings and CRT I wouldn't be surprised if it was a copy/paste with some components rearranged to fit. The yoke is the same model as well.

 

[Garrett B]

I’d give it a shot. Different part numbers may not mean it’s not compatible. I tried a 575 flyback in my Color Classic. It did work, but the image on the smaller CRT wasn’t dimensionally correct (and couldn’t be adjusted to be correct). Oh well. This was a shame as the 575 flyback seem to be more plentiful.

 

[petey293]

I’d give it a shot. Different part numbers may not mean it’s not compatible. I tried a 575 flyback in my Color Classic. It did work, but the image on the smaller CRT wasn’t dimensionally correct (and couldn’t be adjusted to be correct). Oh well. This was a shame as the 575 flyback seem to be more plentiful.

I'll do my due diligence and try to trace the rest of the M1212 circuit to make sure it matches the LC575, but my gut feeling is it'll "just work". I do believe the color classic is very similar but probably has some small circuit changes for the different tube size and horizontal frequency which might explain your results.

I'll probably let 'er rip and give it a try. Will post my results here in case it blows up!

 

[petey293]

No dice - all I get with the LC575 flyback is a light crying noise from somewhere, kinda sounds like an SMPS being overloaded.

Oh well, it was worth a shot and now is documented for others to google!