Flyback replacement for a Mitsubishi AM-1401R

[StarquestMan]

I just received a neat little professional or prosumer grade TV/Monitor from the original owner who gave it to me under the promise that I show him pictures of it working once I get it working again. The TV is a Mitsubishi AM-1401R 14" portable with two sets of BNC video inputs and one of those EIAJ 8 pin TTL RGB inputs for connecting old computers to.

I found that the flyback transformer had arced out to some of the wiring nearby connecting the chassis to the neck board, charring both the wiring and the flyback casing. I am having trouble locating a replacement flyback for the unit since I am unfamiliar with this sort of replacement or substitution of a part. The part has a sticker with the following numbers, with the first being the part number and the second line that I am unsure of.

334P13801
FA21T

I would compare the specs of the existing part and simply find a similar spec part however I am unaware of any sort of data or cross reference for these parts.

I may try grinding away the charred section and coat it with some automotive silicone or something to see if it will power up and tell me if any other components are damaged or maybe this may be a good enough repair to permanently fix the set?

[damen]

Back in the day we would receive all sorts of catalogs from different companies with their various brands of replacement flybacks. Even NTE, ECG and RCA SK had them. I looked in several of these and did not see anything close to your number, the 334P13801 is the number to look for.

[StarquestMan]

Originally Posted by damen

Back in the day we would receive all sorts of catalogs from different companies with their various brands of replacement flybacks. Even NTE, ECG and RCA SK had them. I looked in several of these and did not see anything close to your number, the 334P13801 is the number to look for.

Oops just saw your reply! I found a couple numbers on this website http://www.hrdiemen.com/reparation/flyback/index that seemed kinda close but I have no idea if they are close enough. the closest was 334P13603 which crossed to HR 82460 on their site. seems like I may have gotten a flyback for a Commodore 1084 from them before but i'm not sure.

[StarquestMan]

I went ahead and Dremeled out the carbonized plastic and used some grey RTV to fill in the void and put some heat shrink tubing over any burnt wires. Once I reassembled the set I fired it up and had a horizontal purple line on the screen. I quickly realized I had bumped two of the service switches when putting it back so i fixed them and all was well after that. I still think it would be a good idea to replace the flyback with a new one if I can find one but for now the silicone fix seemed to do the trick! here are some pictures of the TV.

[liammc00]

I'm just curious when that Mitsubishi TV was made?


I have an 1987 13" Mitsubishi which works perfectly and used in the spare room and 1985 13" Mitsubishi TV and it dose work but it could use a tune up.

[StarquestMan]

This one was made April 1986.

[StarquestMan]

Well no joke, I had the TV running a few times today and did on final test for a half hour or so and just started thinking "hmm this thing must be good to go!". I got up and just started to walk to the other end of the room when i heard a loud pop! I turned around and the set was still working just fine but i still ran over and turned it off and unplugged it and carried it to the kitchen island to pop the back off and take a look. I couldn't see anything burnt or anything so I plugged it in and reached for the power button but it popped once again but too fast for me to bring my head back around to see where. I then powered it on and off a couple times to see if i could see where it arced but it didn't do it again. sounds like I still need to locate a new flyback for the set....

[StarquestMan]

So far I am looking at the HR Diemen model HR 7718 flyback transformer as a possible substitute part. I have zero experience in substituting a part like this and was wondering if anyone had some pointers or good links to read up on before I attempt to replace it with an unknown part? I came to this as a possible part by ohming out the pins on the defective flyback to get an idea how each winding was connected. I did find other 10 pin flybacks that were similar but they all had pin 3 tied to a winding that does not appear to be used on the existing part and is tied with pin 7 on the pcb. the following parts are ones that I have found but there may be others.

HR 7328
HR 7461
HR 8185
HR 8204
HR 8752
HR 8772

HR Dieman does not show resistances in its schematics but does show voltages going into and coming out of the windings. is their anyway to power on the TV without a flyback installed to get an idea at least what the primary input voltage is? The TV appears to have a 123V B+ but it appears to go through a 4.7 ohm 5 watt resistor before going to the primary, im guessing I can do some math to figure out what this resistor would drop the voltage down too, if need be? Forgive me if im a bit clueless here but I seemed to have learned some knowledge about electronics but skipped some of the important basics. Thanks!

[StarquestMan]

I thought I would post a little update on my TV in case it helps someone else out with a similar set. I ended up getting what basically is the HR Diemen 7718 although its probably a different brand since it goes under the part number 334P-12602. I went this route to avoid having to import one from Ireland. the same seller on ebay also had a 334P-12603 that looked identical except the wire coming from the base near the screen control was grey instead of orange like the original one in the TV which had a grey wire, though im betting this is simply a manufacturing variance, although I could be wrong. I could not find a cross reference for the 603 so I went with the 602 since I could at least verify the pinout.

when it arrived, the 602 matched all the DC resistances of the original flyback although the primary between pins 1-2 had a lower resistance of about .8-.9 ohms vs the original of about 1.3 ohms. I understand that DC resistances on a transformer are just a guess but i'm unsure how to properly test inductive components, i'm thinking I need an LCR meter for this sort of thing but that's besides the point.

The new flyback is a bit larger than the old one but it still fit snugly once I loosened up the Input board and bracket on the back of the main PCB. once installed I powered it up half expecting something to explode and short out but was greeted with the sound of static from the speaker and the very faint high pitch whine of the deflection/high voltage working just fine. I then turned up the screen control to light the screen and adjusted the focus and everything was normal.

One thing I forgot to mention is that I had tried again to repair the original flyback once more with epoxy, and while it worked fair, it would start ticking and popping after a few minutes of operation and just gave me the feeling that it was trying to arc out again. The new part does not do any of this and is much much quieter overall than the original part I had tried to fix.

Two things I have noticed though is a slight tilt in the picture and a slight gap on the right side of the screen. The screen tilt or rotation i'm sure is easy to fix by simply rotating the yoke slightly but the horizontal deflection does not appear to have any sort of adjustment other than a horizontal hold pot buried under the crt at the front of the chassis with a glob of epoxy holding it in place, the service manual basically says its set at the factory and to leave it alone. I checked the B+ voltage and while it goes a bit low on a snowy screen, it stays right at 123v when a picture is displayed through the inputs regardless of brightness. the screen does show a little blooming too that was not there before (if thats the right term for a growing and shrinking screen depending on brightness although it could be picture bending since I can see the linearity change as an object moves up or down along the screen. I am wondering if their may be some ripple effect on the B+ due to the lower impedance of the new flyback primary winding that isn't showing up on my meter. there is one unpopulated electrolytic capacitor spot on the chassis between the B+ and ground although there is another 47uf 200v cap between the same two traces but the service manual does not give me a value for it.

sorry if I bored anyone with my little novel