Replacing the tube of an Ikegami using a VGA monitor tube

[tisurame]

I have an Ikegami HTM-1517R with some burn-in and the tube seems to have a very high number of hours of usage. I was talking with a technician, and after he took a look inside the monitor, he told me that it is possible to replace the tube (Chunghwa brand) for a regular VGA monitor tube of the same size. And after replacing, it would work normally, including with 15Khz.

I have a new Samsung 15" VGA monitor still in the box and I was thinking of using it as a donor.

Is it really possible? Would it really work at 15Khz?

[tongshadow]

If it's fully compatible, yes, but you have to consider the following:
-CRT Socket compatibility, same pins and same signals going into the tube's pins
-Yoke current and impendance,
-Flyback derived voltages, like focus, screen and the HV itself

There are many many many "regular VGA tubes" around, they're not the same even if the size is.

[tisurame]

If it's fully compatible, yes, but you have to consider the following:
-CRT Socket compatibility, same pins and same signals going into the tube's pins
-Yoke current and impendance,
-Flyback derived voltages, like focus, screen and the HV itself

There are many many many "regular VGA tubes" around, they're not the same even if the size is.

Do you think it's a safe procedure? I don't want to loose two monitors trying to improve one, in case some incompatibility happens.

[tongshadow]

Not safe at all going blind like this, you could lose both monitor and chassis.

[matt]

The biggest problem will be the yoke. VGA monitors typically have lower yoke impedance than broadcast monitors, and if you try to run it on the same chassis you'll probably damage the deflection circuit.

As long as the socket is compatible and the curvature is the same, you could swap tubes and retain the original yoke. However, you'd have to recalibrate the convergence which is a lot of work.

You might be able to find an NOS replacement tube - some are still available. What's the model number of the tube?

[tongshadow]

As long as the socket is compatible and the curvature is the same, you could swap tubes and retain the original yoke. However, you'd have to recalibrate the convergence which is a lot of work.

I have no experience with yoke swaps, except for TVs using the exact part number, but isnt the yoke basically "married" to the tube?

[tisurame]

The biggest problem will be the yoke. VGA monitors typically have lower yoke impedance than broadcast monitors, and if you try to run it on the same chassis you'll probably damage the deflection circuit.

As long as the socket is compatible and the curvature is the same, you could swap tubes and retain the original yoke. However, you'd have to recalibrate the convergence which is a lot of work.

You might be able to find an NOS replacement tube - some are still available. What's the model number of the tube?

https://imgur.com/a/asJI93l

Unfortunately I couldn't take a better picture because it was a very difficulty position.

[MKL]

The tech is correct in saying that you can replace the tube of a pro monitor with one from a PC monitor as they both use CDTs (color display tubes) different from CPTs (color picture tubes for domestic TV). In fact many PC monitors of the same size contain an identical Chunghwa tube:

https://wiki.arcadeotaku.com/images/5/5 ... S83X16.jpg

The only difference in the type numbers is the last two digits (01 vs 16) which designate the deflection yoke. On a PC monitor (31KHz and above) the inductance of the horizontal coil needs to be low (around 0.2 mH). For a 15KHz monitor it's typically higher (around 2 mH). If the yoke of your tube is like that you have two ways to make a donor tube from a PC monitor compatible: swap the yoke (not easy to get the same result as a factory installed yoke) or add a compensatory coil in series with the yoke so you can use the donor tube with its own yoke.

[matt]

Unfortunately I couldn't take a better picture because it was a very difficulty position.

Hmm, the model number isn't really visible in that photo. If you're able to get a better look at it, try googling the tube part number (starts with M36), you might be able to find a new one. The last 2 numbers after the X (X01 in your case) indicate yoke compatibility.

If the yoke of your tube is like that you have two ways to make a donor tube from a PC monitor compatible: swap the yoke (not easy to get the same result as a factory installed yoke) or add a compensatory coil in series with the yoke so you can use the donor tube with its own yoke.

Do you know where to learn how to compensate for the mismatched yoke? I have a 16" JVC monitor with a burnt tube that could use a replacement. It's the same size as a 17" PC monitor, but it has a Philips tube with a bonded yoke so swapping it is out of the question. Otherwise it's a great monitor and I'd love to be able to revive it.

[tisurame]

The tech is correct in saying that you can replace the tube of a pro monitor with one from a PC monitor as they both use CDTs (color display tubes) different from CPTs (color picture tubes for domestic TV). In fact many PC monitors of the same size contain an identical Chunghwa tube:

https://wiki.arcadeotaku.com/images/5/5 ... S83X16.jpg

The only difference in the type numbers is the last two digits (01 vs 16) which designate the deflection yoke. On a PC monitor (31KHz and above) the inductance of the horizontal coil needs to be low (around 0.2 mH). For a 15KHz monitor it's typically higher (around 2 mH). If the yoke of your tube is like that you have two ways to make a donor tube from a PC monitor compatible: swap the yoke (not easy to get the same result as a factory installed yoke) or add a compensatory coil in series with the yoke so you can use the donor tube with its own yoke.

Thanks for the feedback.

This Ikegami HTM model that I'm talking about, besides 15KHz (480i), also works with 31KHz and above (480p/720p/1080i). Does it make any difference regarding compatibility (inductance of the horizontal coil)?

Should I try to search for a PC monitor of the same size containing a Chunghwa tube instead of using a tube from Samsung or AOC PC monitor? It might be difficulty.

[MKL]

This Ikegami HTM model that I'm talking about, besides 15KHz (480i), also works with 31KHz and above (480p/720p/1080i). Does it make any difference regarding compatibility (inductance of the horizontal coil)?

Most likely but you need to measure the inductance of the horizontal coil to know for sure.

Should I try to search for a PC monitor of the same size containing a Chunghwa tube instead of using a tube from Samsung or AOC PC monitor? It might be difficulty.

Same brand ensures that other features have the same requirements, especially the heater voltage which may have small variations depending on the manufacturer but this can be taken care of so yes, you can use an M36 tube of other brands.

Do you know where to learn how to compensate for the mismatched yoke? I have a 16" JVC monitor with a burnt tube that could use a replacement. It's the same size as a 17" PC monitor, but it has a Philips tube with a bonded yoke so swapping it is out of the question. Otherwise it's a great monitor and I'd love to be able to revive it.

There isn't much to it (the other way round, adapting a yoke with higher inductance to a chassis made for lower inductance, is more complicated). Let's say that the yoke on the donor tube has an inductance of 0.3 mH and the original yoke is 2.5 mH. You take a bobbin (and a ferrite core) and wind magnet wire around it until you have a 2.2 mH coil. One end of the coil goes to the yoke, the other to the chassis (or two 1.1 mH coils on each side of the yoke).
But in your case there might be an insurmountable problem if the monitor is a TM-1700PN (or TM-1650SU) as the tube in the schematics I have is an M41EEM311X360 which is minineck and single focus while M41 tubes in PC monitors are almost exclusively double focus and the few that are single focus are small neck so the socket is different.

[matt]

But in your case there might be an insurmountable problem if the monitor is a TM-1700PN (or TM-1650SU) as the tube in the schematics I have is an M41EEM311X360 which is minineck and single focus while M41 tubes in PC monitors are almost exclusively double focus and the few that are single focus are small neck so the socket is different.

Yes, I was worried about that - it is a 1650SU. From what I've learned it seems that these tubes were used in some Megatouch machines, which leads me to believe that they're been in demand over the years and are now hard to find.

I'm keeping it around mostly because it shares a lot of parts with my TM-H1375SU, but it would be nice to have it running properly on its own.