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Keeganjohn
March 9th, 2017, 12:22 PM
Hello everyone, I need some help here. I have been working with old tech, (mostly consoles, not actual computers) for about 5 years now. I don't know much but i know enough to solve most problems I've come across. That being said, recently i took apart a 1702 Commodore Monitor to clean out the insides a bit, and through a series of events, ended up breaking the CRT. Now, i know that it is possible to replace the CRT, however, i have no idea how to find a replacement that will work in this machine. If someone could teach me what exactly needs to be matched up from the original tube to a new tube, i would really appreciate it. Shown below is the label that is on the original tube. The label reads: Hitachi, Type:370KNB22, SER NO:M3H341729, and LR 26413 at the bottom. Thanks in advance to anyone able to help!


36834 (It keeps flipping it upside down whenever i upload it, i have no idea why, sorry)


Also, before anyone says it, I do already have another one, do not tell me to just buy a new one. I want to fix this because i feel awful about breaking it.

MikeS
March 10th, 2017, 09:44 AM
I've scrapped a few 1702s in my time, so it would not be unreasonable to find one that is beyond repair for other reasons but still has a good CRT...

Try Googling the CRT number; looks like it was used in some JVC/Panasonic equipment.

FYI:

http://wiki.arcadeotaku.com/w/CRT_designation_systems

Bish500
March 12th, 2017, 06:33 AM
Just be careful working around picture tubes. They act like a capacitor, and store a large charge. The charge can remain for quite some time, even if the unit has been unplugged.

You need to discharge the anode (the large suction cup looking thing). Underneath the rubber cap (which is only a dust cap), there are two spring loaded leads that go into the actual tube (this is what gives a charge to the tube).

To discharge, its best if you have a specific tool. I've seen homemade ones where someone has taken a long screwdriver, drilled a hole through the shaft, and soldered a wire into it with an aligator clip on the end of it. You clip the aligator clip to the metal framework surrounding the front or sides of the monitor tube, then work the tip of the screwdriver under the anode cap until you make contact with the spring-loaded leads.

After you've discharged it, remove the spring loaded anode clip from the tube, so the monitor can't recharge. (don't forget to put this back in place before you power up the monitor again).

In theory, if you found another dead 1702, you could remove the tube, and swap it into the one where you know the chasis board works. (checking the tag on the tube is a good idea). I believe the tubes were all made by hitachi, and the chasis board (electronics) were made by JVC (don't quote me on this, it's been a long time).

You'll have to carefully work the neckboard (the circuit board that's connected to the back of the picture tube) off the back of the tube, by gently wiggling and pulling at the same time. Often there is also a black ground wire that goes to a metal strap around the tube that you'll have to cut, then reconnect to the new tube.

I hope this helps.

Where are you located, Keegan? I have a 1702 that has bad vertical deflection right now (which you could have, if you're close enough to pick it up). I know the tube is good.

roberttx
March 12th, 2017, 07:15 AM
Just be careful working around picture tubes. They act like a capacitor, and store a large charge. The charge can remain for quite some time, even if the unit has been unplugged.

You need to discharge the anode (the large suction cup looking thing). Underneath the rubber cap (which is only a dust cap), there are two spring loaded leads that go into the actual tube (this is what gives a charge to the tube).

To discharge, its best if you have a specific tool. I've seen homemade ones where someone has taken a long screwdriver, drilled a hole through the shaft, and soldered a wire into it with an aligator clip on the end of it. You clip the aligator clip to the metal framework surrounding the front or sides of the monitor tube, then work the tip of the screwdriver under the anode cap until you make contact with the spring-loaded leads.

After you've discharged it, remove the spring loaded anode clip from the tube, so the monitor can't recharge. (don't forget to put this back in place before you power up the monitor again).

This is very good stuff, thanks. I recently picked up a bunch of TRS-80 Model 4s from a member here and, while I have experience with vacuum tubes in general, I've always avoided CRTs. I was fixin' to ask for a primer on discharging them, which you have just provided.

Keeganjohn
March 12th, 2017, 07:30 AM
Thanks so much for the help everyone! I was having alot of trouble finding any info on the codes for the CRT, and I had no idea I had to worry about lingering charge inside the tube. And I'm located near Orlando, Florida! That's a very generous offer, thank you!

Again thank you all for the info, you've been a lot of help!

Keeganjohn
March 14th, 2017, 10:25 AM
I replied to this like 2-3 days ago, maybe I forgot to hit post or something.

Thank you everyone for the help, I had no idea how to go about reading the tube code, and I really needed the info on how to safely remove and replace them, so thank you all!

Also, I'm near Orlando, Florida. If you're not close to that id be more than willing to pay for shipping, if there is anyway something like that could survive the postal service. Thank you again!

Bish500
March 16th, 2017, 09:03 AM
Thanks so much for the help everyone! I was having alot of trouble finding any info on the codes for the CRT, and I had no idea I had to worry about lingering charge inside the tube. And I'm located near Orlando, Florida! That's a very generous offer, thank you!

Again thank you all for the info, you've been a lot of help!


I'm in Ontario, Canada (Near Toronto). It's likely not economical for my monitor to be shipped to you. I'm sure you could likely find a non-working monitor closer to you, which would be cheaper (the offer of the monitor is still there, of course - but I just think it's going to cost a small fortune to ship it).

MikeS
March 16th, 2017, 09:27 AM
I'm in Ontario, Canada (Near Toronto). It's likely not economical for my monitor to be shipped to you. I'm sure you could likely find a non-working monitor closer to you, which would be cheaper (the offer of the monitor is still there, of course - but I just think it's going to cost a small fortune to ship it).

Sounds like a good excuse for a trip down south... ;-)

KC9UDX
March 16th, 2017, 01:38 PM
It's the wrong time of year for that, eh. Much nicer to go the other direction.

MikeS
March 16th, 2017, 07:09 PM
It's the wrong time of year for that, eh. Much nicer to go the other direction.

Not from where we're sitting...

KC9UDX
March 16th, 2017, 07:29 PM
Not from where we're sitting...

This time of year, I'd rather be in Resolute than anywhere in Florida. Well, frankly, probably any time of year.

I suffer heat stroke just thinking about Florida.

MikeS
March 17th, 2017, 08:06 AM
This time of year, I'd rather be in Resolute than anywhere in Florida. Well, frankly, probably any time of year.

I suffer heat stroke just thinking about Florida.

Come on up! A refreshing -5 degrees F yesterday.

KC9UDX
March 17th, 2017, 01:29 PM
Come on up! A refreshing -5 degrees F yesterday.

That's my kind of weather! All I need is some snow for skiing.