Commodore 1702, I know, I know.

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Sunder
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Commodore 1702, I know, I know.

Post by Sunder » December 15th, 2018, 12:19 am

I thought I'd have better chance posting the question here since you monitor gurus are way more experience than anyone else I've seen.

My 1702 has had some SEVERE burn in (got one that acted as a security monitor), I'm just wondering if anyone knows what's a suitable replacement tube for it.
Would a A36EAM01X16 be suitable for it?

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Re: Commodore 1702, I know, I know.

Post by geotrig » December 15th, 2018, 7:10 am

what tube no is on the current Commodore monitor ?
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<trk>:I remember catching a big fat one and my friend said "throw it back in, that one already tastes like wood"

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Re: Commodore 1702, I know, I know.

Post by PrincessPrinPrin » December 15th, 2018, 8:48 am

Sunder wrote:
December 15th, 2018, 12:19 am
Would a A36EAM01X16 be suitable for it?
Too big and not compatible with neckboard. You would need a A34 but you'll never find one that has the same base (i.e. connection with the CRT socket) as the original tube. You would need to make a neckboard adapter and there's probably not enough space for it. Then yoke compatibility...

edit:

The above was based on this part of the schematics:

Image

But then I scrolled down the whole manual and saw that there can be a different neckboard/CRT:

Image

Googling pictures shows this latter CRT type:

https://www.ussherpress.com/blog/?attachment_id=1296

If you also have this type then you're lucky as that's the most common neck type you can expect to find in a 14" TV.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

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Re: Commodore 1702, I know, I know.

Post by Sunder » December 15th, 2018, 11:32 pm

Thankfully it's the second/later type!
I came across this newer tube in a Toshiba in my collection and it looks to be the exact same form, fit and make, but an Orion and an A34AGT13X98.
I am so curious to see if this will work together.

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Re: Commodore 1702, I know, I know.

Post by PrincessPrinPrin » December 16th, 2018, 11:37 am

Now take measurements on the yokes.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

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Re: Commodore 1702, I know, I know.

Post by Sunder » December 17th, 2018, 9:16 am

1702 370KRB22:
3 ohm
13 ohm

Orion Tube:
5.5 ohm
14 ohm

Do I switch the yokes around?

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Re: Commodore 1702, I know, I know.

Post by PrincessPrinPrin » December 17th, 2018, 10:13 am

5.5 is unusually high (is it known to be in good working condition?). Most 14" tubes will be the same as the stock tube so I suggest you find another tube and save yourself the trouble of converging it properly. If they're not easy to find for you, swap the yoke.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

- anonymous

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Re: Commodore 1702, I know, I know.

Post by Sunder » December 17th, 2018, 11:07 am

yeah the tube looks practically brand new inside, fired it up, everything looks perfect. In fact Iam surprised at the quality of the geometry and everything. I have no idea why I have not been using this tube.
What's the worst that could happen if I put in the tube at that value range?

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Re: Commodore 1702, I know, I know.

Post by PrincessPrinPrin » December 17th, 2018, 2:21 pm

Differences in resistance but especially inductance will result in wider/narrower picture. These differences can be adjusted out with changes to components in the horizontal sweep circuit like the capacitor in parallel with the HOT collector and emitter and the one in series with the line coil. The yoke is also critical for EHT so it would be recommended to check that the anode voltage remains within specs after the yoke swap.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

- anonymous

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Re: Commodore 1702, I know, I know.

Post by Sunder » December 17th, 2018, 3:20 pm

I feel silly for asking this, but I have no idea how to check the voltage on the anode cap. I do have an HV probe handy, just no idea how to use it to check the voltages on the anode cap the right way, last time I did that I fried the chassis on one of my tubes.
Also thank you for guiding me thus far!

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Re: Commodore 1702, I know, I know.

Post by PrincessPrinPrin » December 17th, 2018, 7:01 pm

Is it a digital one that connects to a multimeter? Connect its leads to the meter (red with red, black with black) and the third lead terminated with crocodile clip to the braid that goes around the tube (not the degaussing coil!). Turn the meter on, set it to the lowest DC voltage setting (so no autoranging meter), turn the TV on and carefully slide the probe under the anode cap and read the voltage on the meter. You can also turn the TV on with the probe already under the cap.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

- anonymous

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Re: Commodore 1702, I know, I know.

Post by Sunder » December 18th, 2018, 11:04 am

That's exactly what i did, but it fried my chassis the last time. Maybe a faulty HV probe No idea. It WAS sparking when that happened, so probably the probe's open?

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