开云体育

Dear all,

The screen of my CSA803A developed a problem. It showes flyback lines, low intensity and I could not get it calibrated properly. The size of the picture, focus and convergence are o.k..
After removing the CRT driver board A8 (671-1027-01), it turned out that a (zener?) diode is completely burned and also a 100uF/50V elco did not look healthy. This diode is immediately below the metal box shielding the flyback transformer and alongside what seems to be a very big tantalum elco.
Any help in finding the type of this diode is very much appreciated!

Kind regards, Gerard

Hi Gerard,

Does the CSA803A have a color display or is it BW? Could you give a
refdes for the parts in question or link to a photo somewhere so I can
find their location?

PS: I would suggest the service manual but that thing is near useless.

-Evan

On Sun, Jan 5, 2025 at 9:19?AM gjm45janssen via groups.io
<g.j.m.janssen@...> wrote:

Dear all,

The screen of my CSA803A developed a problem. It showes flyback lines, low intensity and I could not get it calibrated properly. The size of the picture, focus and convergence are o.k..
After removing the CRT driver board A8 (671-1027-01), it turned out that a (zener?) diode is completely burned and also a 100uF/50V elco did not look healthy. This diode is immediately below the metal box shielding the flyback transformer and alongside what seems to be a very big tantalum elco.
Any help in finding the type of this diode is very much appreciated!

Kind regards, Gerard

Hi Evan,

Thanks for replying. The CSA803A has a color display. I have put some pictures of the A8 video driver board in the photo album under:
/g/TekScopes/photo/299921/3873248?p=Created%2C%2C%2C20%2C2%2C0%2C0

I realized that my 11403A has the same A8 video driver board. Fortunately, I could make a picture of this diode without removing the board (Pic4 in the album). It is a glass diode with thick wires and a white ring at the kathode and partial identification "H-7".

Kind regards,
Gerard

Hi Gerard,

Since you have the 11403A do you need me to open one of mine up to
take photos and try to ID parts?

-Evan

On Mon, Jan 6, 2025 at 1:42?PM gjm45janssen via groups.io
<g.j.m.janssen@...> wrote:

Hi Evan,

Thanks for replying. The CSA803A has a color display. I have put some pictures of the A8 video driver board in the photo album under:
/g/TekScopes/photo/299921/3873248?p=Created%2C%2C%2C20%2C2%2C0%2C0

I realized that my 11403A has the same A8 video driver board. Fortunately, I could make a picture of this diode without removing the board (Pic4 in the album). It is a glass diode with thick wires and a white ring at the kathode and partial identification "H-7".

Kind regards,
Gerard

Hi Evan,

No need to open up your scope. From other group members, I have received additional information. The driver circuit of the line transformer is very close to the one used in the 11401/11402. This shows that the diode is a fast switching Si diode (600V, 3A). In the coming days I will replace the diode and hopefully this solves the problem.

Kind regards,
Gerard

Dear all.

The problem has been solved by replacing the burned diode by a (rather over-dimensioned) fast recovery diode (SURF1560). Now image intensity, gray scale and color can be nicely set according to the provided calibration scheme. Fortunately, the flyback transformer was not damaged by the failing diode.

With kind regards,
Gerard