RGB 1401 IGT Silver Jubilee Video Slot

[freds]

I have an early 1980's video slot. It has an RGB #1401 monitor. It has vertical collapse. I have done a few simple cap kits for monitors with no problems. I have done caps on this and also the hot transistors and a video chip. Still have same problem. Anybody have some guidance or maybe a lead on a chassis. Tube is still good. Thanks for any replies.

[Chris-socal]

I am no expert but I have an RGB stuck in shut down that I have been researching. The big white resistor is notorious for failing open, I would check all of the larger 1w resistors on that board just to verify none are open. Check the vertical size pot too and follow the trace to verify all solder joints are good. There is a partial schematic for the 1401 in the file system.
Hopefully someone with more experience will jump in here. At least your flyback is working.

Chris

[freds]

Thank you Chris-socal for the response. I will check along the vertical line. I did reflow the chassis. I have a feeling it is something simple.

[Richard S]

I have an early 1980's video slot. It has an RGB #1401 monitor. It has vertical collapse. I have done a few simple cap kits for monitors with no problems. I have done caps on this and also the hot transistors and a video chip. Still have same problem. Anybody have some guidance or maybe a lead on a chassis. Tube is still good. Thanks for any replies.

Is this a 1401A or 1401B? There isn't much difference in the vertical circuit, but there are power supply differences.
Is this a new problem or did it start off with vertical collapse?

Have you checked the vertical output transistors, Q134 and 138?
Do you have a vertical drive signal at the base of Q134?

Depending on where you are located, you could send the chassis to Alan at KLAR (Badbaud, on this site), or contact him to find out if there is someone near you who can repair it.

[4evervintage]

Thanks for your reply Richard. This is marked as 1401a chassis. The chassis on this 1401 is not mapped. Maybe they are not mapped. What is the location of Q134 & 138 ? I have tried some component changes. I am not familiar with crt repair. I have done a few cap kits. The board in this was repaired by Klar. It worked fine for 3 years then went vertical collapse. It plays blind. I was hoping to resolve this myself. Only have a multi-meter for troubleshooting.

[Richard S]

I don't have a 1401A handy, but attached is the layout of 1401B which, as I recall, is close, except the the 1401A uses a different voltage regulator (LM723 instead of STR30123).

[Chris-socal]

Are the vertical ICs on these as subject to failure as the 7 pins used in other monitors? If I recall it’s a 14 or 16 pin IC on the left side and it isn’t a common IC. TDA2530 I think.

As you troubleshoot there can be variations but the concept of operation is the same. I have a 1401 that varies from the schematics that I posted a few weeks ago, the schematic shows two components in some sections but my board only has one. Not sure if that is a difference between A&B, newer version or design for different environment.

Either way, vertical collapse is likely to be a shorted diode, open resistor, shorted cap, Vertical IC.

To clarify, Vertical Collapse means you have a thin line going across the width of the screen, not a line going up and down. H collapse is less common but it does happen.

You are lucky to have this problem because you know the flyback works.

Chris

[freds]

Here is a pic of the chassis. I have replaced the 2 transistors along the heatsink. I have replaced the TDA chip and the LM324 ic's. I saw no physical damage to any other components. The caps have been replaced.  The collapse is a horizontal line so vertical collapse. I have not replaced any resistors or diodes.

[Chris-socal]

I could be wrong but it looks like the insulator behind the HOT has slipped out.
I would definitely check diodes and those big resistors.

[Richard S]

I could be wrong but it looks like the insulator behind the HOT has slipped out.
I would definitely check diodes and those big resistors.

I agree that the insulator does not appear to be behind the 2SD478 transistor on the left, but that is not the Horizontal Output Transistor. Instead, it appears to be one of the two vertical output transistors. However, as I mentioned in an earlier post I don't have 1401A chassis handy - and the parts layout is missing from the RGB 1401 manual that I have.
The schematic shows the vertical output transistors as being 2SD386, not 2SD478. They are similar, but the 386 has a higher gain. That is unlikely to change the symptom.

If that transistor is not properly insulated from the heat sink, it may be the cause of the lack of vertical deflection.
Easy to check by checking the resistance from the collector of the transistor to the heat sink. Should not be low.

[Chris-socal]

Oh shoot we have pics of two different monitors here. Yes, whatever that is with the slipped insulator needs to be addressed.
Interesting timing, I am currently watching a video on Youtube by Arcade owner Mike. He is working on a 13” with vertical collapse. Not RGB but concept is the same. He found two diodes shorted and an open resistor.
Attached is a cleaner expansion of the vertical circuit.
I recently uploaded a full manual and schematic for 1401.

[Richard S]

I recently uploaded a full manual and schematic for 1401.

Thanks for the upload.
I'm relatively new to this site, so novice question:
Where do I find that manual?

Thanks

[freds]

Thanks for the responses. I have taken care of the insulator that slipped out. When I get a chance I will replace diodes and resistors in the circuit. If there is a resolution I will post it.

[Chris-socal]

I recently uploaded a full manual and schematic for 1401.

Thanks for the upload.
I'm relatively new to this site, so novice question:
Where do I find that manual?

Thanks

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