Dragon power supply boards

[zephyr]

I have a question for our electronics experts:

I have two power supply boards that I would like to swap over if possible. One is an issue 3 board from one of the very early Dragons, the other is an issue 7 board from a much later Dragon which also uses a different modulator for the TV output. The issue 3 board has a UM1286 modulater on board, and the issue 7 board has a much smaller UM1233 modulator on board.

Is it safe to swap these boards, and if so, will they work correctly without making any modifications?

[admin]

Hold fire on that.... I have a service document somewhere that I'll dig out tonight that describes the differences between the main board revisions and the PSU boards and the mix & match combinations that work...

[zephyr]

OK, Thanks!

[admin]

Okay...have now uploaded some service sheets into the Publications\Technical area of the main site (look at the side bar down the left hand side).

Based on this info the UM1233 is a MK2 PSU board and has been depreciated and should be replaced with a MK3 PSU (which might indicate there is a known issue with this MK2 PSU).

The UM1286 is a MK1 PSU and that would match the early issue 3 board in terms of date.

Reading through the service sheets, the best course of action is to obtain a MK3 PSU and update both the PSU and CPU boards or, if its working for you - do nothing...

I have swapped PSU units without modifications before, but with some varied results - including killing a CPU board.

[zephyr]

Thanks Simon!

[zephyr]

According to the information you posted, it looks like my issue 7 mainboard (listed as 16x16 in tech info) and the issue 3(listed as MK1 in tech info) PSU board should work together with just a slight modification.

Code: Select all

MK1 PSU and 16x16 CPU 

1K resistor across PL6 Pin 9 and 0v. If background lines are prominent, fit 0.22uf capacitor in C58 position.
    *Sony Mod.

[admin]

*Should* do... but take note of the disclaimer.....at your own risk..... but I'm sure if it all goes wrong there are a couple of people round here who can get things working again..

[zephyr]

I did the mods today, and it worked like a charm. Thanks Simon!

BTW, Do you have any service information that mentions Dragon mainboard overheating problems?

[admin]

No... those are the only service sheets I have managed to get......