MB6582 not getting 5V. Causing reboots

[renepela]

Recently I have build an 8 sid MB-6582. It works, but is very unstable. Sometimes it reboots.

I tried to investigate the problem and noticed a voltage of 4.35V on J3 (and J4 etc.). I think this is to low. It should be 5V. Also the 7809 voltage regulator is getting quite hot but that's normal I guess.

I use powersupply option A because all my sids are 6582's which require 9V.

When I don't attach my lcd my 4.35 volts become 4.5 and the reboots are gone. So I think the 5V is just to low.

How can I solve this? Why is my 5V voltage to low?

[Wilba]

Some C64 PSU "bricks" can't deliver the fully rated current of 1.5 amps for some reason (being old most likely). Thus the 5V supply will drop down under a big load, which is what happens with 8x SIDs plus high-powered LCD drawing 280+ mA.

What kind of C64 PSU is it? I have had good results with the large black ones with ventilation slots, and others have had the problem I described with the sealed light beige ones that came with late model C64s.

[renepela]

It's a an old brown power supply from the first C64 model.

on this picture it's the one on the left: http://jope.fi/cbm/cbm/c64psu.jpg

I've never seen a black power supply for the C64.

Is there an alternative for the C64 powersupply wich can handle more current?

The C64 power supplies are hardly capable of handling the current.

[renepela]

I was lucky. A neighbour gave C64C. That's the newer white C64. The power supply can deliver 1.7A instead of 1.5A.

The reboots are gone now.

Also the 7809 doesn't get as hot as before. I don't know why.

However I'm still not convinced this solves the problem. With the LCD attached the voltage on J3 is 4.85A. Without the LCD the voltage is 4.91A. Still a little more so the 5V still can drop.

At the moment I didn't attach the front panel (it's not finished yet, I hate soldering those leds  :()

I'm affraid all those leds will cause the MB6582 to reboot again. Or is the 1.7A power supply capable of handling the current for the base pcb and the Control surface?

If it's really a close call, I could use higher resistor values for the leds. They won;t be very bright than, but at least they wont draw so much current.

[Wilba]

What kind of LEDs have you got? If you use 1K resistors with (for example) SmashTV's red LEDs, it probably won't be a problem.

My MB-6582 has 4.86V under full load, and that's with a lower current draw from the display.

A 1.7A supply is more than enough... I estimate the current draw should be around 1A, including 100mA for LEDs.