Setup is drawing too much current

Testing/Troubleshooting
1

Hi everybody,

I had a working Core+SID+LCD on a C64 PSU with optimization circuit on a separate board. Before equipping the IC’s on this setup I tested the voltages: 5,12 vor all 5v connections, and 12,00 for the 12v line.

Then I decided to add some more stuff: 2 extra cores plus 2 sids, with no IC’s equipped yet. Soldered all wires according to the Optimized PSU PDF. Result: no backlight. No mios. Nothing.

I began measuring the voltages in the psu: 9vAC stable, but on the 5vDC board in the PSU it’s 0,3xx volts!? My first tought was that I fried another psu, that seems to happen to me lately. So I desoldered the PSU wires from the optimizer board. Last night I wanted to be sure, so I measured the voltages without midibox equipment connected to the PSU: 5,12v. OK, cool, it’s not broken, let’s connect it again! Fired it up: nothing. Mesured again: 0,3xx volts. Damn!

Then my neighbor suggested we measure the current (amps) on the 5v circuit, so we placed the multimeter in between the white wire from the PSU and the optimizer board: more than 2A!!! Looks like a short, right?

So we began measuring the resistance between all 5v + and - connections on all cores and sids (like + and - on core 1, then + and - on core 2, etc.) but they’re all good. resistance was 1 kOhm if i remember correctly, with the occasional 1,1. On one occasion we got 0,8 tough…

I’m going to try to remove all boards, and then connect them one by one, and watch the increase in amps, to check which one is faulty.

Any other suggestions? 3 cores and 3 sids (of which 2 cores+sids ICs are not stuffed yet) and 1 LCD should never draw 2A right? More like 1A I think. Before connecting everything I did check for shorts optically, and what we found we fixed (some minor tinflow on tricky spots). Any tips are welcome!

Cheers,  Alex.

2

If you made the PCBs by yourself even the smallest (thinnest) copper film can bring up some short.

If you find the short you can use a scalpell or similar to go through the copper lines (you dont have to press to much). With that way, all thin and small stuff is away.

Good luck!!!  :)

3

The PCB’s are mike’s… I’ll let you know the outcome of the test as soon as i’m done.

Cheers.

4

I am having a similar problem. I built a seperate power supply that supplies 15V to the SID board and 7V to the CORE. The initial voltage check was OK with no chips installed. Loaded up all boards and 12VDC measures fine but 5VDC drops to about 2VDC and display does not light.

If I turn it on I get random light configurations each time. One time all lights may light, next time only a few, next maybe none. None of the buttons or encoders function. What a mess!

I will check all my wiring again and look for shorts in boards and report my findings. In the mean time, any and all seggestions will be appreciated.

Thomas

5

Did you try giving the core more voltage? I am using 9 volts on mine, b/c it’s what I had handy, but i only have one core and sid running ATM…I believe the core can handle safely up to 10 volts.

6

I recheched all my boards (from Smash TV) and they look OK. I have just over 6VDC going to J1 on the core modules and it drops to less than 3VDC at the other end of the regulator section. If I go directly to J2 I can light everything up but nothing functions, i.e. buttons don’t change status, encoders don’t change anything and display shows black squares, no symbols.

Unplugged all modules and reconnected one at a time with no real change. How much current is the CORE module supposed to draw> I have a 12VA transfermer (5V @ 2.4A) and it saggs terribly.

Thomas

7

@ Thomas. do you have the mios and app loaded yet, I only asked b/c you didn’t say yet.I think with nothing loaded you get the black row on the screen…otherwise

I have no idea…sorry…

8

yo Thomas

flip your regulator round, sounds like you got 'em in backwards, does it get real hot? (should have a good constant 5v after reg)

peace

9

Regulators are placed correctly. They do not get hot to touch.

Regarding the program, I tried loading MIOS via JDM programmer but I think I just overwrite what is there instead of adding to it. I will reload the Bootstrap loader and try via MIDI. In the interim, I ordered a larger transformer for my power supply so maybe I can get the voltage up a bit to J1 and have less sag.

Thomas

10

I got a larger transformer, 6.3v 3.4A for my power supply and now the modules work, more or less. The issue with current draw at least is solved.

11

I’m having this problem too, how much current draw for should I expect for a SEQ V4, I get 1.3A on my 7805 which then thermally shuts down.

Doin’ it rong indeed..

If only a Wilba SEQ was easy to get a hold of…