N64 - red light no video, no audio

I know this a typical issue on the n64 but i have tried quite a few things.

All resulting in no video no audio.

Swapped power supply with a known good one.
Cleaned the cartridge slots and jumper pack slots.
Swapped jumper packs and expansion packs with a not the console to test.
Swapped AV cables

I couldn't see any real issues with the joins on the board, but I also:
Resoldered the points under the cartridge slot
Resoldered psu connector
Resoldered AV connector

At u13 I have 12v and 5v, the other silk screen points also match the expected values.

I then realised the reset button didn't seem to have the normal amount resistance in its action.

Measuring the resistance of the switch on the board gave me 47k ohms (it didn't matter if it was pressed or not, same value (which I thought was strange) ). I would of expected it to be NC when it wasn't pressed.

Does anyone know what is meant to be the resistance between the points before I start desoldering the switch?

Thanks

 

3 of the n64 reset switches pins go to ground only one goes too pif reset.
strip the console down and check the QFP's neare the cart socket, I had one in once where it had corroded the CPU lines, ended up having to re-work a few traces off the cpu iirc..

 

I'll strip it and take some more detailed photos and check continuity.

Is there a service manual or schematic available anywhere?

for the reset switch (not my photos, but explains where I measured). all tested as ground except for what is listed as 'reset solder point'. which was 47K. Measuring directly off the chip reset line to ground was 47K.

http://assemblergames.com/l/threads/i-want-to-add-an-external-reset-switch-to-the-n64.43538/


and
the bottom of the switch

 

Searching round on the internet turned up this for schematics:
http://forums.modretro.com/viewtopic.php?f=33&t=11227&start=20
I attached the file to the post incase the mega.co.nz links go down.

But if anyone has more information it would be great.

 

I have checked all the VCC and VSS pins on CPU_NUS and the cartridge slot and it looks all good. the cartridge slot looks dodge but I have tried it on another console, so its only if the points underneath are corroded.

Anyone able to spot anything from the photos?

 

first photo, pin 26 trace on the top ram chip looks odd
last photo pin 61 looks odd also
did you check the ram for corrosion?
check the 7805 regulator?
check the power switch?
check for a short in the ext. port
check the av out connector, solder some wire temporally to be sure



what does the under side of the mobo look like?

 

Thank LeHaM,
Ill check pin 26 on the RAM Module. I have been plugging in an memory expansion pack to bypass the onboard RAM but maybe that was a flawed theory.
RE: pin 61, I think you mean pin 59, that was my first thought but I have GND on pin 59 (VSS) @ 0 Ohm resistance
Where is the 7805 regulator? The Top regulator has 12v input and outputting 5v
The power switch has correct voltages on the pins.
Ill solder to the AV Port

 

Does anyone have the external power supply ripple measurements?
I started to hear a crackling noise from the power supply (which powers up my mates N64 without issue) and I had almost 1000mV of ripple on both the 3.3v and 12v lines (which seems excessive) .

I just finished replacing the ESR caps and its now down to 200mV but this still seems way out of spec. anyone have a power supply to check for me?

Measured on the main board:
Top Regulator
VI (12v) - 13.2v 200mV
5v - 5.04v (160mV ripple)

Bottom Regulator
3.3v - 3.43v (60mV)
vTerm 2.58v (80mV)

The 12v value seems high.

 

Did you manage to fix your N64?

The images of the top side of the motherboard seem to be fine, are all the passives on the underside intact as well?

If you are using a multi-meter, you can check to see if the hardware has actually initialized or if the PSU is just feeding power to the console that is in "limbo." You can boot up the console with a cartridge and a regular jumper pack - then take voltage readings of pins #1 and #9 of the PIF chip. Pin #1 is the clock output to the cartridge CIC, pin #9 is the PIF clock driven by the RCP - you can probe the adjacent corresponding via rather than the actual pin #9. Both should read around 1.6 to 1.7V if a clock is being driven successfully by the RCP and PIF. If the meter reads 0V on both pins then there might be an issue with onboard passives or with circuits pertaining to RCP and/or RDRAM initialization.

I wouldn't recommend touching any RDRAM (including RCP portion) circuitry with a soldering tool unless used very carefully, since even the slightest addition of solder to a pin, via, or solder pad all the way up to the non-VTerm side of the termination resistors can change the impedance of the Rambus channel - system will be more unstable and might not boot.

I don't quite understand what you are trying to do, you are bypassing the onboard RAM with a memory expansion pack?

 

Work has been pretty hectic this week planning to hit it again this weekend.

My understanding with the memory expansion pak was that the internal ram was disabled when using it. Is this not the case?

I didn't try resoldering the ram as they looked ok. The bottom of the board is actually in better condition that the top.

I'll check the voltages at the points you specified. And reply to the thread

Thanks for the extra info

 

Hey eb1560,

I have checked the voltage output on the PIF chip
Pin1 - GND =1.74
Pin9 - GND=1.69

I also have a scope, but in fairly new to N64 repair (I have repaired numerous c64, arcade machines, amplifiers etc)

Where would you recommend to check next?

 

It seems the console is generating a clock.

I am assuming you checked for continuity for the 3.3V, Vterm/Vref, 12V, 5V and GND lines (with and without an expansion or jumper pack)?
Do any particular cap(s) or either of the two voltage regulators abnormally heat up rapidly after powering up the console. Or even if any chips or the expansion pack chips heat up abnormally fast upon booting up.

Regulators/LDO: 7805 – (fixed) 12v to 5V ; Sharp PQ070XZ5: (adjustable) 3.3V to 2.54V.
Electrolytic caps on 3.3V rail for NUS-CPU-04: C81, C131, C134, C140, C141, C145

If you hear a constant clicking sound emanating from the power supply, it is probably a relay acting up. If your power supply works on another N64, you could compare the 3.3V output routed to the controller port as a reference without opening another console.

A scope would be an interesting tool. (Either jumper or expansion pack mounted)
You could probe one of the eight 3.3V vias between C81 and the power switch to see if your scope captures an abnormal looking power signal.

Probe R33 (left of PIF, X2, and U15) to verify the clock signal is a distorted or a near perfect 250 MHz sinusoidal wave. PIF pin #9 (or via) can also be probed to see if the 15.6 MHz square wave is distorted or intact.

If all clocks and power rail readings check out fine, then probe PIF pins #3 and #5 when powering up the system to see if data is transmitted and received from CIC.

Probe PIF pins (or vias) #11 and #13 during powering up - the PIF communicates code from its own boot ROM to RCP-CPU upon booting up.