A full Spectrum of emotions

[HigashiJun]

I 'might' come over to Japan in 2025, not 100% sure as yet, but my Karate club do a trip to Okinawa annually and I might go.

You definitely should !

[rubber_jonnie]

I 'might' come over to Japan in 2025, not 100% sure as yet, but my Karate club do a trip to Okinawa annually and I might go.

You definitely should !

Bit of planning to do first

[rubber_jonnie]

Well, that was a narrow squeak!!

I stole the missing transistor for the + from the spares board, figured out the pinout using my component tester and installed in the board.

Since the 12v side of the power is all I need now the RAM has been replaced, I had the multimeter ready to check the voltage as soon as I plugged the power in.

Well I got a shock, suddenly the circuit is delivering 29v!!!

Luckily I was on the ball and unplugged immediately, so no harm done, but more than a little confused that the 12v circuit was suddenly delivering more than twice the voltage it's supposed to be. Ho hum.

I bloody hate power supply circuits at times

At least no harm done because I was quick off the mark pulling the power.

[exxos]

Is there a circuit for it ?

[HigashiJun]

@rubber_jonnie

29 volts !!! You were really lucky not to fry your machine...

[stephen_usher]

@rubber_jonnie

29 volts !!! You were really lucky not to fry your machine...

Only one chip would be on the +12V rail with all the RAM replaced with hacked 4164 chips, the LMxxxx video encoder.

[rubber_jonnie]

@rubber_jonnie

29 volts !!! You were really lucky not to fry your machine...

Only one chip would be on the +12V rail with all the RAM replaced with hacked 4164 chips, the LMxxxx video encoder.

Luckily the LM1889 survived, and I have spares at least.

[stephen_usher]

Is there a circuit for it ?

Here you go...

Spectrum-Power-Circuit.jpeg (74.54 KiB) Viewed 1010 times

TR4 isn't marked, but it's the lower of the two transistors.

[stephen_usher]

If the coil is faulty and the output side is partly shorted then I guess the ratio between the two coils would be different causing the voltage to change.

Those coils are well known to fail.

[rubber_jonnie]

Is there a circuit for it ?

Here you go...


Spectrum-Power-Circuit.jpeg


TR4 isn't marked, but it's the lower of the two transistors.

What issue is that Stephen? Mine is closer to the issue 5 (I can't find a 4s specific schematic) IIRC I did check for shorts in the coil but I can do so again. It's a fairly rudimentary device that's for sure.