[Restoration] Frogger - why did the frog cross the road?

[Superully]

well, basically that's hooking up the speaker to the wires, isn't it? there must be a way to measure something with a DMM ...

btw, what is this?

[Lee]

A Walkman?

[Etienne MacGyver]

yes, you can "beeb" the wires ofcourse to see if there is a break in one of the cables.

Or here the connections :



Or simply cut off an existing cable:



The "bare wire" is the ground, the white and red wires are the right+ or Left+ leads..

[Superully]

since the old monitor seemed to have stopped working properly, i pulled out another spare monitor from my shelf: a matsushita. those monitors are known for their poor construction, but i knew that it was working when it was pulled. unfortunately, it doesn't need separate positive sync like the electrohome monitor, but composite negative sync. with the help of a friendly klover (thx michael ) i managed to make the correct adjustments to the wiring and hooked everything up. after living in a wiring / parts mess for weeks, here's how my study looks



so i anxiously plugged in the game, pulled the interlock switch, heard the high voltage crackle, watched the neck starting to glow and walked around the monitor to see this picture



F    R    O    G    G    E    R



the picture is somewhat distorted at the top (adjusting the pots didn't change anything), so i might do a cap kit on the chassis, but i'm afraid to touch that matsushita monitor because i've heard so many bad things. nevertheless, i'm thrilled!!!

now all i need to do is throw everything into the cab and try to fix that sound problem, because i'm not getting ANYTHING from the speaker -  not even a hum or a crackle. from what i've read, the frogger boards are notorious for sound failure, so i might have to ask a professional to look into this ...

[Belike]

As far as I know, there were a separate pcb for the sound in Frogger cabs, my old friend built a nice hack to my Sega pcb, he told me, that without this modification there will be no sound.I've just heard it, I'm not sure it is true for all kinds of Frogger pcbs.
(Sorry for the bad quality pics, poor light here)

[Etienne MacGyver]

Great Ully ! 

So there is image now, and the monitor is on the 120 volt line ?

Anyway, there must be something wrong with the other tube, and personally i think its fried now...

@ Bela:
You still ow me some pictures of your old's friend workshop 

I like that dude !

[Superully]

So there is image now, and the monitor is on the 120 volt line ?
Anyway, there must be something wrong with the other tube, and personally i think its fried now...

yes, running on the 120v line! don't know what went wrong with the old monitor, but i'll probably dump it ...

[Superully]

As far as I know, there were a separate pcb for the sound in Frogger cabs, my old friend built a nice hack to my Sega pcb, he told me, that without this modification there will be no sound.I've just heard it, I'm not sure it is true for all kinds of Frogger pcbs.

as far as i know, that 1/2 pcb on top of the full pcb is responsible for the sound. will have to dig into it a little bit deeper. i'm just confused that i don't get ANYTHING from the speaker at all. shouldn't there at least be a hum?

[PunkRockCaveman]

Frogger neccessarily needs a volume pot on the 6-pin connector (labeled 6P) on the upper board to play sound. It is a 200 ohms, when I remember right wire it like this: pin 2 of 6P goes to pin 1 of the pot, pin 4 of 6P goes to pin 2 of the pot and finally pin 6 of 6P goes to pin 3. Then you hear sound

[Superully]

Frogger neccessarily needs a volume pot on the 6-pin connector (labeled 6P) on the upper board to play sound. It is a 200 ohms, when I remember right wire it like this: pin 2 of 6P goes to pin 1 of the pot, pin 4 of 6P goes to pin 2 of the pot and finally pin 6 of 6P goes to pin 3. Then you hear sound

thx mr caveman, but if you look close enough at the "mess picture", you will see that there is a connector attached to that 6-pin connector. a grey wire runs from there to the coin door into a potentiometer. i haven't checked that wire yet and the poti is untested as well (don't remember how to test a potentiometer atm), this is the first thing i have to do before doing anything else.

just to make sure: it is of utmost importance which wire goes into which speaker terminal (+ and -, right)? how do i know which wire and which terminal is what?

[Etienne MacGyver]

In general, yes, it should be wired + to +  and - to -
but no matter how you connect it you should hear sound anyway

sometimes there is an indicator at the terminals of the speakers on the "white tap" which is which

Got a pic of the speaker terminals ?

[Superully]

sometimes there is an indicator at the terminals of the speakers on the "white tap" which is which
Got a pic of the speaker terminals ?

not yet, i'll take one tomorrow. however, i don't know which wire is which polarity either ...

[Superully]

just "beeped" through the potentiometer wires: the black one is fine, however, with the red and the white one i get a beep no matter which wire the multimeter lead is touching. to make it clearer: both leads at the ends of the white wire give me a beep, but one lead at the white wire and the other at the red wire also give me a beep (and the other way round). note that the wires are still attached to the potentiometer. is that a factor to be considered?

[Etienne MacGyver]

A potmeter is a variable resistor...  so measure ohms instead of continuity

i'll try to explane as far as i know it,
Experts here, please correct me if i am wrong, so i learn also 

I made a sketch of the inside of a potmeter in 4 situations:



As you may know, the path that electricity likes is the one of less resistance..

so lets say this is a 100K ohm potmeter, the red line represents the resistance in the potmeter, the blue with the arrow represents the contact that is variable.

I drew the green line as an example path if you enter the potmeter at terminal "A" of the potmeter and terminal "B" as the "exit"

Lets say in an optimal situation that the resistance in example "1" is 0 Ohm, since that is the shortest path.
in example 3 the resistence should be 100K ohms, as for example 2, it should be a around 55 -60 K Ohm

In theory if the potmeter is broken (example 4 where you see that the axle is not there) you should not have any connection at all

measure in that case "A" and "C", and it should be 100K.

I hope you understand it, and that my theory is correct 

[Superully]

thx etienne, but i've already tested the potentiometer and it came out fine. what i did was "beep through" the wires (from the connector TO the potentiometer) and this is where i got the mix-up described above with the white / red wire beeping when it is not supposed to do that ...