Roadblaster restoration help

[PetitMorte]

Hi folks!

I managed to pick up a non-working Roadblasters cab this weekend, and I'm looking for any resources or hints that I can get for restoring it back to working status.

As of the moment, the cab will power up... marquee lights, monitor glows, fan hums... but that's it.  The PCB has a few LEDs on it, but none of them are lit.  When I turn the volume knob on the audio board, the speakers crackle a bit. 

There's an ugly elecrtical "hissing" sound that comes from the back of the monitor when the system has power, but I'm betting that will clear up after I replace the power cord with one that hasn't had the ground pin cut off.  (Yes, I'll be very careful around it!)

I pulled out the power supply and tried to see what power, if any, was going to the PCB, but my cheap tiny analog mulitmeter got itself hosed a bit back and doesn't like to show proper DC voltages.  (saving up for new digital multi)  From what I could tell, however, the power going to the PCB was nothing like they describe it HERE.  The closest I could tell is that most of the 11 pins are ground, 1 is some volts positive and another is the same volts negative.

The power supply I have is the one with the 2 big blue caps, and the transformer... not the one with the gray box that is shown in the Atari System 1 manuals I've downloaded.

Until I get a real multimeter I won't be able to tell for sure just what's going on power wise, but if you guys have any hints or advice, I'd love to hear it!

Thanks!

[SirPeale]

There's an ugly elecrtical "hissing" sound that comes from the back of the monitor when the system has power, but I'm betting that will clear up after I replace the power cord with one that hasn't had the ground pin cut off.  (Yes, I'll be very careful around it!)

That sounds like either a blown flyback, or a broken neck.  Since you said the neck had glow, I'm betting the former.

[Kremmit]

There's an ugly elecrtical "hissing" sound that comes from the back of the monitor when the system has power, but I'm betting that will clear up after I replace the power cord with one that hasn't had the ground pin cut off.  (Yes, I'll be very careful around it!)

That sounds like either a blown flyback, or a broken neck.  Since you said the neck had glow, I'm betting the former.

Echo that.  I had one that was making a noise like that, and then it got worse and started shooting a big scary blue arc out of the flyback to the monitor frame.  Amazingly, the fix was to seal the hole in the flyback with rubber cement.  Worked, too, and still is, two years later.

As for the ground pin on the power cord, of course you should fix it... but of the 50 or so games at my house right now, probably 40 have the ground pin cut off.  It doesn't make any difference in how the game works, and as long as everything is working right, that ground pin never does a darn thing.  But it is a safety hazard not to have it there, so, again, you should fix it.

[ElGwako]

There's an ugly elecrtical "hissing" sound that comes from the back of the monitor when the system has power

i agree with the others...check the flyback or the neck. It is the exact problem i had with mine when i picked it up. A terrible hissing sound, after the second plug-in i got the arc to verify the source of the hiss...a big crack in the flyback. Upon investigation on these message boards i found it is a common problem with those.
Of course it is only the start. Even without a monitor you should be able to hear the game startup, even play it blind. My game has 2 LED's on the mainboard, but only one lights up(not sure if the other is suppose to).
The ground on the cord has no effect to your problem. If you have power to the marquee light and the fan, you know power is there. Replace it anyway, it does not hurt.
 Aside from  checking fuses and connections, you definitely need to get a new meter to go any further i believe. If the Led is not on at the board, it is not getting power to it.
good luck

[grantspain]

you-have two seperate issues here,you have to deal with them one by one.
first disconnect the monitor supply we will deal with this later,now we have to prove your game is running-one quick way is put a credit on press start and listen for game sounds(make sure your volume is up)if no sounds then we have to prove your voltages are present-you have to use a good working meter,there is no option otherwise your gonna be going round in circles.you must prove you have good 12v and more important 5v.once all this has been done and you know your game is running then we can deal with the monitor.(if voltages poor or non existant then replace psu with new switch mode type)
two-the monitor makes a hissing sound,this could be down to a few things-the tube is damp therefore arcing out of the ht cap(dry off and clean ht cap and tube),lopti is arcing(replace or if its just a hole fill with a plastic cement),dry joints(solder them up) or what we dont want a broken tube neck(that will be obvious you will have all sorts of flashes coming from the nack card area),then a replacement tube is required.

[clanggedin]

If no lights are on the board then check the fuses. I believe the 25A 32V slo-blo powers the board, but replace the flyback first...  If it has a K7000 in it then new flybacks are $30.

[PetitMorte]

I will definitely deal with the flyback ASAP.  Currently the monitor is disconnected and not hissing at me anymore. 

I found some "test points" on the PCB labeled GND and +5V.  Putting my hosed meter across them to test voltage shows nothing at all.  Nada.  Zip.

(The meter, connected to a known +5V source usually shows something like 30-40 volts.)

I will be picking up a new meter this evening to see what's going on.

There are several fuses on the power supply, but I do remember seeing a large slo-blow fuse.  It looked semi-toasted, sorta burnt, but it continuity-tests just fine.  I'll replace it anyway and see.

Thanks!

[PetitMorte]

Well, after some real voltage testing, the power is definitely wrong.  These are what the pins of the power connector going to the main board gave me.


Pinout from manual                  What I got
--------------------------------------------------------------------
1 - GND                                     GND
2 - + Sense
3 - +5vdc                                  +4 mv
4 - +10.3vdc reset                    +15.3v
5 - -sense
6 - -15vdc                                 -15.8v
7 - N/C                                      no pin here
8 - GND                                     GND
9 - +15vdc                                 weird reading (see below)
10 - +5vdc                                 +4 mv
11 - +5vdc                                 +4 mv
12 - GND                                    GND

The weird reading I got off of pin 9 started at +7v, and slowly got larger and larger.  After a minute or so, it had hit +10.5 and was still rising.

I'm guessing that the problem lies in both the power supply, and in the sound PCB as well.  Power goes from the supply, to the sound card, then from there to the main board.  I found some test points on the sound board, and the voltages are off there as well.  The +10.3 measures +15.3 and the +22 rings in at +24.5

What I'd love to get hold of are the specs for the sound board, and for the power supply itself.  That way I can fix it, as opposed to spending the cash to replace them both.

Any ideas?

[Rocky]

If you're sure your voltage readings are reliable, then you need to fix/replace the power supply.

I personally don't like relying on the A/R II boards for DC voltages. I just use them to amplify the audio.  I am using an old PC power supply in my RoadBlasters.  I can successfully bench test it on a regular switching power supply.

You can substitute -5 or -12  for the -15 asked for. It is only used for audio, so you won't get as much power.

You can substitute +12 for the +15 and +10.3.  The 10.3 is only used to get the CPU to start and is unregulated.  And the +15 is used for audio only.

If you get the voltages you need, you can test the Mainboard alone. If it is working you will get a "no cartridge" message.

If it is working partially, it may be difficult to tell where the problem is without a known working mainboard or spare cart.

Good luck,
Rocky

[PetitMorte]

w00t!  I'll break out the spare power supply then.  I've got a nice one left from another cab.

This also means that I'm going to have to deal with that flyback sooner than I had thought.

anyway, cool...  Thanks for the advice!

[PetitMorte]

BOOYAH!!!

That did the trick, Rocky!  I connected up the other power supply I had and up came the board as happy as can be!  One LED on solid, and one flashing.

Since the monitor was sitting on my bench anyway, I hooked it up to the board and powered it up. .. and just like you said, the screen was flashing "No Cartridge" in time with the blinking LED.  I powered it all down, slotted in the RoadBlasters board, and BAM!  Next thing I know, there's a beautiful roadblasters screen showing off!

To top it all off, the monitor's not hissing at all!  A little further checking found that the hissing is coming from the flourescent light behind the marquee!

Now all I have to do is figure out how to get the sound up and running, and I'll be a very happy guy.

Thank you guys so much for all your help!!

[Rocky]

That is awesome!  I love it when it's a power supply problem.  Your RB cabinet should have a sound board in it.  There are a couple of versions.  They provide sound amplification and they convert the AC power to DC. 

On mine. I still leave the input to the A/R board plugged in. (That's the one that is coming from the power block.) That should be enough to power the audio amp.  I disconneced the output from the A/R board that goes to the System 1 mainboard. Instead I send it power from the computer power supply.

Mine has a separate plug for the audio in (from game board) and audio out (to speakers).

Good luck,
Rocky

[PetitMorte]

Looks like I've got the same setup.  It's a Regulator/Audio III.

Thanks again.