New Monitors without ISO Questions.

[Halo]

As someone who's used to seeing ISO transformers used with monitors in mainly older games, I have a few questions about the new monitors that state 'No ISO transformer needed'.

1) How are these new monitors protected, as some are connected directly to the mains? If I replace an old monitor, what is now protecting me if I touch the chassis on the new monitor? Just curious as to how the safety works on an open frame arcade monitor.

2) To eliminate herringbone on on old monitors, Ken Layton gave me the perfect solution, by putting a jumper between the Frame Ground and the DC output Ground, which has worked seemlessly in every case. However, I think it was also Ken (possibly a follow up post) that stated this was only if there was an Isolating transformer present, or possibly the boards could be blown (and someone else said the PSU could also blow). So my question is this .. if I swap to a new ISOless monitor, would herringbone still be a possible issue, and if so, presumably without the ISO present, the jumper is a no-no. Is there a work around?

Thanks  

Tony

[Ken Layton]

The new monitors that are called "free voltage" or no isolation transformer needed have a built-in switching regulator power supply which in itself isolates the chassis. Hence, no isolation transformer is needed since the new monitor's switching regulator supply has a transformer in it. There are, however, times when you do need an isolation transformer with these new monitors and that's when servicing them. The primary side of the switching regulator is not isolated and your test equipment WILL BE DAMAGED if the monitor is not connected to an isolation transformer during service work. You don't need one during normal operation of the monitor in a game cabinet.

Since the new "no isolation" needed monitors were introduced you should have no problem leaving the jumper in place on your game power supply with one of these monitors. I have never tried it myself, though.

[Halo]

Excellent, thanks again for the advice!

[Jomac]

Tony ,

All cabinets are wired using that method here in Australia , it is perfectly safe on the freevoltage types as well .
Only problem is that if the CRT gnd isnt good we have problems with RSD's tripping out , also if there is a power supply fault on a freevoltage chassis is almost always trips the RCD's (Residual Current Device ) and can get site owners very annoyed when half their shop blacks out because of a single chassis fault.

Always make sure you have your DC Gnd connected to your earth (Field Ground ) if you are going to earth your chassis .
The reason Power supplies and sometimes game boards blow up is because some people dont realise the importance of the CRT gnd ( braided earth strap around the CRT) if this is not connected and you have your dc gnd and earth joined the crt will actually try to discharge through your dc gnd and sometimes the monitor gnd itself as in the RGB, GND , Sync , this can spike the board and p-supply .
In games wired this way we have been able to spike the electronic coin mech into giving free games if the CRT strap is removed .

[Halo]

Thanks Joey for the explanation .. It's always nice to be able to tell people why the jumper is there if the occasion arises. Most people simply say 'Hey .. if it clears the picture, I dont care!' .. but from a safety point of view and also bearing mind some systems put in the cabs costs a lot of money, it's always good to be able to check it out and make sure it's going to be cool.