Stupid Piggyback Question

FrizzleFried

Well-known member

Donor 2011
Joined
Mar 20, 2007
Messages
54,197
Reaction score
5,253
Location
NAMPA, Idaho
Question: Can a person piggyback 2101 RAM "on the fly" ... meaning can I install/remove the RAM while the game powered on to test or is it best to power down, piggy back, power up, check, power down, repeat if necessary with a different location?

Heck, if a pro would go through the generalities of a PCB as far as what you can touch and what you should avoid I know I would appreciate it. I always have treated the majority of a PCB as a "hands off" while powered point of view... how accurate is this? What can and what can't be touched/tested/etc with bare hands?

I've always treated electrical items with an abundance of caution. That said, being that most PCBs run at 5VDC, I imagine I am being a little more paranoid than necessary? Can a finger "bridge" legs of an IC by accident (for example)?
 
Usually you can't screw anything up because like you said the highest it'll go is 5 volts... which is what it's looking for anyways (logic chips get either ground, or 5, or back and forth).

i'm not a pro.... but yes, you can piggyback ram on the fly... there are different ram used for different things, and piggybacking them won't always fix your problem anyways, but by doing that you'll get different things reacting on the screen which will show you what that particular ram controls if you're lucky.

Sometimes when you do that (piggyback) it'll lock the game up, and if you do it to 'work' ram that the CPU is using, it will make the game reset. If you piggyback a 2101 though, and notice all the character sprites dissapear, or double up, or something then you can reasonably assume that's something that that particular ram controls.

Only thing I'd be careful with is CLOCK signals, I'm not sure what shorting one of those to 5 or ground, or shorting the clock signal somewhere it shouldn't be will do.

Also of course you might have a problem if you've got chips that use 12v, or even -5, but on a lot of boards that's just used for audio.

Hopefully a pro can chime in with more info....
 
Before you go touching ANYTHING, touch a ground or use a ground strap...it is like a watch band and attached to an earth ground. Static is often overlooked and one of biggest killer of working boards. It may not kill it right away but sometime down road, it will die. Just make sure you line up pins.

What board is this? Certain ram on PacMan boards are very sensitive to static.

I hate it when I get boards that are wrapped in the clear bubble wrap, working or not.
 
I don't understand how this even works. how does touching a good ram to a bad one make it work right? that's the theory I thought.
 
I don't understand how this even works. how does touching a good ram to a bad one make it work right? that's the theory I thought.

It work for me a time or two, you need to make certain the ram is not shorted first. I did this with an Op Wolf main board. The static ram was suspect, piggybacked the two and game board worked. I posted this someplace but not going to look 4 it now. On tiny phone and can't see well and fat fingers.
 
I have piggy backed Ram on a DK and a Galaga and got it working. Was in a hurry on one of them and just soldered the legs together and left it piggy backed :)
 
I have piggy backed Ram on a DK and a Galaga and got it working. Was in a hurry on one of them and just soldered the legs together and left it piggy backed :)

I have a board just like that and it is also a Galga. That particular part is still good, believe it was a ram and or a ttl chip. Something is up with the 2nd or 3 z80.
 
piggybacking RAM/IC's only works when the soldered on the board IC's gate is open or otherwise not held in any position (hi/low/floating). If the gate is shorted piggybacking will not "fix" the board but may cause other anomalies.
 
piggybacking RAM/IC's only works when the soldered on the board IC's gate is open or otherwise not held in any position (hi/low/floating). If the gate is shorted piggybacking will not "fix" the board but may cause other anomalies.

I agree. Piggybacking ram does not work (most) of the time for the above reason. It does not hurt anything to try. It would be best to power down because the data in the ram can become corrupt when you piggyback and usually wont clear until you start a game or reboot.
 
Back
Top Bottom