Golden Mask 1 repair

[Koala]

Hi got a GM1 that's not happy.

Very poor detection and the threshold does nothing.(Probably the same problem.)

Disc works fine. Only getting 3" on a coin. Not sure the history of the machine. Could be the threshold in not wired correctly. Close up photo of the threshold wiring would be appreciated. Found a photo on here but not quite enough detail.

[Koala]

Had a quick look and looks like a resistor has melted



Any info on the Golden Mask Please

[Merc]

Not sure what that is but I''ve never seen a surface mount resistor melt. They will burn, they will crack, but I don't think they melt.
I don't have a a schematic. Sorry.

Merc

[kt315]

now you can see WHY I ask people to share high resolution pics. I am READY to help but wherewith?

Anatloy

[Koala]

Dam. It's not the problem value is 100K

[zelkos]

Hi Merc,

First clean that black plastic or glue from the surface ("Ear-wand" & nitro thinner). Check the resistor, it is possible that is OK.
SMD resistor is a thin plate of ceramics, with a thin metal surface ... from SMD resistor "no leaks".
Then check out all the elements that are associated with these resistor, the first SMD trany (?). I do not see the mark, I'm not sure.

Best wishes!

[golfnut]

Try the resistance of the Rx and Tx windings


scope the Tx, see if the freq and the amplitude are right


See if the Rx cap is on the board? It may be the Rx coil not peaked close enough.. So loss in sense..

[Koala]

Made a bit a progress. The one end of the threshold POT is GND the other is 5 volts. If I inject 5.3 volts at the center then the threshold comes back but unstable.

Boy it's quite impressive for a 7" DD. Over 11" on a copper clad 2P


Cant see any obvious blown components ? Looks like the coil is more than okay. Wish I could get that performance from my coils.

[Koala]

Nearly there with this one. Re-flowed all the main IC's. Looked a bit dry. Now works.

Have one slight problem. If I touch the coil connector it stops and if I touch the threshold POT it starts again. Both are connected to the same GND point ????