DT amp problem

[norty303]

Hi

I've just taken delivery of 2 more sets of DT30, and one of the amps appears to not work.

I have swapped input signal to the good amp, and it drives both galvos fine (so both galvos are confirmed working on the good amp)
When I take the signal from the bad amp and plug it into the good amp, the good amp works fine.
When I take the good signal from the good amp and plug it into the bad amp, it doesn't work.

The bad amp has 2 steady green LEDs just like the good amp.

Also, the galvo fixed solid straight ahead when driven by the amp, so it is getting power. It's just not getting a signal by the look of it.

I'm not sure I have time to get another amp in time for a show now, so I need to see if this is something I could look at myself.

[logsquared]

If the galvo "stiffens up" when power is applied the optical feedback is working. I would "jiggle" or apply pressure with a finger to the pots and other components near the input connector. Maybe with luck its a loose solder joint and you may find it that way. Next would be to put the same signal to the bad and good amp and use a scope to trace the signal starting at the input connector until it stops. Using the good amp as a reference for what to look for.

[DZ]

Could the image size pots be turned all the way down? I don't remember which pot is which or if it's labelled.

[swamidog]

Could the image size pots be turned all the way down? I don't remember which pot is which or if it's labelled.

i think this is right, but make no promises.

[absolom7691]

i think this is right, but make no promises.

I think that's almost right. This was sent to me a while ago from Dave:

[dave]

The invert jumpers are fitted?

[norty303]

Could the image size pots be turned all the way down? I don't remember which pot is which or if it's labelled.

Very nearly totally the problem!

I turned the scale pot and the image magically jumped back into life! Turn it back again, nothing, so its actually a dodgy pot, rather than just turned down.

I have about 8 of the daughter boards here that are redundant now I have 506's ina lot of projectors, so I'm hoping one of the pots on there is the correect value.

[norty303]

All sorted, thanks very much chaps!