Need help with a circuit board (any electricians out there?)

[Anti]

This super cool item has ceased to function and I'm at a loss for how to fix it. This is serious, because if I'm boarded by a Gorn, I currently have no way to sound Red Alert.

Here is the system in question (click for larger picture):

View attachment 45439

Standard Starfleet issue duotronic corridor communications unit. Runs off the secondary EPS taps but in a pinch will also run on a 9 volt battery.

Here's what it's supposed to do:

Two things. First, clicking the intercom button turns on the intercom light. That works. Second, clicking the red alert button turns on the red alert light and a klaxon/siren that sounds through the speaker. The light flashes on and off as the siren sounds.

Here's the problem: When I hit the red button, I get no light and a garbled, brief (1 second) squawk. This is what happens the first time I try it. Subsequent attempts get no reaction unless I unplug the battery. Reattaching the battery gets you one more garbled squawk.

I don't recall if (when fully functional) the light and siren sequence continued until you hit the button again, or if it went off by itself. I think when it worked, you could hear a clicking sound as the light went on and off.

The only parts I recognize are the relays, which are 1 inch cubes that remind me of the things that made the turn signals blink in my '74 Ford Grand Torino Elite (oh yea, I was stylin' back in the day).

Anyway, my best guess it that I have a power drain in the tertiary EPS coupling. Or maybe the entire assembly has phase-shifted (which would explain why my hand passes through it . . . after a lot of bourbon). Or it could be the flux capacitor. Or a Cylon logic bomb.

Any help would be appreciated.

 

[scottinthebooth]

Based solely on your description of the problem it sounds like the sound IC (where the actual sample is stored) has been corrupted somehow. Have you tried a brand-new 9V (or a different EPS tap?) If voltage is low then the IC may be unable to accurately reproduce the sample.

EDIT: This is also a known Borg tactic so you might want to go for extra security patrols until the unit is repaired.

Scottinthebooth

 

[Mr.Engineer]

Let's just hope its the 16 ohm speakers that' is giving way. Have you tried touching the wires for any loose solder connection?

 

[Anti]

Tried a new battery (no change) and can't find any loose connections.

When I hit the alert button, the red light clicks but does not come on (at least, I think it's the light clicking), and the speaker squawks a little. This lasts about 5 seconds. The speaker also emits a constant low volume, high frequency whine which continues until you disconnect the battery. If you reconnect the battery right away, the whine is still there and pushing the alert button causes no reaction at all. You have to leave the battery unplugged for a few minutes to get the first reaction describe above.

Ach. Is i' time tae tow the ol' lass oot to the salvage heap?

 

[scottinthebooth]

If your comfortable doing a little bit of testing and have a few basic electrical supplies (clip leads) around you can see if perhaps you have a blown speaker. I doubt this is the case as you'd likely not be getting ANYTHING from the speaker but it would at least rule that part out.

To check out the audio:

Clip the two yellow wires going to speaker. Strip the insulation back about 1/4" so you can put a clip lead on the wire again. Grab any pair of headphones with an 1/8" plug and put a cliplead between one yellow wire and the ring of the headphone connector that is closest to the cord. Place another cliplead between the other yellow wire and the ring farthest from the cord (the tip). Then try the red alert button again. You will only hear sound out of one side of the headphones (and they may be quite loud -- you've been warned). If this sounds correct though, you probably have a bad speaker. If not then the two yellow wires can be easily resoldered to the speaker terminals.

Scott

 

[exoray]

If your comfortable doing a little bit of testing and have a few basic electrical supplies (clip leads) around you can see if perhaps you have a blown speaker. I doubt this is the case as you'd likely not be getting ANYTHING from the speaker but it would at least rule that part out.

To check out the audio:

Clip the two yellow wires going to speaker. Strip the insulation back about 1/4" so you can put a clip lead on the wire again. Grab any pair of headphones with an 1/8" plug and put a cliplead between one yellow wire and the ring of the headphone connector that is closest to the cord. Place another cliplead between the other yellow wire and the ring farthest from the cord (the tip). Then try the red alert button again. You will only hear sound out of one side of the headphones (and they may be quite loud -- you've been warned). If this sounds correct though, you probably have a bad speaker. If not then the two yellow wires can be easily resoldered to the speaker terminals.

Scott

To test the speaker itself, cut the wires to the circuit (aka remove and isolate the speaker from the circuit) and simply tap the speaker wires to a battery (aa, aaa, c, d will do fine) if the speaker produces a clean clear pop when you tap the wires together it's likely still good...

To me the "stuck" phase you describe it doing that requires the batteries to be pulled or at least some time to elapse could be a sticking relay...

The sound module itself (green board) is the $10 voice recorder special form Radio Shack, you could record the sounds and swap that part out in short... But that would still leave you with the logic circuit, or relay possibly being defective...

9V Recording Module - RadioShack.com

It's actually a stock item in most stores... Catalog #276-1323

Personally the relays really are overkill in this application unless they are using real bulbs vs LEDs but still they are kind of overkill...

 

[stromo]

I doubt the speaker is screwed, and I doubt even more that would make the light not come on. Of course I could be wrong.

My money is on a dodgy wire or some sort of short.

Your picture appears to show a few overlapping components. I'd be concerned that the leg from one was maybe touching the leg of another. Maybe check for that.