I have an early Fed Sig Touchmaster TM4 built just after the Dunbar Nunn buyout and before Federal Signal began using the Delta tones on the later TM4's. This particular unit is acting up and I can't figure out what's going on with it. The internals are identical to my fully functional Dunbar Nunn-produced TM4 and as far as I can tell there aren't any shorts or sloppy solder jobs. When the Bypass is turned on and the red siren toggle is in the neutral position, the wail goes to peak and stays on, as if you're holding it on manually. The same thing happens when the slide switch is in position 3, again with the red siren toggle in the neutral position. The only way to get it to stop is to toggle the red siren switch up to wail or down to hi-lo and back to neutral. Further, when the Ring is wired to the RLS and the siren is on and in sweep mode, the RLS is not tripping the siren to sweep through the tones. A voltage check of the RLS screw shows good, 13.4 volts upon toggling. This problem and the first may be related but I don't know how. Welcome to any thoughts or insight!
Fed Sig Touchmaster TM4 siren stuck on
- Thread starter jseramur
- Start date
For fun, would you use your voltmeter to check for a difference in voltage between the Ring terminal and ground?
Video of the TM4 siren stuck on
I didn’t check voltage on the Ring because that post is awaiting electrical signal to trip the sweep mode.
Exactly. Although I have never owned a TM4, I have owned other Unitrol sirens over the years. I imagine both the peak and hold problem and the not sweeping problem can be explained by the unintended presence of voltage on that terminal.
You're on to something - there were 6.6 volts on that terminal when I anticipated none. So, now what?
The ring and horn terminals share the same relay. The horn terminal did not have any voltage on it. I suppose the relay could have gone bad and is stuck in the ring side rather than remaining neutral until voltage is applied, so I will try to trip/test the relay. Unless something else on the board is causing the relay to engage.
I think I have the problem narrowed down to the switches on the top board. When I toggle LEFT, RIGHT and AUX into their up/lock positions, there is good voltage on the corresponding terminals. When I toggle them down into their momentary positions, there is no voltage on those terminals. The siren still does not sweep when in sweep mode and verifiable current is sent to the Ring terminal.
Sorry if this is the wrong thread but it was the only one that I could find that was close to the issue that I am having. I have the Federal Signal/Uniden/Unitrol UTMD and am having an issue with the light terminal (pin 1) - the one you connect to your dash light circuit. Applying power or ground to that pin does nothing with the front-panel backlighting. If I hook the siren wire up I can press the 6 switch buttons and they light up green (red if I hook up the accessory wire). Or they stay lighted in green if I hook up the yellow accessory wire. Is there an issue with my backlighting circuit if anyone knows.
There is a chance that all of the grain-of-rice backlighting lamps have burned out. I relamped my TMD a couple of years back. I can probably dig up the part number of the lamps I ordered, if that turns out to be the problem you're having.
JohnMarcson
Administrator
If that relay is somehow getting engaged would it explain the symptoms based on the modes required to replicate the problem? Meaning are both the conditions under which this can occur conditions that would be affected by power to that relay? I had an older SVP siren that shared the manual button and the horn input; I'm not sure how it was doing it but anything affected or controlled by the auxiliary horn input or manual button would occasionally activate. I ended up soldering a different relay in and the problem went away. The only way I was able to track it down was looking at what mode the siren allowed the manual button and the horn activation to perform the same task. I will admit I am not a federal signal or unitrol expert. I am not fully familiar with what conditions allow what functions. I do think you're on the right path troubleshooting this and looking to see what conditions allow this to occur should help you narrow it down to the switch the relay or something similar. When you get it figured out please update us this is a pretty good troubleshooting mystery.