[Jukebox-list] AMI Carriage junction box RR relay arcing

[Aaron Heverin]

Argh!!!! Steve and Ron...you guys may have hit it right on the head!!! I always swap out those old GE rectifiers with brand new ones and the voltage always tops off at 32 volts even under load. I don't have any clue where my manual is, but I thought the voltage in the circuit was at least 30 volts. Not thinking that 32 volts was too high, I never thought about bringing the voltage down with a power resistor. Darn it! I want to try that right now, but my son isn't feeling well so no jukeboxes tonight.

You mention a 5w resistor - obviously a power resistor... but what value would you recommend? This is great stuff because this will solve this annoying problem for all of us that own these jukes. At first I thought about putting a diode across the relay to short the arc to ground (like I do in the credit units), but for some reason I never did it. Using the diode in the credit unit almost eliminates the annoying popping sound that comes from the credit unit when a selection is made while the juke is playing...or when you press a button and no credit is available. My G was notorious for that. The diode fixed it.

I'll have to really look into the dynamic braking thing. I know that the RR is shut off by the action of the tone arm cam against the cam switches....which are the only switches I can think of in the circuit that could cause the "should not be open or closed, but they are" deal. 

Joey....I'm going to look into my G sometime over the weekend and I'll see if I find anything that could be causing the arc based on what's been discussed here. If I find anything, I'll post it to the list for everyone.

Aaron Heverin
-----Original Message-----*\*From: "Steve Wahl" steve at pro-ns.net*\*Sent 3/9/2007 10:31:09 AM*\*To: "Jukebox mailing list" jukebox-list at lists.netlojix.com*\*Subject: Re: [Jukebox-list] AMI Carriage junction box RR relay arcing*\**\*On Thu, Mar 08, 2007 at 01:14:39PM -0800, Ron Rich wrote:

 Aaron,

 As for the fuse--AMi did increase the value of that fuse in later

 production from the 8/10 to a 1 amp SB. 
1. Since it doesn't stick out very much the way Ron said it, I thought

 I'd stress the *SB*, which means slow-blow. Aaron, if you've been

 using regular fuses there, the slow blow type will probably cure

 the problem of blowing fuses. (Slow blow lets you draw much more

 current for a very short time period, but blows for a sustained

 high current draw.) It won't do anything to cure the arcing, but

 it'll at least keep you going while you fix the problem, if you're

 not satisfied to just leave it that way.
2. Esp. to Ron, if this is in the dynamic braking circuit, is there a

 chance that contacts are mis-adjusted? That is, as I understand it

 dynamic braking puts a dead short across the motor so it stops

 quickly rather than slowing to a stop (and overshooting the desired

 stopping place). If the shorting contacts "make" before the

 contacts supplying current "break", that would be a quick dead

 short across the power supply, causing a lot more current to flow

 and thus a larger arc when the contacts separate.
 I haven't looked at the schematics nor the actual relay(s) to see

 if that question makes any sense at all.
3. I've heard of capacitors being put across contacts to prevent

 arcing. Would this be a possible place to apply this idea? How

 would one choose the propper size capacitor?
Just trying to be helpful, although I'm paying close attention in case

I ever see this on my F, which for the time being is still running

with the original rectifier, to the best of my knowledge.
-- Steve Wahl

-- 

Steve Wahl steve at pro-ns.net
I write to make people think. Sadly, in many cases my writing makes

people think, "Man, this guy is really an idiot".

 -- Nizo, on Slashdot
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