Continental fuse blowing problems

[a4skyhawk]

I restored a wonderful AMI Continental 2 over 20 years ago and it has provided great family entertainment. Last week it stopped working and I believe from my notes that this is the same problem I had with it back in 2018. Back then I suspected Cam Switch 2 and after working the switch and spraying contact cleaner the problem went away. Since then it has worked flawlessly through about 1,000 selections - until last week!

The symptoms are:
- The bottom right fuse in the junction box blows. This is listed as a slo-blow 1 Amp fuse but this was a 1.5 Amp when I got it and I have always used 1.5 Amp Slo-Blo in that position. This is the fuse that feeds the 29V to the transfer and mechanism motors.
- Replacing the fuse causes the fuse to blow immediately
- The turntable spins, the record plays but the record is not returned at the end
- The amplifier works OK and the audio is normal
- When a selection is made, the carousel 'write in' arm rotates, but the latch relay is not triggered and the buttons stay locked in. The only way to reset them is to manually push the latch bar

Has anyone else had this same issue and what are the recommended troubleshooting steps? I have all the manuals, meters and tools.

[jukenorman]

Firstly you need to do something about the fuse like temporarily install a resettable fuse for example. Then you need somehow to break the circuit into sections. You could start by powering up with the operate/scan switch set to off, does the fuse blow (unlikely)? Then try it on scan, does the fuse blow? If it does, that would point to a faulty magazine motor although there also might be a back feed to ground so not absolutely guaranteed. There are different ways to approach this, maybe you're more comfortable fault finding with power off?

Incidentally, the original transfer motor would have been AC although it's possible to fit the older style DC motor there; is that what you have?

Norman.

[a4skyhawk]

Thanks so much for getting back with me. I spent some more time on this today checking out the wiring and checking for shorts. I confirmed that with the mechanism switch 'Off', current draw on the 29V circuit is low, the turntable rotates, the amplifier is energized and the music plays through the speakers. When the mechanism switch is in the 'On' position, the current draw is high (~2.5 Amps). This is why the fuse is blowing. Also when the mechanism switch is on, the speaker sound is muted - which is strange to me.

I verified this two ways. 1) By using an external regulated power supply to feed the 29V circuit and monitoring the current and 2) By connecting in an ammeter instead of the right hand fuse and reading the current.

From looking at the schematic, this is indicative of a problem with the Reversing Relay, Muting relay, the toggle shifter solonoids or popularity meter.

The hunt continues!

Paul

[jukenorman]

Hi Paul,
What state is the jukebox in when you are doing these checks - is it in the play position with a record on the turntable? The on/off/scan switch can be a bit confusing sometimes because it only switches the DC circuits with your blown fuse. Assuming you are in the play position, cam switch 6 (which is a changeover switch) is what switches the muting relay so that may well be a clue as to where to look.

Norman.

[a4skyhawk]

Thanks Norman. You are correct in that a record is on the turntable, the gripper arm is down and the turntable rotates with music out of the speakers. When the tone arm finishes playing, nothing happens. The record is not returned. Because there is a record on the turntable and the gripper arm down, the top trim cover cannot be removed making inspection of the cam switches difficult. However it looks like CS1-5 are all 'Up' - un-actuated. CS-6 is depressed. The cam plate (the one with the adjuster screws on it) is tipped down at the front and up at the back.

It's as though - and I am not saying this happened - there was a mechanical 'jam' which locked up the mechanism and blew the DC fuse. I'm a little unsure how to proceed. I think to try and isolate each leg of the circuit and try and identify what is causing high current draw. From the Continental II schematic, the only one I have and I am not sure how close that is to this Continental 1, this could be the record magazine motor, the popularity meter, transfer motor relay, reversing relay and toggle shifters. Now given the current state, I need to work out if these are in-circuit with the current state of the cam switches. Difficult when you can't take the top cover trim off to get at the switches, but I'll work it out.

It would be easier if I knew the Continental 2 schematic I have applies to the Continental 1 model. Is there a pdf of the Continental 1 box? From my experience working on this box, it is 95% identical, but there are some subtle differences. I need for example to determine if the Transfer motor is AC driven, as the schematic indicates or DC driven as some have said the later boxes were.

Thanks for this great worldwide forum of experts. Someone will have the answer!

Paul West

[jukenorman]

Hi Paul,
The Continental 2 schematic is what most of us use, I'm not aware of any differences in the operating logic between 1 and 2 Continentals. The AC transfer motor was introduced in the automatic selector Ks so your Continental should have the AC motor if it's original. It is possible to use the older DC motor because an interposing DC relay was used to switch the AC for the motor. I think you should be able to remove the transfer motor link through the back doors (provided it's an AC motor) and that would allow you to manually return the record, assuming the transfer assembly is not jammed. Or alternatively by removing the popularity counter?

Norman.

[a4skyhawk]

Thanks Norman. This all makes sense. I am unclear what the 'Transfer motor link' is that you refer to. Can you describe where this is? Once removing this link, how is the gripper bow moved back to the rest position? I have looked on this site but can't see any further instructions.

Paul

[a4skyhawk]

Further to this, I have done some more looking today and cannot see how to manually operate the transfer motor to return the gripper bow.

What I did find is:
1) The relay box, which I believe should contain the transfer motor relay is not present on my machine. This should be on the left side of the mechanism near the scan assembly and play meter but I am sure doesn't exist. I cannot see any other non-stock relays wired in anywhere with one exception. The latch relay in the selector mechanism has been replaced at one time with a more modern closed relay and base.

2) On the junction box, there are two terminals labeled '1' and '2' and one of the wires is broken. I suspect I did that when I removed the junction box and will extend and re-make that connection but I cannot see what those wires do. The manual lacks a schematic of the junction box and it is not apparent from the main schematic what those two wires might do. I think all AMI Junction boxes from this era are very similar and also have the two screw terminals marked '1' and '2'.

Paul

[a4skyhawk]

UPDATE: I think I just answered my own question on #2 above. Those wires go to the red 'skip' switch on the rear volume control. Consequently they have no bearing on the problem I am troubleshooting. There is a schematic on the side of the volume control box showing the switch wires going to Junction Box terminals 1 & 2.

[jukenorman]

Hi Paul,
If you look at the manual pages RCS-22 & 23, you can see the the AC transfer motor and link. The link will be held in place with circlips so not too difficult to remove one end. You can then manipulate the transfer assy using the gripper arm - provided it's not really badly jammed. I once had one to repair where some grit had got into the gripper assy which is only alloy, but we got there.

Isn't the relay inside the box that the turntable motor (and transfer motor) plug into? As I said, it's possible to fit an older DC motor there - driven by the wires going to the transfer motor relay coil - but instead of being coupled by a linkage, it's gear driven so probably much more difficult to do something with the covers on if the gripper arm is over the turntable.

Norman.

[a4skyhawk]

OK - success I think. I persevered with checking things out, cleaning things up and lubricating the linkages. Everything moved fairly freely before the lubrication including the toggle shifter bar. While monitoring the current on the mechanism DC feed (the one that was blowing the right hand fuse) I noted that with the current with them mechanism switch in the center 'Off' position was 0.11A and the line voltage was 30V. This went to 2.7A and the line voltage went down to 22V when the mechanism switch was moved to 'On'. I only did this for 1-2 seconds at a time but it was (to me) a sign of something jammed in the mechanism. I found if I left it in the 'On' position for more than 5-10 seconds I detected a'hot electronics' smell from the top left of the machine when looking at the rear. Having removed the power I touched all the solonoids, motors and relays trying to find out where the heat (and hence current draw) was from. Nothing was hot.

The machine state during the above diagnosis was a record on the platter, finished playing and in the centre grove rotating.

I then 'worked' the mechanism and checked the cam switches while toggling between the 'Off' and 'On' positions on the mechanism switch. This eventually resulted in the gripper arm replacing the record in the carousel and I was able to shut the unit off with the arm in 'mid swing'. This allowed me to remove the turntable and the mechanism cover/trim and gain access to the cam switches and mechanism. The gripper bow moved freely but I lubricated it anyway. I could move the arm by turning the armature in the gripper motor. It took a while but I was able to ensure that wasn't a mechanical problem with the motor or gearbox. I then removed the transfer motor which was an easy three screws and was able to confirm it is a DC motor. The oiling holes were had rubber plugs in them so all the oil I was adding on an annual basis wasn't going anywhere. I removed those small rubber plugs and oiled the motor. To be honest I am not sure this did anything and I hooked up the motor to a supply. It ran totally silently and drew only 0.3A. See video linked below.

Before replacing it I checked out the operation of the toggle shifter bar and lubricated that. I checked the four wires from the two solenoids and found that the wire from Toggle-shifter #1 (Odd) to CamSwitch 5 was very loose. The spade was loose on the micro switch blade. I cleaned that up and re-crimped the contact before re-connecting it.

Having checked everything out and confirmed that nothing was binding, I re-assembled the transfer motor and ran everything through about fifty cycles and all works perfectly.

It may have been the loose wire on CS5 or the transfer motor has a piece of debris in it that causes it to lock up. The fact remains that prior to this I was blowing fuses on the 30V DC feed and I saw the current rise to 2.8 Amps and above. After cleaning, lubing and checking everything out it draws 1.3 amps when the mechanism is returning a record and about 0.3Amps normally. The fuse is specified as 1Amp slo-blow but that was with the AC transfer motor. With the DC Transfer Motor I have, I am thinking that fuse needs to be 1.5 or 2Amps.

Thanks for all your help. I am hoping this helps someone else.

Paul

Here's the video of the transfer motor running on the bench: photos.app.goo.gl/dXcZQJtte2boqKfi6

[jukenorman]

Hi Paul,
I'm pleased you got it "fixed". However, I believe your thinking is flawed with regard to the increase in fuse size. The DC transfer motor is similar in size to the magazine motor, they never run together and the 1 amp fuse is sized to operate the magazine motor. Also if you look back to AMi's originally fitted with a DC transfer motor (eg the J), that DC fuse is 1 amp.

There is a sizeable increase in transfer motor current draw between no load on the bench and its operating state. This would make me suspect that there is too much mechanical resistance in the transfer assy. At the very least, I would suggest that you seriously clean / lubricate the transfer assy, maybe with some gentle heat?

Norman.

[a4skyhawk]

Thanks Norman. I concur that a 1A fuse is probably sufficient. Without the motor in place, the transfer assembly was very loose to actuate.  That's to say that it would move down to the horizontal position under its own weight.  I cleaned and re-oiled it and will strip it down if it blows the 1A fuse I have put in there now. 

thanks for all your timely guidance on this.  I am now trying to get the Total Play counter working.  The way I see it, it should increment when the pin-pusher solenoids actuates with the ~29V pulse.  The counter works on the bench with between 20-30V but does not increment in the jukebox.  I connected a 24V bulb (actually two 12V bulbs in series) to the wires and while there is a good solid pulse, I could tel it was nowhere near the 29V the supply puts out. I then measured the voltage of the pulse at the counter connections and it was 14V. Somewhere in the box there must be a poor connection which is dropping the voltage.  

Have you seen this before?  The 1,000uF capacitor in the junction box looks like it has been replaced but that could be a possibility?

Paul

[jukenorman]

Hi Paul,
Yes the 1,000uF capacitor is a possibility. I have seen it recommended in the past on another forum that the value of that capacitor be increased and that would do no harm at all. The other thing to look at is the time delay on the pulse control relay, there's a 100uF capacitor there. If that hasn't been replaced it would be worth doing not least to make sure that you get a good fat pulse for the selection solenoid.

Norman.

[a4skyhawk]

Hi - I did some looking around the search mechanism box and found that:

1) The only capacitor that looks like it has been replaced is indeed the one that generates the PCR delay. This is in series with a 100 Ohm resistor and is connected across the PCR relay coil. The capacitor is of a later style but is still probably 30-40 years old so should be replaced. It is marked as a 'Arcolytic CT/A-1165 150uF 50WVDC'. I am guessing the 150uF will give a slightly longer pulse than the stock 100uF and that a good quality 150uF/50 or 100V Electrolytic will work well there.

2) The above components are mounted on a terminal board on the right side of the search mechanism and the two 0.15uF/400V capacitors are also mounted there. I believe they are the ones across the PCR and MCR contacts. These look like large 1960s polyester caps. What is the best substitute for those?

3) There is also a mystery component on the board that has me stumped. It's a large device looking like a ~3W resistor. It's 13mm in diameter and 35mm long and like a resistor, it has color bands and no writing. To me they look like Yellow, Violet, Orange, Black then a space and a Blue band I assume is tolerance or something. The thing is that it measures open circuit. Is this some sort of capacitor too? 4700uF? It looks like it is wired between the black coil contact of the Search motor and a contact on the Sprag Relay. I can't see anything like it on the schematic and it is original.

The only reason I'm delving into this is that if I am replacing the PCR Capacitor to ensure that the pulse width is solid, I may as well replace these capacitors. I have already re-capped the amplifier. I haven't yet dug into the junction box to see the 1000uF power supply capacitor by will in all probability be replacing that.

Thanks,

Paul

PS: Sorry I would post a picture but I can't find a site that allows http links.