Rockola 425 cam switches ??

[shrimpeater]

So I adjusted the cam switches (micro as they are sometimes called)as per manuel. # 1 micro switch setted on bottom of cam groove in home position.

I can push a level and everything works fine,until the end of the record.It will not eject or technically speaking,reverse.

IF I move the gripper motor a little more than the position it stops at,then I here the click and gripper will reverse.

I;m not sure what I'm doing wrong or not doing.If the #1 switch is adjusted,I would think everything would be in proper order.But apparently the gripper motor stops early.Not to early to put record on properly,but to early for the #3 switch to open(or closing circuit to interlock relay) .I think its suppose to go in the cam groove.

So,I'm lost as to what to do.

Not sure what return cycle means on Pg 11 of manuel. 

Not sure if I removed this cam when I removed the gripper assembly,but as another person said on here,Is it possible I put it back on wrong??

[jukenorman]

You might need to consider that the #1 micro switch is faulty! It's a changeover switch so performs two functions. And do remember Ron's mantra, don't test the switch on continuity with a digital meter. The "return cycle" surely just means returning the record to the magazine?

Norman.

[shrimpeater]

Thank you as always. And,no,I did not remove cam.

[shrimpeater]

Change the #1 micro. No change. I was sold a used part,so I'm assuming the seller which has a big presence in the community,test it first.

I'm going ahead and order more switches and change all 3 with known new ones.

[jukenorman]

These switches are invariably troublesome one way or the other. If you test them using a test lamp (battery and light bulb) as opposed to continuity with a digital meter, then you know the status of the switches and whether or not they're serviceable. Then you know that if switches are good, what you're dealing with is adjustment!

Norman.

[shrimpeater]

Looking at the tonearm control just above the switches,it's not going far enough when it stops. It picks up record fine,puts it down fine,but then it won't cancel until I use the motor knurl to move the cam some more. I think it may be switch 3 that goes in the groove and then the eject switch works.
I've tried adjusting the cam,but it has to be switch 1 in cam groove at home.Nothing else (as you know) will work.
Seems the cams not working the switching in proper sync,but I have no idea how to make any other adjustments in that area.

[jukeboxmarty]

I don't have a schematic in front of me, but doesn't this model have a gripper motor slowing resistor? Maybe the resistor is open.

[jukenorman]

The slowing resistor for the gripper motor is brought into circuit by cam switch 2. There are quite a number of circuit operations taking place during the transfer so it's difficult to be specific other than to say that the micro switches are known to be troublesome after sixty years. If the reject is not working, the best way to determine the problem is to refer to the schem-a-gram on page 45 of the manual to determine why the reversing relay is not energising - cam switch 1 maybe?

Norman.

[shrimpeater]

 I have the switch assembly out.Continuity checks are OK. I'm going to get a battery and bulb and test next.I'm guesing this make sure it works under a load.

What voltage battery/light should I be using.

I don't find Rons post anywhere.

Thank you

[shrimpeater]

-whatever is going on with this machine,I can,in no way,get the gripper to move to end position adjusting the cam.
Tested all resistors in control box and all have continuity.

[jukeboxmarty]

One of Ron's posts....

jukeboxaddicts.proboards.com/post/2254

Edit:

BTW, I disagree with the concept that a digital meter can not be used to accurately test continuity. If you have the right meter, and know how to interpret the results, it shouldn't be a problem.

[jukenorman]

Of course a digital meter can be used to check continuity but that's not the issue we're concerned with. In service, Shrimpeater's Rock-Ola cam switches are passing substantial amounts of current. If you consider a scenario where 99% of the switch contacts are damaged by pitting etc, the contacts simply will not work in service but will test OK with a digital meter because the remaining 1% of servicable switch contacts are still capable of passing the miniscule current generated by a digital meter on the ohms range. This has caught out many people with quite a few instances on this forum.

I just use a pinball lamp holder and a 9V battery.

Edit - I should have said to use an incandescent lamp, rather than an LED lamp so that's the circuit is passing a decent current!

Norman.

[jukeboxmarty]

Jun 14, 2023 18:43:40 GMT jukenorman said:

Of course a digital meter can be used to check continuity but that's not the issue we're concerned with. In service, Shrimpeater's Rock-Ola cam switches are passing substantial amounts of current. If you consider a scenario where 99% of the switch contacts are damaged by pitting etc, the contacts simply will not work in service but will test OK with a digital meter because the remaining 1% of servicable switch contacts are still capable of passing the miniscule current generated by a digital meter on the ohms range. This has caught out many people with quite a few instances on this forum.

I just use a pinball lamp holder and a 9V battery.

Edit - I should have said to use an incandescent lamp, rather than an LED lamp so that's the circuit is passing a decent current!

Norman.

I've been an engineer for many years, and have professionally repaired thousands of jukeboxes, and have never had an issue testing any switches with my digital multi-meters (all of them are Flukes). I've never had one (switch) test good that was actually bad.

You may try to 'put me in my place' on this issue, but my results are based on my experiences. Your results may vary.

I still do not agree with the notion that a digital meter cannot reliably check switch contacts.

EDIT: Some very knowledgeable posters in this forum have left the board because they had a different but acceptable solution to a problem. Let's try to play well with others. Disagreements, especially among forum leaders can be taken to private messaging.

[jukenorman]

Hi Marty,
I was not trying to put you in your place, I just fundamentally disagree with your take on checking switches (ie switches that pass substantial current) with a digital meter on the ohms range. I'm also quite clear that the exact same position was held by Ron Rich and that is covered in his "sticky" on contacts. The theoretical example that I presented above was an attempt at justification, not a smart ass riposte and I stand by that as an example. My Fluke 79 that has served me well might be a bit old and I've just measured the current on the ohms range using an AVO8 analog(ue) meter - it barely registers, it's a fraction of 1mA. Using another equally old Fluke 77, I measured 0.48mA. This is the crux of the issue, using a digital meter on the ohms range injects very little current through the switch.

I know Ron could be a bit abrasive at times, I would hope that I might be less so and not cause anyone to leave the forum! I have posted this on the board because I believe that others users should see my argument and proceed as they see fit. However I won't be discussing it further.

Norman.

[jukeboxmarty]

I do not have thin skin and can hold my own in an internet forum.

I was hoping that this forum could avoid the "I'm right" and "you're wrong" attitude that permeates other groups. Quite frankly it has stopped me from posting here and other platforms.

I guess I was wrong to say I disagreed with a position that was highly held on these threads. This has been an issue in the past, and it looks like it continues to be an issue.

So am I to conclude that my experience is not valid? Am I to post my own technical rebuttal to defend my stance? I think not, I gain no benefit to 'be right'.

So I may not be right, but I will continue to successfully apply my experience and knowledge not here, but in the real world!