ROCK-OLA 480 TECHNA SELECTING WRONG RECORDS

[johnnywossom]

Hi,

I am new to this forum so forgive me please if I make any mistakes with my first posting!

I have a Rock-Ola 480 Techna bought a few months ago, and it often selects and plays a different record to the one selected.  The display shows the correct number as you press the number keys, and it displays the same/correct number when it picks the record up, but plays a different record.  There is no apparent set pattern to what it selects (ie. it's not the next record in line, or 2 slots away etc etc).

If I select 100 it always plays that one OK and will generally play subsequent selections OK correctly providing I start with 100 (but not always).  Sometimes it will play correctly even when I select a record further along, but there is no regularity to the error.

The guy I bought it from suggested that I clean the optical disc with Isopropyl Alcohol, which I did.  I assumed he meant the metal disc with holes in it, but I am a complete amateur so possibly this isn't even the part I was supposed to clean.  However, it seemed to be fine for a few days (just the odd b-side it played wrong), but then it went back to picking incorrect records again, so might have just been a fluke?  He mentioned that there may be a sensor somewhere on the opto disc but wasn't sure.   He emailed me some images from the service manual but all they show is the main parts of the mech.

I have researched the problem and there is very little online, but one guy mentioned an opto switch on a Rowe Ami in one of his videos, a plastic slot that the opto disc runs through, that needed cleaning.  I can see something similar on my jukebox just a way back from the home position but there are no wires attached which makes me think it can't be the opto switch?

I am hoping this is just a case of cleaning something to remove accumulated dirt/dust that may be causing the machine to mis-select?  But I am struggling to get any information to help me identify exactly what I need to clean, or indeed whether it's a more technical/serious issue.

To all you experts this is hopefully a simple issue and you can give me some advice on how to fix it?

Any information and suggestions will be grateful received 😊

All the best
John

[jukenorman]

Hi John,
The first thing to look at is that disc for the opto (the one you cleaned). Is it loose on the shaft? The centre plastic piece often cracks and with the disc now loose, this can result in incorrect positioning. You might be able to tighten it up with a cable tie, if I remember correctly? You could also search the forum, I seem to recall this being covered before.

Norman.

[johnnywossom]

Many thanks for your reply Norman. I have checked the disc and it's not loose or wobbly. There is the slightest bit of movement (half a millimetre) side to side or front the back but feels pretty solid.

I did a search for Rock-ola 480 and Technna but could only find the threads about an amplifier issue. Is there another way to search for this?

So it sounds like I did clean the right part then?

Any other suggestions?

Thanks again, appreciate your advice and help.

[jukenorman]

The last thing to do is to clean the opto coupler itself, see page 23 of the manual. The opto board should come off by removing the screws "D". Clean both sides (light source and photo transistor) with a Q Tip type swab stick, you can use the same alcohol as you did for the disc.

Norman.

[johnnywossom]

Hi Norman,
I don't have a manual, the guy I bought it from kept the manual, annoyingly!
Any chance you have a scan of page 23 you could attach?
From what you are saying it does sound like a case of cleaning the right parts as opposed to anything more sinister?
Thanks again for your advice.
Best,
John

[jukenorman]

It's a double page so too big to scan and attach here. I will message you a link where you can download it, checck messages at the forum header.

Norman.

[johnnywossom]

Morning Norman.

I managed to find some time this weekend to remove the opto coupler and clean it.

The result is, now is correctly selects all records up to position 155, which is the last one that it selects correctly, after 155 it displays the number you have keyed in but plays the next record in line, so the result is that record no. 165 no longer plays at all, as it jumps onto 175. It does this until it gets back to home position and then plays all selections correctly until it gets to 165.

The work-around here is that I leave slot 165 empty and move all the tickets up one one place so that the corresponding record I select does play, leaving the very last title card position blank, so 79 records in the juke compared to the 80 it should have. But that's still better than the previous scenario where it was a lucky-dip as to what record would play. At least now there is a pattern to the issue.

But, do you have an idea of what's causing this. I remember on page 23 it mentions opto assembly adjustment proceedure, and I wondered if I need to do something along those lines?

I have cleaned the disc again (front and back) around position 165 and used a soft brush to ensure there is no dust etc in the slots, but it's the same.

Hope to hear back from you.

Thanks as always
John

[jukenorman]

Hi John,
Yes, it's definitely progress! It might be the opto alignment that's your problem but it could also be the indexing adjustment on page 22 and that's a fairly straightforward procedure so I would try that first. It may actually be a combination of both but the indexing will hopefully correct it!

Norman.

[johnnywossom]

Brilliant! Sounds positive. Thanks Norman, I will give that a try and let you know how I get on.
All the best
John

[johnnywossom]

Hi Norman,

I did the logic board test, but it only selected 100 and 194, none of the other 4 selections that it is supposed to pick up. Does that tell you anything?

I read about the record alignment on page 22, and turning the trim pot right or left to position the record between the left and right separator of the record slot, but that seemed to be an adjustment of the record position, rather than the position it stops at?

What should be my next move?

Thanks
John

[johnnywossom]

Morning Norman,

Sorry to be a pest but have you had any further thoughts on my jukebox problem? Am I right in saying if the logic board test only completed 2 records out of the 6 that it should, then could that suggest an issue with the logic board, which could be the root cause of the problem?

Knowing little or nothing about the workings of a jukebox I have been reluctant to tinker any further, such as turning the trim pot left or right. This bit confuses me as I don't know whether I am supposed to stop the basket at position 165, and then try adjusting it, and do I leave the power on whilst doing this? Will I see the basket move when I adjust the trim pot? The cover on the logic board says disconnect from mains before removing, hence I am unsure about this bit.

Likewise with the opto alignment, it starts by saying "if the trim pot cannot be adjusted to produce the proper record alignment the encoder disc must be re-adjusted". My own logic tells me this is about the position the record is taken in and out of the basket (so perfectly aligned in the middle ideally), but I have probably misunderstood that, but it does make it difficult for me to tackle these adjustments without fully understanding the effect they will have. I hope you understand the reasons for my reluctance to make these adjustments, and the reason for so many questions ☹

At the moment, I have moved all the tickets up one position and the juke plays whatever I select, perfectly. I really won't be offended if you suggest that this is beyond my skills and maybe I should settle for the improvement I have achieved so far.

All the best and look forward to hearing from you,
John

[jukenorman]

Apologies, I seem to have missed your Aug 27 reply! I don't know how much can be read into the logic board test, I'm inclined to ignore it!

Let me see if I can explain in simple terms how it works. When the jukebox carousel parks, a zero datum is established and from there the opto simply counts slots. When the gripper picks the record, ideally you want the record centrally in the slot. The trim pot does that - you make an adjustment, then you test it by making a further selection until the record is central. Obviously there is a bit of interaction between the opto position and the trim pot adjustment.

Having got the record positioned centrally, it's now down to opto counts. If the selections are going out, it can only be because you are gaining or losing an opto pulse - which I think takes us back to my first reply, is the disc tight on the shaft with no play?


Norman.

[johnnywossom]

Hi Norman,

Thanks for your reply, and no worries.   I think I understand the way it works regarding the opto count from the parked position, and certainly it counts accurately, right up to 165 when it skips that slot and takes the record from the next one (175).

Generally, when I watch the mech operating, I would say the majority of records are placed neatly and centrally back into their slot in the basket, and certainly it doesn't seem to be trying and failing to pick up any of the records. I can hear the odd one scrape against the side of the basket as it is put back but I would say maybe only 2 or 3?

So on that basis I would say if 75+ records out of 80 records are aligned centrally that wouldn't be causing the issue with it by-passing position 165, which it does every time. Am I correct in saying if I adjust the trim pot it will make the adjustment for ALL slots, not just one? Or do I have to stop the mech as it is placing a record on or off the turntable and then adjust the pot for that slot only? I am really sorry if I am being dim, but this is completely new territory to me, and I am learning as I go.

I have checked again and the disc feels reasonably tight on the shaft. There is a tiny amount of play, as I mentioned before, maybe 1mm back and forth and side to side, but would that be sufficient movement to cause the issue, especially as it's the same position every time that it misses, selecting 175 instead of 165? Also, if the disc were wobbly/loose would I be right in saying the selection that it skips would be random, and not the same one every time?

It seems to be a quirky error and presumably not one you have encountered before?

I would love to get it 100% perfect, but I am increasingly wondering if I should leave it alone as it is working fine, bar one record? (especially considering my evident lack of skills)

Best regards
John

[jukenorman]

I agree, it does seem very strange that it happens at exactly the same position every time and that it continues and then resets itself at the datum! I know you said that you cleaned the encoder disc but I wonder if there could be grease or some sort of contaminent inside the disc aperture at position 165 that's resticting the light signal through it? Maybe you could try cleaning through it at that selection, it has to be something like that!

And yes, the trim pot is a global adjustment.


Norman.

[johnnywossom]

That was the first thing that I thought of, so I cleaned the disc front and back with the alcohol, at position 165 and 2 or 3 positions either side, and also used a brush to clean inside the 165 slot, so I am pretty confident that there is nothing stopping the light getting through. It's a proper head-scratcher!

Like you say, if the opto is simply counting the slots from its home position then it seems logical that something is stopping the light going through the slot at 165, hence it stops counting at 175 and plays that record. I will check it again but I am 99.9% certain nothing is blocking the slot.

I think I mentioned that it often does a full scan of the magazine after you select a record, right round to and past the home position, and then selects and plays the record (correctly) on the second scan. I don't know if that helps at all? Thought I would mention it.

I am happy that my jukebox plays the record that I select, and, touch wood, it has done this consistently since I cleaned the opto coupler, which is a big improvement. The workaround might be a bit quirky but it works, and for that I am grateful. It would be great to get it 100% right, but this one seems to be proving difficult, and I don't want to take up any more of your time than I already have. But if you do have any other ideas then I'd be happy to hear from you.

Thank you again Norman, for your time and patience with me.

John