Greetings! Need some help with a resurrected Rock-Ola 440

[gic440]

Greetings,

A few years ago I acquired a Rock-Ola 440.   Story is, I'd been musing about acquiring a 45 juke for a while, and then when I somehow saw a pic of a 440 I knew *that* was the one I had to have.   Something about its schizophrenic style I guess.   So I bought the first one that turned up locally, for better or worse (mostly worse given its condition but I didn't know that at the time).  I've since come to learn that Rock-Olas are rather unloved in the juke world but no matter - I like it for what it is.   

I'm a juke newbie but have extensive tech/mech background so I got the manual and figured it out and then some.  I've managed to significantly improve it from its state when I got it: it's now mostly cleaned and shined up, the mechs are smooth, it plays reliably, and I even wired in an AUX input and added some extra light enhancements.    But there are a couple issues still bugging me / as I've only learned about them, and I'd appreciate some guidance:

1) One of the few things I didn't have to deal with, is somehow the juke was already set to "free play".   I presume a relay or coil in the credit mech was hacked or disabled, but paid this no mind until I recently realized that the keypad lockout solenoid is staying engaged all the time with a buzz that is sometimes distracting.   What is the preferred way to enable free play without frying this solenoid?

2) I recapped the amp, but it still generates a somewhat annoying hum.   The hum doesn't change with main volume.  Most records overpower the hum, but it's noticeable during song lead-in/out and quieter sections.    The cap kit came from Bill at JukeboxFridayNight - but he cautioned that he doesn't deal with these and understandably had to approximate replacement values.  Anyone have experience with late-60's era Rock-Ola amps?

3) Anyone have a source for good 5x7 speakers that will fit this thing?  It's ridiculous how small the upper fascia is.  The only "5x7" speakers readily found today are for car audio, but now those are mostly "compatible / adapterized" 6x8 or 6x9 which are too wide and/or too thick.   I'd like to replace the speakers with some that yield a better mid-high range.   Or should I ditch the original Shure cartridge (has a new stylus) first?

4) I *cannot find* title strip holders that aren't yellowed to heck!  Retrobrite hasn't helped.   I've looked all over the net and ebay.  Seems the hinged/drop panels R-O introduced with the 436 have all suffered this.   Earlier models haven't yellowed as bad, and *maayybe* could be made to fit, but I've not had any luck finding those parts either!   So if anyone knows of a secret stash, I'd be grateful.


Anyway I rambled on too long. Here's some pics of its current state.   It was completely filled brown with gummy nicotine and just barley worked (and poorly) when I got it.   First pic is animated and shows a brief clip of the color-change strip I hid in the door.   I'd also cut a viewing window in the translite, since it was already shot.  Second image I ditched the translite entirely for a stained-mosaic overlay with diffuser, and illuminated the keypad buttons (I suspect this was part of the original design intent as there are clues there). 

I do have a motor for the animation wheels en route; I rigged one that works but it's far too slow.





Thanks for any help,

-Tony L. 
 

[jukenorman]

1 You would need to examine the credit unit to check how free play was achieved. You could cut the AC supply to the latch solenoid and install a small single pole relay (rectify the AC to power a DC relay, DC relays are cheap), route the AC to the solenoid through the relay contact. Take the neg. of the DC relay to the two parallel pushbutton latch switches that go to ground. When you now press a button the relay will come in and pull in the solenoid latching the button. If you leave one button depressed, the solenoid will remaain energised - if you consider this a problem, incorporate a timer.

2 Hum can be difficult to diagnose remotely. Did you replace all the electrolytics in the power supply?

3 5" speakers should be OK, fabricate a baffle from plywood to fit them in the existing locations. I don't see any reason at all to ditch the Shure cartridge, indeed I would consider it a bonus!

4 I cannot help with the title strip holders other than to suggest making their yellowing a feature - could you backlight them with LED strips?

You jukebox looks good! Norman.

[Ron Rich]

Hi Tony,
From what you wrote, I need to ASSume the "hum" is a worn latch bar solenoid-- these are NOT designed for constant duty ! Ron Rich

[gic440]

Thanks for the replies and suggestions gentlemen!, I appreciate it.

That latch solenoid circuit sounds properly sophisticated, and I like the logic behind it. I'll do some more research on figuring this out. Any recommendations for relays, in terms of fit? And having the solenoid latched if/while only one button is pushed certainly isn't as bad as it being on all the time so that doesn't sound like much of a problem to me. I'd read somewhere that replacing the selenium rectifier in the power module could quiet the solenoid while addressing other issues so I did that and indeed, it's a little quieter and cooler. But no need for it to be on all the time.

As for the speakers... pure round 5" units would probably be easier to find and in 8ohms too - I wish I'd thought of that!

And my issue with the title strip holders isn't so much illumination but aesthetics: yellow/brown looks nasty, no way around it. LED bars simply amplify the nasty into radioactive dung. I'd really like white in order to maintain proper contrast on the strips themselves, especially for using colored strips.

As for the amp hum: it's a 60hz (or maybe 120hz) hum from the amp. I've removed the tubes and unplugged the credit / latch solenoids while the amp is on to confirm. Unplugging the pickup, swapping pre-amps, and adjusting the volume makes no difference. I did fully recap the amp (power, AVC, driver) with a kit from Bill @ JukeboxFridayNight. Not much room to work in this amp, so I even cut the terminals off the old cans - keeping the original factory solder connections otherwise intact - and soldered the new caps to those liberated terminals. Everything works, there's still just a hum. Maybe some of the values Bill came up with weren't correct? I'm not sure what else to try.

Still plenty to keep me busy meanwhile. My 13yo daughter has serious affection for this thing, and we spent the evening cleaning the scattershot assortment of records I've acquired over the years to populate it with. Some nice bonding moments from this thing already so it's been worth it. I hope to make it last a long time.

[jukenorman]

Hi Tony,
Mouser part number 653-G5PZ-1ADC24 is a suitable relay (or similar from elsewhere). You can prepare the relay and encapsulate it in a piece of heat shrink sleeving with three flying lead - two for the latch solenoid and one for the latch switches. Changing the selenium rectifier to quieten the latch solenoid is an interesting theory - particularly since the solenoid is AC powered!

What amp number is fitted? The original amp would have been a transistorised one with an integrated magnetic pickup pre-amp to match the Shure cartridge. I'm fairly sure that Rock-Ola tube amps of that era were only capable of a ceramic cartridge input. Do you know if any mods were done for the Shure. I wonder if that is contributing to your hum in some way?

Norman.

[gic440]

Norman,

Sorry for the confusion!  When I typed "tubes" I meant fluorescent tubes and not vacuum tubes, oops.    You're correct that the amp is transistorized with no tubes (or IC's for that matter).   The pre-amps are swappable modules and I actually have two of them (I had to source a spare amp to get the "Raysistor" photocell module used for the AVC, so that's where my spare pre-amp came from as well.  Nice to have a spare for troubleshooting).  

Attached a photo for clarification.   The new electrolytics for the power cans are inside the chassis - they barely fit but thankfully just do.    The black wire coming from the amp is the AUX input I wired internally to the socket for the pre-amp.   I have wondered if this might be the source of the hum, but I'm not inclined to think so.   When I place the amp on the bench and plug it in, and hold my ears close in an otherwise silent room, I can just barely discern a hum from the transformer area   It almost seems like this is what's being amplified, but it doesn't change with volume. 

It's not terribly distracting, but it seems wrong in the sense one might expect and prefer dead silence during lead-in / lead out, and not want *any* distractions in quiet songs.  Or maybe these R-O amps always had a bit of this?  As I said, I've come to understand that Rock-Ola's were never quite as good as contemporary Seeburgs and Wurlitzers for pure audio fidelity.   




You may notice I have treble cranked up but bass only half-way.   The lows on this juke are impressive, but the highs are often subtle and muddy.   Hence my desire to test replacement speakers - the original 5x7's are pretty sad looking and as they were hooked up improperly when I acquired it, I assume they're not up to snuff.    Which doesn't help, as it seems clear that R-O didn't pay much mind to speaker design, tuning, and placement in the first place, compared to other makers. 

The selenium replacement was mostly to address output drift that inevitably happens from age: when I measured it was indeed leaning a little low so it made sense to address it.  I still need to add the inline fuse for the silicon replacement, though. 

Anyway, I've added that relay to my next Mouser cart.  Pity is I just ordered some caps for the pre-amp modules last week!   But I'm sure I'll be back there again soon enough tho    Speaking of, the original pre-amp caps are 125uf which is pretty much NLA.   And even 120uf and 130uf are scarce.   But I ordered a set of each to see what if any difference is made - nice to have that spare pre-amp to compare. 

Thanks,

-Tony

[jukenorman]

Hi Tony,
I would actually be concerned about that black cable as the source of hum - is it screened? And if it is screened, is the screen tied to ground at the amp end only?

It's strange, in Europe we seem to have a much greater selection of can capacitor availability. In forty years or so, I have refurbished a fair number of amplifiers and every one has had the electrolytic cans replaced.

Norman.

[Ron Rich]

Tony,
To Norman's point-- if tied to ground at both ends, try dis-connecting it from the end farthest away from the amp-- that makes it a "drain" rather then a ground-- Ron Rich

[gic440]

Hi gents, been a few days... I was working on other stuff to round up at one time. 

So for the aux input, here's what I used.  I took an RCA "Y" input cable  and cut the joined end off to expose the conductors.   Red/Right and White/left each has its own shrouded signal wire.  The grounds were common within the main black cable shroud.   So, I connected the exposed wires using the schematic:



 
On J-1, pins 4, 6, and 1 take input from the cartridge.  Pins 2 and 8 are the R/L signals out to the amp.  Ground is joined from pins 1 to 7 on and then onward.  So I connected my RCA cable as R signal to pin 2, L signal to pin 8, and the combined internal R&L ground/shield to pin 1/7.   The other end of the cable, for input connections, is as it left the factory with nothing broken or connected.  

~~~~~

I've been dialing it in otherwise.  My guy suspicion of the original 5x7's was correct: thanks to the hint to try pure 5" cones I managed to find an inexpensive set that *just barely fit* the upper shroud.  I created some quick and dirty foam baffles and brackets to use the original mounts, and mounted the cones such to provide better spatial separation and imaging... and my zeus the improvement is *phenomenal*!    Finally have balanced mids and highs with good crispness and response, even with the bass cranked up to max!   I figured the old speakers were bad but I simply wasn't prepared to discover just how bad they were.   This thing truly rocks now!!





In other news, I acquired some NOS art discs for the animation windows with some images I'd never seen before for this model.   AND I found a motor that works!  The proper RPM seems to be 30.   For simplicity's sake I found a 110VAC motor and routed it to the convenience outlet.  As the motor doesn't share the exact dimensions of the original, I had to create a custom mount - it's still the wooden prototype but since it's working I'll leave well enough alone.  I also wired in a switch to turn on the animation as desired, so that it doesn't run all the time and burn out otherwise.    The effect is really cool and worth figuring out!   I'm surprised how well the flowery/artistic images change colors through the full spectrum, while the photos add to the vibrant look.  No video yet, though. 





The Juke-Aux switch turns off the turntable motor during playback, to keep the amp on when an AUX source is connected.   This simple modification works very well.   Using the 440's extra operator-info window, I added convenient instructions for this feature. 

You might have noticed the record visible in the "record now playing" window.   When seen at certain angles that's the appropriate view you get   But to spare the eyes of those making selections and/or peering directly downward, from the light tube in the door, I added a light baffle over the tube in that area.  It works well.





Anyway, sorry for the photobomb spam.   We're all pretty excited with how well this is turning out.   

I may have found a source for NICE CLEAN WHITE title trays too!  They are from a 425 and thus their mounts are a bit different, but I'm fairly confident I can find a way to make them fit.  It'll be worth the effort.   If/once that's successful I may share a final pic/vid. 

[jukenorman]

Hi Tony,
It's not possible to say whether your "auxilliary" modification is the cause of your hum. When I do these types of mods or even rewiring, I give the audio ground its own conductor wire and use any screens just as shielding (in your case I would use 3 core with overall or individual screens). You might think it's overkill, but you're guaranteed no hum loops and it doesn't actually matter what happens to the screen along the way although I endeavour just to ground it at source.
Norman.

[gic440]

Hi Norm,

Thanks for the advice, but I'm afraid I must admit some stupidity on my end. When you refer to "screen" or "shield" versus "ground", what is the difference? I always thought the metallic "shield" elements in a cable ultimately went to ground?

In any case, for my cable - which has an R signal conductor, L signal conductor, and combined metal "ground/shield" conductor - how would you connect that type of cable? Or which type of input cable (not sure what you mean by "3-core") would you use instead?

Thanks,

-Tony

[Ron Rich]

Hi Tony,
"3 core" would mean 3 separate wires inside the cable, regardless if shielded or not-- A "ground" usually refers to a wire connected to a common ground/earth, at one or both ends. A "drain" is a braided wire, encapsulating the cable, and connected only at the source end. You would need to connect your cable exactly as you have-- A "shield", or, a "screen" is also a braided wire surrounding the cable -- can be either internal, or external, connected as wished at both, or only one end. Ron Rich

[jukenorman]

Hi Tony,
You get hum on an audio circuit when you have a route to ground at more than one point. You are correct though, there is no other way to connect RCA (or phono connectors as we call them) - that's why I don't particularly like them! For example when I do a Wurlitzer Cobra to magnetic carridge conversion, there is an intermediate RCA plug/socket which I mount on a plastic plate - otherwise there would be a secondary route to ground from the RCA socket resulting in hum! And it doesn't matter what I do with the screen because it is divorced from audio ground so I can connect that to the chassis for mechanical stength if I choose.

In your case, it's what that auxilliary cable is connected to at the other end - does it have RCA plugs for example, and then does what it connects to have a metal chassis?

Norman.

[gic440]

Thanks for the clarifications. To my understanding then, it sounds like I've made my aux connections within the amp as they should be. As for the other end of the cable, I'm pretty sure I did that right too but here's a pic:



The cable in the amp is a dual-male RCA cable.   There is a F-F coupler in the cardboard panel I can plug that cable into (thus availing easy amp removal  when necessary).  On the other side of the panel, the two female input jacks would be self-explanatory for connecting any other device as a source.  We've tested phones and dedicated audio players and it works perfectly (normally nothing is connected).   So as you can see, that cable isn't otherwise grounded or drained... so that cable is really nothing more than an extension of the same "exposed" terminals within the amp.   Yet the hum is present with nothing connected.  I've a feeling it's in the power caps somehow, but they are new... and I'm sadly not yet knowledgeable enough to trace any specific potential defects. 

(By way of explanation, that cardboard panel covers a cabinet hole that has always baffled me.   It's a clean, factory-cut hole, through both the metal and wood rear facades, with mounting holes for a cover plate... but whatever OEM panel might have been there was long missing before I got the juke.   Yet from what I can tell from the few photos of the rear of 440's on the internet,  there should be NO HOLE in that area.  In fact, those same other photos show a fully solid wall with the handles in that area, and no "cover panels" of any sort!   So I've no idea what happened here, or if my juke was unique in some way.   The manual offers no clue as to options that I can tell - and besides, any "option" should have fit any cabinet right?   I'm not worried because at least everything otherwise works as intended and I was able to put a blanking panel to good use.   But it sure is a fun little mystery).

[Ron Rich]

EZ trouble shooting hint-- Remove the connections from the amp--hum still there -- if so, cables ain't the cause ! Ron Rich