Rowe R74 Jukebox Rebuild

With all due respect Ron, I disagree, when dealing with a state of 0 (OFF no continuity) or 1 (ON yes continuity) this is a perfectly valid test

These switches have 3 legs one is the common and the other two correspond to Normally on and Normally off

A run of the mill multi meter set to continuity testing is the perfect way to test a switch that is normally on or normally off

While Testing "normally on legs" if you press the Switch button continuity ceases and there is no more beep from the multimeter.

While Testing "Normally off contacts" if you press the switch continuity is established and there IS a beep from the multimeter.

I am however open to any suggestions regarding a better way ?

With all due respect Ron, I disagree, when dealing with a state of 0 (OFF no continuity) or 1 (ON yes continuity) this is a perfectly valid test

As seems often the case Ron is correct here. MOST DVM's do not respond fast enough for testing these types of switches. I have a 1988 B&K 2905 which does -but my others do not. Touch the probes together, if a beep does not occur instantly you may miss dead spots when testing micro-switches. As the actuator is compressed or released failing switches will show an intermittent or resistive contact. In many cases the switch may still function adequately, but anything other than a clear-cut "on-off" indicates failing contacts.

As per your vids, when the search unit 'stalls" it means that the chase wipers have hit the first 'hot" section from the keyboard and the right relay which has a sprag tooth and locks the gears. This should occur for only a fraction of a second and that relay will fallout allowing the motor to turn a fraction of a second to find the second 'hot" and this time the other sprag relay detents and in rapid secession punches the desired pin and simultaneously pulses the scan coil.

Things that go wrong here:

1) Broken continuity with the keyboard. this can be a wire, a sliding contact in the keyboard itself or the edge connector at the search unit.

2) Worn chase wipers losing contact with the traces on the search boards. Easy to check visually.

3) Pitted-misadjusted contacts on the two sprag relays.

I do hope that no one has messed with the setup of the search unit wiper timing positions. This is a bitch to re-set if you are not familiar with it.

There are two relays (IIRC) in a case up on the keyboard assembly along with an electrolytic capacitor which determines the pulse length of the punch.

You are going to have to remove the keyboard assembly (unplug-slides out) See you service data on procedure for removal - not a big deal.

ALSO: Manually punch a pin and lift the gear in the scan unit. the mech should scan, stop at pin and transfer record.

Understand: Other than power supply and scan coil, the select and scan-play functions are totally independent. BTW: Is that search motor turning when both buttons are pressed? It should.

NEVER manually turn the search unit wipers against their proper position. The wipers can be damaged if they are forced in the wrong direction.

Rob

I stand corrected.

Although I am curious. in my case where the Microswitches passed the continuity tests While detached from their wires and tested passed the tests both on (regularly on) and (regularly off) positions.

Does this mean they may still be bad ?

Regarding you r advice and many others here it is taking me a while to figure out what each component is according to the given name, the CAM switches for instance didn't make sense until I reached the diagram in the manual that talks about them, these are practically identical to the ones we use on Arcade Machines but have never heard them called this.

I apologize beforehand because not only is my electronic experience poor but English is a second language to me, I do greatly appreciate all the advice and trust with proper guidance and dedication will sort this out eventually.

Kindest Regards.

Tony

Hi T,
No problem--yes, the digital meter will show you the contact is either open or closed--but many times it will not show you that the contact won't pass current. The GOOD (damped) analog meter will--needle will "jump", on finding a "bad" contact ( I learned this at the School of Hard Knocks-- )
Also--see sticky above on switches---
Your English is excellent--wished many kids born here were as well spoken !
Ron Rich

Although I am curious. in my case where the Microswitches passed the continuity tests While detached from their wires and tested passed the tests both on (regularly on) and (regularly off) positions. Does this mean they may still be bad?

It some cases switch contact resistance is critical. Here it is less-so. Frankly, it would've been better to wait and not take that section apart until other things have been dealt with. Other than cancelling a selected pin on the memory via the stop switch assembly when the mech finds the record, these switches have no bearing on the selection or memory. The term 'cam switches" simply refers to where that are located and how they are actuated.

Language is no problem. You should see me with a Thai keyboard:-)

Rob

Good Morning and thank you everyone for your advice.

To be honest I was compelled to work on the switches after manually attempting to press one which appeared to not "Click" into contact, after removing the two screws and hearing a Clanking piece fall out of the back, it became obvious the screws didn't fit into a thread on the mounting plate of the cam but what I later discovered a small threaded plate in the back, seemed like an inconvenient way to design the unit until I dismantled the whole thing and noticed the notch on the back intended for adjustments of the switches.



Also... in my mind it was a task I was qualified to handle assuming I could figure how to put it all back together.

One more inquiry if I may.

given it looks like this is the next portion I will be working on just want to make sure, by "Keyboard Assembly" I believe you are referring to the following.



Is this correct ?

Thanks.

Tony

Yes the top assembly with buttons is the keyboard.

Regarding the microswitch plate; the oblong holes are to be at the actuator end of the switch. That is how the switching point is set as the cam raises/lowers the actuator.

Rob

EXTRA SUPER DUPER AWESOME EXCITING NEWS REGARDING

3) Pitted-misadjusted contacts on the two sprag relays.

so after the first sprag relay locked into place (RIGHT ONE) I gently pushed down on the second one which suddenly released, the entire record carousel mechanism began spinning, it actually picked up a record, put it on the record payer unit and Played the whole thing afterwards it returned the record back to the carousel.

Tomorrow I will post a video

sadly looks like the only way to make it work is by unsticking this second relay each and every time so obviously these relays need some servicing so.. question being.. given they are attached to the same mechanism with the round contacts I have been warned not to touch.

is it feasible for me to remove these relays and clean them without messing up anything else ?

Also... I don't understand why but all of this works only with the original relays installed on the record player mechanism (no wiggling necessary), if I install the new one I just bought. it does not.

Any ideas regarding this particular issue ?

getting real close to actually having a working Jukebox and oober excited.

Thank you, Thank you, Thank you, Thank you,

Tony

You do not remove the two relays to deal with this area. With power off press down on the relay armatures (line them up with a notch in the wheel so that the relay will bottom) and check the contacts for pitting and proper wiping action. "Wiping" means that when contacts mate they slightly travel a little further to make sure they have solid contact.

Check those relays before removing the keyboard. However, at some point the keyboard should be removed to examine/clean the relays in there.

I suggest reading Ron's post about the care and feeding of contacts: viewtopic.php?f=3&t=6404

Rob

Understood, and I have read Ron's Entry on proper cleaning and adjusting of relays, I will attempt to tackle this one over the weekend although am concerned as to how I am going to get to these relays without removing or disassembling anything.

Ron. any input on these particular two and how to best address them ?


Last night I re-addressed the issue of one of the cam switches mounted upside down, after fixing it and adjusting the wires so they looked pretty, I noticed some sloppy repair work done in the past, and would appreciate some input on the matter if possible.

• Couple of wires spliced and then crimped and wire nuted back into place
• One Missing screw
• One screw with a different size Hex head (I believe this "should" be the same size as all the ones on the cam switch mechanism?)

I intend to determine if cam switch plate Hex head screws fit into the missing position and where the presumed Incorrect size screw are, replace them and then attack the hanging wire holder clip to one of them to keep the cables out of the way of the record carrousel unit





Words of advice are as always highly encouraged.

Thanks.

Tony

Tony,
It appears to me as if a couple of Rob's "Geppetto friends", have been "afixin'" on that thar jukebox.
I can only ASSUME the following--as it's been "years" since I looked at that model--
The missing screw, is either because the hole is stripped, or some Geppetto just forgot it--
The different size screw is either for the same above reason, or possibly the factory installed a larger one there {yes, I ASSUME the wire retainer should be secured under that screw}
The two "dangling wires"--Not knowing where they are going, I suspect they are the turntable motor power (117vac), and someone was using the motor turn on, to power a speaker switching relay ? IF, I am correct, this is dangerous--those wires should be correctly spliced, removing the dangling ones, and the wire connector, IMHO--
As for the relays on the selector unit--if you can not see/reach the relay contacts with a burnishing tool, you will need to remove it, dress the contacts, and replace it--the service manual does tell you how to do this !
As for the two new relays, not working--I dono ? Measure the coil resistance of the old ones, compared to the new--
Ron Rich

Latest Updates.

Over the weekend took out the Keyboard Mechanism as suggested.

Blew out assembly with compressor and cleaned contacts to the best of my abilities, found a Broken Spring on what the Manual calls START RELAY (F5) and after pondering on if the added Tension would make a difference and taking into account it has probably lost tension throughout the past 40 years instead of replacing the spring threaded it into the spring holder 2 turns, I am interested in receiving feedback for this fix please.



Also thoroughly cleaned out Keyboard Keys leaving them overnight in a Soap/Bleach sink and then rinsing out next morning and drying in a pillow case in the dryer for 15 minutes.


Took me a while to realize they removed the "I" and "O" Keys as to not be confused with 1s and 0s.



Also Washed records and thoroughly cleaned

(I am aware I will likely invoke the wrath of several professionals by my technique but please bare in mind most of these records are already beyond salvation and will be replaced)

Used sink with one tub full of HOT water with hand soap to submerge momentarily

And one tub full of cold water to submerge and rinse off with sink head in Sprinkle position.

Gently Dried with Plush Towel.


Afterwards we created a spreadsheet with all the titles and artists, sorted alphabetically (BY artist) and Selection Mechanism Order


And reinserted them all (In the correct order) into record carousel.


After fiddling a bit with the Selection Mechanism Sprag Relays (and reinstalling the old ice cube relay in the record player selection Mechanism).

It would appear we have some real functionality.

http://youtu.be/HTMKkT12Kxw

Still lots to do but very excited at advances so far.

Comments and suggestions as always encouraged and Welcome.

Kindest Regards.

Tony

Looks like your about 90% 'there".
Some impressions from the video:

Mech motors sound "chattery" have they been lubed?

During scan-out it sounds like the stopping switch hopped a pin.

I assume the distortion is from the damaged stylus or badly worn record?

ALL those Rowe mechs are god-awful fast. this can be dealt with later-on if you wish.

How are the rubber components around the motor (grommets and idler). I do hear a bit of rumble which is typical of dried rubber.

With the amp balance control centered, play a mono record and alternate removing RCA plus from the pickup. The overall sound will be lower with only one plug, but both channels and bass should be equal. It is probably a good idea to wait till you have an undamaged stylus for this test.

While in play mode and volume at minimum listen for any 120Hz hum and after a few minutes feel the heatsinks. Slight warmth is Ok -hot is not. These amps used good components (better than what I finds in today's HD tv's and computers) but it is still nearly 40 years old and a rebuild will eventually be needed.

Rob

Good Morning Rob, thank you for all your feedback.

I will respond to these once at a time

Mech motors sound "chattery" have they been lubed?

Only things Lubed so far have been the pivots and pivot holes for tone arm and record player spindle (Where the record sits on), if you could provide advice on how to properly lube them I can do next.



Not sure which is the Stopping Switch but if you could please provide a minute/second reference in the video it would aid in me pinpointing it.

I assume the distortion is from the damaged stylus or badly worn record?

The stylus is a brand new (EBAY) $10 Stylus, I also have a $40 SHURE Brand name stylus I intend to use after refurbishing is complete, all these records are in horrendous shape, scratched badly 3 of them where outright cracked and several have chunks taken out of the side (I am assuming from the record player arm being maladjusted and smacking up against them), currently seeking sources for cheap new records

ALL those Rowe mechs are god-awful fast. this can be dealt with later-on if you wish.

Unsure of what this statement means ?

How are the rubber components around the motor (grommets and idler). I do hear a bit of rumble which is typical of dried rubber.

most of everything is 40 years old and has been in storage for god knows how long, if you can offer advice on treating these rubber components I would be grateful as well

With the amp balance control centered, play a mono record and alternate removing RCA plus from the pickup. The overall sound will be lower with only one plug, but both channels and bass should be equal. It is probably a good idea to wait till you have an undamaged stylus for this test.

While in play mode and volume at minimum listen for any 120Hz hum and after a few minutes feel the heatsinks. Slight warmth is Ok -hot is not. These amps used good components (better than what I finds in today's HD tv's and computers) but it is still nearly 40 years old and a rebuild will eventually be needed.

Will also address sound quality issues to further extent once the mechanism is perfect (or near to)

Have been studying my blurry scanned manual in an attempt to understand how exactly to adjust the tone arm settings, in particular I have 2 problems

1. at times the tone arm will hit the side of the record and pick it up just as it is being droped on to the record player
2. At times the needle will land just a bit too far left and get caught in a perpetual skipping loop before ever starting to play.

Thanks