R-91 magazine motor buzz

[wdln]

I'm not sure they're related; I only mentioned it because I wasn't sure if the heat from the triac was being dissipated well. It would appear that it is. But it is odd to me that it can make that chunk of aluminum fairly warm inside of 60 seconds. I suppose it is only designed to be activated intermittently, and it is now essentially passing some current to the motor constantly.

As for the mechanism control schematic, it appears that is one I don't have in my field service manual/parts catalog. I have schematics and component parts lists for the preamp and amplifier, but not the CCC or MCC. In the parts list, it says to refer to the schematic for the MCC for a parts list of the board's components, but there is not one in the book, and so far I've been unsuccessful in finding one online.  The closest I have is in the sequence block diagrams, which shows what the circuit looks like and the pinout for P203.  But no parts list.  Sorry for the quality of this photo... had to use the bezel camera on my machine to take a pic.

[Ron Rich]

Hi Dave,
That's on accounta'acuuse Rowe never printed schematics in their 45 rpm manuals for either one ! They did print an EXPENSIVE, Shop Manual, which has them in it. Ron Rich

[wdln]

Just keeping the thread up to date in an effort to help others who might be reading and researching... I found a deal on eBay for a replacement mechanism control board, the same part number & revision so it would still work with all the other original hardware. I installed it, calibrated the index and home sensors, and voila... it works. No buzz from the motor. So either this one will work for the long haul, meaning that there's a problem in the original circuit board other than just the triac, or it will develop the buzz again, meaning there's a problem elsewhere in the jukebox that is burning up the triac (like the optical photointerrupt sensors). I'll update again as I learn more.

I have a party at my house on Wednesday... I had to do SOMETHING! :-)

[wdln]

Continuing the saga... the replacement MCC had a different problem after a few hours. It started randomly activating the transfer motor. It would pull a record, put it on the turntable, and immediately put it back without playing it. The rest of the time I heard a weird ticking noise from the transfer motor. Seems like it has the exact same problem as the magazine motor on the other board... a leaky triac or another component. Replacing the triac did not help. The magazine motor, however, worked fine, so the problem is definitely on the MCC.

Interestingly enough, someone had scrawled "transfer motor" in marker on the board I bought.  In hindsight that probably is indicating the problem it has.  Buyer beware!

So today I'm going to replace some other components. Without a schematic to go from, I made the images below by overlaying a color-changed, flipped image of the back over the front of the board, and another with the labels from the outside of the MCC. That way you can see both the components and the paths at the same time.  It's actually useful to have this in photoshop so you can monkey with the transparency of the circuit board trace layer, so if anyone wants the PSD file let me know and I'll send it to you (it's too big to post here). Using the info gleamed from the trace paths, I'm going to replace pretty much the entire chain that drives the magazine motor (because why not... I have all the replacements and they cost almost nothing). I came up with this list:

R218, 1.5k ohm
R250 & R251, 22 ohm
R220, 220 ohm
R221, 470 ohm
C210, 50V 22uF electrolytic
C208, .01uF 400V
possibly in the future diode CR217, which seems to prevent leak-back from the detent driver area of the board.  I'll leave that alone for now.

I'll test the components I remove and maybe I'll find the culprit.  If this works, I'll do the same thing for the other MCC on the transfer motor circuit. Then I'll have a spare board.  I'm interested in a copy of the shop manual, or at least just the page with the MCC schematic, if anyone wants to sell me one.

More later.


     

[Ron Rich]

Hi Dave,
I have a shop manual for the R-90--gotta look, don't know which mech controller is in it-- the thing is a three page fold-out-- I won't sell it but, I will have it copied, and send it to you if you pay the costs-- Ron Rich

[wdln]

Absolutely I would, thanks Rich! The MCC board revision I have is 6-08708-05. The field service manual says -02 and -03 are both compatible if you swap the optical switch, so the differences in the transfer motor/magazine motor sections of the board must be minimal if any at all.

[Ron Rich]

Hi Dave,
OK Ill dig it out and take it to "Kinco's" --
Give me your mailing address--use [e-mail] , to send it to me-- (with a note !)
Ron Rich

[wdln]

Update... I've been out of town on business and finally got a chance to install some parts I ordered while I was gone. Ron pulled some schematics from his library that also had some very useful handwritten notes in them. Having replaced everything else on the board in the signal path, the culprit was the optoisolator chip. This IC only had a Rowe part number listed but someone wrote in NTE 3047 next to it in Ron's book. As I said above, I bought a second mechanism control board that had an identical problem with the transfer motor instead of the magazine motor, so I started with that one and replaced the 6-pin optoisolator (Z200) and the transfer motor is no longer clicking and randomly activating. I'll work on the original board and do the magazine motor optoisolator on that one (Z201)... I have high hopes it will work. Then I'll have a good spare.

One note... I decided to install an IC socket for the NTE chip, both so I wouldn't overheat the pins soldering the chip directly and so it would be easily swappable in the future. With the extra height of the socket, the board just barely fit back into the plastic housing. I'll probably grind away some of the plastic underneath it so it's got some room to breathe.

Huge shout-out to Ron Rich for helping me out with invaluable information!! I'm currently cranking Tom Petty's "Learning To Fly". :-)

[Ron Rich]

Hi Dave,
Glad you gottit !
Ron Rich

[wdln]

Just closing this out once and for all: both mechanism control boards are working with the replacement 3047 IC's. One has been running for a couple weeks now without a hitch, so the chip was the problem all along... it must have been passing erratic, random switching signals to the triac, especially after warming up. I made notes in my field service manual and kept the plastic NTE pouches tucked between the pages. I also did take a rotary tool to the underside of the black plastic housing to add some clearance for the replacement chip and socket; it didn't take much to give it enough room.

I hope this thread helps someone in the future.

[stingman]

Hi Dave,
I too have R-91 innards in my Antique Apparatus bubbler. When the unit is turned on, I have a relatively loud and annoying humming noise coming from the upper part of my jukebox. The layout of components is very different than my R-90 which is nice and quiet while idling. I cannot tell where the humming noise is coming from. After the juke is on for a while, the noise disappears but sometimes returns. Everything works fine and if I keep the volume up, I can't hear the loud hum until the record stops. You mentioned a buzzing noise, I hear a loud humming noise. Are we describing the same noise? Did you isolate the noise to the mech motor?
When I put my juke in the service mode and press the scan button, the noise is still there.
I have the components that you changed on your MCC board along with a spare -05 PCB. I am awaiting a soldering station to perform surgery.

Stingman

[Ron Rich]

Hi Stingman,
On your "bubblier"--you are probably hearing the bubblier tubes --they sometimes make all types of noise. If you have the model with the Rowe 130 watt amp on the rear or side wall, of the cabinet, try un-plugging it, to see if you still have noise. After that, if there is still noise, un-plug the A-MP plug from the power supply--still gotz noise-- it's the tubes for sure-- If anything else is "making noise", it is a cause for concern !! Ron Rich

[stingman]

Hi Ron,
Yes, the bubble tubes do make some noise, but very little compared to the loud humming that overrides the bubble tube motors.
The only time I hear the bubble tube motors is when the loud humming noise subsides.
So it is OK to unplug sub-assemblies like the power supply and power the unit up? I was afraid to run the juke without loads.
BTW, what is the A-MP plug?

Stingman

[Ron Rich]

Hi Stigman,
Sure, you can un-plug anything--just to be safe, do so with that phono "un-plugged" from the wall--also un-plug it prior to inserting any internal plugs back on. A-MP is the brand name of the white "nylon" plugs Rowe used inside that phono. Ron Rich