Rowe R-81 Right Channel Out

spookyblue

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Neither base nor mid-range speakers on the right channel make a sound on this jukebox that I'm cleaning up for my wife as an anniversary present (July 23!). I've followed the instructions in the repair manual. Here's what I've done/found so far...

- Adjusted balance control. Left channel volume changed, but nothing on the right.
- Swapped tone arm outputs (cartridge leads). Only get sound from the two left speakers regardless of what is plugged into the amplifier.
- Touched a 9V battery to the speaker terminals. Got a pop.
- Verified that all LED power indicators are lit.
- No blown fuses, no noticeably poor/cold solder joints on the amplifier board.
- Checked preamp: If I did this right, I measured 0.40VAC on the right and 0.35VAC on the left. I may have misinterpreted the instructions, though. With a selection playing, I unplugged a cartridge lead(R) and measured on that "test jack"(R), then switched for the other side.
- There are no extension speakers.
- I just realized that I've never cranked the volume up very high. Could one channel drop out if the master volume level is set very low?

This seems to point to a bad "output device" on the driver board, Q1(MJE 6041 64W), or Q2(MJE 6044 64W). I've highlighted and attached fig 2-24 to show what I'm looking at.

We have a big Grainger supply house here in Louisville, so I'm guessing I would have a reasonable chance of getting the correct transistors from them if I have my manual with me.

I'm seriously not an expert in these areas, so I would welcome any thoughts or recommendations.
 

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Hello,

Sorry I don't have your name.

What is the pre amplifier board number?
It is etched on the pinted circuit side.
The standard board board number is R-3788 B, this is a two wire volume contol pre-amp.
The other board number is R-3805 this is a split channel 5 wire volume control pre amp that needs a dual control (10k log) and need the volume control cable to be screened.

The transistors in this amp do not have any mechanical/electronic equivalents so the Motorola MJE6041 and MJE6044 must be sourced it required, if the fuses are intact more than likely the transistors will be ok. Check for dry joints on the driver board where the transistors fit into the sockets.

You can test if the output boards are good by plugging the phono input into the test sockets, the level will be low but you can tell if the sound on the effected channel is good.

It could be that you have an issue with the phono input have your tried reversing the phono plugs.

Also if you have the manual you will see that to get enhanced bass Rowe Ami reverse on side of the cartridge wiring. With the other Rowe Ami amps both of the black wires on the cartridge would be on the two connections nearest to the stylus tip with the red wire within the same sreened cable above it. On the 64 watt amplifier there is one red wire on the bottom (nearest the stylus tip) and a black with their corresponding wires within the same screen above them.

The valve bass type socket that the cartridge wires go to on the mechanism/carousel should be checked to make sure they are still soldered to the back of the valve base socket connection.

Please let us know how you get on.

Regards
Alan Hood
ami-man
UK
 
Troubleshooting - Round 1

Thanks for the reply, Allan.

- The amplifier board number is R-3788 B. There were a few cold solder joints on that board which I repaired.
- I get sound from both phono outputs if each one is plugged into the left channel.
- Continuity from the phono pins to the end of each jack seemed okay.
- I wasn't brave enough to attempt removing the driver boards without first consulting an expert. The stand-offs look easy enough, but I think I could find several ways to break something beyond that. You wouldn't happen to know the *correct* steps for removing the boards, would you?
- Plugging the phono inputs into the test sockets did result in faint sounds, so it may not be necessary to pull the driver boards after all.

Is it possible that this machine is rigged for monaural operation? When I adjust the stereo balance, I notice that the left speaker does get louder when I give it more left channel. However, if I adjust it full-right, I still hear sound out of the left speaker. Another poster suggested I check for a certain jumper that should be in place on the back panel in order for it to play in stereo.

I have attached a photo of the back panel, for what it's worth. It may not tell you anything. The manual does mention that it's possible to configure the box to play in mono, and now I wonder if that may be what I'm looking at.

Thank you again for your input,
Bill
Snug Harbor, USA
 

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Hi Bill,

One way to test the drivers is to connect the test sockets to the output of a cd/tape player (a hifi separate unit) which will have an output of around 500/600 millivolts.

If that is good on both channels then the issue is with the pre-amp board.

If you do need to remove the driver boards then then you need to remove the three screws that go through the two transistors and the bias diode board for each driver board. The plugs can be removed and the boards pulled off of the pillars (note there is a locking pawl on each of the pillars).

There is a number of Ebay sellars in the USA that have your pre-amp board for sale.

Regards
Alan

Alan Hood
ami-man
UK
 
Okay ... what to do with a "bad" preamp?

Alan,

I plugged an MP3 player into each of the test plugs and got sound from both channels, so it does look like the preamp is hosed on the right side. I pulled it out again and did a close inspection, looking for obvious things like loose pins on the edge connector or broken or cold joints, but I didn't find anything. Continuity from the RCA jacks tested fine, too.

There don't appear to be any R-3788 boards available on eBay at the moment and I'm really down to the wire now. D-day is Friday. I'm *capable* of troubleshooting this board given enough time to study the schematic, but time's the issue. Are there perhaps bits in particular that are prone to failure on the R-3788 that I can focus on? I have time for one last Hail Mary.

In any case, you have helped me to better understand how this thing works and I appreciate that. Thank you for your help.
Bill
 
Hi Bill,

Here is the details of a cased pre-amp board that would be the same as yours.

Rowe/AMI R-4372B Pre-Amplifier for a Jukebox
Item number: 390314012905 BIN $35.00
Gaithersburg, Maryland, United States

The company also has another one on Item number: 230621320746 same price.

Here is another one but quite expensive but they say all items are tested.
ROWE AMI TI2 PRE-AMP with FREE SHIPPING
Item number: 120672036365
If you look at the pictures you will see your number.

Without a signal generator and a dual trace oscilloscope to check each stage on the pre-amp it would be difficult to repair. I would check to see that no components are touching each other check for dry joints on any power regulators and larger capacitors. more than likely it will be one of the transistors but there is around 8 or 9 on each channel.

I would get one of the above on the BIN and get it shipped on a next day.

Regards
Alan

Alan Hood
ami-man
UK
 
Thanks, Alan. I will order a new pre-amp soon and post the results. I'm experiencing a plethora of mechanical issues with this box at the moment. After those are fixed I'll come back to this.

Thanks again,
Bill
 
Hi Bill,

You need to start at the adjustments section in the manual and work your way through all the adjustments. But first you need to check that the crank & pin assembly that is fitted on the other end of the transfer motor. This pawl/activator is made up of two pins that are riveted into the small casting and can become loose which causes an random operation of the gripper bow gearing.

The pins can be tightened by tapping up with a punch and hammer once the motor is out.
Once this is checked/repaired then all the adjustements can be completed.

Regards
Alan

Alan Hood
ami-man
 
Up and running

It has taken a lot of tweaking, but it's running like a top now. I also replaced the preamp board, and now both channels play loud and clear.

Thanks to everyone for their help. Especially Alan. Thanks also to Lloyd at Coin Op Warehouse for the quick delivery on the new board. Maybe someday I can repay the favor, or pay it forward if I come across a topic or question that I actually know something about, and can help someone else. :)

The next project on my list is to bring back to life our Choice Vend CVC 168-5 soda machine. Looking forward to the day when everything downstairs in the "arcade" actually works. I'm getting there, though.

Later,
Bill
 
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Hi Bill,

Just one thought, the 64 watt amplifier fitted in your jukebox needs the cartridge to be wired one side out of phase to give the correct enhanced bass.

Look at wires connected to the back of the cartridge the normal configuration on jukeboxes earlier and later was that both black cables are at the bottom of the cartridge (nearest stylus) with the corresponding reds (within the same screen) above the black cables.
On your jukebox to put the cartridge one side out of phase reverse the cables on one side of the cartridge so that a red is on the bottom connection and the black is above.

Regards
Alan

Alan Hood
ami-man
UK
 
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