Roland cube 60 broken lead channel.

[moto420]

The mode selection on the lead channel of my Roland 60x cube guitar amp is broken. It doesnt seem to switch to any modes on the lead channel.

[Enzo]

Are you saying that it doesn;t switch anything, it is as if you had not pressed the button at all? or are you saying that it does in fact switch to a different mode, but no sound comes out.

[moto420]

im saying, the channels switch from clean to lead but the lead has no distortion and the modes on it dont work. It just sounds a little distorted clean but cannot change from acoustic to stack or metal, etc.

[Marcos Hu]

Hi All,

Here's one more Cube-60 with Lead channel broken, please help !!

[DrGonz78]

I had posted a request on another thread that was missing the schematic for this the newer Roland Cube 60 model. I am posting on this thread now as it describes the exact symptoms as the amp that I am working on. There is a clean channel without the amp models and that channel works great. Then switching over to channel two it passes signal perfectly but as you try to switch between amp modeling settings nothing changes. It almost sounds like it is stuck on the first setting on that channel which is "acoustic" mode. The chorus, flange, reverb, and delay all work on both channels. This might not be something that can be fixed, but I have some thoughts to pour out anyway.

There are two chips on the preamp board... Part: 74HC4051AP --- Description: 8-CHANNEL ANALOG MULTIPLEXER / DEMULTIPLEXER.

The other chip on the preamp board Part: BU2090 --- Description: 12-bit, serial IN, parallel OUT driver - Rohm

I have attached the datasheets for both of these chips. I am pretty sure that the BU2090 chip controls all the LED's on the amp. All the LED's are working great too when switching channels or turning on chorus/delay etc... Could a faulty 74HC4051AP chip cause miscommunication with COSM on the main board? Maybe I am only assuming this to be the cause, but if this chip is not causing the problem then the hopes for repair is impossible for me. Well I blabbered enough really sorry... But if anyone has some ideas on the matter that would be greatly appreciated.

[DrGonz78]

So I guess I have a question here if anyone knows... I have no logic probe to test this 74HC4051AP chip. Is there a way to use the scope to observe a DC pulse from the appropriate leg on the chip. I know we are looking 1's and 0's, but can that pulse be seen through the scope? I really feel that if this chip is not sending the word length impulses to the main DSP chip then the amp simulator switch will not function correctly. Perhaps the main DSP chip is fried, but still I need a way of testing the 74HC4051AP chip to make sure. Anyone?

[Steve Conner]

You don't need a logic probe to test a logic chip. The waveforms (square waves toggling between 0V and 5V, or 3.3 or whatever the supply voltage is) show up just fine on an ordinary scope with an ordinary probe.

Having said that, an analog multiplexer is not the sort of chip you would use to read the front panel switches. It is more probably used for routing analog signals in the preamp. If it's the kind of front panel where the switches are actually pots read by an A/D converter, then the multiplexer may well have something to do with it.

If you're getting chorus and flanging, the DSP must be working, so keep looking for the keyboard scanning part of the circuit whatever it is.

[teemuk]

If it's the kind of front panel where the switches are actually pots read by an A/D converter, then the multiplexer may well have something to do with it.

It's probably like that. Pot works as a voltage divider for low DC voltage reference. Signals from wipers of all such potentiometers go to multiplexer and the multiplexer output feeds an A/D converter / CODEC (there are usually a limited amount of them while a single multiplexer can handle several channels). The CODEC feeds the signal processor that interpretes the amplitude of the signal and converts it to corresponding value of potentiometer's "dial setting". CPU handles automatic channel selection of the multiplexer so all wiper DC voltages are send to CODEC and read in a sequence, each wiper "data" at it's own time.

The switch -type selector may work similarly (being a simple resistive voltage divider) and it may or may not be routed through the multiplexer. All this really depends on how the stuff was designed; how many channels they had available for the multiplexer, how many channels in codec etc.

This stuff is easy to test with basic "analog" tools: Do you get a DC signal from the wiper/switch output? Does it respond to dial/switch setting? Yes, something upstream is broken (e.g. multiplexer, codec, solder connection), no, something downstream is broken (pot, switch, dc supply, possible current limiting resistors, solder joint)...

Alternatively the switch may also be encoder -type so it will automatically output digital data. The encoder will have terminals for each bit plus one for common. Testing one will probably require more sophisticated instruments than a simple multimeter.


Edit:
I know it's not the schematic we're after but it enlights the principle of operation because the interface in just about all of these amps is realized very similarly:
http://support.fender.com/schematics..._schematic.pdf

[DrGonz78]

The switch -type selector may work similarly (being a simple resistive voltage divider) and it may or may not be routed through the multiplexer. All this really depends on how the stuff was designed; how many channels they had available for the multiplexer, how many channels in codec etc.

This stuff is easy to test with basic "analog" tools: Do you get a DC signal from the wiper/switch output? Does it respond to dial/switch setting? Yes, something upstream is broken (e.g. multiplexer, codec, solder connection), no, something downstream is broken (pot, switch, dc supply, possible current limiting resistors, solder joint)...

Well I really have to thank you Teemuk and Steve too!! I did not understand that the switch was a simple resistive voltage divider. I was not getting DC signal, even though I thought I was... I was getting the 3.2vDC that was part of the circuit to the muliplexer VCC. Still as I turned the switch no voltages were changing in any manner. At this point I pulled off the switch to do some continuity testing and realized right away that the switch had no function. Taking it apart I noticed the wiper blade had broken loose a bit and was not able to make contact with the circuit. I was able to secure the wiper better and got the switch working again. The amp is all back to normal now! Thanks again, you guys got me thinking much clearer about the function of the switch and that is what I was missing in this case.

BTW Teemuk really enjoyed reading your online book!!

[Jazz P Bass]

BTW Teemuk really enjoyed reading your online book!!
Oh yeah.
Good writing!

[DrGonz78]

Hi there , I saw you post about cube mod channel switch , I have the same problem ,it does nothing or takes few minutes of turning to switch between mods,
I read your post but don't get info about blades and how you fixed the switch ,
Could you help ?
I bought secend hand cube and seller did not let me test it now it's too late .
I'm stuck with it , Roland Canada is asking some outrageous money for just diagnosis.
I know its switch .
Thanks
George

Received a private message from Badkeeper today regarding this repair. The picture I have attached shows exactly the problem that I had with the switch. (Please note that this picture is not the ACTUAL switch but only used as a reference.) I super glued the wiper contact back into place because the plastic tabs had broken off. It was a rather simple fix but still quite finicky since the pieces are very small. I always wonder how long these MacGyver type repairs will last... I did get a text message from the owner of the amp this past December to let me know he sold off the amp and the repaired switch was still working great.

Now Badkeeper the attached info is in regard to the switch information and the schematic I used as reference to repair this amp. However, I am not sure exactly what model you have there. Also, note that the amp I had was a Blues Cube 60 but the Blues Cube 60 service manual that I have are not the same as the version I had. The one I had was an early model, and the Cube 60D version attached was almost exactly the same. Not sure your amp has the exact same problem, but it could.

I will leave it there for now and the community here can all help out to figure a plan to fix this amp with you.

The link below is for a similar rotary switch but the shaft length is 20mm instead of 15mm. I could not locate any 15mm shaft length part.
SR1712F-0108-20F0A-N9-N Alpha (Taiwan) | Mouser

Here is the data sheet for that part too, it's on that main mouser page too.
Untitled Document

[DrGonz78]

So I had originally posted about the rotary switch replacement being something like this one...
https://www.mouser.com/ProductDetail...EaAoTUEALw_wcB

Only thing is that one has 3 positions and I am pretty sure that is not the right part now thinking about it. You see my repair on this switch did not include finding a replacement as I was able to the salvage the original one. However, it has come to light that other people are now having trouble with that switch and need to find the correct replacement. Channel 2 on the amp has 8 different settings to choose from so that makes me think the switch is 8 position type. Not sure how we can figure this out. What I do know is that the data sheet in the link I just posted say's they come in 2-9 position types, but I can't seem to find one. The picture of that switch looks correct to me as well and I believe it is the right fit. Anyone have ideas where to source this part?

[DrGonz78]

Of course a minute later I might have finally found the right switch...??? I hope this is the one. Someone PM'd me about looking for a replacement switch so hopefully we can help a fellow out and suss this one out once & for all.
SRBV Series - Basic information

https://www.mouser.com/ProductDetail...bZTSllc6Pt4%3d

Edit: Original part number is SR1712-0108-15F0A-N9-N and it relates to the apha part...
http://www.taiwanalpha.com/english/p_e_141.htm

Double Edit: So when a part is sourced through Mouser but it is on order how long do you have to wait? For example it says 117 days lead time but from what start point?
https://www.semikart.com/product/SR1...F0A-N9-N/80592

[Cesar]

Hi everyone I am new to this web site . I have a Roland cube 60 with the same problem lead channel doesn't functions if I move the switch. It does change form clean channel to lead channel but the lead stays as it was having a little gain . But nothing more. Please if one of you guys could help me with indications or steps on how to take apart the switch for repairing myself. I have removed the chassis but don't know how to get to the switch . Any indication will be much appreciated . Thanks in advance.

[DrGonz78]

I have a Roland cube 60 with the same problem lead channel doesn't functions if I move the switch. It does change form clean channel to lead channel but the lead stays as it was having a little gain . But nothing more.

Welcome to the site!!

So to clarify... the amp is stuck on the clean channel? When you turn the switch to any other setting are you still only getting the clean channel, no change? If that is the case then it does sound like the switch has failed. Does the clean indicator LED stay lit regardless of which setting it is on?