Roland Cube 20X Power Transformer

[miraha]

My son in law was changing strings on his guitar when one of the new strings pierced into the back of his powered up Cube 20x and caused a spark. No power after that. Brought it to me, someone who knows enough to get into trouble, and so I pulled the back and did some checking with the multimeter. The fuse on the small board where the power comes in checked OK. Power transformer checks open.

My question is where would one go to find a replacement or send PT off to be repaired (if that is a possibility). Much thanks in advance.

[52 Bill]

The fuse on the small board where the power comes in checked OK. Power transformer checks open.

Welcome to the place. How did you test the power transformer? Is the primary winding open or the secondary? Have you tried to contact Roland?

That amp sells for around $150, so you will need to determine if the cost of the part is low enough to make the repair practical.

[miraha]

Being a novice, not knowing much on electronic amp stuff, I used a multimeter (set to ohms) and checked for continuity between wires going in at top and coming out on bottom. Any advice on how to do it correctly would be much appreciated. Roland quotes $53 plus shipping backordered. Again, thanks for replying.

[52 Bill]

I used a multimeter (set to ohms) and checked for continuity between wires going in at top and coming out on bottom.

I can't really see, but it looks like there are six wires coming out of the transformer. Three for the primary and three for the secondary. The primary windings are the ones that go to the fuse and power switch wires. Because the amp is sold in the US and other countries the primary has a tap for use with 100 volt circuits.

Take your ohm meter and read across all three of the primary wires. See if you get any continuity from wire to wire. Remember that one of these wires should be connected to a terminal that does not connect to anything at all.

[miraha]

Three wires topside, yellow, white and blue, going to power supply.
Three wires bottom side red, black and red with all three set in a plug, plugging into board.
All three wires topside, yellow, white and blue, show continuity [YW-BL 4.2, BL-WHT 20.0, YW-WH 23.7]
rolandcube20X Schematic.pdf
transformer.pdf

[52 Bill]

All three wires topside, yellow, white and blue, show continuity [YW-BL 4.2, BL-WHT 20.0, YW-WH 23.7]

That would lead me to believe that the primary is ok.

Have you tested the two secondary fuses with your meter? The schematic shows 2- 2 amp fuses on the secondary winding. These will be near where the other wires connect to the board.

[miraha]

I suppose it might be these two T 1.25A 250v, F3 and F2? If so, then how would I check them. Thanks.
T1.25A 250V.pdf

[J M Fahey]

You'll have to measure below the board; each one should show a short between its legs.
I think they will not (open).
You'll have to get a new pair of direct solder PCB mount fuses, same value.
Just in case something else has problems, build a Lamp Bulb current Limiter and plug the amp in it.
Use a 25W lamp, roughly equivalent to the amp power.
For now, disconnect the speaker until further testing.
EDIT: I think you need a couple of these:
http://search.digikey.com/us/en/prod...1112-ND/614994
Of course, order a couple extra ones.

[miraha]

Will do. Can't thank you enough for the help.

[Dodger]

Three wires topside, yellow, white and blue, going to power supply.
Three wires bottom side red, black and red with all three set in a plug, plugging into board.
All three wires topside, yellow, white and blue, show continuity [YW-BL 4.2, BL-WHT 20.0, YW-WH 23.7]
[ATTACH]18198[/ATTACH]
[ATTACH]18203[/ATTACH]

I realize I'm posting in a 4-year-old post, but is there any possibility someone has another copy of the Roland Cube 20X schematic diagrams somewhere? It seems these links to the uploaded schematics in the quoted post no longer work - I only get a blank white page.

Any help would be very much appreciated.

[Darek40]

Can you please post again "rolandcube20X Schematic.pdf"?

Thank you very much!

[DrGonz78]

Go look on this thread it has the 20x and the 30x schematics

https://music-electronics-forum.com/...ad.php?t=43254