Synth module (blown transformer)

[BJG]

Hi -

I recently picked up a Roland GR50 guitar synth module on Ebay. Unfortunately the seller neglected to mention that this was a US unit, although it was fitted with a standard UK plug.

It worked for about 8 seconds before it failed with a puff of smoke. I don't know much about electronics but I was wondering if there was any chance of getting it going again. The transformer is visibly damaged, but the rest of it looks OK.

The markings on the transformer are:

Kitamura Kiden
P: 0V WHT, 120V YEL
S: 19.2V RED, 8.9V ORG
K1G1P

**broken link removed**

**broken link removed**

I guess I need to provide 19V, 9V, and an earth to the plug that clips onto the circuitboard. Don't know how to go about that though, or whether it's AC/DC etc. I recently posted the same query on another forum, and was advised:

"The black wire may be a centertap for the red (19V) wires. You'll have to measure (Ohm) that to be sure. After doing that you can cut them close to the transformer.

Otherwise your biggest challenge is how to lay out the replacement transformer(s) within the the physical constraints of the case. That won't be easy..

The replacement(s) should be at least as heavy (in sum), and have similar or less resistance (on the 9 & 19V wires) - as the original."

So far I haven't been able to track down a suitable multi-tap, and I'm not really sure what I'm looking for. Could I use two separate transformers instead...? (I'm not worried what it looks like. I don't understand why it matters how much it weighs.)

Cheers for any suggestions...

 

[mneary]

There's very little doubt that the output of the transformer is AC. The two bridge rectifiers nearby confirm that.

The transformer probably blew a thermal fuse in its primary. Can you describe or show where the damage is?

If the windings are reasonably intact, you might be able to get it working by applying a single 8.9 (9V) to the 8.9V output (leave the existing transformer in place). The 9V will pass through the original transformer in reverse making 19V where it is needed. Beware the 120V terminals may be live. Also if the transformer is badly burned it might not work in this mode.

The weight of the replacement transformer is a general measure of its power capacity since the amount of iron and copper at 50/60 Hz varies as the power goes up. It's not an accurate way of rating it, but you don't have much else.

 

[BJG]

(Thanks for the info...I'll give that a try...)

 

[cowana]

Check the resistance of the primary coil. If it is open circuit, you are in luck - a thermal fuse has probably gone. If you carefully unwrap the plastic tape around the primary, you should find a small thermal fuse in line with one lead - replace this with a new one, and the transformer should work again. That's if nothing else is broken...

Andrew

 

[mneary]

Check the resistance of the primary coil. If it is open circuit, you are in luck - a thermal fuse has probably gone. If you carefully unwrap the plastic tape around the primary, you should find a small thermal fuse in line with one lead - replace this with a new one, and the transformer should work again. That's if nothing else is broken...

Andrew

It might work again if he sends it back to the States....... but the unit and its owner are now in a 240V country.

 

[cowana]

You can get a 240v to 110v transformer quite cheaply and easily. Not sure what wattage it would need, though...

Andrew

 

[Sceadwian]

It's gamble really. Doesn't matter if you don't see visible damage to the rest of the circuit, there easily could be. You fed (unintentionally) twice the voltage the circuit is rated for, since you said it worked for about 8 seconds and then failed you could have fried any number of a dozen components on the secondary side of things before the primary fuse tripped, if that's even the case. If it's just a primary thermal fuse great, replace it, if it still doesn't work start from the secondary sides bridge diodes through to it's regulator.

Obviously the 2-1 downconverter on the front end would be needed after it was repaired =)

 

[wkrug]

I think it will be better, you'll visit your local music instrument dealer and ask there for a spare part with 240V primary voltage.
A transformer must be orderd in any way - why not the original?
Ask for the price before ordering that part, it is often very expensive.

Roland instruments are distributed world wide and so it should be no problem to get that part.

 

[Sceadwian]

Never buy anything from a music store, find out what the equivilant part would be and get it yourself. The markup from a typical music store is hundreds if not thousands of percent.

 

[wkrug]

The markup from a typical music store is hundreds if not thousands of percent.

Thats right. But the delivered Spare Part fits into the Roland.
The Connectors match to the old one.
An equivalent part must be tight-fitting into the Sound Module.

BGJ must decide by himself.