Keyboard amp died

"Hamad bin Turki Salami" wrote in message news: snipped-for-privacy@Spam.aol.hotnet.ibm.net...

Your problem is almost certainly one of simple dry joints. On group equipment, these commonly occur on the front preamp board, where the power supply from the rear power amp board comes in, and is zenered down by two damned great wirewound resistors, and two zener diodes, to provide the ( typically ) +/- 15v supplies for the preamp ICs. The power on LED is also usually fed from one of these rails.

I would suggest that you open the thing up, and run it open, providing you are confident enough to do so without risking electric shock, and then gently tap and poke components using a long plastic stick, such as a ballpoint pen. Go for any large components, as these suffer transport vibration when you carry the thing to gigs, which can result in fractured solder joints, and anything which looks as though it runs hot, and may have discoloured the board material in the area.

Chances are that you will rapidly find the area or exact component that causes it to go on and off, when disturbed. If you don't then know how to locate the exact component or bad joint, you can at least then take it to someone who does, and point them to where the problem is.

Don't be afraid to at least have a go, it's the only way to learn. The only area that you should be careful to steer away from for your personal safety with this type of equipment, is any exposed wiring where the power cable comes in, or on the back of the power switch. Avoid attempting repairs to tubed kit though, as there can, and usually will, be very high and dangerous voltages present. Good luck with it

Arfa

"Hamad bin Turki Salami" bravely wrote to "All" (17 Dec 05 00:49:13) --- on the heady topic of "Keyboard amp died"

HbTS> From: Hamad bin Turki Salami HbTS> Xref: core-easynews sci.electronics.repair:351712

HbTS> I have a Roland KC100 keyboard amp that died on me. First, HbTS> I started noticing an annoying low level ring from the HbTS> speaker when my keyboard was hooked up. I thought at first HbTS> it was a ground loop, but I couldn't get it to go away. HbTS> Then, the amp started cutting out for brief stretches of HbTS> 2 or 3 seconds. The sound would die out and the power light HbTS> would fade off. But it would usually come back on by itself. HbTS> When it didn't come back, I could sometimes get it back by HbTS> jostling the unit. Finally, it died altogether. When I power HbTS> on, I hear a faint "power on" sound from the speakers, but HbTS> I get no sound from my inputs anymore.

HbTS> A guy in a local music store told me, "Sounds like you blew HbTS> a capacitor in your amp."

HbTS> Does anyone here have a good idea of what might have happened?

HbTS> I have no experience with such things, but I'm hoping I HbTS> might be able to do the repair myself, to save the $100 or HbTS> so a shop would charge me. Does anyone have any comment on HbTS> how advisable that would be or how I'd go about figuring out HbTS> how to fix it?

Just a small analogy to outline the problem: If you had no experience of brain surgery would you really even consider attempting it to save money?

Similarly, sophisticated electronics require knowledge to diagnose and tactile skills to make a repair. There is a steep learning curve to each too. It isn't brain surgery however but it can't be done without any experience at all. Forget DIY, send it to the shop.

A*s*i*m*o*v

... []

If you know how to solder already, it doesn't take a great deal of additional skill to open up a piece of gear and replace all the big electrolytic caps. Caps are usually a good bet for some reason if you're stumped, especially if the noise you're talking about is of the

If you're not experienced at all with this kind of work, though, $100 sounds cheap for an easy and guaranteed solution. If you have to buy two caps and a soldering iron, and a roll of solder and a braid, you might spend half that before you know it'll fix the problem.

Success! I gathered some tools and my 4 year old son and I opened the amp up and took a look. I figured at the very least I could teach him the little I know about electronics. But following your advice, I quickly located a transistor with two cracked solder joints. After resealing those, the amp came back to life.

I saved $100 and had some fun with my son, so it turned out to be a good gamble.

Thanks for the advice.

Your son is convinced you're an electronics sorceror now, too. :)

Soon all his son's friends will be coming to him for repairs. :-)

"Hamad bin Turki Salami" wrote in message news: snipped-for-privacy@Spam.aol.hotnet.ibm.net...

Glad to have been of help. What the group's all about ...

Arfa

I think he's ready to take his share of credit. The problem is, he can't wait for things to break now.