Technics KN800 MIDI keyboard no sound

I've never seen the inside of a technics board, but I do frequently see synths with a "protect relay" that keeps the amplifier isolated until the digital circuitry has stabilized. They will click, but their contacts get oxidized and don't transmit audio.

You can temporarily rejuvenate them by cycling them a few hundred times (try connecting a function generator to the transistor that drives it for a few seconds/minutes), but for the amount of work involved I just replace them.

I've also seen volume c> I was given a Technics SX-KN800 keyboard and am trying to repair it. I ha=

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" snipped-for-privacy@gmail.com" wrote in news: snipped-for-privacy@x25g2000yqj.googlegroups.com:

I suppose the isolating relay would be on the power amp baord if it existed, but I can't see it. I'll have another look for it though. I have been using a scope for signal tracing, but your tracer idea has its merits too, since it will be very quick.

Also, I have read the manual for the next model up which mentions a method of resetting to factory defaults, and also a MIDI out only mode. I'll try these too.

Hi!

Such a relay may not exist. If this thing's amplifier is anything like the Technics stereo receivers from the same time frame, it may turn the output on and off electronically. (An interesting aside: this electronic protection method won't save your speakers if the amplifier itself fails!)

If you do find a relay, I'll practically guarantee it has burned contacts. It seems that people didn't think about turning these off with a signal still being amplified, which probably resulted in arcing at the relay contact points. In all of my receivers that have one (an SA-929 and 560) the protection relay can be opened without too much violence and the contacts cleaned. I did break the magnet wire on the SA-560's relay, but that's another story.

William

Geoff C wrote in news:Xns9DE733AE1C5EEGeoffC@188.40.43.230:

I have fixed it so I thought I'd follow up the fix. There was no -15 volt rail due to a 4.7 ohm fusible resistor on the main board being open. This was adjacent to the connector which received the power supplies from the power amp/power supply board.

open original image

Hi,

I have the same Pb, 14 years after...

Geoff C, can you help me to locate the famous resistor with image attached (KN800 Technics) ? Do you remember please ?

• User FidoNet address: 1:396/45 Hello All.

E> Hi,

E> I have the same Pb, 14 years after...

E> Geoff C, can you help me to locate the famous resistor with image E> attached (KN800 Technics) ? E> Do you remember please ? E>

May be a bit late, but I'll post the following link to a good fusible resistor; the 10-ohm value is the closest that I've been able to find. It will more than likely provide the same protection level required for this circuitry. Link:

Best regards, Marc Lewis, CET Service Manager QTI Service Centre Huntsville, AL USA

A: Because it disrupts the train of thought. Q: Why is top-posting frowned upon?