Schematic needed for Korg DTR-1000 Tuner

[W3KQ]

Hi All,

A customer brought in a number of items suffering from a nearby lightning strike - one item in the bunch is a Korg DTR-1000 Tuner. I've tracked down the problem to the input board (I can feed a signal directly into the front panel board and the tuner works OK). Korg uses some sort of a conformal coating or something similar on their boards, and I cannot make out any identifying markings on a number of the SMT semiconductors on the input board. I also cannot afford to put much time into figuring out what is on this board, as the repair price will get way out of hand fast. There's not a whole lot of components on the input board, so if I had a schematic, it should be a quick fix.

Tried Korg, but my shop is not an authorized service center, so they will not even give me a part number for a service manual or schematic so I could order through CE Distribution. Can anyone help me out with either a schematic or a suggestion of who/where to look for one? No luck on Google so far.

Thanks in advance for any help,

Rick

[Enzo]

Here you go

[W3KQ]

Thank you!

Enzo, Thanks so much for helping me out! Not that I can imagine having a manual or schematic you don't already have, but I hope I can return the favor someday!!

Thanks again, Rick

[Enzo]

Well, so far I do not have the documentation on the HP 5710A Gas Chromatograph (Turbocharged floor model.) The model used by FBI Special Automotive Instructor George Wilbur.

[brent]

I know this is an old thread, but I'm curious if someone might help me figure out why I suddenly get a hum on the first input of this device? I suspect something might be leaking to ground but I'm not sure. HUM only happens when my guitar is plugged in and volume is turned up. Plugging the same guitar into input 2 does not produce the same hum.

I'm fairly good with electronics/troubleshooting. However, I can't figure this one out.

Thanks for any and all help!
-Brent

[Enzo]

REsolder the jack. Most likely you have lost the ground connection there.

[brent]

Thanks Enzo.

I reflowed the solder to several of the connections, the input jack being one of them. When the unit is powered up, I can confirm continuity to ground on both input one and two. Without power, no ground. I do suspect there is some grounding issue somewhere tho.

Any other suggestions? I really love this tuner. I'm hoping it some simple part to replace to get it quiet again.

Thanks again!
-Brent

[Ronsonic]

Here Enzo, this might help.

[brent]

There's a 4 ELNA electrolytic caps on here. would they show exterior signs of leakage if they were to fail?

[Enzo]

Your caps don't know which jack you are using. So they probably are not going bad only when using the one jack.


How did you "confirm continuity to ground" on the jacks. Having power on should not open up a ground connection. Unplug the unit from any power. Plug a guitar cord into the noisy input jack. DO not plug the cord into anything at the other end. Now from the shell of that cord plug, measure resistance to the chassis of the unit. STill get zero ohms?

[brent]

Thanks Enzo. I'll put this sucker back together and check. So, test the resistance from one end of the cord to the chassis ground?

Yeah, for some reason, I only get a chassis ground when the power is on. I'm not an expert, but I really am interested in learning. It looks like there are no chassis grounds without resistors or capacitors in the way. So with no power, no chassis ground... at least in my unexperienced view.

I suspected caps first because of the electrolytics. My other thought is relay 1 and 2. Although the unit wasn't changing inputs when the buzz started. Relays being the only moving components in the system...

I'll check the resistance to ground, but I don't think it'll be zero. does this help in t-shooting?

I'll report back on the

[Enzo]

Use a cord as a convenient place to connect th meter. Ground and chassis ought to be the same thing here. Plug the cord into the jack that works right. measure resistance from the shell of the cord plug to the chassis of the unit. Should be low resistance - continuity. Now do the same reading plugged into the jack that does not work right. ANy difference in readings?


You see, when you say you "only get ground" I don't really know what you mean. Any resistance reading is between two points. I don;t know what TWO points you are using to make that reading.

And the reasin we don;t want the other end of our test cord plugged into anything is that we don;t want any inadvertant alternative ground path being made.


I am NOT asking for a reading from the TIP of the cord, I am asking for a reading from the shell of the cord plug, we call that the sleeve connection. I want to know if in the bad jack if the shell of the cord plug has continuity to the chassis of the unit. DOn't plug the power cord onto the unit, don;t plug any cable from the unit to some amplifier. Just the tuner unit sitting by itself on a table with the one end of one cord plugged into the jack. Take the reading.

[brent]

gotcha.

145.7 ohms on both input 1s (front and back input 1). 145.7 ohms on the single input 2 in the back.

[brent]

when the circuit is energized... i get just aboutut 1 ohm of resistance to chassis ground.

[Enzo]

Well then, I'm not sure. I don;t see how the relays could introduce hum, but I guess it is possible. I don't see why power on makes a difference either.