CS-80 Question: 70 ohm Resistance Between+15V and GND

[Jonathan40]

With the power off, I'm getting a 70 ohm resistance between ground and the +15V card riser supply rail on a Yamaha CS-80 - does anyone know if this is this normal? Not sure if the decoupling capacitors on the new 4000-series sockets are contributing to this.

[synthRodriguez]

By the math that's 214 mA which sounds about right to me.

My CS-50 (with a couple of extra voice cards in it) pulls around 187 mA on the +15 rail when it's running, so a 214 mA value on a CS-80 with all the extra overhead would be a perfectly acceptable value I would think. I wouldn't give it another thought.

The caps shouldn't have anything to do with it regardless with a static measurement.

Scott

[Jonathan40]

Thanks, Scott. The 500mA fuse blew on the power supply before I did all this testing, and a tech told me to check for shorts between the 15V rail and ground, hence my question. Need to make sure everything's safe before powering this thing up again.

[synthRodriguez]

Of course working load and unpowered resistance are two different things so there still could be a problem. Just saying it's not like it's a dead short or something, and at least it makes somewhat reasonable sense.

I get 187 ohm on the CS-50 from the ground rail to the +15 rail. Please let us know what you find.

[Jonathan40]

Of course working load and unpowered resistance are two different things so there still could be a problem. Just saying it's not like it's a dead short or something, and at least it makes somewhat reasonable sense.

I get 187 ohm on the CS-50 from the ground rail to the +15 rail. Please let us know what you find.

Am a little confused - are you getting 187 ohms or mA from ground to +15?

[Jonathan40]

Well, I heard from another CS-80 owner, and he's getting 69 ohms from the +15V rail to Ground. Things are looking up!

[Jonathan40]

Here are the resistances I'm getting between the power rails on my CS-80 and ground:
+15V = 70.3 Ohms
-15V = 64.5 Ohms
+8.5V = 337 Ohms
-6.5V = 878 Ohms
+10.6V = 540 Ohms
The rails can be accessed on the power supply just behind the output molex connector. The +15V is the brown wire at the top and they go down from there. I'm thinking my -6.5V could be low as a friend is getting 3.95 Kohms on his currently working unit, as well as 456 Ohms on the +8.5.

[lukaskupasz]

With the power off, I am getting a 70 ohm resistance between +15V card riser rail and ground on my CS-80 - does anyone know if this is this normal?

[synthRodriguez]

CS-80 s/n 1274

Unpowered resistance readings at the power supply plug and current draw when operating.

==================
+15.0 __ 66.2 ohm __ 2.5 A
- 15.0 __ 65.6 ohm __ 2.4 A
+10.6 __ 532 ohm __ 674 mA
+ 8.5 __ 349 ohm __ 126 mA
- 6.5 __ 3.9 kohm __ 106 mA