Crate V18 does anyone have schematic for the smps pcb?

[chrisfelser]

I have a crate v18 112 that i had been using for a direct recording preamp. To eliminate microphone bleed i unplugged the speaker and used only the line out, until recently i hadn't realized this was a bad idea. the amp somewhat suddenly cut out and started ticking? i guess you could call it and the red led started blinking and i could smell burning plastic. i assumed it was a fuse, it was not. i assumed power tubes, it was not. i even tried new preamp tubes and no dice same problem persists. upon further inspection the power board between the standby and power switch has a bit of heat damage on a few of the components . does anyone have a schematic?

[Jazz P Bass]

Crate SMPS

All that I have is the V50 SMPS.
If that does not help, you could try calling Loud Technologies.

[chrisfelser]

i think that this should be good there isnt anything on the smps that specifies v-18 its just "v-series" so thanx much.

[Jazz P Bass]

SMPS Repair

Be careful in there. The mains cap holds charge for a while.
It may be that the SMPS failed or was made to fail.
Last one that I repaired I kind of remember R103 & 104 of the supply getting hot.
Check the output section real good.

[olddawg]

Your problem may not be the SMPS at all. (in case you don't know that means SWITCHED MODE POWER SUPPLY) Make sure you measure all of your power supply rails to ground. If you have shorted output device or something else most SMPSs will whine, click, or otherwise shut down. I don't know if the amp is layed out that way, but it would probably be advisable to unplug/unsolder the SMPS from the main board to test it. If you do not understand how SMPSs work you should probably leave it to a professional. Is the amp under warranty?

[Jazz P Bass]

SMPS Testing

Be aware certain SMPS need a load on the output rails to function at all.

[olddawg]

Be aware certain SMPS need a load on the output rails to function at all.

While that is certainly true (all SMPSs need a load and feedback), it has been my experience that most modular types will usually run free standing. If they don't the service info will have directions for a jig (usually a couple of resistors) to make them so. My point is that it isn't a simple power supply, overcurrent will shut it down, and you need to know where the problem is before you can fix it. In an authorized shop you would probably just swap the damn thing out if it is modular, at least for testing purposes and probably for repair. If you don't have an electronics background SMPSs are a daunting thing and even intimidating for some experienced techs at the component level.

[lotechrules]

This might be helpful
Index of /new/schem/misc_amp
When it comes to the crate v18, Steve has a lot of experience
Good luck

[Enzo]

Those Crate SMPSs will run free standing on the bench.

My guts tells me you had a power tube failure or at least an arc in the output. And that shorted a rectifier in the B+ section of the SMPS. The SMPS will sit there trying to start. new tubes won;t cure the shorted diode. But once the SMPS is repaired, a old bad tube could destroy the new diode just as easily.

Here is a test. Look at the SMPS board, upper right. Are there not two individual wires - I think orange wire and purple wire? Those are the B+. Pull the wires off and power up the amp. Now does the rest of the system power up? If so, then probably something on the B+ is loading it down. If the SMPS STILL won't start, then start looking for shorted rectifiers.

The V18 and V50 use the same SMPS board, but the V18 doesn;t use the center of the three B+ transformer secondaries.

[jboots00]

V18

I think if you see that light flashing in the "on" position its probably the SMPS sensing an overcurrent condition and shutting itself down over and over. You'd think the fuse on the supply would blow but apparently its really sensitive to overcurrent demand and shuts down before the fuse can blow. I'd disconnect the supply from the amp (POWER OFF AND UNPLUGGED, OF COURSE) and ohm the supply input to the amp. If I remember, the B+ is 300 something and the fuse in the SMPS is around 300mA (I don't remember exactly). So if you see a relatively low resistance, something is loading it down. Do the OHMs law math. Also, remove all the tubes from their sockets and measure the resistance from B+ input to ground on the empty socket board. I know that doesn't seem to make sense, but I've actually seen where the B+ pin would arc across to a heater pin under the socket leaving a nice little carbon trace that acts like a low value resistor. Removing the socket and cleaning that trace will solve the problem. Just my 2 cents.

[Steve Conner]

You probably blew one of the protection diodes that go between the power tube plates and ground, by running it without a speaker. This shorts the B+ to ground.

The current limiting is how it's supposed to work. SMPS can't rely on fuses for protection, because transistors blow faster than fuses.