Crate GTX65 HELP!

[ConorStevo]

Model: Crate GTX65UB
Serial #: DDOUQ80020

I get no sound, but I do get power to the power LED. The SAVE/TAP LED is continuously flashing blue and i do not even get a buzz from the speaker.

Things I know...
-I have tried the Factory Reset (hold the SAVE/TAP button whilst switching on technique)
-The speaker does work as i tried it on another amp
-The two wires for the speaker do not have breaks in them as i have tested them.
-The fuse is working
-From sight there are no obviously burnt out components on the PCB but I am no amp technician, my expertise lie in computers


I have spoken to a technician from whom i am awaiting a reply about the op amps on the PCB, he told me to check the voltage across pin4 and pin 8 and he said i should get +-15v....

I get 33 to 33.2V??


Any ideas? Am i likely to have done something wrong when testing these voltages?

[ConorStevo]

Or is that 33V rail to rail so the combined 2 15v?

[Jazz P Bass]

The opamp power pins should be read with respect to chassis ground.
Pin #4 referenced to chassis: -16Vdc
Pin #8 referenced to chassis: +16Vdc

Crate GTX 65 (279XXSCH_3).pdf

Verify the DSP board power supply voltage.
On page 1, coordinate 3-D, connector J10 is for the DSP board.
Pin #4 should read +10Vdc referenced to ground.

Unfortunately the DSP board is not on the schematic.

For troubleshooting purposes, verify that you have a signal going in to the board (pin #2)
If the signal goes in, it should come out at pin #1.
If not, then you have a DSP problem.

You may be able to jumper pin 1 & 2 if the DSP board connector is removed.
If the amp then functions, you know it is solely a DSP board problem.

[ConorStevo]

Thank you for you reply!!!

I do have a 10Vdc supply to the DSP Board via pin 4

By checking the signal, do you litterally mean plugging in my guitar or ? please excuse my incomptetence

If you could possibly explain a method that would be so much help

[nickb]

Have you tried plugging in to the INSERT jack? If you get an output you then know the power amp is working. Also, try cleaning it by plugging and unplugging into the jack a few times. It might just be the dreaded switching jack problem (Google it).

[ConorStevo]

thanks for your response but i think the problem is more sinister due to the fact i get no sound as all to the speak, not even a pop and the flashing LED, which leads me to believe it could be a DSP problem

[nickb]

thanks for your response but i think the problem is more sinister due to the fact i get no sound as all to the speak, not even a pop and the flashing LED, which leads me to believe it could be a DSP problem

Yes, you may be right. I find it odd that you get no pop sound at all from the speaker as it is still connected to the power amp and there is nearly always something, even if slight. I do note there is a power on-mute circuit that will suppress a switch on pop. This simple 3 second test will very quickly tell you for sure if the power amp is OK. Also, you may have more than one problem. A much smarter and wiser man that I once said to never come up with reasons for not testing something.

The flashing LED suggests the DSP is alive, but not happy.

JazzP is suggesting you unplug the DSP board and bypass it by wiring from pin 1 to 2.

[ConorStevo]

I have tried the unplug and bridge 1 and 2 method and i got nothing however, do you think i should completely isolate the board by uplugging all connections from the DSP board and the bridge?? only problem being, there is a stubborn ribbon cable that doesnt want to come off :/

[Jazz P Bass]

Thank you for you reply!!!

I do have a 10Vdc supply to the DSP Board via pin 4

By checking the signal, do you litterally mean plugging in my guitar or ? please excuse my incomptetence

If you could possibly explain a method that would be so much help

'Checking for signal' means injecting a signal into the input jack and taking a reading at specific points.
Use your volt meter, set to read Volts AC with the black lead connected to chassis ground.

Any signal will do.
CD, I Pad or you can strum the guitar.

The expected signal amplitudes are well marked on the schamatic.

[ConorStevo]

Right, I think i have done as you described,

(with audio input from CD input via phone @ max volume and mid gain on rhythm channel)

PIN1 to Ground = 0.9mV
PIN2 to Ground = 2.2mV
PIN1 to PIN2 = 2.4mV

[nickb]

I have tried the unplug and bridge 1 and 2 method and i got nothing however, do you think i should completely isolate the board by uplugging all connections from the DSP board and the bridge?? only problem being, there is a stubborn ribbon cable that doesnt want to come off :/

The important thing is that when you bridge the pins on the main board the DSP is not connected to the those pins. The ribbon connector may well have a latch on it.

On the insert jack, You need to insert a signal in the jack, bridging it only tells you if you have a switching problem. Plug your guitar in and try.

[ConorStevo]

I bridged the pins 1 and 2 as shown in the attachment...

I then tried both normal input and insert and i got nothing

I then unbridged and reattached to the DSP board and still the same problem (LED flashing, no sound)

The only thing i noticed was that the LED flashes as different rates depending on the channel (which is probably irrelevant)

[ConorStevo]

I bridged the pins 1 and 2 as shown in the attachment... (i wrapped the clip around the cable to stop it from shorting)

I then tried both normal input and insert and i got nothing

I then unbridged and reattached to the DSP board and still the same problem (LED flashing, no sound)

The only thing i noticed was that the LED flashes as different rates depending on the channel (which is probably irrelevant)

[Jazz P Bass]

The flashing LED is the Tempo/ Tap button is it not?

Storing Your Own Presets; Restoring The Factory Presets; More About The Save/tap Button - Crate GTX65 User Manual [Page 8]

You may not have a DSP issue.

[ConorStevo]

Yes thats the LED, like a said i have performed the factory reset?