Peavey Digital Reverb

[Billy R aka DynaFreak]

I am repairing a Peavey Supreme XL with a broken reverb that has the little digital reverb board. The board is getting signal, and the 5 volt power supply on the board is ok, so I suspect the chip is faulty. However, since this is a microprocessor, I wonder - is there any way to "reboot" it that might cure the problem?

[Jazz P Bass]

Can you post the schematic?
I would think the microcontroller would be running on 3.3Vdc.
Is there not another regulator on the board?
Is there any signal at all at the reverb level pot?

[tedmich]

the Belton modules run with just 5vdc and ground. I'd check the pot out but others also have problems with these units, contact PV they are great people, as there is little or nothing you can do with the module typically.

[Billy R aka DynaFreak]

You are correct the folks at Peavey are great, I'm calling them tomorrow to order a replacement. I should have mentioned the chip is a CS4811. It runs on 5V, which is output from a LM2594K5. The reverb pot is after the digital board. There is no signal at the output of the digital board.

[Enzo]

Or just ask them what a whole new FX card costs.

[Billy R aka DynaFreak]

I am definitely going to order the entire board, I have no desire to get into repairing it, I was just curious about the possibility of resetting it somehow.

[tedmich]

I am definitely going to order the entire board, I have no desire to get into repairing it, I was just curious about the possibility of resetting it somehow.

according to the sheet "RST pin 72 should be asserted during power-up until the power supplies have reached steady state" this resets all registers and mutes output,

[Billy R aka DynaFreak]

can you tell me exactly what they mean by "asserted"?

[tedmich]

NO! either high or low ??

[Gtr_tech]

can you tell me exactly what they mean by "asserted"?

Anything microprocessor based usually has a power up reset. This just means that when it first powers up, the supply voltage is not right where it should be, so random information gets loaded. If you just left it that way, it would crash and not operate. The reset fools the uP into thinking that it was power'd off and back on again, only with stable supply voltage now. Correct info gets loaded into ram and the code can run.

So if you can locate the datasheet for the main DSP chip and find the reset pin, you can watch that pin on power up with a scope and see if it changes states (it will do this quite fast) from low to hi (or the inverse). The datasheet should specify what state the reset line should be in for a reset condition. "Res" or "Reset" with a line over the top of the term means that line is active low, so if it was stuck in reset, that line would remain low. The absence of the line over the term indicates active high. So, if the reset is active low, the reset line should start low (0v) and jump up to high (5v). The datasheet will tell you how long the reset period should be, measured in mS.

You can force a reset just to see if it runs with a manual reset. If the reset is high for run, use a 1k resistor and a clip lead to gnd. Power it up, touch the reset pin (or something connected too it) briefly and see if it makes the DSP run. If not, its likely hosed or has severed solder connections.

[Billy R aka DynaFreak]

Great thread, you all have answered my basic question, now I have another: how does the chip, which is a multifunction effects processor, know to be a reverb only? I read the datasheet, so please dont quote that. I understand that there is a boot sequence that most likely is involved, but is the chip itself "pre-programmed" using some external connected device prior to being installed in the amp?

[Jazz P Bass]

Great thread, you all have answered my basic question, now I have another: how does the chip, which is a multifunction effects processor, know to be a reverb only? I read the datasheet, so please dont quote that. I understand that there is a boot sequence that most likely is involved, but is the chip itself "pre-programmed" using some external connected device prior to being installed in the amp?

Have you read the datasheet?
Page 1: Header: Fixed Function Multi-Effects Audio Processor
Features: Audio Processor for embedded reverb/effects applications.
- Firmware for the CS4811 is provided by Cirrus Logic.
There are two different firmware codes available; one for
guitar effects and one for audio mixers. The guitar effects
firmware provides a host of electric guitar effects including
spring reverb, delay, chorus, flange and tremolo.
The mixer effects firmware provides a suite of effects
such as digital reverb, delay and chorus which are suitable
for use in audio mixers, karaoke and acoustic
instrument amplifiers.
So apparently the IC runs two different firmware versions, provided by Cirrus Logic.
Link: CS4811 pdf, CS4811 description, CS4811 datasheets, CS4811 view ::: ALLDATASHEET :::

[Billy R aka DynaFreak]

Yes, did you read my post?

[Jazz P Bass]

Yes, I read your post.
Sorry, I missed the part about "don't quote the datasheet".
The question that I thought you asked was " how does the chip, which is a multifunction effects processor, know to be a reverb only?"
The firmware < according to the datasheet (oops, I quoted it) is loaded from an EEprom.
"A serial control port allows the device to boot firmware from a compact and low cost SPI or I2C serial EEPROM."
Where that is on the PCB board I do not know.

[Enzo]

How does a multieffect IC know to be just a reverb? How does a guitar know to play only the E and A strings? How does a piano know to play only middle C? More to the point, how does your computer know to come to this web site instead of Fender's? Like anything else, the IC has control inputs, it does what you instruct it to do.


Belton makes a multieffect IC. I often think how easy it would be to make a line of various single effect pedals, all using the same stupid IC. Just wire each one up to enable the different effects.


DOn't confuse reset (a simple action that makes sure the programming starts at the start each time it is powered up), with restoring factory setting or reinitialization. ANy microprocessor will have a power-on reset function. A basic little circuit that sends a reset pulse to the IC a moment after power is applied. All it does is start the program at step 1.


ANy computer device that has alterable memory - like latches and presets that are editable - also has the possibility that it will have that memory corrupted. I recall one synth that liked to decide now and then to put maximum vibrato on every patch. You'd have to to a factory reset - a reinitialization - to clear that. That is not the same as the power up reset. That is not the function of the reset pin on the IC. In fact, even with scrambled memory, that reset happens each time you power up. Just that in that case, the program starts at step 1 but with still scrambled memory.


If I read the schematic correctly, the instructions for this particular effect are in U1, the EPROM.