Heating a TI DSP chip for reliable operation.

Warm Up a Problematic DSP IC
Using a CH-25 Crystal Heater
By Frank Setliff K4OAJ

The Problem:

I have a Yamaha A-V receiver. This uses a Texas Instruments DSP chip made around 2010-2012. They are known for not working until something heats them up. I've used a blow dryer on the chip and it starts working around 130 degrees and keeps working down to about 90 degrees. The wife and I were joking about just duct taping a blow dryer to it with a remote switch when I remembered crystal ovens. I believe your CH-25 Crystal Heater will be the perfect solution to my problem.

The display is showing the failed state. Instead of "Decoder Off" it should be showing "PCM". Click on any photo for a larger view.

I used my scope to trace the signal from the HDMI input through the various ICs to the TI DSP chip. I found a signal going in but no signal coming out. I started looking for a replacement "'Digital board" and came across some posts in the Yamaha Forum about this same problem with the TI DSP chip that was also used in Denon and Onkyo receivers from around 2009 to 2012. I found a YouTube video where a technician used a hi-intensity lamp to heat the chip enough such that it started working. I tried using a hair dryer and, sure enough, the chip started working at around 130 degrees and remained functional until it cooled down to around 90 degrees. Since the receiver is about 9 years old, new boards are no longer available, and used boards would have had the same problem. My wife and I were joking about duct taping a small hair dryer to the receiver when my light bulb came on and I remembered 'Crystal Heaters'. A search on the internet brought up your "CH-25 Crystal Heater Kit" so I ordered one.

Preparation:

While waiting for the kit to arrive I began looking for a power source. The receiver provides a trigger voltage on the rear that can be used to turn other equipment on and off, such as a secondary amplifier for another zone. Since that is not being used in my setup, it was disconnected and the 18 volts will be used for the CH-25. This power source is not part of the receiver's standby circuit but comes on almost as soon as the Power Button is pressed. A relay, controlled by the CPU, has to operate but it normally comes on within a second after the Power button is pressed.

I received the CH-25 kit and put it together with no problems. I made certain to install the optional Zener diode to limit the heater current since 18 volts was being used to power the unit. I spliced the CH-25's voltage connector into the 18-volt supply line and mounted the CH-25's circuit board to a grounded screw on the receiver's Digital board.

I used super-glue to attach the heater resistors and temperature sensor to a 3/4 inch square of 1/16 inch aluminum plate. I also used some high-heat epoxy (not shown) to be sure the parts remained attached to the aluminum and provide good heat transfer.

I attached the aluminum plate to the DSP chip with a piece of double-sided heat transfer tape that I found on Amazon. This is often used to hold heat sinks to computer CPU chips. I plugged the connectors into the CH-25 and before powering everything up I preset the Temp Set pot to 1k referencing ground.

Fire It Up:

I turned the receiver on and adjusted Vout (TP2) for a stable 1.2 volts to give me 120 degrees Fahrenheit at the DSP chip. After about 5 minutes of warming up the music came on and the display shows "PCM". SUCCESS!!

I put the receiver back into my home theater setup and it has been working great thanks to the CH-25 Crystal Heater!

Update: I had to increase the temperature from 120 to 138 degrees a few days later. That's still not very hot and that temp doesn't seem to bother anything else.

Thanks Kevin,
Frank Setliff K4OAJ

This page originally posted on Wednesday 01-Jul-2020.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.