Audio fades out

only during the summer or hot weather, after turning on the radio, it only puts out audio for a short time and then quits. Turn if off, wait a little, turn back on and it comes back on but for a shorter time. Eventually won’t play at all. Display never goes out. Cold weather works great. Can anyone tell be where to start?

Henge …

What year is your car and is the radio still original ?

maybe you have some electronic components in the radio that drift in value with hot temperature and so the circuit fades away. Generally are electrolitic condensers.

Sounds like a solder joint or other component expanding with heat and breaking the circuit. It could be very difficult to find, depending on your knowledge and experience with electronics. Consider options for replacing the head unit.

I have been in the electronics field since 1974. Not having a schematic is a challenge. Just wondering what typically is the defective component with the symptom I have. The final amp? Is it available for purchase? Thanks for your help

JP was on the right track.

You said the main display never goes out that indicates the tuner section is working OK

You said it works when cold that indicates radio and all its caps and parts can work well. That means Tuner, preamps power amps all can work.

Its one of the tricks in electronic repair to spray Freeze Mist with pinpoint nozzle straw on various parts to see if thermal expansion will revive a circuit and depending on what parts are hit will indicate where problem is. Though many times visible failed joints will lead the way

Your radio

Heat areas is likely the best place to start the search. That would be the power amplifier usually in back of radios. This is where all the power semiconductors, and or IC (integrated Circuit) power amp or amps (powers the speakers) are located attached to rear chassis heat sinks for air cooling. Power amps usually have the largest semiconductors and largest capacitors for audio (ignoring AC amps power supplies) . You will know it’s the audio output power area just from the parts size-look. Yes a schematic would help sad to say today much harder to get service manuals and schematics for any electronic devices and again today even if you do sometimes the information is not clear or lacking legends and diagnostic information. Sadly services manuals have taken a full speed downhill slide since the golden days Hewlett Packard made superb test equipment and Tektronix too. We seem to have lost all our good tech writers. But yes, a schematic might have been a help though today likely unobtanium.

Joint Failure. What to see and tools:

Thermal Failures

The culprit usually called a “cold” solder joint though cold maybe a misnomer as:

1 It’s not a typical solder joint at all its a new crack and

2 Thermally stressed connections in commercial gear mostly fail after excessive expansion contraction not bad soldering causing a cold joint between solder and part lead or solder and printed circuit copper trace.

Mechanical failures

Largest parts, large capacitors eg like large electrolytic, sometimes even large SMD surface mounted parts can break lose, transformers NIR, connection headers, ground connections, and any parts mounted perpendicular to main PC (printed circuit) board like semiconductors screwed to chassis heat sink or interconnection headers or any IN or OUT plugs, any switches or volume type controls have big leads too. All are good candidates for mechanically stressed failures and prone to visible mechanical break in solder joint.

NIR = likely not in radio

With good sight (magnifiers a plus low power stereo microscope 10x-20x or so is great )

Looking at mechanically or thermally failed solder joint from above will look like a volcano most times with crack ring surrounding the components lead. Other times the parts wire lead itself may show a solder air gap failure. Good magnifying eyeglasses will help or good handheld magnifier with lots of lighting from side angle to accentuate the solder failure crack line.

Summary your radio does work so that rules out any electrically failed parts, open it up and in rear of chassis look at PC board solder pads for any failures and I’m sure you will see a few. If in doubt solder all the visible bad ones and adjacent ones too and all the ones with mechanical or stressed pins as discussed above. This likely will get it working.

Hope it helps, any questions ask

If it’s the factory radio then there are some pointers to common faults in the radios section of the XJ40 Ebook.