Easy sound fix for Jaguar with no or low sound

[adolobe]

Im posting this just in the sake of archiving for possible trouble shooting in the future. Hopefully it can be of help for someone down the road.

 

This is an easy fix requiring zero to basic skills. The help of a multimeter and soldering iron is optional.

 

I recently picked up a Jaguar unit that was having sound issue ( in this case extremely low sound). I later fixed 2 other units that had no sound with this same method.

 

The culprit in all my Jaguar units was the REG1 chip. its located down and to the left of the DSP. This chip regulates the Jaguar voltage to 5v for the sound system. In the case of the low sound system it was only putting out 1.3v and in the other jaguar units it was putting out 0v. This photo is after I completed the project.

 

 

Test with a multimeter

You can check this on Pin1. If you do not know how to look at a chip and determine Pin1 its the one with the small notch on the top of the chip beside it. In this case its the bottom row left furthest pin. You can confirm if power is going into the chip set with Pin 8, this is the pin directly across from Pin 1. It should be 9v but depending on the accuracy of your multimeter it may be slightly higher or lower.

 

Test with out a Multimeter

If you do not have a multimeter you can still check to see if this chip is the culprit. You need about 8 inches of wire cable. You can sacrifice a CAT5 cable or any other old cable for this. Strip off about 1/4 on each end of the wire.

 

Now you need to access a source of 5v on the Jaguar motherboard. The Jaguar AV Port offers just the source.

 

Behind the Jaguar Cartridge port locate (L7)

 

 

Take one end of your wire and touch it to L7 the silver part only and the other end to Pin1 on the REG1. You should now have sound. If not then your culprit could be more severe but less likely.

 

Now if your handy with soldering iron solder the wire in place at both contact points. Optional you can firmly tape the wire down at both locations with some electrical tape. Third option is to pick up some conductive wire glue and permanently glue the wires into place. Conductive wire glue runs about $5.

 

Below is a few photos of the finished project on one of my Jaguar's. FYI this does not hinder the AV port so if you use Composite or Svideo you are fine as they do not require the 5V lead.

 

 

I ran all 3 Jaguars for 36 hours to test. One was playing Fight For Life, One was playing Cybermorph and the other one was playing Rayman.

[Gunstar]

The Reg1 chip needs to be replaced about 99% of the time when the power regulator is blown too (wrong power-pack syndrome), so replacing this chip is already archived. But, it will help some people with your way of testing the Reg1 chip (and apparently a McGyver-type fix). I'll use this info myself in the future I'm sure. I bet I could have fixed several of my Jaguar sound issues without repacing the chip like I have been doing. I might even be able to re-use the REG1 chips I replaced for future repairs using your technique! Good thing I keep them (for identification purposes if another chips number is burned off).

Good stuff!

Edited September 3, 2012 by Gunstar

[goodtofufriday]

Gotta say thanks for this. Worked great and didnt need to buy a new chip

[omf]

there is an easier way

see attached picture (red line)

 

for models that do not have the adc chip just connect to the main board as 5v is still present

[jvas]

I have 5V on reg1, but still no sound. What else can be the problem?

[Songbird]

I discovered yesterday that one of my old developer Jags with a Stubulator ROM did not output any sound. REG1 was the problem and the wiring fix did the trick! Now I just need to solder it in place.

 

Edit: and now it is soldered! Awesome to have another fully functional Jaguar in the house.

 

Edited August 4, 2020 by Songbird

[Stephen Moss]

Perhaps there are different schematics out there showing L7 as being in a different position in the circuit place but all those I have found are dated 21 September 1993 which shows L7 as being connected to one of TOMs I/O pins. If that is and always has been the case (and the schematic I have suggests it probably will be on at least some revisions of the PCB)  then I have I would have to classify the advice given in the first post as another example of nonsense posted by people who do not know what they are talking about purporting a bad fix found by blind luck as an proper solution to a problem.

 

1st, there must be a reason why a separate regulator was used for the sound instead of using the output from U38, probably something to do with the switching noise getting onto the audio and so the best solution would be to replace Reg1.

 

2nd, if you cannot do that then although the I/O pin of TOM in question is presumably unused and always output high (otherwise the suggested solution would not work) that is no reason to use it as a power source. I/O pins are not intended for that and have limited current capabilities. Consequently, any power short in the audio stage risks damaging TOM via that I/o pin, although if you are lucky any possible damage will be limited solely to the pins I/O stage.

Surely a more sensible place to suggest taking power from would be the supply pin of any IC's powered by U38 or from C150/C175 on the output from U38, not an I/O pin.

 

3rd, pin of Reg 1 is not a good place to connect to as with Reg1 still in place and connected it will still be trying regulate the voltage for the audio circuit power. A better suggestion would be to connect to TP6 and desolder/cut off pin 1 of Reg1, thereby isolating its defective output from the rest of the circuit.

 

   

Edited August 5, 2020 by Stephen Moss

[Songbird]

Thanks, Stephen. For what it's worth, I connected to the ADC pin 1 as suggested by @omf.

[Zerosquare]

I agree with @Stephen Moss

If you want to check whether replacing REG1 will fix sound, unsolder REG1, then connect pin 1 to VCC (not pin 1 of the ADC chip, as it isn't connected to VCC).

I wouldn't recommend using it as a permanent "fix" either. While it won't damage your console, the signal/noise ration of the audio output will be worse than normal.

[omf]

On 11/14/2014 at 12:40 PM, omf said:

there is an easier way

see attached picture (red line)

 

for models that do not have the adc chip just connect to the main board as 5v is still present

 

13 hours ago, Stephen Moss said:

Perhaps there are different schematics out there showing L7 as being in a different position in the circuit place but all those I have found are dated 21 September 1993 which shows L7 as being connected to one of TOMs I/O pins. If that is and always has been the case (and the schematic I have suggests it probably will be on at least some revisions of the PCB)  then I have I would have to classify the advice given in the first post as another example of nonsense posted by people who do not know what they are talking about purporting a bad fix found by blind luck as an proper solution to a problem.

 

1st, there must be a reason why a separate regulator was used for the sound instead of using the output from U38, probably something to do with the switching noise getting onto the audio and so the best solution would be to replace Reg1.

 

2nd, if you cannot do that then although the I/O pin of TOM in question is presumably unused and always output high (otherwise the suggested solution would not work) that is no reason to use it as a power source. I/O pins are not intended for that and have limited current capabilities. Consequently, any power short in the audio stage risks damaging TOM via that I/o pin, although if you are lucky any possible damage will be limited solely to the pins I/O stage.

Surely a more sensible place to suggest taking power from would be the supply pin of any IC's powered by U38 or from C150/C175 on the output from U38, not an I/O pin.

 

3rd, pin of Reg 1 is not a good place to connect to as with Reg1 still in place and connected it will still be trying regulate the voltage for the audio circuit power. A better suggestion would be to connect to TP6 and desolder/cut off pin 1 of Reg1, thereby isolating its defective output from the rest of the circuit.

 

   

 

8 hours ago, Zerosquare said:

I agree with @Stephen Moss

If you want to check whether replacing REG1 will fix sound, unsolder REG1, then connect pin 1 to VCC (not pin 1 of the ADC chip, as it isn't connected to VCC).

I wouldn't recommend using it as a permanent "fix" either. While it won't damage your console, the signal/noise ration of the audio output will be worse than normal.

i believe this was a quick bodge help while i was at work from what i recall so couldn't do any descent research

 

this should be a better answer to the correct point, i may of got the side mixed up when i drew the line