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Goldscan 5 damaged:sadwalk:
- Thread starter Draco
- Start date
Hi draco,
The -4v is about what I figured. It is supposed to be 0V. So, now we need to figure out what is bad and to do that, you will have to lift up the audio board so you can check a couple of outputs on the last amplifier on the main board on the side the audio pigtail comes in on. Check the last OpAmp and see if it is a LT1112. What is wrong is most likely associated with this opamp.
Before doing that, check the voltage again on the audio board but adjust the gain pot from min to max. The gain pot could also be called the range pot. I think you changed that in your video and it didn't seem to make much difference. So, if this is the case, you will have to measure the outputs of the opamp chip.
On the LT1112, pins 1 and 7 are the outputs. You will need to check both and find out if one or both of the outputs are wrong. Pin 1 can cause pin 7 to read bad if pin 1 is too negative of a voltage. Both should be 0V.
With luck, we will be able to change the opamp and solve the problem. If not, then maybe the offset voltage correction circuit is not functioning correctly. If that is the case, I may be able to fix that also.
Reg
The -4v is about what I figured. It is supposed to be 0V. So, now we need to figure out what is bad and to do that, you will have to lift up the audio board so you can check a couple of outputs on the last amplifier on the main board on the side the audio pigtail comes in on. Check the last OpAmp and see if it is a LT1112. What is wrong is most likely associated with this opamp.
Before doing that, check the voltage again on the audio board but adjust the gain pot from min to max. The gain pot could also be called the range pot. I think you changed that in your video and it didn't seem to make much difference. So, if this is the case, you will have to measure the outputs of the opamp chip.
On the LT1112, pins 1 and 7 are the outputs. You will need to check both and find out if one or both of the outputs are wrong. Pin 1 can cause pin 7 to read bad if pin 1 is too negative of a voltage. Both should be 0V.
With luck, we will be able to change the opamp and solve the problem. If not, then maybe the offset voltage correction circuit is not functioning correctly. If that is the case, I may be able to fix that also.
Reg
The IC is the 8 pin IC right at the edge of the board. It is the LT1112 and is right under the headphone cable. Do you see the LT1112? If so, double check the pins 1 and 7 again. It should be pin 7 that is -4V.
Actually, measure each pin of the LT1112 and let me know what each reads.
Hopefully, from the measurements I will be able to determine if the IC is bad or some other component is causing the problem.
If you have another dual opamp like a TLO72 or TLO62 and the LT is in a socket, you might try carefully remove the LT1112 and install a different dual opamp. Make sure to get pin 1 in the right place.
Reg
Actually, measure each pin of the LT1112 and let me know what each reads.
Hopefully, from the measurements I will be able to determine if the IC is bad or some other component is causing the problem.
If you have another dual opamp like a TLO72 or TLO62 and the LT is in a socket, you might try carefully remove the LT1112 and install a different dual opamp. Make sure to get pin 1 in the right place.
Reg
Hi Draco,
I am curious as to where you are located. Hopefully, you will have access to other dual opamps (two amplifiers in the chip). I am betting that changing the TLC2262 will cure the problem. If it does correct the problem, then we saved time and money.
The GS 5 underwent an evolution. I think originally, the LT1114 and the next opamp were TL064 and TL062. Then the operational amplifiers were changed to the LT series for stability. Ideally, the LT series work best because you don't need some of the small 0V balancing pots installed. In fact, on one of my older Goldscan 4's, I installed LT's and eliminated some troublesome pots all together.
Reg
I am curious as to where you are located. Hopefully, you will have access to other dual opamps (two amplifiers in the chip). I am betting that changing the TLC2262 will cure the problem. If it does correct the problem, then we saved time and money.
The GS 5 underwent an evolution. I think originally, the LT1114 and the next opamp were TL064 and TL062. Then the operational amplifiers were changed to the LT series for stability. Ideally, the LT series work best because you don't need some of the small 0V balancing pots installed. In fact, on one of my older Goldscan 4's, I installed LT's and eliminated some troublesome pots all together.
Reg
OK