T4148 diode

[Carlosraj]

Hi


I came across this diode marked T4148 on the input board of the Crest Audio PL9100 amp. There was no signal coming into the preamp board and on checking the input board, I found that 3 out of 4 of this diodes show a open circuit testing on my analog multimeter. I guess this diodes supply the voltages for the three OP275 ICs on the board. What is this diode and can it be replaced by an IN4148.


Thanks

 

[JonSnell Electronic]

T4148 (just a branded 1N4148) signal diode in a DO-35 case.

 

[JonSnell Electronic]

PL9100? Can't find that anywhere.
I think the diodes are most likely protection diodes, as a guess.

 

[Carlosraj]

There are 4 of this diodes on the input board. One end of 2 diodes are connected to the incoming +20v dc(from preamp board) and the other end is connected to pin 8 of OP275. One end of the other 2 diodes connect to the incoming -20V dc and the other end to pin 4 of OP275. I replaced all these 4 diodes with IN4148, but still I am not getting any signal going into the preamps for both channels, the signal LEDs on the front board for both channels are dead with active signal plugged in. Or can it be both the OP275 opamps.


Thanks

 

[avtech]

Do you have said voltages present on the Pin 4 and 8?

 

[Carlosraj]

I have not checked the actual voltages at these 2 pins yet, I have to remove the input board again tommorrow and check the voltages at these pins and also across the diodes. I will inform 2morrow. It is late night here.


Thanks

 

[avtech]

Thought it was afternoon tea time back in Blighty?

 

[Carlosraj]

I checked the voltages at Pin4 and Pin 8, they read -12 and +12. I resoldered the board and then I managed to get the signal back.


Thanks