240V stereomour

[srhombeus]

Does your 100K pot look OK?

You may have had the solder joint on pin 1 of the 9 pin socket touch pin 2 of the 9 pin socket, which would warm up your pot pretty quickly.

-PB

There was a smoke on the 100k pot,I've ordered alps blue velvet for replacement. And also 2 red leds dont glow.I've ordered new cs4 board from mrs. Eileen tonight.  My question is how can I test power supply board?  Because i dont want to burn another parts when i turn on the amp again.

 

[Paul Birkeland]

You can run the amplifier with the 2A3's installed to test the power supply board.

A DC voltage of 55-65V on pins 1 and 4 of each 4 pin socket would indicate a working power supply PC board.

-PB

 

[srhombeus]

How can i disconnect c4s board while doing that? Do i have to take off all the cables coming from power supply board to c4s board ?

You can run the amplifier with the 2A3's installed to test the power supply board.

A DC voltage of 55-65V on pins 1 and 4 of each 4 pin socket would indicate a working power supply PC board.

-PB

 

[Paul Birkeland]

How can i disconnect c4s board while doing that? Do i have to take off all the cables coming from power supply board to c4s board ?

If the C4S board is out of the amp, you're OK.  The two black wires that go to bA and bB should be temporarily soldered together.  The red wire leaving the high voltage supply on the PC board can poke up in the air, just don't touch it while you're testing.

 

[srhombeus]

You mean the two black wires coming from -reg of each side? And there are also two red wires of high voltage of power supply board. Do i have to take two of these wires and also black ground wire?

If the C4S board is out of the amp, you're OK.  The two black wires that go to bA and bB should be temporarily soldered together.  The red wire leaving the high voltage supply on the PC board can poke up in the air, just don't touch it while you're testing.

 

[Paul Birkeland]

Yes, sorry, the -reg wires need to connect to each other.

The red high voltage wires can be left floating in the air.

 

[srhombeus]

Ok,and the ground cable leaving the power supply board,do i have the take it out also? Because I am planing to take completly out the c4s board before connecting to new one ..

Yes, sorry, the -reg wires need to connect to each other.

The red high voltage wires can be left floating in the air.

 

[Paul Birkeland]

The GND cable leaving the power supply board is one of the two black wires that you need to connect together.

If you disconnect it at the power supply end, then you will open the circuit that would allow current to flow through the power supply, and you will be unable to test the board.

-PB

 

[srhombeus]

Sorry but I totally dont understand it.. Because there are three black cables leaving the power supply board.Two of them are K cables going through terminals and the third one is GND cable..

The GND cable leaving the power supply board is one of the two black wires that you need to connect together.

If you disconnect it at the power supply end, then you will open the circuit that would allow current to flow through the power supply, and you will be unable to test the board.

-PB

 

[Paul Birkeland]

The K wires are not ground wires, they allow the cathode bypass capacitors to attach to the hum pot on the 2A3's.  Those wires need to be left in place.

The black cable leaving the power supply PC board GND pad needs to connect to the black wire that connects from -reg to the terminal strip at the front of the chassis.

 

[srhombeus]

Ok,thank you.I got it know.The ground cable coming from terminal 8. 

The K wires are not ground wires, they allow the cathode bypass capacitors to attach to the hum pot on the 2A3's.  Those wires need to be left in place.

The black cable leaving the power supply PC board GND pad needs to connect to the black wire that connects from -reg to the terminal strip at the front of the chassis.

 

[srhombeus]

I've made the measurements.All the values for the power supply board and 4 pin sockets are in range.There is no problem with them.But while checking the 220 ohm resistors,I saw that the value for the terminal 7U to B2 is around 240 ohm and 9U to B7 is around 170 ohm. The amp was turned off and unplugged. Is this a problem,this resistor could be damaged also?

The K wires are not ground wires, they allow the cathode bypass capacitors to attach to the hum pot on the 2A3's.  Those wires need to be left in place.

The black cable leaving the power supply PC board GND pad needs to connect to the black wire that connects from -reg to the terminal strip at the front of the chassis.

 

[Paul Birkeland]

The 220 Ohm resistors are an arbitrary value.  The could be 0-5,000 Ohms without noticeable operating changes.

 

[srhombeus]

Hi,Can i use 240 ohm 1/4 watt resistor instead of 237 ohm in the c4s board?

 

[Paul Birkeland]

Yes.

 

[srhombeus]

Hi,I've newly assembled c4s board.4 leds are ok,all tubes are ok.Voltage checks are ok except terminal 2 and 14.they are a little lower than range.The right channel sound ok.There is also sound in left channel but there are some cracks,pops in left channel.I dont use potentiometer now,i am waiting for alps potentiometer to arrive.Where should I check for this left channel problem?  Thanks again.

 

[Grainger49]

I would first clean the left channel tube socket and tube pins.  Just remove the 2A3 and insert it 10 times.  Do the same thing with the 12AT7, it serves both channels.

Although Bottlehead buys new tubes and sockets either one could have been sitting on a shelf for a decade and have some oxidation on the metal.

 

[srhombeus]

I've tried this but my problem still continues.I think side C is left channel and side A is right channel.Where do you suggest to look at it for this weird sounds?

 

[Paul Birkeland]

Please post the actual voltages that you have.

-PB

 

[srhombeus]

Here are the voltage checks :