JCM 900 SLX 5881 conversion to EL34 question

[Amp Mad Scientist]

Its reading 7.15VAC across pins 2 and 7 together on socket 1 and 7.17VAC on socket 2

OK
Turn power off and disconnect mains power.
The power is now UN-plugged from the amp.

Set meter to ohms.
black probe on output socket pin 3.
red probe on other output socket pin 3.
What is the ohm reading?

 

[Amp Mad Scientist]

 

[Clockworkmike]

OK
Turn power off and disconnect mains power.
The power is now UN-plugged from the amp.

Set meter to ohms.
black probe on output socket pin 3.
red probe on other output socket pin 3.
What is the ohm reading?

81.7ohm

 

[Amp Mad Scientist]

1.13k Ohm

Power disconnected as above.
Measure with the ohm meter between pin 3 of one output tube socket, and one terminal of the standby switch.
Black probe on pin 3, and red probe on the standby switch terminal.
Then,
measure the other socket pin 3, and the one terminal of the standby switch.
The two readings from each pin 3 should be equal, but I don't think they will be.
What is the reading from each pin 3 to the standby switch?

 

[Clockworkmike]

Power disconnected as above.
Measure with the ohm meter between pin 3 of one output tube socket, and one terminal of the standby switch.
Black probe on pin 3, and red probe on the standby switch terminal.
Then,
measure the other socket pin 3, and the one terminal of the standby switch.
The two readings from each pin 3 should be equal, but I don't think they will be.
What is the reading from each pin 3 to the standby switch?

I had given the wrong measurement above, it was 81.7ohm, sorry
Pin 3 to one side of the standby is 2.33Mohm from each socket

 

[Amp Mad Scientist]

I had given the wrong measurement above, it was 81.7ohm, sorry
Pin 3 to one side of the standby is 2.33Mohm from each socket

Try the other terminal of the standby switch...there's 2 terminals on the switch.
should be reading between pin 3 and standby switch 40 ohms.

 

[Amp Mad Scientist]

 

[Clockworkmike]

Try the other terminal of the standby switch...there's 2 terminals on the switch.
should be reading between pin 3 and standby switch 40 ohms.

The other side of the switch is 2.02M ohm to pin 3 on one and 2.04Mohm pin 3 on the other

 

[Amp Mad Scientist]

The other side of the switch is 2.02M ohm to pin 3 on one and 2.04Mohm pin 3 on the other

OK looking at the schematic...standby......

 

[Amp Mad Scientist]

I had given the wrong measurement above, it was 81.7ohm, sorry
Pin 3 to one side of the standby is 2.33Mohm from each socket

Do you have a little tiny fuse on the printed circuit board that is labeled "F4?"

 

[Clockworkmike]

Do you have a little tiny fuse on the printed circuit board that is labeled "F4?"

Yes sir, looking at it now

 

[Amp Mad Scientist]

Yes sir, looking at it now

Does it read 1 ohm or less + 2 ohms meter error? = 3 ohms total.
Black probe on one side of the fuse, red probe on the other side of the fuse.

 

[Clockworkmike]

Does it read 1 ohm or less + 2 ohms meter error? = 3 ohms total.
Black probe on one side of the fuse, red probe on the other side of the fuse.

2.6ohms , fluke is supposed to be getting back to me for a calibration issue. It reads fine on certain components, off on others. Voltage measurements are right it seems but resistance is wonky

 

[Amp Mad Scientist]

2.6ohms

OK
measure 1 side of the fuse to pin 3 on the output socket and it should be 40 ohms.
Then measure the other side pin 3 to the fuse and it should be 40 ohms.

 

[Clockworkmike]

OK
measure 1 side of the fuse to pin 3 on the output socket and it should be 40 ohms.
Then measure the other side pin 3 to the fuse and it should be 40 ohms.

43ohms, 3ohm error

 

[Amp Mad Scientist]

43ohms, 3ohm error

OK
Now measure with the ohm meter between pin 8 of the output tube socket and ground.
Now measure between pin 1 of the output tube socket and ground.
Do this for both sockets and write down the readings.

 

[Amp Mad Scientist]

Will be back in 10....smoke break of the unusual kind.

 

[Clockworkmike]

OK
Now measure with the ohm meter between pin 8 of the output tube socket and ground.
Now measure between pin 1 of the output tube socket and ground.
Do this for both sockets and write down the readings.

Socket 1 pin8: 14.3 ohm
Pin 1: 14..3ohm
Socket 2 pin 8: 14.3ohm
pin 1 : 14.3ohm

 

[Amp Mad Scientist]

Socket 1 pin8: 14.3 ohm
Pin 1: 14..3ohm
Socket 2 pin 8: 14.3ohm
pin 1 : 14.3ohm

Are there 2X 500ma fuses on the back of the amp?
Push and turn the fuse cap with a screw driver test the fuses.

 

[Clockworkmike]

Are there 2X 500ma fuses on the back of the amp?
Push and turn the fuse cap with a screw driver test the fuses.

Just the one, its good