JMI AC30/6 NO SOUND

[Travis8]

No volts between 9 and 4/5

[Travis8]

So have you got any decent HT voltage anywhere in the preamp chassis? eg on the big filter caps.

Nothing :/ I try some Big caps

[Travis8]

All valves and lamp turns on but not HT :/

[Stevem]

If the tubes are lighting up then you DO have voltage between preamp tube pins 4 and 5 which are jumped together and then pin 9, but that AC voltage, not D.C. Voltage like your testing on the other pins on the tubes!

I don't want to sound mean, or cut you down, if you don't know this simple basic detail then a can't see how when you introduce yourself here that you posted / stated that you build amps I am sorry to say.

[Travis8]

Everyone can make a mistake, I build some amps but I had a mistake now XD

Sorry you are right, it's voltage between 9 and 4/5 (6.40volts)

[pdf64]

All valves and lamp turns on but not HT :/

OK, you'll have to see what's going on inside the power amp chassis.
There may be a problem around the rectifier or the choke.
What are the VDC on the can cap terminals?

[Travis8]

http://www.pisotones.com/Alfonso/JMI/3495.jpg

Ok, I will check there.

[sluckey]

You forgot to connect the rectifier tube pin 8 to the filter caps! That explains no high voltage.

EDIT... Looks like the HT fuse is mistakenly connected to rectifier pin 4. Should connect to pin 8.

[Travis8]

This is my ones

https://drive.google.com/file/d/11OB8En ... p=drivesdk

https://drive.google.com/file/d/11NkxC5 ... p=drivesdk

[Travis8]

You forgot to connect the rectifier tube pin 8 to the filter caps! That explains no high voltage.

EDIT... Looks like the HT fuse is mistakenly connected to rectifier pin 4. Should connect to pin 8.

It was working without problems with this wiring

[sluckey]

Really! That would mean the PT yellow wires are the high voltage wires and the PT red wires are the 5 volt wires. That's a very unusual color code for a PT.

[Travis8]

Really! That would mean the PT yellow wires are the high voltage wires and the PT red wires are the 5 volt wires. That's a very unusual color code for a PT.

Yes! How can I check if the problem is the choke or the rectifier?

[sluckey]

Measure the DCV on pin 8 of the rectifier. Then measure the DCV on each choke lead.

But first, check the HT fuse.

[Travis8]

Fuse it's okey, pin 8 of rectifier 0.640 vdc

[sluckey]

Measure resistance from pin 8 to chassis with power off. Should be very high.

Can you see the rectifier filament glowing?

Measure the ACV from pin 4 to chassis. Looking for approx. 300VAC.
Measure the ACV from pin 6 to chassis. Looking for approx. 300VAC.

Measure ACV ***BETWEEN*** pin 2 and 8. (This means one probe on pin 2 and the other probe on pin 8.) Looking for approx. 5VAC.