SVT-VR bias issue

[Gregg]

Hi,

Do you have the PSU schematic as well?

[Enzo]

Power transformers burn up when copmponents they serve fail.

Perhaps the song in question has a loud passage and a big transient is generated which aggravates an arc somewhere.

[lowell]

thanks guys.

[catstrat]

Ampeg

I'm having the same problems with an SVT AV. The bias LEDs don't work at all. I found 3 of the screen resistors open so i replaced all 6 with 3 watt resistors. I need to check the grid resistors as suggested. However i checked the good screen resistors i removed and they seem to check upwards of 200 ohms. All the schematics i've seen for the SVT show 22 ohm resistors for the screens. Should they be 22 ohms or 200 ohms? Somebody "hep" me.

[lowell]

The schematic for SVT-VR is 220ohm screen resistors, 1/2watt.

[catstrat]

220 ohm screen resistors. That explains alot. However i did try 220 ohm screen resistors and the amp raised hell with crackling and humming.The original resistors i removed had the color codes so badly faded i really couldn't tell what they were. There seems to be so many different SVTs on the market now days i can't keep them all sorted out.I sometimes question the people at Loud technologies because they tell me the output stage of an SVT 2 pro is the same as CL or an AV SVT. Can somebody tell me if this is true or is Loud Technologies off base on this one?

[Enzo]

The power amps in the SVT-AV and SVT-CL are the same.

[lowell]

Ok so finally got a power transformer from Ampeg and threw it in the other day. I also replaced a bad filter cap for preamp supply and 2 power tubes. The amp is back up and running. The only issue I'm having is that the orange led for the balance adjustment on the back is not functioning correctly. I biased the 2 green leds to turn on and the orange led is ALWAYS on regardless of signal or no signal. Any clues anyone? Also any response to my previous post to this one in regards to a pedal overloading an amp?

[Enzo]

Are you SURE the 12AU7s are in the right sockets? Are you sure they are good?

[lowell]

yes they are in right sockets for sure. are they good? would I still be able to set green bias leds if they were not good?

[Enzo]

Quite possibly, yes. I sometimes find the red and green coming on together or even the red one coming on first.

[BassManJon]

SVT-VR Power Supply Schematic

Lowell, I really appreciate the schematics you have posted. By any chance, do you have the Power Supply page for the SVT-VR ?

[lowell]

hey sorry but that's all i got... you could call or email Ampeg they should get it to you.