Valve junior Humming a tune

flcmcya · 11-22-2008, 05:38 AM

Bought a used version 1 that had been heavily modded..........finally quit working after I tinkered with it some....kept burning up an added resistor ........swapped out the old Pcb with a stock version 1 board that I tweaked a little.....When I fired it up all I got was aloud deep hum and
the OT was way hot to the touch........... Does that sound like a bad OT or
a ground issue somewhere else?

mikeboone · 11-28-2008, 01:42 PM

This may sound silly, but did you have a speaker cab plugged in while you were doing this or was the hum coming from the head cab?

Do you have any type of tone generator and a volt meter? You can check the OT with these two devices by removing the power tube and speaker, then injecting a tone (400Hz will suffice) into the primary. Measure the level of the tone going in and then the level at the secondary. It should be higher, how much higher depends on the ratio.

You need to find out what the ratio of your OT is. For instance if your OT ratio is 20:1, a 1VAC signal at the PRI will be 20VAC.

Can you post a schematic of the changes that were made?

11-22-2008, 05:38 AM	#1
flcmcya Junior Member Join Date: Nov 2008 Location: Twin cities Posts: 2	Valve junior Humming a tune Bought a used version 1 that had been heavily modded..........finally quit working after I tinkered with it some....kept burning up an added resistor ........swapped out the old Pcb with a stock version 1 board that I tweaked a little.....When I fired it up all I got was aloud deep hum and the OT was way hot to the touch........... Does that sound like a bad OT or a ground issue somewhere else?

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11-28-2008, 01:42 PM	#2
mikeboone Senior Member Join Date: Nov 2007 Location: Houma, LA Posts: 169	This may sound silly, but did you have a speaker cab plugged in while you were doing this or was the hum coming from the head cab? Do you have any type of tone generator and a volt meter? You can check the OT with these two devices by removing the power tube and speaker, then injecting a tone (400Hz will suffice) into the primary. Measure the level of the tone going in and then the level at the secondary. It should be higher, how much higher depends on the ratio. You need to find out what the ratio of your OT is. For instance if your OT ratio is 20:1, a 1VAC signal at the PRI will be 20VAC. Can you post a schematic of the changes that were made?

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