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Hoffman Amps Forum image Author Topic: V2 tube in blues junior conversion  (Read 1171 times)

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Offline playindabluz

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V2 tube in blues junior conversion
« on: February 05, 2025, 06:34:55 am »
I completed the Hoffman blues junior conversion. this is my 16th amp build. I am running a 12AY7 in v1 and a 12AT7 in V3. Using a 5751 or 12AX7 in V2 the amp is fine. If I try a 12AY7 in V2 the amp is silent. I have tried several new and NOS 12Ay7 in V2 to no avail.  Is this normal?

Offline acheld

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Re: V2 tube in blues junior conversion
« Reply #1 on: February 05, 2025, 10:30:58 am »
Quote
If I try a 12AY7 in V2 the amp is silent.

Not normal, but seems unlikely. I'm assuming you've got the MV up . . .

Suggest scoping the input to the MV pot.  I suspect you'll see a signal present.

My experience with that circuit suggests that you need higher mu at that position, ie either a 12AX7 or a 5751.


Offline Latole

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Re: V2 tube in blues junior conversion
« Reply #2 on: February 05, 2025, 12:01:06 pm »
Not normal, at all 12AY7 must work .

Offline playindabluz

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Re: V2 tube in blues junior conversion
« Reply #3 on: February 07, 2025, 06:25:14 am »
Thank you gentlemen.  Yes, the master is dimed. I don't have a scope with me at the moment. I'll check that out at work next week. But AX7 and 5751 work great!

Offline stratomaster

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Re: V2 tube in blues junior conversion
« Reply #4 on: February 13, 2025, 06:41:31 pm »
My money is on a dead tube.

What do the plate and cathode voltages look like?

 


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