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Hoffman Amps Forum image Author Topic: Stout kit cuts out at high volume  (Read 2329 times)

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Offline 6v6Pin1

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Stout kit cuts out at high volume
« on: July 09, 2015, 09:39:02 pm »
I just finished a stout amp and when I turn it up all the way it starts cutting out. From reading, I gather this is parasitic oscillation.
I was hoping someone could give me some things to check.

I checked my voltages against the schematic (I disconnected the feedback resistor):

v1
1: 191.0
3:     1.8
6: 198.0
8:     1.8

v2
1: 275.0
2:     0.0
3:     8.2
6: 289.0
7:     0.0
8:     8.2

v3
3:   10.8
7: 297.0
9: 304.0

v4
3:   10.8
7: 297.0
9: 304.0

Caps
A: 310
B: 308
C: 285
D: 278

Offline markmalin

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Re: Stout kit cuts out at high volume
« Reply #1 on: July 10, 2015, 03:43:21 pm »
Can you post some pictures of the inside?


Mark.
"... there are Flying V's and then there are the ones shaped like peanuts..."  - my son at age 9

Offline EL34

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Re: Stout kit cuts out at high volume
« Reply #2 on: July 10, 2015, 05:41:55 pm »
Hard to say
Your voltages are different from mine here
http://el34world.com/Hoffman/files/Hoffman_Stout.pdf


What power transformer are you using?

Offline 6v6Pin1

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Re: Stout kit cuts out at high volume
« Reply #3 on: July 16, 2015, 12:30:38 pm »
I finally figured out that I made a mistake wiring the lugs together. The v2 voltages were way out of line and that was the clue. I fixed that and the amp sounds great now.

The transformers are by Hammond for an 18w Marshall.

Offline Willabe

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Re: Stout kit cuts out at high volume
« Reply #4 on: July 16, 2015, 01:49:06 pm »
I finally figured out that I made a mistake wiring the lugs together. The v2 voltages were way out of line and that was the clue.

Good reasoning! 

I fixed that and the amp sounds great now.


              :bravo1:   

 


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