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Hi all,

Channel one isn't passing signal, but channel two seems fine. More detective work. Here are my voltages. Some seem right on the docs, some are off by a bit. I don't know how much variation is cool, anybody see anything significant?

Thanks

Mains: 110.8 VAC!!!! It's very hot here and the utility must be struggling

EF 86:
Pin 1: 69.7
Pin 3: 1.6
Pin 6: 115.3
Pin 8: 1.6

12AX7 - 1:
1: 133
3: 1.17
6: 133
8: 1.17

12AX7 - 2:
1: 156.9
3: 1.18
6: 256.7
8: 157

12AX7 - 3:
1: 234.2
3: 61.8
6: 238.5
8: 61.8

EL84 - 1:
3: 7.3
7: 326

EL84 - 2:
3: 7.26
7: 321

5AR4:
8: 331

Here are pictures of my input jacks - clearly there's something wrong but I'm not seeing it. They're oriented with the terminals pointing away from the transformer end of the chassis and they're upside down - Lo is on the top and Hi is on the bottom in the pictures. What am I doing wrong? Thanks.

EF86 channel input jacks:



12AX7 channel input jacks

Actually jacks look fine. Voltages are within range.

You should be getting something out of both channels. So the EF86 channel is Ch. 1 and it's not passing signal?


Check continuity from input jack. Plug in a cable and measure from tip of cable to 68K grid resistor.
If OK, turn on amp, touch end of cable with finger - any sound?
With the volume low, carefully touch pin 9 of the EF86 with a small screwdriver and see if you get a pop.


Is the contour switch hooked in correctly?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks Stephen. I'll do more checking today.

The problem was that there were shorts in the coax cables from the jacks to the grid resistors. I must have nicked the conductors when I prepared them or overheated them. I redid them and everything tests fine now. I can't fire up the amp again because we're having electrical storms and the power is blinking on and off. As they say, if you don't like the weather in New England, just wait.

Now, that's a pretty rare one! Keep us posted.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Stephen, actually that's not rare at all, especially with the RG 174. That stuff will melt fairly easily if you're not used to it, and it looks like it did from the pictures.
Good question... How are people shrinking their heat shrink? A good heat gun is fairly expensive for the average weekend amp builder, so what are some alternatives? My rule of thumb for the guys at work is "if it's too hot for your fingers, then it's it's too hot for the wire". Hold it in your fingers while you heat it. You'll never over heat the wire again! Also, keep moving the heat source quickly around the heat shrink while you shrink it. You need to shrink all sides!

Run for your lives!!! Another "Resource" topic!!!!

Joe G

_________________
Some assembly required,
Brain sold separately...

I haven't been able to test the amp out because my power went out literally five minutes after my last post and just came back on. There's nothing more helpless than an electronic musician with no electricity. I have a good Master heat gun that I've had for many years, but even on the lowest setting it's still easy to overheat stuff if I'm not careful.