Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rosincore on February 06, 2016, 02:40:33 pm
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All done for today, ran out of parts... need the power tranny and I could fire this up.
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Looks nice. Is this a single channel AB763 in a PR chassis?
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Yeah, very nice! :icon_biggrin:
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It's looking mighty fine!
Only one question. You've got the purple and yellow wires going over your heater wires and all the rest under, what's up with that?
I don't think that will cause you any problems, I was just wondering.
Was it because you connected those after wiring up the heaters?
Why the deviation from the established pattern? :dontknow:
You have such a pretty build going, reminds me of mscaggs work. :worthy1:
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Yes, one channel, no trem , phase inverter and output section. I got the bare board from Doug and drilled my own and installed his turrets with my tiny jewelers drill press. Worked like a charm....
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Just the way it turned out as far as the heater wires and the wires above them. .... wanted to try something different. I will look at it some more and decide if I want to keep it like that.
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Only one question. You've got the purple and yellow wires going over your heater wires and all the rest under, what's up with that?
Same reason as; Why did the chicken cross the road, to get to the other side. :icon_biggrin:
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Thank for the comment. I think I have a touch of OCD maybe. I like things organized...lol
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Thank for the comment. I think I have a touch of OCD maybe. I like things organized...lol
Ok, then you will probably make yourself redo those wires even though you don't need to. :l2:
That comment was not meant to criticize your work, it looks outstanding. :worthy1:
It's like all the other chickens took the tunnel beneath the road to get to the other side,
and those two chickens decided not to for some reason. :w2:
I guess those two are roosters. :laugh:
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Well, you were correct, I stood there and looked at them and changed them...lol. Thanks guys...... Updated jpg attached
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And they are yellow like the rest of the wires now.
Very nice work! :icon_biggrin:
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Thank you.
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Well, you were correct, I stood there and looked at them and changed them...lol. Thanks guys...... Updated jpg attached
The pair of yellow wires from phase inverter coupling caps to pin 5 of the output tubes should probably be dressed down next to the chassis.
Right now they run over the heater wires, and for a stretch are parallel to the heater wires. This may not cause a problem, or it might transfer hum from the heater wires right to the output tube grids (you won't know for sure until you fire it up).
The existing twisting may/may not alleviate the risk of hum, but the other part of the equation you can attack is distance. A.C. coupling reduces as the square of distance, so any added space you put between those pairs of wires (heater & grid) will improve your odds of avoiding coupling hum into the output tube grids.
Read "A.C. coupling reduces as the square of distance" to mean:
- Wires a distance of 1 unit apart = 1 unit of hum-coupling
- Wires a distance of 2 units apart = 1/4 unit of hum-coupling
- Wires a distance of 3 units apart = 1/9 unit of hum-coupling
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One other thing I learned running audio wires as an A/V tech (many moons ago), is that if you MUST cross an audio line over a power line, do it at exactly a 90 degree angle. That helps in a significant way in noise cancellation. The same goes here I'm sure. I've always tried, when I had no choice, to run all signal wires directly across the power lines as perpendicular as possible.
I'm sure almost everyone here knows that, but just in case someone didn't ;)
~Phil
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Thanks for the info guys. This will get it fired up and depending on what I hear it may look completely different there when I am satisfied. I took Doug's idea and converted an old Radio Shack 70V amp to use on the bench. You can check your signal from the input jack right to the speaker out and find any little noise you are looking for, simple .1 Orange Drop to stop the DC from coming in to the chain-checker--- Thats what I do, input jack, at the tube, #6 pin on tube out to the coupling cap, right to the input coupling cap of the PI, follow through both sides now of the PI, finally hit the speaker out, turn volume down first on your chain-checker cause by this time gain has been amplified twice and it will distort the little amp.
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Not much of a football guy so I went to the bench just to look and I saw something and it worked. I rerouted the twisted pair so it's all in the clear now. It pays to walk away and come back later.
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It is all OCD squared away now! :icon_biggrin:
Very nice work! You are starting to give mscaggs a run for his money. :worthy1:
He's got some Teflon tubing he puts on his leads.
That might help to avoid accidental shorting between components.
If you are clumsy like me, and accidentally drop metal items in your powered up amps. :blob8:
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The tranny arrived in the mail, installed and connected to the dim bulb. Wouldn't light the bulb at all till I put the 6L6's in and then dim. Checked whole circuit from input jack to speaker jack with the little circuit checker amp---just fine, even though it was running through the bulb it amplified the guitar. Pulled the power tubes back out, and plugged directly to 120V pre-amp works as it should, PI works as it should. Put the power tubes back in and fired back up-----sounds just like a Fender...success !!
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Very, Very nice work! :bravo1:
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Thank you. Mojo cabinet ordered with aged grill cloth, and working with them on the faceplates.
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Finally connected to a speaker in a cabinet after running for 5 or 6 hours into a dummy load. First instrument to get plugged in=Fender strat, so nice, sounds just marvelous and is very quiet . Now waiting on the faceplates and the cabinet.
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Couple of shots while in the cradle running into a dummy load.
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Other end of chassis.