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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 1:19 am
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BMW2002Ti wrote:
Looks like you have no current running through the cathode of the 12AT7 phase inverter. :(

+1

Pins 3 and 8 have 4 times too much voltage, the 12AT7 do not work properly.
upnorth2, check your wiring you may do a mistake.

Are the filter caps under the dog house send the right voltages at the right circuits ? Check wiring .


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 2:10 am
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My mistake. The 12AT7 position is shifted over. What I was looking at was the 12AX7 for the vibrato/tremolo. Which was turned off. Sorry! :oops:


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 2:18 am
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BMW2002Ti wrote:
My mistake. The 12AT7 position is shifted over. What I was looking at was the 12AX7 for the vibrato/tremolo. Which was turned off. Sorry! :oops:



If you are looking the wrong tube, you where right when you said;

"Looks like you have no current running through the cathode of the 12AT7 phase inverter."
______________________

With 94 volts at 12AT7 cathodes, tube not working =low output power.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 6:21 am
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Regarding the PI cathode, + 77v is correct according to the schematic. Mine is at + 94v.

There's no filter board, I'm using a multi can cap - 40/20/20/20 for filtering. B+2 is daisy chained this way:

Reverb transformer > LDR > choke/6V6 screens > B+2.

UN


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 6:44 am
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upnorth2 wrote:
Regarding the PI cathode, + 77v is correct according to the schematic. Mine is at + 94v.

UN


You are right I read 17 volts :oops: :(


It is 77 volts on schematic.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 6:56 am
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All voltages are not too bad IMO .

Check all the circuit ; wiring resistor and capacitor from the input to the output if you do a mistake or forget something.
Check for a bad solders.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 3:18 pm
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Checked everything, it's all good as far as the wiring is concerned. I measured the 1 meg audio pots (nothing attached) and they drop off super slow until you get to about 7 on the dial. Close to 1M at zero and about 800K at 7 or so. A linear pot will help.

After being biased correctly I have a 120Hz hum (Bb on my guitar, thanks BMW2002Ti) when the volume is turned up with nothing plugged in so I'll try some other grounding ideas.

UN


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 5:21 pm
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Most grounding loops are between the low voltage area (guitar input) and the high voltage area (PSU). These areas create the biggest ground voltage differential. And hum injection.

Good luck! These things can be a pain and take a lot of patience.

:)


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 8:08 pm
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I moved a couple of grounds around, moved the cathode grounds from the preamp away from the PT to the middle of the chassis and that got rid of the hum. Seems like it solved the volume issue also (don't know why, bad ground maybe). First time I've tried a new production Accutronics tank, reverb is a bit much. Think I'll put an 12AU7 in to calm it down some. Anyway, the amp sounds pretty darn good now.

Thanks for all the help everyone, I really appreciate it. Maybe I'll post a clip when I can.

UN


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 8:13 pm
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I don't see the 1 Meg resistors on either of the input jacks. Maybe its hidden on the normal channel by the jack, but the vibrato channel doesn't show one either.
That could fit the symptom.


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Post subject: Re: Deluxe Reverb Build Help
Posted: Thu Apr 13, 2017 11:39 pm
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upnorth2 wrote:
Think I'll put an 12AU7 in to calm it down some.


That's pretty low-gain for a reverb driver -- try a 12AY7 instead.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 8:43 am
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The 1 megs are there, just can't see em' in the picture. Here's a few photos of the finished product. The Tele is a pinecaster I built over the winter.

UN


Image

Image

Image

Image


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 10:23 am
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Did you also build the chassis? That really looks great!


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 10:47 am
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I still don't see the 1Megs in your second iteration. Nice caps, though.
But I'm also looking at the Black ground buss wire. These are common in the kits, but are very unFenderish. Mostly ground wires were soldered directly to the chassis or a brass ground plate. Since this takes a powerful iron, most kits use this buss method.
I have found it problematic in the kits I have built. I have cut the ground buss to isolate V1 and V2 grounds. I hooked that buss end to the input jacks and all the hum went away.
As to the low relative volume, the two things I wonder about is what value do you have for the feedback resistor and what brand output transformer do you have?


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Post subject: Re: Deluxe Reverb Build Help
Posted: Fri Apr 14, 2017 11:24 am
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Bill Moore wrote:
Did you also build the chassis? That really looks great!



Look all kit to me, not hand made.


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