New Build: Ceriatone Replica OTS 50W

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martin manning
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Re: New Build: Ceriatone Replica OTS 50W

Post by martin manning » Sun Jun 18, 2017 2:23 pm

dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
The red wire going into the 150k 2w resistor is its power source
Ah, good, you're thinking beyond paint-by-number.
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
I think I have this wired up correctly but the layout and my brain seem to conflict for some reason.
What you have there looks good to me.
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
Is there anyway to test that the Switched FET Jack and NOR jack are acting properly before I go on?
Of course. Any unused input is grounded, and should measure zero ohms to ground. Any input in use should show a high resistance to ground, 1M for normal, 3M for the FET. Any input in use should show zero ohms to the input grid (or gate). The FET stage output is also grounded when it is not in use.
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
I am also a bit confused on the layout (areas circled) especially the Green line and A reference on the NOR jack. Can someone clear that up for me?
The green wire is the shield on the coax "A" going to V1a's grid.

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Sun Jun 18, 2017 4:33 pm

martin manning wrote:
Sun Jun 18, 2017 2:23 pm
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
The red wire going into the 150k 2w resistor is its power source
Ah, good, you're thinking beyond paint-by-number.
I still don't quite understand where the voltage is coming from. Is it off the relay board?
martin manning wrote:
Sun Jun 18, 2017 2:23 pm
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
I am also a bit confused on the layout (areas circled) especially the Green line and A reference on the NOR jack. Can someone clear that up for me?
The green wire is the shield on the coax "A" going to V1a's grid.
So are all the circled areas expecting coax wiring?

Thanks again Martin!
Coax Wiring.png
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martin manning
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Re: New Build: Ceriatone Replica OTS 50W

Post by martin manning » Sun Jun 18, 2017 4:59 pm

dwietzel wrote:
Sun Jun 18, 2017 4:33 pm
I still don't quite understand where the voltage is coming from. Is it off the relay board?
It comes from the last node on the high voltage rail... follow it back upstream.
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
So are all the circled areas expecting coax wiring?
Yes, and note only one end of the shield is grounded on those runs.

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Sun Jun 18, 2017 5:41 pm

martin manning wrote:
Sun Jun 18, 2017 4:59 pm
dwietzel wrote:
Sun Jun 18, 2017 4:33 pm
I still don't quite understand where the voltage is coming from. Is it off the relay board?
It comes from the last node on the high voltage rail... follow it back upstream.
dwietzel wrote:
Sat Jun 17, 2017 8:37 pm
So are all the circled areas expecting coax wiring?
Yes, and note only one end of the shield is grounded on those runs.
Is this the right coax wire I need? First time to use coax for me https://www.amplifiedparts.com/products ... -stranding

So if I am getting this right whether I plug into NOR or FET both exit point A on the normal channel. Looks like the FET goes through the boost then back to the jacks and flows to the NOR jack back through point A. Is that right?

And then on the A end by the socket, is the 22K resistor the RF filter? On my other builds the first things after the jack on my Deluxe Tweed and Bassman was a 68K RF resistor filter.

Thanks Martin for all the great information!

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norburybrook
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Re: New Build: Ceriatone Replica OTS 50W

Post by norburybrook » Sun Jun 18, 2017 6:07 pm

yes that cable looks fine. It's basically a shielded cable to help with possible noise/oscillation issues. You attach the braided shield at the pot end ground along with the center conductor in it's prescribed place, the other end you just fold the braid back and put some heat shrink over it and just connect the center.


The voltage comes from the last B+ node (the node of the two plate resistors for V1 220k and 150k) it come in there from the power board and straight out to the FET.

actually looking at their diagram it goes from V2 to the separate power cap on the side back to V1 and the FET.


M

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martin manning
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Re: New Build: Ceriatone Replica OTS 50W

Post by martin manning » Sun Jun 18, 2017 9:52 pm

dwietzel wrote:
Sun Jun 18, 2017 5:41 pm
Is this the right coax wire I need? First time to use coax for me https://www.amplifiedparts.com/products ... -stranding
Yes, that will work.
dwietzel wrote:
Sun Jun 18, 2017 5:41 pm
So if I am getting this right whether I plug into NOR or FET both exit point A on the normal channel. Looks like the FET goes through the boost then back to the jacks and flows to the NOR jack back through point A. Is that right?
Correct.
dwietzel wrote:
Sun Jun 18, 2017 5:41 pm
And then on the A end by the socket, is the 22K resistor the RF filter? On my other builds the first things after the jack on my Deluxe Tweed and Bassman was a 68K RF resistor filter.
Yes, but the 22k resistor (commonly called a grid stopper) is not a filter by itself, it combines with the effective input capacitance of the stage to form a low-pass filter.

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Mon Jun 19, 2017 2:26 pm

Thanks Martin and norbury.

Could anyone suggest a good stripping tool for this size of coax? https://www.amplifiedparts.com/products ... -stranding

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Mon Jun 19, 2017 3:14 pm

martin manning wrote:
Sun Jun 18, 2017 9:52 pm
dwietzel wrote:
Sun Jun 18, 2017 5:41 pm
And then on the A end by the socket, is the 22K resistor the RF filter? On my other builds the first things after the jack on my Deluxe Tweed and Bassman was a 68K RF resistor filter.
Yes, but the 22k resistor (commonly called a grid stopper) is not a filter by itself, it combines with the effective input capacitance of the stage to form a low-pass filter.
So I googled guitar cable capacitance would be about 30 picofarads per foot. So assuming a 10 ft. cable calculates a low pass at

Enter the Resistance, R: 22K
Enter the Capacitance, C: 300 picofarads
Frequency: roughly 24 KHz

Is this what you mean?

Thanks
Low-pass-filter-diagram.png
cut-off-frequency-formula.png
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martin manning
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Re: New Build: Ceriatone Replica OTS 50W

Post by martin manning » Mon Jun 19, 2017 3:55 pm


dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Mon Jun 19, 2017 4:16 pm

martin manning wrote:
Mon Jun 19, 2017 3:55 pm
No, this: http://www.valvewizard.co.uk/gridstopper.html
Thanks! Such a great explanation.

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drew
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Re: New Build: Ceriatone Replica OTS 50W

Post by drew » Mon Jun 19, 2017 11:12 pm

dwietzel wrote:
Mon Jun 19, 2017 2:26 pm
Thanks Martin and norbury.

Could anyone suggest a good stripping tool for this size of coax? https://www.amplifiedparts.com/products ... -stranding
If you were going to be working with this stuff all day long, buying a special tool might make sense. But if you're only going to need to prepare a few lengths of cable, use a single edge razor blade, your pocket knife from when you were in Cub Scouts, or any other sharp thing you have laying around. Lightly score around the outer rubber and try not to go deep enough that you're slicing into the braid. You can pick apart/unbraid the braid with a pin, dental pick, etc. And strip the inner wire with your normal wire stripper.

If you want to see some nice shielded cable work, read the first couple pages of this thread: viewtopic.php?f=5&t=4084 . The author, funkaliciousgroove, is now Mr. Bludotone, amp-maker to the stars.

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norburybrook
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Re: New Build: Ceriatone Replica OTS 50W

Post by norburybrook » Tue Jun 20, 2017 8:59 am

drew wrote:
Mon Jun 19, 2017 11:12 pm
dwietzel wrote:
Mon Jun 19, 2017 2:26 pm
Thanks Martin and norbury.

Could anyone suggest a good stripping tool for this size of coax? https://www.amplifiedparts.com/products ... -stranding
If you were going to be working with this stuff all day long, buying a special tool might make sense. But if you're only going to need to prepare a few lengths of cable, use a single edge razor blade, your pocket knife from when you were in Cub Scouts, or any other sharp thing you have laying around. Lightly score around the outer rubber and try not to go deep enough that you're slicing into the braid. You can pick apart/unbraid the braid with a pin, dental pick, etc. And strip the inner wire with your normal wire stripper.

If you want to see some nice shielded cable work, read the first couple pages of this thread: viewtopic.php?f=5&t=4084 . The author, funkaliciousgroove, is now Mr. Bludotone, amp-maker to the stars.
yes....no need for special tools, a sharp knife is perfect, practice on a few bits first to get the feel, it's a good skill to have as it's the same technique when making mic/guitar cables.

Marcus

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Tue Jun 20, 2017 2:32 pm

norburybrook wrote:
Tue Jun 20, 2017 8:59 am
drew wrote:
Mon Jun 19, 2017 11:12 pm
dwietzel wrote:
Mon Jun 19, 2017 2:26 pm
Thanks Martin and norbury.

Could anyone suggest a good stripping tool for this size of coax? https://www.amplifiedparts.com/products ... -stranding
If you were going to be working with this stuff all day long, buying a special tool might make sense. But if you're only going to need to prepare a few lengths of cable, use a single edge razor blade, your pocket knife from when you were in Cub Scouts, or any other sharp thing you have laying around. Lightly score around the outer rubber and try not to go deep enough that you're slicing into the braid. You can pick apart/unbraid the braid with a pin, dental pick, etc. And strip the inner wire with your normal wire stripper.

If you want to see some nice shielded cable work, read the first couple pages of this thread: viewtopic.php?f=5&t=4084 . The author, funkaliciousgroove, is now Mr. Bludotone, amp-maker to the stars.
yes....no need for special tools, a sharp knife is perfect, practice on a few bits first to get the feel, it's a good skill to have as it's the same technique when making mic/guitar cables.

Marcus
OK...thanks for the feedback. But you know some people should just not play around with knives :-) Remember this?
http://www.nbc.com/saturday-night-live/ ... 8667?snl=1

dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Tue Jun 20, 2017 7:05 pm

Charlie Wilson wrote:
Fri Mar 03, 2017 7:26 pm
Also, your layout is for a high plate Skyliner. You could look at the schematic for 124 and swap in the higher plate loads, cathode values, and OD trim and drive.
CW
Bumping this post to the top. Charlie is this the right schematic to look at?
ods-124-schematic.jpg
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dwietzel
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Re: New Build: Ceriatone Replica OTS 50W

Post by dwietzel » Fri Jun 23, 2017 1:45 pm

Maybe I will try a different approach to my last question. In my last build (Bassman) it was taught to me from another amp builder who checked it out for me that he would have done the grounding much different than I had. I have read several articles but the light bulb just has not gone off yet.

Is there a particular grounding scheme that most follow on this type of build?

Would appreciate any guidance. Thanks!

Dave

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