Vibrochamp - choke?

[angelodp]

On the choke placement. Do I pull the jumper between the 44uf cap ( parallel 22uf ) and the 1k 2w Resistor and insert there. The 1k stays is that right.

Thanks


[IMG868]http://i260.photobucket.com/albums/ii9/angelodp1/VibroChamp-1801-build-plan_zpsb792994b.jpg[/img]

[Stevem]

In that schematic the .1 is not taken off a center tap point though!

[Leo_Gnardo]

1. If you want to use your filter choke in the "traditional" manner, for the screen grid supply on down, substitute it for the first resistor in the hi voltage supply.

2. If you want to have a "pre-filter" as I suggested, pull the jumper between your paralleled 22 uF primary filters + points, and wire in your choke there. Run the OT + from what's now the second filter node. All else stays the same.

3. Off topic but I have to say I'm not to thrilled to see output and rectifier tubes jam up behind the controls. You'll be lucky to not have some objection from the amp as buzz, hum, and/or hi frequency feedback squeal. Most layouts keep rectifiers & output tubes & their wiring away from input and low-signal zones for this reason. If you haven't already committed to building according to your layout, I'd suggest a re think and place your circuits accordingly.

Short wiring runs between your preamp/EQ and controls will help keep hum pickup to a minimum.

If you have already built with this layout, and you find noises from proximity of rectifier & output to controls, you might try to shield your control area and wiring with a grounded sheet of copper or brass.

Although you've made a great looking layout drawing, I'm having a hard time seeing the .1 stevem mentioned.

If you're trying the Ampeg filament trick, and have no filament center tap, you can make a virtual CT from a pair of matched resistors. 100 ohms is the most popular value but anything from 75 to 270 will work fine. Resistors in series from one side of the filament line to the other, then you can ground the junction of the 2 resistors directly OR connect that junction to a 0.1 uF cap and the other lead on that cap goes to ground. Whichever way gives you the least hum, leave it that way.

[angelodp]

1. If you want to use your filter choke in the "traditional" manner, for the screen grid supply on down, substitute it for the first resistor in the hi voltage supply.

Is this instance the I would loose the 1k resistor.

2. If you want to have a "pre-filter" as I suggested, pull the jumper between your paralleled 22 uF primary filters + points, and wire in your choke there. Run the OT + from what's now the second filter node. All else stays the same.

Ok I see that.

3. Off topic but I have to say I'm not to thrilled to see output and rectifier tubes jam up behind the controls. You'll be lucky to not have some objection from the amp as buzz, hum, and/or hi frequency feedback squeal. Most layouts keep rectifiers & output tubes & their wiring away from input and low-signal zones for this reason. If you haven't already committed to building according to your layout, I'd suggest a re think and place your circuits accordingly.

Yes I can see that. The idea was to use the existing chassis with the sockets in place. I might just rearrange things if i do get a noisy build.

Short wiring runs between your preamp/EQ and controls will help keep hum pickup to a minimum.

If you have already built with this layout, and you find noises from proximity of rectifier & output to controls, you might try to shield your control area and wiring with a grounded sheet of copper or brass.

So a sheet of copper about 2" x 8" placed in between the tube sockets and the pots might work. I would run a chassis ground to the sheet.

Although you've made a great looking layout drawing, I'm having a hard time seeing the .1 stevem mentioned.

I do not understand the .1uf idea. This transformer does have a center tap and the filament wires are set up with that center tap. In the layout the blue wire near the white/red wire is that center tp for the heaters.

If you're trying the Ampeg filament trick, and have no filament center tap, you can make a virtual CT from a pair of matched resistors. 100 ohms is the most popular value but anything from 75 to 270 will work fine. Resistors in series from one side of the filament line to the other, then you can ground the junction of the 2 resistors directly OR connect that junction to a 0.1 uF cap and the other lead on that cap goes to ground. Whichever way gives you the least hum, leave it that way.

[angelodp]

I managed to find the specs on the choke that was in this build. Very low henries so I suspect that this will not be a good coke to use? Is that correct.

[IMG:791:1024]http://i260.photobucket.com/albums/ii9/angelodp1/1801-choke-1_zps40136606.jpg[/img]

[IMG:791:1024]http://i260.photobucket.com/albums/ii9/angelodp1/1801-choke-2_zps6f82c179.jpg[/img]

[angelodp]

Maybe my downloaded spec sheet was tough to read. The choke that was in the doner build seems to be at .025 henrys. I take it that would not be so useful.

[matt h]

(deleted)

[angelodp]

Matt, take a look at the schematic on pg 1. That represents the original build. It was an amp used in a film editing system. Are you able to see the dos that has the specs on it. I see a .025H on there.

[matt h]

(deleted)

[angelodp]

It does appear to be a power supply choke, I was hoping you could look at the schematic and confirm what I am seeing.

[matt h]

(deleted)

[angelodp]

No worries. So even at the low H it might be useful, easy enough to try it I suppose.

Thanks

[matt h]

(deleted)

[tele_player]

It should be noted that the formula for calculating an appropriate inductance in a capacitor input filter uses the capacitance value as one of its terms. Different caps would need a different choke.

It's probably harmless, but might not be very effective. I'd probably just stick a small Fender choke in there, or a resistor.

-Robert

[angelodp]

MM has this cool idea.

http://www.mercurymagnetics.com/pages/c ... ichoke.htm