D-lator Tutorial step by step as I do it.

[ChrisM]

When you rectify an AC voltage the voltage increases.

You can approximate it by multiplying your AC voltage by 1.414

So 135 doubled is 270V AC.
270V AC x 1.414 = 381.8V DC

[erwin_ve]

By the way, I did read your thread where you built 3 Dumbelators.

Do you recall what your secondary voltages were and your B+ nodes?

http://ampgarage.com/forum/viewtopic.ph ... sc&start=0

Tom, please read: http://ampgarage.com/forum/viewtopic.ph ... highlight=

There's a schematic with 230v on the pt secondary's.
My voltages on B+ are: To recover triode=345v; to cathode follower triode= 268v.

[Structo]

Sweet!

Thanks a lot and Merry Christmas!

Tom

[Funkalicousgroove]

those voltages are WAY too high

[erwin_ve]

those voltages are WAY too high

These are measurements taken at the dropping string. What voltages should I be aiming for? I always thought these were the right ones(after reading many of your posts).

[Structo]

those voltages are WAY too high

Brandon, going by your schematic,
I think I came up with around 255v on pin 1 and 230v on pin 6.

Around 28-31V on pin 3 if using the 27K/1.8K combo.

Is that in the ballpark?

[martin manning]

I think the voltages on the schematic Brandon posted in this thread are a little out.

It appears to be showing the 135VAC rated secondary voltage for the original transformer, which goes with 115VAC on the primary. The node voltages, however, look like they are for a higher line voltage.

If you go with the first dropping resistor shown (15K) and assume a 2.5 mA current draw, "spec" 135VAC secondary voltage would give about 380VAC out of the doubler, and 342V at the first node. A line voltage of 122 and change would match the node voltages on the schematic pretty closely (368V at node 1), with the same current draw assumption.

Without being too rigorous about it, I'd guess the anode voltages are different by around 30V, but both triodes will be operating at about the same quiescent Va-k. Maybe that was the original plan? Some experimenting with the dropping resistor might be in order.

MPM

[Structo]

Yes you are right and since I will be using a PT with higher secondary voltage, I will have to figure out the dropping string.

I am figuring using a bridge rectifier, two 47uf caps, a choke, then the filters and dropping resistors.

Kind of borrowing from the Dumbleator II on that one.

[Structo]

In looking at the schematics and layouts of #124, there seems to be some variation in the way the FX jacks on the amp are wired.

The layout shows the 220K/250pf right on the tip lug of the Send jack.
While the schematic shows the wire from the Master going to the resistor cap combo then to the tip of the Send jack.

Which is the right way and is this network needed on a 50 watt version with a Dumbleator?

It appears that the 220K/250pf is taken out of circuit when there is a cable plugged in to the Return jack.

And by the way, which is the definitive version of the #124 schematic?
I have about 4 or 5 in my files and the versions don't seem to follow any pattern.

Thank you,
Tom

[Structo]

Here is the picture of #124.

If you look at the jack on the left which is the send jack, the brown wire from the Master volume looks like it goes to the Return jack on the switch lug.

So to me it looks like the 220K/250pf goes from the tip of the send jack to the middle lug or switch lug of the Return lug.

I am now thinking the ver. 182 schematic is correct.

The Layout is incorrect.

[Structo]

So I think this is the correct way to wire it like #124 shows.

[bluesfendermanblues]

Tom, a little off topic.......but isn't the 220K/250pf combo meant to be turn the Dumbleator into parallel operation as opposed to the ordinary serial Dumbleator mode??

[Structo]

No I don't believe so.
The way somebody told me how it works is:
that resistor and cap helps with the loading on the PI.
The cap across the resistor is mainly used to keep the low end focused after the signal is amplified in the loop.
It also lowers the impedance helping with the loading on the PI.
It works great w/.022 PI input cap

I haven't personally tried it yet, but if it does those things then I think it is a worth while addition.

I just brought it up because I haven't seen too many mention it and the fact that the layout is wrong compared to the photo of #124.

[bluesfendermanblues]

Hmm, ok (perhaps I've got parallel loops spinning around my head too much )

[llemtt]

The way it's wired put the cap/resistor combo in series with the send output, and it's bypassed when nothing is plugged into the return jack. So if the loop isn't used the combo isn't in the signal path.

It's purpose is to compensate the capacitance of the cable plugged into the send output.

my ,02
teo