Working on a Dumbleator

[martin manning]

The internal height of the Bud is a hair over 1.5" and the 262A12 is going to be a tight squeeze into a 1.625" space. I just ordered a Hammond chassis, and supposedly the internal height is exactly 1.625"

Hope that works out. The one I used has a 1.58" high U-frame and is is fully enclosed. It was from Allen, and is no longer available. The Hammond 262A12 at 1.5" across the bobbin should fit if the internal height of the box is 1.625". There aren't a lot of transformer options with HV and filament windings out there that will fit inside 1u.

[Vertigo]

The internal height of the Bud is a hair over 1.5" and the 262A12 is going to be a tight squeeze into a 1.625" space. I just ordered a Hammond chassis, and supposedly the internal height is exactly 1.625"

Hope that works out. The one I used has a 1.58" high U-frame and is is fully enclosed. It was from Allen, and is no longer available. The Hammond 262A12 at 1.5" across the bobbin should fit if the internal height of the box is 1.625". There aren't a lot of transformer options with HV and filament windings out there that will fit inside 1u.

Thanks. I hope it works out too. I was fully ready to get to work and finally had the time to commit to it. The new chassis is coming from Hawk Electronics and they're taking their sweet time to ship. Hopefully I'll have it before my kids winter break starts as it's likely to be the next time I have big time blocks to work on anything interesting.

[sluckey]

oops! Wrong thread.

[Vertigo]

A few weeks ago, I wrote that the Bud chassis I ordered wouldn't work with the Hammond 262A12 transformer. I ended up with a Hammond RM1U1908VBK 1U enclosure, and the fit is perfect. Another thing about this particular enclosure, is that there isn't a separate faceplate. The front, back and sides are all an extrusion which get bolted together with self-tapping screws, and then the top and bottom can be bolted on. The upside here is that the front and rear panels are only about 1/2" thick and if you have a drill press, or milling machine, it's easy to setup a stop or a fence and drill your holes all on the same line, much more accurately than doing it by hand.

I've only messed around with it for a few minutes without any effects plugged into it, but I now understand a bit better what everyone is talking about when they say it fattens up the tone. It also dirtied up the cleans, but I'm hoping that trying out a few different tubes will get me where I'd like to be.

IMG_1267 by Sean Chaney, on Flickr

IMG_1266 by Sean Chaney, on Flickr

IMG_1265 by Sean Chaney, on Flickr

[Vertigo]

As promised earlier in the thread, here's the layout I made. This is a circuit that Martin modified here: https://tubeamparchive.com/viewtopic.ph ... 73#p413673 with the blend pot idea provided by Engle' Claus/Tony here: https://tubeamparchive.com/viewtopic.ph ... light=engl

Bumble-ator.pdf

I have a question and a couple of notes. Tony, I've looked at the pot wiring on that schematic dozens of times and have been convinced that I'm doing it wrong, but every time I trace the paths from the dual gang pot, I come up with the same thing. Would you please take a look at the layout and let me know if I've missed something. If it needs to be fixed, I'll make the changes and will repost it. At the moment the knob just blends whatever is in the loop. On and off. if I turn it full right, the effect is gone and once the knob hits the 3:00 position, it's pretty much full on. Is this the way it's supposed to function?

I had a few of these LEDs that already have a resistor in the housing: https://www.mouser.com/ProductDetail/593-L79D-G12-W. With the circuit as shown, the LED is too dim for my liking so I pulled the dropping resistor and replaced it with a solid wire.

The spec sheet shipped with the 262A12 transformer says that the hole centers are 2 3/8". They are actually 2" on the transformer I was sent. I'm not sure if it was a misprint on the spec sheet or if they have rolling changes in the casings.

[martin manning]

At the moment the knob just blends whatever is in the loop. On and off. if I turn it full right, the effect is gone and once the knob hits the 3:00 position, it's pretty much full on. Is this the way it's supposed to function?

For that reverse scheme to work correctly you need a symmetrical linear taper pot.

I had a few of these LEDs that already have a resistor in the housing: https://www.mouser.com/ProductDetail/593-L79D-G12-W. With the circuit as shown, the LED is too dim for my liking so I pulled the dropping resistor and replaced it with a solid wire.

You now have it wired the way it's drawn in the schematic, the 2k2 shown there is the current limiter. With the internal resistor you had two.

The spec sheet shipped with the 262A12 transformer says that the hole centers are 2 3/8". They are actually 2" on the transformer I was sent. I'm not sure if it was a misprint on the spec sheet or if they have rolling changes in the casings.

I'd guess typo. Does the height dimension match the spec sheet? Could be they are showing the dimensions for mounting with the core rotated 90 degrees.

[donvan]

The pictures show the boards mounted perpendicular to the bottom of the chassis. What is the hardware called that allows you mount a board in this position and where can it be purchased?
Thanks in advance!

[martin manning]

The pictures show the boards mounted perpendicular to the bottom of the chassis. What is the hardware called that allows you mount a board in this position and where can it be purchased?

Generically an "L" bracket. Keystone makes various sizes, sold by Mouser.

[donvan]

Thanks Martin! That got me there. Looks like they also call it an angle bracket.

AngleBracket.JPG

[lonote]

Not to go all the way back to the basics, but I have been looking at the Dumbleator circuit, while going down a different rabbit-hole.

The circuit seems pretty itself seems pretty straight-forward, but are there particular reasons the power supply is configured the way that is is?