New (sort of) Dumbleator build

[ElectronAvalanche]

Many moons ago I built a preamp/loop testbed using a salvaged Router 19" rack enclosure and some flat-pack transformers.

This testbed will now be converted into a Dumbleator.

I will buy a new 19" enclosure (from these guys: http://www.modushop.biz/ecommerce/cat066_l2.php?n=1).

I really wanted to try making a PCB for the Dumbleator. Since I have the tube socket laying down, the PCB will be laying down as well as opposed to the real deal.

I bought some plain vanilla copper-plated PCB and FeCl3 and a 7000 series Edding (Sharpie).

The layout was first put onto a piece of paper. Since the layout needs to be mirrored I pointed a strong light from behind the paper and then transfered the layout "freehand" to the PCB using the Edding.

Etching took almost 45 minutes since I did not heat up the solution to avoid any "undercutting".

Parts were assembled and the copper was tinnend (messy!).

So since the power supply is ready and the PCB as well, all that is left to do for now is to wait for the 19" enclosure to arrive which needs to be drilled.

For labels I will use Decals again on the brushed Aluminium front. This worked nice on the CE 100W chassis (see other thread: 70s Hybrid build).

Cheers,

Electron

[ElectronAvalanche]

Here is a pic of the "testbed"

Excuse the sloppy work, it was for experimentation only!

Forgot the preetched pic in the original post. Here it is

And the board is still missing the two 10M resistors.

[Structo]

Nice price on that enclosure.

I see two tubes, is this a Dumbleator II?

[alvarezh]

Hi Electron, I built my 'lator using the same physical layout as your preamp/loop testbed. I had never seen the inside of a real 'lator so I went with what I knew then.

Nice thinking on those trannies!

If I spend a couple of hours googleing maybe I can come up with some info, but since you already have it, could you be so kind as to post specs and purchase place of these flat PTs? I am using the Fender standalone reverb PT, its a tiny bit too wide to fit on my 2" hammond enclosure, I had to make a cutout (Traynor does it, so I guessed I could do it too) but since I am using rubber feet, it lifts up off the surface enough so that its not causing any bother.

Thank you in advance.

@ Structo:

Tom, that is his preamp/loop testbet photo with the two tubes, not the 'lator.

Cheers.

[ElectronAvalanche]

Hi Alvarezh,

the flatpacks were purchased from a store in Germany (Conrad Elektronik) many years ago.

The company ERA does not produce the 0-9 , 0-9V 770mA anymore. I found a 0-9 , 0-9V 1333mA at RS Electronics online store:


http://de.rs-online.com/web/p/printtrafos/2075955/

but this might be of bigger physical size.

You do not need a 770mA transformer, since the secondaries are paralleled.

These 9Vs are rectified and the regulated to 12V DC for the heaters. The second flatback (0-9V 222mA) is fed the 9V AC from the first flatpack into it's secondary side, putting out 230V on its primary.

These 230V are then used to get the B+.

The heater current of a 12AX7 is 150mA in the parallel 12.6V mode.

So your first flatpack should only need to supply say 500mA in total. (150mA for the heater, give it 100% overspec => 300mA and 200mA for the B+). The second one only 200mA)

I will try to find a european source for the ERA transformer tonight.

Cheers,

Electron

[markusw]

Hi Electron,

this one might be an alternative to the "back-to-back-xfmr" approach:

http://www.musikding.de/product_info.ph ... --14V.html

I used it for a D'lator. It fits nicely in a 1 HE 19" enclosure.

https://tubeamparchive.com/viewtopic.ph ... t=%2Alator

Edit:

So since the power supply is ready and the PCB as well, all that is left to do for now is to wait for the 19" enclosure to arrive which needs to be drilled.

Should have read your post more carefully



Peace,

Markus

[alvarezh]

Thank you much Electron, E$ 13.00 is close to US$20.00, that is an excellent price!

But I will be having a hard time ordering in German!

Thanks again for the specs.

[alvarezh]

Ah! got it, you need both trannies and you run the last one inverted to get the B+.

Anyhow, we run 120v in this little Caribbean island, it would be better to run and easier arrangement really. Did not know you were at the Old Continent, I would of not have bothered you. The double and inverted trannies arrangement is interesting knowledge, its a good exercise on solving with what you have on hand. Who knows? maybe one day I might get into a situation where I could use your solution. Thanks!

@MARKUSW

Yes your solution is more in line with my needs, but then I would need a small step up transformer for the primaries. We do have 220v service, but those are usually used on our air conditioning units and are not usually available close to stages, specially not with a socket to draw from.

But I do thank you (both) for your efforts. Hopefully someone from a country with 220-240 primary service can benefit from your information and your efforts will be beneficial to them.

Kind regards,

[markusw]

Hi Horacio,

maybe you can order from RS-components?

They have lots of small toroid transformers with 115/230VAC primary you could use for the "back-to-back" approach.

http://export.rsdelivers.com/catalogue/ ... /2202.aspx

They also have PCB mount transformers (toroid and conventional) with 115/230V in case you prefer them over chassis-mount toroids.

Edit:
Alternatively, you might order a Hammond 229E230 PCB transformer at Mouser. It has 115/230V Primary and 115/230V Secondary. It delivers 10mA at 230V which should be fine for a D'lator. You just needed to get some transformer for the heaters.

Regards,

Markus

[alvarezh]

Markus, thanks a million, I like both of your recommendations.

Will dig deeper into this as the hammond PT its by far my easiest solution (cheaper freight), even if I have to install a 6v heater tranny. I have some Radio Shack 6v trannies on hand that will fit, I will check to see if they provide enough juice, but these 6v transformers are not hard to find. There are a couple of alternatives on that British store also.

Very helpful, thanks again,

[ElectronAvalanche]

HI gang,

the Dumbleator is almost finished. Still waiting for two parts, so have not had a chance to fire it up yet.

The 19" enclosure is really nice with the brushed aluminium front.

Still have to design the front logo decal.

Hope you enjoy!

Cheers,

Electron

[Luthierwnc]

There are some great enclosures available from the computer industry. Once they are last year's model, people can't get rid of them fast enough. sh

[alvarezh]

Nice build Electron, congrats!