Dumble - help needed urgently!

[Mousey Dung]

Hi everyone!

I recently purchased a kit from BN, which includes a real choke and reverb. It's my first amp build, although I have some experience designing and building some stomp boxes.

M. at BN has really been helpful and patient with me, but has suddenly gone AWOL for some reason. Hope he's okay! Maybe he just got tired of me :-p In any case, I've been stuck, unable to complete the last section of my build before I leave on tour in a few days -- when I'm supposed to take the new amp with me!

I'll try to start with one question at a time:
Q1) Are there any hard & fast rules about positioning the OT?

The chassis I received was not matched to the output transformer. I am about to drill some new holes for it. This being a Dumble, I'm not taking anything for granted about positioning and distances between components. Is it alright for the OT to be on the opposite side of the chassis, under the preamp board and near the preamp tubes? That would entail running the wires from the OT all the way to the center of the chassis, where it will connect with the output selector switch - 4 Ohms, 8 Ohms & 16 Ohms.

Thanks in advance!

[drew]

The odds of a first time builder, working on a kit version of an amp as complex as a Dumble clone with reverb, that is so poorly QC'ed that one of the transformers doesn't even match the chassis, being able to finish up a fully operational, tour-ready, amplifier in just a few days are very bad. My advice to you is to line up a reliable amp you can take on tour, and keep after Moss until he either ships you the right OT or tells you what he expects you to do with the one you have now to make it work. (He essentially "went AWOL" for years, so it's not surprising that you're finding it hard to get a response from him; I'm amazed to hear that he's still apparently in business and people are still ordering from him.)

If you don't want to follow that advice, there is something called the "headphone trick" that you can Google, which will help you find a spot on the chassis to mount the OT with the least hum. But it involves having the PT connected to your home's power, so if you don't know what you're doing you could shock yourself.

[xtian]

Agreed. We would be most happy to help you through this build, but it's not a speedy process, especially for novice builders.

[Mousey Dung]

The odds of a first time builder, working on a kit version of an amp as complex as a Dumble clone with reverb, that is so poorly QC'ed that one of the transformers doesn't even match the chassis, being able to finish up a fully operational, tour-ready, amplifier in just a few days are very bad.

Thanks, Drew.

There's more to the story than that.

When I placed the order, M. did say that he didn't have everything ready , but I was running on a schedule. He asked if I would be able to handle slight adaptations of the chassis and I said yes.
Also, I gave myself a full month to build this, but the delivery was unusually delayed, then lost at customs for more than a week, etc. Considering that I live in a different time zone, M. was really quite accessible, until he suddenly disappeared, I suspect for personal reasons, but not because he can't be bothered. All our communication does not indicate any such leanings on his part.

If you don't want to follow that advice, there is something called the "headphone trick" that you can Google, which will help you find a spot on the chassis to mount the OT with the least hum. But it involves having the PT connected to your home's power, so if you don't know what you're doing you could shock yourself.

OK, glad I followed my instincts... I've already drilled some new holes right near where the OT was intended to be (if the holes had matched), so I think I'll be fairly safe in terms of hum.

[Mousey Dung]

Agreed. We would be most happy to help you through this build, but it's not a speedy process, especially for novice builders.

Actually I'm already at the last stage of the build. Any help would be greatly appreciated! I didn't adhere 100% to the generally recommended order of doing things. I used the assembly-block approach, creating a few separate as-complete-as-possible blocks -- assembled the boards, wired the controls to the chassis, put the leads in as much as possible... I've checked and triple-checked and checked all the wiring and routing... all that remains is splicing together all the parts. What I need to know now, is which pairs of wires should be twisted together with which. If you'd be willing to help, I'd really appreciate it.

[xtian]

Sure we can help. Photos are invaluable. The schematic you're following, too.

Paul Ruby's "first time power up" advice is good:

http://www.paulrubyamps.com/info.html#FirstPowerUp

Ask away.

[M Fowler]

This is a Dlite 44 gut shot showing wiring.

Not sure if your amp has same style of OT? This is a regular Brown Note chassis probably 22w version.

[Mousey Dung]

Sure we can help. Photos are invaluable. The schematic you're following, too.

Paul Ruby's "first time power up" advice is good:

http://www.paulrubyamps.com/info.html#FirstPowerUp

Ask away.

Thanks! I'm enclosing a pic of the pictorial I've been following and some pics of my build so far.

You'll notice that the pictorial I received has no indications regarding how to hook up the transformers. I used this image from the BN website to do the AC wiring and to hook up the bias/rectifier board on the left.

I need to wire it for 230 V, so I followed the indications on the last two images.

(MORE PICS TO FOLLOW...)

[Mousey Dung]

PIC UPLOAD CON'T...

So that's as far as I got with my build. How am I doing so far?

[Mousey Dung]

I should mention that I will of course shorten and insulate the unused wires from the transformers. I just didn't want to cut anything until I was sure I had it right.

I'm about to make a bulb limiter as shown in Step #11 at the bottom of this page:
http://bad-domain/DumbleLite/BuildersGu ... 0Guide.htm

[Mousey Dung]

Paul Ruby's "first time power up" advice is good:
http://www.paulrubyamps.com/info.html#FirstPowerUp

This is invaluable info! According to this page, I should desolder the secondaries. I'm going to do that now and attach the bulb limiter as recommended in Step #11 of this page.
http://bad-domain/DumbleLite/BuildersGu ... 0Guide.htm

Now for QUESTION #2:
Can anyone tell me the two wires from the choke should be connected to?

[xtian]

Choke connections are marked on your layout.

[xtian]

Your other question is about how to hook up the OT, right? First do the headphone trick to make sure it's positioned with as little induced hum (from the PT) as possible. NO POWER should be connected to the OT when you do this, but you will apply 220vac to the PT primary. You get the idea? The PT puts out an alternating magnetic field when active, and this can induce hum in the OT if positioned improperly. Ask if you need more.

What's the model number of your OT? Is it the black ClassicTone in the photos? Did you find the wiring legend for the OT? For the primary, the red center tap goes to the standby switch, same place as the choke (see your layout). The other two secondary wires, usually brown and blue, go to pins 3 of your power tubes. You can see these in your layout appearing from under the board, and going to pins 3.

For the OT secondary, this is pretty clearly marked on your layout, going to the speaker jacks.

[Mousey Dung]

What's the model number of your OT? Is it the black ClassicTone in the photos?

Yes. The OT has "40-18001" and "166-1429" on it.

Did you find the wiring legend for the OT?

I only have a legend for the PT (uploaded above).

QUESTION #3a:

According to the latter image, am I correct that to get 230V, I am to connect the Black-White wire with the Brown wire together, and connect the Black and White wires to the main Power on/off switch?

QUESTION #3b:
To do the first bulb-limiter test, am I to connect the Black and the White wires from the OT to the main Power on/off switch, ensure that all other wires from the OT are disconnected and then turn on the switch to see if the bulb lights up?

For the primary, the red center tap goes to the standby switch, same place as the choke (see your layout). The other two secondary wires, usually brown and blue, go to pins 3 of your power tubes. You can see these in your layout appearing from under the board, and going to pins 3.
For the OT secondary, this is pretty clearly marked on your layout, going to the speaker jacks.

I'm such a noob that only the speaker-jack part was obvious to me. Thanks for spelling it out! That's the kind of help I need!

[Mousey Dung]

QUESTION 4:
Do any of the transformers need to be earthed? As in, do I need to file away the powder coating and use star nuts to ensure the iron connects to the chassis?