New Dumblator / questions

[hans-jörg]

Hello,
I fired up my Dlator this morning and have to confirm the open sound of it.
BUT, where I have some problems is the seriell/parallel swich.
I built it wiht the origin board from the forum and added the swich plus the bypass, wich is a very helpful tool.
This problems are first:
big banging when swiching, bypass sw. too when its in seriell but not in parallel mode. Here we are with the secind: big noise in seriell mode. But not in parallel.
Parallel is much easier to handle, absolutly no noise.
In seriell itsdifficulter, there is humming and a lot of grid nois.
I have to say, that I had the D´lator in the head under the amp and whe I try to put a coverplate (steel) between them you can here every touch to the D´lators chassis. I mean, its definitly the grid wire from the swich. You can see it on the picture. The blue solid core in front of the board.
I think the noisy seriell is because of the open grid connection wich is def. in the air and collects everything floating around.
Should shield it.Maybe all the wires around of the swich. Helps this against the banging when swiching?
Please dont beat me because of the poor build. Iàm trying to use everything I have at home. So it can somethime look like ...

[hans-jörg]

some more

[erwin_ve]

Did you ground the pots?
Is the 2nd filtering node grounded at the grounding point near the signal board?

[hans-jörg]

Hi,
the Pots are grounded through pin 3.
Both filtering caps are connected under the board (minus) and grounded on the connection of the bypass cap and the 27k tail to "starground" near the signal board.
As I wrote: in parallel mode its absolutly noisless, no humm.
I have the grid conection (blue long wire) to the swich under suspect.
Do someone have this banging too when swiching?

Sorry, my pet is a bunny, so I didn`t brought my problem up in the neighbour thread

Best

Hans-Jörg

Edit: if you wonder about the resistors in the heating line: I had to use the 220V primary (230 regular) to push the secondary a little bit (it helped, I have exactly readings on pin 1 - 254 V, pin 3 - 29 V, pin 6 - 230 V and pin 8 - 1,76 VDC) but I had then 7,4 VAC to the heater. So this are 2x 1Ohm resistors, so I am now on 6,6 VAC and thats ok so

[hans-jörg]

Do someone have this banging too when swiching?

Any body out there

[T Wilcox]

I've never seen the donut style power supply used in a Dumbleator or anything tube amp. Was that parts you had on hand?
I am in no way saying it's a bad idea, actually impressed.
As a matter fact I have a few of them myself, just never even considered them.

Todd

[bluesfendermanblues]

Hi,
the Pots are grounded through pin 3.
Both filtering caps are connected under the board (minus) and grounded on the connection of the bypass cap and the 27k tail to "starground" near the signal board.
As I wrote: in parallel mode its absolutly noisless, no humm.
I have the grid conection (blue long wire) to the swich under suspect.
Do someone have this banging too when swiching?

Sorry, my pet is a bunny, so I didn`t brought my problem up in the neighbour thread

Best

Hans-Jörg

Edit: if you wonder about the resistors in the heating line: I had to use the 220V primary (230 regular) to push the secondary a little bit (it helped, I have exactly readings on pin 1 - 254 V, pin 3 - 29 V, pin 6 - 230 V and pin 8 - 1,76 VDC) but I had then 7,4 VAC to the heater. So this are 2x 1Ohm resistors, so I am now on 6,6 VAC and thats ok so

Sounds like you have a grounding problem....the loop is more prone to picking up hum in serial mode than in parallel ditto. I have build the DUmbleator loop a number of times, both as build-in and stand alone and with and without serial/parallel switch.

Add a) Build-in loop
Make a separate ground connection for the loop components. I ground the loop at one of the bolts on the loop tube socket. Works for both serial and parallel mode. On the first build-in loop I made, I used the preamp input ground near the (amps) input jack, which gave me a lot of hum, when the loop was used in serial mode.

Add b) Stand alone Dumbleator
With a stand alone loop like yours, its VERY important that you follow the EXACT same grounding scheme as you can see in the files section

https://tubeamparchive.com/download/file.php?id=14586

As you can see, the pots must be grounded to the same point as the board and the jacks are connected to the chassis. If you do it this way you will have a trouble free setup - in both serail and parallel mode.

Keep us posted on your findings

[hans-jörg]

Hi,
this kind of transformer not bader and not better than iron ones. They are cheaper and for something like a Dumblator ideal I would suggest.
Mostley the are used in 19" rack.
But I never would use it for a Dumble clone or so becaus I want to be identical with the original. To be honestly I gave it a chance in my planing periode of my D´clone (half price, same power) but I`m old fashioned, so I got a custom wided Marsha EL 34/100Watt for good money for the Dumble project.
This what you see is a 250 VAC secondary plus 6,3 VAC 1A. Fully enough to be hidden on the bottom of a Dumble clone head

Any suggestions about my swich plopping?

Best

Hans-Jörg

Edit:

Oh, I see FENDERMAN.
Thank you

[hans-jörg]

As you can see, the pots must be grounded to the same point as the board and the jacks are connected to the chassis.

Hi,
you mean the jacks should be grounded direct to the chassis. I gave them the starground and isolated to chassis - all 4.
So, NO ISOLATED jacks - right?

The only different I see to your link (the hardcopy lays on my desk beside your schematic and Toms layout) is that I have a second grounding point for my front jacks (send/return) and Pots but very close to. This could make enough difference?
Whats about shielding of the wire form the swich?


Hans-Jörg

[T Wilcox]

Thanks
Yeah I've used those in Fire/life safety systems that I used to work on.
I replaced a lot of parts in those panels but never had to replace one of those trannies. I'll have to dig one out of my garage and check the specs!
Anyways good luck with your Dumbleator

Todd

[hans-jörg]

I have to tell you a dark secret:
For the Send and Return Pot I had no more 250K. So there there is now (until monday only, I hope) 100K on both.
Is it a tragedy or how strong is the rule for the 250K. I mean, I will change them but how big is my crime?

Hans-Jörg

[bluesfendermanblues]

I have to tell you a dark secret:
For the Send and Return Pot I had no more 250K. So there there is now (until monday only, I hope) 100K on both.
Is it a tragedy or how strong is the rule for the 250K. I mean, I will change them but how big is my crime?

Hans-Jörg

I often tweak pots with parallel resistors between pin 1 & pin 3.

E.g. on #183 you need a 311k bass pot, which does not exist, so you could either try scraping of a little of the cole inside the pots (no kidding) or make one with a 500k paralleled with a resistor to get the right value.

In your case - with 100k pots - try the scraping method - its quite easy with very fine sandpaper to go from 100k to 250k.

So you don't stand to punishment for your crime

[bluesfendermanblues]

you mean the jacks should be grounded direct to the chassis. I gave them the starground and isolated to chassis - all 4.
So, NO ISOLATED jacks - right?
Hans-Jörg

No isolated jacks - I repeat...follow the layout and you'll be fine.

[bluesfendermanblues]

BTW, your wiring looks a little 'fast'.

Especially, if you are using solid core wiring, make sure wires cannot move around too much inside the cabinet. You might risk the unit breaking on you in the middle of a gig.

I'm not talking about aesthetics here, but securing operation.

[hans-jörg]

Hi,
ok, no isolated jacks.
The scraping I´ve heard already. But wath I cant understand is to scap from 100k to 250 or more? the opposit I thought it works.
The coil provides resistance. So when I scap a bit - I have less resistance. I might blame my poor technical skills but ...?

With adding resistors I worked before - works fine.

Oh, yes, the core. I will/have to rewire the whole thing when it wor as I expect because I want to mount this unit on the bottom of the head and forget. Therefor it might look "fast" for the moment, you are right.
Thats the pitty with me - I do every thing twice, mostly wireing

Hans-Jörg

Hans-Jörg