Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Skilpadda on December 10, 2018, 03:35:19 pm

Title: Weber 6M18 kit
Post by: Skilpadda on December 10, 2018, 03:35:19 pm

(http://i18.photobucket.com/albums/b146/Skilpadda/Weber%206M18.jpg) (http://s18.photobucket.com/user/Skilpadda/media/Weber%206M18.jpg.html)
Got myself this kit as a build for christmas :icon_biggrin:

https://www.tedweber.com/media/kits/6m18tmb_schem.jpg

https://www.tedweber.com/media/kits/6m18tmb_layout.jpg

This 1 M resistor to ground on the input. Does it make a big difference if it is moved to between the junction of the two 68k resistors and the grid of the preamp tube?

Title: Re: Weber 6M18 kit
Post by: sluckey on December 10, 2018, 04:23:34 pm

Quote from: Skilpadda on December 10, 2018, 03:35:19 pm

This 1 M resistor to ground on the input. Does it make a big difference if it is moved to between the junction of the two 68k resistors and the grid of the preamp tube?

No big difference other than it will be harder to mount. Why don't you like the nice neat method of mounting it directly on the high input jack?

Title: Re: Weber 6M18 kit
Post by: Skilpadda on December 10, 2018, 04:56:43 pm

Only thinking out loud. My idea was to move this and the two 68k and mount it directly on the tube socket. And only have wires connected on the jacks. Hoping it would be less need for shielded wires...
Tinkering with the idea to add reverb to this amp... :think1:

Title: Re: Weber 6M18 kit
Post by: PRR on December 10, 2018, 07:41:00 pm

I vote for doing it like Leo Fender did it. He was not too dumb.

Title: Re: Weber 6M18 kit
Post by: Skilpadda on December 11, 2018, 06:05:54 pm

It comes with a beautiful brushed aluminum chassis, big contrast to the slightly homemade looking chassis on the 6M45 kit i built some years ago :grin:
The cabinet is very beautifully made too. But chassis only mounts to the thin backplate with 4 screws, there are no mounting points inside the cabinet :w2: is this normal on an 18watt cabinet.
Looks to me there shall be easy enough to add some wood blocks on each side of the cabinet interior and the chassis have already some holes drilled that on my view can only be for such mounting....

Possibly it can be intended for the 45 and 50 watters with heavy transformers.... The 18watt is not very heavy....

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 10, 2019, 07:33:14 am

(https://i18.photobucket.com/albums/b146/Skilpadda/1547067083769_2.jpeg) (https://s18.photobucket.com/user/Skilpadda/media/1547067083769_2.jpeg.html)
Got started with the heater wiring now

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 10, 2019, 08:25:08 am

(https://i18.photobucket.com/albums/b146/Skilpadda/1547128880458.jpeg) (https://s18.photobucket.com/user/Skilpadda/media/1547128880458.jpeg.html)
Found this in my stash of parts. An ecc 83/12dw7 and an made in usa accutronics reverb tank. It is a short 2 spring short decay. Will it be too wimpy for a  reverb on this amp. It have an imput impedance of 1975ohm and and output impedance of 10k. Will the 10k output impedance make the output signal too weak to be useful....

Title: Re: Weber 6M18 kit
Post by: sluckey on January 10, 2019, 09:13:48 am

The 10K output is not a problem but the 1975 input will not work with the typical transformer driven circuit as found in most Fender amps. Probably gonna need a cap driven circuit. Look at some Ampeg schematics.

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 10, 2019, 01:02:22 pm

Yes i was planning on a cap driven reverb. Will a 1.0uF cap be good for this..?

Title: Re: Weber 6M18 kit
Post by: sluckey on January 10, 2019, 02:02:05 pm

I've only had two cap driven reverb pans. One used a .47, the other used a 1.0.

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 10, 2019, 04:18:12 pm

Then 1.0 shall be a good starting point. If it will not work i can butcher my peavey triumph which have a transformer and long pan...

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 12, 2019, 10:09:45 am

(https://i18.photobucket.com/albums/b146/Skilpadda/1547309030918.jpeg) (https://s18.photobucket.com/user/Skilpadda/media/1547309030918.jpeg.html)
Almost finished now. Only have to add reverb circuit...

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 12, 2019, 10:15:43 am

I only have hi inputs to the two channels so the holes in the chassis  for the lo inputs can be used for the reverb pots :smiley:

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 12, 2019, 10:30:39 am

(https://i18.photobucket.com/albums/b146/Skilpadda/PR%20transformerless%2012DW7%20reverb.gif) (https://s18.photobucket.com/user/Skilpadda/media/PR%20transformerless%2012DW7%20reverb.gif.html)
I was thinking of using this circuit. Only change the input capacitor to 1.0 uF and the resistor between R and RV to 150k. Any thoughts about this....?

Title: Re: Weber 6M18 kit
Post by: Skilpadda on January 22, 2019, 04:27:55 am

Reverb application have so far been a complete fiasco :help:
But amp actually sounds good on both channels. I have to fix some noise and hum though.
I think i will make a new turret board for this because of some layout issues. Mainly having the PI tube between the two preamp tubes. On a TMB circuit on my view it make no sense, but on a trem circuit i may look some more natural...
I will then implement some room for the reverb circuit components as well on the turret board...