Dogears...

[Icetech]

Hello, i wanted to make a new thread rather than keep hijacking glasmans:)

i had asked bout mods for this layout

http://maximoaudio.com/forum/files/dclo ... ut_310.jpg

I changed the OD master to a 250k today from the 1meg (only had a 250 laying around) and that got rid of alot of problems... like squeeling with the amp dimed..

you had mentioned to change the Pro-od network to 180k into 100k. although my layout im using has a 22k into 100k? am i looking at the proper area?

you said too add a .1 or .2uf cap onto the v1b cathode, wouldn't this just make it a 1.1 or 1.2uf then? can yuo really hear the difference? im not doubting you, just not sure if im understanding correctly what your suggesting..

I also changed the Od feed resistor to 220k with a 51k to ground per your advice.. that worked out nice.. my OD went less crunchy and a touch smoother.. but not outa control when its really turned up:)

P.S. thanks for the help... i can build em following a layout.. but when it comes to tweaking im lost:)

[dogears]

Hi Icetech,

The 180k into 100k trim network replaces your whole preOD network. Look at Hybrid A. I sub a 180k for the 220k. Remove everything you have between the relay and the 68k grid. THe trimmer is a voltage divider.

The OD master is a 1M. You need to add a 100k voltage divider between the 150k series resistor that comes after the .0047 cap an the input of the
OD 1M master. Try 56k/47k or something like that. You can try a trimmer or pot on the inside instead. Or the "od feed resistor and gorund" you already did would replace the 150k series resistor. Maybe it would be easier to "see" if you left the 150k and used the divider idea. That simulates the 100k OD level pot.

Try a 470pf to bypass the 220k grid on Cl2.

Try adding about .22uf in parallel with the 1uf bypass on CL2. I do hear it....
Shoot for 200v on the plates of V1 and V2. Hang a 220k from the last dropping resistor to ground to remove some volts if need be. That simulates the fet.

Let me know what you think of all this....

[Icetech]

well now i have more work to do:) thanks... will let ya know..

[ElectronAvalanche]

Maybe it is just me, but this layout has some errors:

The 150k plate resistor with the 0.0047uF decoupling cap of V2b should NOT be connected to the Drive pot.

The 220k plate resistor/0.01uF combo is the one connected to the 100k and OD Drive Pot.

And the cathode resistors are mixed up as well:

Normally the V2a would be:

68k grid stopper (2)
220k plate resistor
3k3 cathode resistor (4.7uF)
0.01uF output cap, over 100k to Drive pot

V2b should be:

150k grid stopper (7)
150k plate resistor
2k2 cathode resistor (2k2)
0.0047uF output cap to 150k to OD Level

Or were this changes done on purpose??

Cheers,

Electron

[Icetech]

To tell the truth i just went off the layout... so not sure...

And i left my mouser manual at home.. so damnit:(

[Normster]

Electron, the layout does indeed have a few errors. That was my first build into a Bassman donor and I made quite a few corrections during the build process using Ben's drawing. I know I keep promising to update the layout, but in the meantime I can only continue to emphasize..."Recheck wiring and component values to the Hybrid-A schematic!"

Another minor thing to note, the board layout was designed for turret construction. When I build using eyelets, I use a slightly different layout the joins the cathode grounds at a single point rather than lacing them. I also moved the 470k resistor from the reverb pot to the board as in Gary's layout.

[dogears]

This is true.... I had already pointed the layout errors to Icetech in another thread. I think I understood that the build is correct but the layout was incorrect.... If not, add all these fixes

Maybe it is just me, but this layout has some errors:

The 150k plate resistor with the 0.0047uF decoupling cap of V2b should NOT be connected to the Drive pot.

The 220k plate resistor/0.01uF combo is the one connected to the 100k and OD Drive Pot.

And the cathode resistors are mixed up as well:

Normally the V2a would be:

68k grid stopper (2)
220k plate resistor
3k3 cathode resistor (4.7uF)
0.01uF output cap, over 100k to Drive pot

V2b should be:

150k grid stopper (7)
150k plate resistor
2k2 cathode resistor (2k2)
0.0047uF output cap to 150k to OD Level

Or were this changes done on purpose??

Cheers,

Electron

[Tdale]

Maybe it is just me, but this layout has some errors:

The 150k plate resistor with the 0.0047uF decoupling cap of V2b should NOT be connected to the Drive pot.
Electron

Hmm. Where should it be connected then?

Tommy

[dogears]

The .01 and 100k connects to the OD Drive pot. The .0047 and 150k connect to the 100k OD Level pot or the 1M OD master volume (provided you add a 100k divider before it).

Maybe it is just me, but this layout has some errors:

The 150k plate resistor with the 0.0047uF decoupling cap of V2b should NOT be connected to the Drive pot.
Electron

Hmm. Where should it be connected then?

Tommy

[Tdale]

I thought it was just the oposite.. The output of V2A goes to drive, and the output of V2B to Level....

Tommy

[dogears]

You are correct. The layout had the parts reversed! That is what is confusing things.....

I thought it was just the oposite.. The output of V2A goes to drive, and the output of V2B to Level....

Tommy

[Icetech]

K dog, just ordered all the parts, will let ya know by the weekend how it goes:)

BTW.. i couldn't find PS caps.. i got 715's... and i couldn't find the damn pots on mousers page.. too many choices:) ill get em from hoffman or somethin:)

[dogears]

Fwiw, Gil likes the Xicon MPP series.....

tubesandmore.com carries the PS series and pots.

Let us know how it all works out....

K dog, just ordered all the parts, will let ya know by the weekend how it goes:)

BTW.. i couldn't find PS caps.. i got 715's... and i couldn't find the damn pots on mousers page.. too many choices:) ill get em from hoffman or somethin:)

[Tdale]

You are correct. The layout had the parts reversed! That is what is confusing things.....


Tommy

[/quote]

Ahh...it feels so good to actually understand something from time to time

If I don't get started on my Dumble soon, I'll go crazy, reading about all this, and not being able to try all the mods..

This probably isn't the right forum for this, but does any of you have any experience with Matchless amps? I built a couple of DC30, and I'm very happy with them. I haven't modded them anything, except adding a small cap in the tone stack, to get a more marshally sound.

Any tips will be appreciated...

Sorry if I offended anyone by writing about non-dumble amps

Tommy

[Tdale]

Do you guys recommend PS caps?

Tommy