General Electric BA-9-B Info needed

[Kid Squid]

Bore Da Chaps,

just wondering if any of you kind gents got any info at all, on one of these, Schemo's, factory data , etc,etc..............

One of my mates, asked me to have a look at it for him - seems like a crazy fool been 'avin a go :shock:
Check out the black tape :wink:

Valve line up is :

1x 6386,
1x 6AL5,
2x 6V6,
1x 5Y3 GT ( rect)

more pics at -
http://www.twin-x.com/groupdiy/thumbnails.php?album=116

:thumb:

 

[NewYorkDave]

Schematic? Bah. It just about draws itself when you list that tube complement.

6386 push-pull variable mu amplifier stage, which is coupled to...

6V6 push pull output stage, across which is connected...

6AL5 dual rectifier for gain reduction control voltage, and the whole shebang is powered by B+ rectified by...

5Y3 fullwave rectifier.

Let's look at the other clues in the photos.

Three transformers: power, input and output, no interstage. So the variable-mu stage must be R-C coupled to the output tubes.

Two big attenuators, must be for input and output. The output attenuator is almost assuredly a T or ladder after the output transformer. The input atten. will either be a T or ladder before the input xfmr, or a dual stepped potentiometer between the input xfmr and the 6386 grids.

As for the particulars, a half-hour's worth of circuit tracing will yield those.

 

[NewYorkDave]

Oh, look at what I found (courtesy of our own Miko K.)

http://photobucket.com/albums/v473/MikoKensington/GEuniSchem.jpg

Looks like the attenuators on yours were a later addition.

 

[emrr]

For the 4000th time; the GE BA-9 Unilevel and the Collins 356E and 26J are the same thing. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself.

The timing is essentially same as the Stalevel.

 

[Kid Squid]

Hiya Chaps,

Schematic? Bah. It just about draws itself when you list that tube complement.

Sorry for the Laziness and total incompetence :wink: , Just been working a pile of nasty nightshifts, and thought i'd just put a feeler out.
anyhoo -

Just slowly getting my head around the vari - mu fundamentals ( I think :wink: ), still need to do a bit more research .

Three transformers: power, input and output, no interstage. So the variable-mu stage must be R-C coupled to the output tubes.

what are the advantages / disadvantages of being R-C coupled instead of , for instance interstage transformer coupled. will there be more interaction between the stages ?
( sorry for being so green on this !)

Oh, look at what I found (courtesy of our own Miko K.)

http://photobucket.com/albums/v473/MikoKensington/GEuniSchem.jpg

Looks like the attenuators on yours were a later addition.

Cheers for this Dave :thumb:

For the 4000th time; the GE BA-9 Unilevel and the Collins 356E and 26J are the same thing. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself. I'm repeating myself.

hell, I feel touched by being the 4000'th :wink:

:thumb:

 

[MM1100]

Your Uni-Level can be modified to have many options: Phil Moore at http://www.retroinstruments.com/index.html also performs crazy good mods for these units like HPF and Growl control as well Wild and Mild modes!!

 

[MM1100]

Example Unilevel mods for in/out/attack/threshold/release/dual/single

http://twin-x.com/groupdiy/displayimage.php?pos=-1119
http://twin-x.com/groupdiy/displayimage.php?pos=-1118

 

[vcode]

i have a g.e. ba9b. spoke to retro and theyre pretty slammed w there own stuff. anyone know boris? phil said he mods them as well....

 

[Dmichel123]

Example Unilevel mods for in/out/attack/threshold/release/dual/single

http://twin-x.com/groupdiy/displayimage.php?pos=-1119
Loading...

Hey I clicked the links for the uni level mods but they do not work. Is there anyway i could get you to send these too me? I will venmo you. Im in process of modding mine and would love to see these drawings. [email protected]. Thanks

 

[MM1100]

Hey I clicked the links for the uni level mods but they do not work. Is there anyway i could get you to send these too me? I will venmo you. Im in process of modding mine and would love to see these drawings. [email protected]. Thanks

Hi - let me look into my archives and see what I have.

 

[mjrippe]

Hey I clicked the links for the uni level mods but they do not work. Is there anyway i could get you to send these too me? I will venmo you. Im in process of modding mine and would love to see these drawings. [email protected]. Thanks

Google "Gates Sta-Level Schematic" Ignore the 12AT7.

 

[MM1100]

Attaching pic here that shows the mods implemented. All of these can be found in the GE BA9 and Collins 26J schematics.

The mods are essentially:

• adding or bringing the variably of the controls to the front panel (threshold, attack, release, single/dual/triple)
• in/out variable pads to the front panel
• implement meter
• recap
• enjoy!