Building AO-44 PeeWee.

[1blueheron]

I just acquired a Hammond M-103 organ.  It contains an AO-29 and a AO-44.  The AO-44 looks like a pretty simple conversion and a cool amp looking at Sluckey's PeeWee build.  I see where there is a caution that it is for the "E" model and not all AO-44's are "E"'s   On mine the AO-44-1 is clearly visible but the model number encountered a finger before it was dry and the ink is badly smudged.  I have a blob model.

Can anyone tell me what to look for to verify it is or isn't an E

It has 2 hammond branded ECL86 tubes and a hammond branded EZ81.  It is in great shape other than the ink smudge.

Pics will be posted in a few minutes.

Thanks.

[1blueheron]

Here's a couple pics.

[MWaldorf]

I've built two AO-44 conversions using Sluckey's VoxyPeeWee - check this thread for details: https://el34world.com/Forum/index.php?topic=26320.0

Mine didn't have any stamp on them, so maybe they were E's or maybe they weren't?  Either way, a fun project and great sounding amps!

[sluckey]

The fuzzy schematic has the info you seek.

[1blueheron]

So work has begun on my PeeWee build.

Yesterday I pulled out the compression circuit, the old cordset, un-needed standoff, terminal strips, jacks etc.

I installed the socket base for the 12AX7 and gathered components.   

Had to order pots and some caps and a fuse holder.  Hope to get a faceplate built tonight and do some more soldering.

[1blueheron]

Here's a few more pics of the progress for anyone interested with a picture of Sluckey's which is my goal to compare to.

[1blueheron]

Was able to get the front bezel cut, installed, and all the internals wired up and soldered. Only thing left is to connect the power indicator LED and label the controls.  I need to pick up a fuse this AM in order to power it up and check voltages.  Hopefully the original multicap can is still in good shape and I won't get any smoke.

[1blueheron]

back

[1blueheron]

Front.  Hoping to get it fired up and take a listen today.

[sluckey]

Hopefully the original multicap can is still in good shape and I won't get any smoke.

That was step one in my project. Hopefully yours is still good. Now would be a good time to use a variac and bring it up slowly over the course of a day. I've been surprised at how many of those Hammond cans are still working. I'm still using the originals in my AO-63 conversion. Gotta say, your looks tidier than mine.   

[1blueheron]

Thank you for the kind words.   

unfortunately I don't have a variac.  I'm just keeping fingers and toes crossed.  This reportedly worked not to long ago before the cat chewed the cord off so I feel reasonably safe.

Picked up some fuses this AM and fired it up.  A 3/4A fuse will not sit in this.  Had to bump up to 1A to get it to hold.

At 123V wall current I am seeing 277VAC ground to pins 1,7 at the rectifier.   Heater voltage looks good.  This seems normal.

However, with only rectifier installed  and checking voltages, I am seeing the following measured to ground:

A = 384
B = 383
C = 377
D = 376

Seems high.  Should I be suspecting a bad resistor or is this in normal range without tubes installed? 

[sluckey]

Voltages will be high until you plug the tubes in. The cap can should be be room temp. Is it?

[1blueheron]

Put the tubes in and plugged in.  Cap can seems fine but 12AX7 preamp tube didn't seem to light. Must have something wired wrong or bad tube.  Sounded like an approaching hurricane.  Shut it down.       Details...  Will trouble shoot further tomorrow.  Thanks for the help so far.   

[sluckey]

It can be very difficult to see filaments in some 12AX7s. Turning the lights off helps. You do have a jumper between pins 4 and 5, right?

Speaking of jumpers, I don't see a jumper between the two yellow tonestack caps?

[DummyLoad]

You do have a jumper between pins 4 and 5, right?

steve, it looks like he does...

--pete

[1blueheron]

Yes, pins 4 and 5 are bridged.  I did miss the jumper on the tone stack though.  Thanks for catching that.  Fixing now.

It might be an issue with the tube socket not making good contacts.  It is a recycled piece.

[1blueheron]

Installed the missing jumper in the tone stack.

Cleaned the pin sockets on 12ax7
Turned out the lights and powered on.  12AX7 is lit!

Installed a 8ohm 10w dummy load at the output jack and took the following readings:

[DummyLoad]

v3-a is very upset - bias that is...

--pete

[DummyLoad]

missing ground jumper on input jack - also ground tag for V3-A cathode R and the reason for V3-A upset bias - also explains the noise and hum without a guitar plugged in.

see attached.


--pete

[1blueheron]

OK, thanks, will install jumper.  I just changed out some resistors at the cap.  Changed 5.6K to 10K and 1.2k to 2.7K

Voltages are now:

A = 322
B = 309
C = 283
D = 278

[1blueheron]

Installed ground jumper at input jack.  Pin 1 now reading 180V pin 2 is 0V  pin 3 is 1.35V

[sluckey]

Should be ready to make some noise now.   

[1blueheron]

Got it fired up and running!

Sounds awesome.   Cap can is running nice and cool.

I do hear a slight bit of 60hz hum but overall, pretty quiet and plenty of power.  Definitely could gig with it in small venues.

This is probably the best 20.00 in parts I have ever spent!


Now I need to build something to put it in.


Thanks guys for the help in getting this up and running.

Now what to do with the AO-29 that came in the same package 

[1blueheron]

Need some advice.

Before I wrap this thing up in a package and call it done, I am thinking about another gain stage or "boost" for a high gain sound without a pedal. 

I have room to squeeze in 1 more socket and 1 more pot or switch.  Was considering 6AU6, or 5654/6AK5W.

Do you all think my transformer can handle the additional load?

Has anyone got a working schematic for a 5654 or 6AU6 boost stage they can point me to.

Assuming this would go best in front of the 12AX7?

[shooter]

before going crazy;
play it for 5-10min
then gatorclip a 10-25uF cap to the 2nd gain stage cathode
repeat what you played n evaluate.
IF you like the "boost" add a 5-10 to the 1st gain stage cathode
repeat n evaluate


those can be done with 1 or 2 switches

[1blueheron]

before going crazy;
play it for 5-10min
then gatorclip a 10-25uF cap to the 2nd gain stage cathode
repeat what you played n evaluate.
IF you like the "boost" add a 5-10 to the 1st gain stage cathode
repeat n evaluate
those can be done with 1 or 2 switches

You mean like this?

[AmberB]

I think that would be the second gain stage on that schematic...

[shooter]

yup, I start with the 2nd gain stage so the 1st one can focus on getting good clean audio in without risking gremlins sneaking past 


If that moves the needle in the right direction and you want more, then sneak up on the 1st gain stage

[sluckey]

I originally had two 25µF caps in my peewee. Quickly removed them because the amp sounded too muddy. Liked the sound without any bypass caps so I never experimented with smaller caps.

[sluckey]

Has anyone got a working schematic for a 5654 or 6AU6 boost stage they can point me to.

I used a 5654 in my little Smoky. Could probably be adapted to your peewee. I have no idea what it will sound like.

     http://sluckeyamps.com/smoky/smoky.htm

[1blueheron]

Thanks for the suggestions.  I worked a little on building a cabinet and some more metal work last night.  Didn't get around to trying the cap as son was studying for an exam.  Sounds like I may want to start with something a little smaller than 25uF...  I will also take a look at the Little Smoky schematic and see what my feeble brain can come up with as an adaptation.

Probably Thurs/Fri. before I try anything.

[bmccowan]

I think its a good idea to try those and other options before adding an additional tube socket. If you do decide to add a pentode stage, Matchless Clubman and some of Geezer/Tubenits HoSo preamp circuits are proven and documented. But they are more than add-ons to the preamp you already have in the amp. For example the Clubman preamp would involve rewiring the first stage and then inserting the pentode 2nd stage. I think its a great sound, and would be fun to do, but don't believe it can be done without losing the sound that you already identified as great. 

[1blueheron]

I think I am going to leave it as is.  Been working on the cabinetry.  Still needs painted up and something other than orange knobs but this is pre-paint.  Wood is Eastern Red Cedar sides back and top with a Red Oak base.   Base will get a coat of clear urethane.  Remainder of wood will be black.

[sluckey]

You're gonna paint eastern red cedar black? Shame on you!

[shooter]

get a quality stain!!!
my preference for ceder is a dark Mahogany, then finish clear coats till you can't stop smiling
buy a canvas if you gotta paint 

[AmberB]

That certainly looks better than my cabinet work!

[bmccowan]

Agree with no paint! Pure Tung oil works well on cedar (Eastern Red is really Juniper I think) as do Tung oil based vanishes such at Waterlox. Even wipe-on Minwax poly will look much better than painting that wood. You can get a preview of how it will look with Tung oil by wetting it with a bit of mineral spirits or turps.

[1blueheron]

Used a Ebony Minwax stain.  Came out pretty close to black.  Oh well.  Its pretty much finished, still need to get some red or black knobs and put feet on it.  Here is a link to sound clips.  Will post them up in the videos section.    This was my son having fun on it.