4-4-0 [2 NEW BUILDS WITH PICS; THE 2 WATT WRECK]

[GainMaster]

Hello guys

I'm starting a AX84 4-4-0 (mini Express Trainwreck clone).

http://www.ax84.com/4-4-0/AX84_4-4-0_Studio_100216.pdf

1. - Can someone explain me the purpose of the resistor (R-13 220R/5 Watts) at the output jacks ? It is a saftey resistor to prevent damage in the event the amp is on without a load.

2. - Under C-10 there a resistor that I can't read the value, what is the correct number or correct value ? .022uf/400v

3. - The cap can is a 40/20/20/20 uF, on the layout witch of the four hot wire go to the 40uF ? The 40uf is the far right one on the can going to R2.

Thank for your help, Jean

Have fun. It is a great little amp.

[godi]

Thank you.

Using the layout, I'm asking for the resistor value under C-10 not the capacitor value.

Does that resistor (safety output resistor) is lift by inserting a jack or it's stay in the circuit all the time ? The drawing does not seem to use the ''switch'' of the jack (center lug).

Why did the designer select 220R instead of 8 Ohms / or 16 Ohms resistor as dummy load ?

Thank, Jean

[GainMaster]

Thank you.

Using the layout, I'm asking for the resistor value under C-10 not the capacitor value. That should be R23 and is either 100k or 82k. R22 and 23 feed the plates of the phase inverter. One is 100k and the other is 82k. You should be able to figure it out from there.

Does that resistor (safety output resistor) is lift by inserting a jack or it's stay in the circuit all the time ? The drawing does not seem to use the ''switch'' of the jack (center lug). It stays on all the time. Not switched.

Thank, Jean

It stays on all the time.

[godi]

OK, I've got it for the 82k and 100K in the phase inverter.javascript:emoticon(':D')

Now, an other question, does the output transformer will ''see'' a 8 Ohms load (if I use a 8 Ohms cabinet, with the selector set to 8 Ohms) or the transformer will see the 220 Ohms load plus/or minus the 8 Ohms cab ?

Thank you, jean

[GainMaster]

OK, I've got it for the 82k and 100K in the phase inverter.javascript:emoticon(':D')

Now, an other question, does the output transformer will ''see'' a 8 Ohms load (if I use a 8 Ohms cabinet, with the selector set to 8 Ohms) or the transformer will see the 220 Ohms load plus/or minus the 8 Ohms cab ?

Thank you, jean

It will see the 8 ohm and 220 ohm in parallel so it will see a tad under 8 ohms. Without the cab it will see 220 ohm.

[godi]

Thank for your help, I've learn something

Just starting a new personal web page that will show the progress during the construction :

http://www.jeangodbout.com/trainwreck/e ... 4-4-0.html

Thank you, Jean GODBOUT

[Decko]

Just a suggestion. I have built 4 of these amps. I have found that the dual 6SN7 version sound fuller and not much louder.

Decko

[godi]

I like the suggestion, my chassis already have two holes for power tubes and I already have some nice NOS 6SN7GT in match pair.

Does someone have draw a layout (or a schematic) to parralel two 6SN7GT ?

My Output Transformer have 22500 Ohms with 4, 8 and 16 Ohms tap witch is a OT5PP from Musical Power Supply, now if I use two output tubes, running a 8 Ohms cabinet, should the impedance selector set to 4 or 16 Ohms to compensate ?

http://www.jeangodbout.com/trainwreck/e ... 4-4-0.html

Thank you, Jean

[Markusv]

Jean

Love your plexiglass amps on the website!
Beautiful

[godi]

Hi guys,

Starting today (April 14, 2011) Magnetic Components offer Trainwreck transformers. My little Hammond power transformer is a ''lemmon'' blowing fuses with lots of buzing, so I just bought a transformers set from Triode Electronic and I will convert my 4-4-0 to a full size amp with EL34 or maybe a pair of Shuguang Treasure 6CA7-Z

Cheers, Jean

[amplifiednation]

I just cut a chassis to start this build for a friend. Should be fun. I havent done a fixed bias amp before. Does the bias on this amp control the balance of each half of the 6sn7? Any suggestions before I start wiring?

Jean, your site is awesome. I remember seeing your Dumble build and I was very impressed. I bet you have a lot of tools. Haha

[godi]

Yes, each potentiometer control the bias on one triode (or haft of a 6SN7).

On my build, since I'm using two powers tubes, each bias pots control two haft tubes. The bias are not really balance pots, but two individual and independant bias control. I just follow the AX84 schematic and layout.

Well you are right, as a retired machinist (for disability reasons) I own lot of precision tools, but belive it or not, I builded all my guitars and amps whitout a table saw, living in a appartement, a table saw would be to noisy for my nabers and to dirty for my wife. I make all my cuts on a small band saw then I grind straight my cuts with a press drill equip with a drum sander.

But I own a little lathe 7'' X 14'' and a small milling machine, plus all the precision tools require in a machine shop, jo block set, micrometers, calipers etc...

[amplifiednation]

Haha...no table saw? You know amazing what you can get by with...

What are the dials by your test points? Am I gonna need a network of parts for the test points our are they pretty straight forward?

Anyone use the hammond ot in the bom? Its a weird piece of equipment with connection on the outside fit the secondary

[godi]

The ''dials'' are the trimpots that control the bias. These are one Watt from Mouser just like : http://ca.mouser.com/ProductDetail/BI-T ... vElPB80%3d

[amplifiednation]

Is that an add on for your amp our should I order up those parts for my one tube build?