AC30 home built amp

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stantana
Junior tube assistant
Posts: 8
(2/17/04 6:14 pm)
 AC30 home built amp
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 Hello, I have started building an AC30 type amp. I have the weber 6v30 chassis and a hoffman type turret board which I loaded already. I just have a few questions about building this beast. The design is the hoffman ac30 non tremelo model. Several questions that I have is: What is the value of the vertical can capacitor near the power tubes, and 2. Does anyone have a jpeg of the finished weber chassis that they would not mind sharing? Thank you for any information that you can share.  
 
6bq5
Junior tube assistant
Posts: 9
(2/21/04 3:44 pm)
 Re: AC30 home built amp
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 hello there, you can use a 30 or 50 mf dual cap like an lcr or f/t or jj brand, these are available lots of places. use one section for the plate filter and one for the screens. 30mf provides less filtering and provides a spongier feel with a bit of ghost noting and more vintage feel. i believe the original ac30's used 16mf caps in these sections but the current lcr dual cap is smaller diameter now and will not fit the hole, plus i would want the extra filtering for the power section. hope this helps. rh
 
dough
Junior tube assistant
Posts: 1
(2/26/04 4:07 pm)
 AC30 home built amp
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 This is just my 2 cents. I used the lcr 16+16 cans in my AC30 built on a Weber 6v30 chassis. It has worked out fine. You can see a pic of my chassis here:

AC30 project

There are F&T 16+16 cans available also.

Doug

Edited by: dough at: 2/26/04 4:24 pm
 
stantana
Junior tube assistant
Posts: 9
(3/6/04 9:23 am)
 AC30 home built amp
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 Thanks
 
stantana
Junior tube assistant
Posts: 10
(3/6/04 9:25 am)
 AC30 home built amp
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 The link didn't work.
 
dough
Posts: 3
(3/6/04 2:02 pm)
 AC30 home built amp
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 Sorry. Sometimes I am over my band width and you have to check back later. You could also try going to the home page:

www.geocities.com/flyt4721

Doug

Edited by: dough at: 3/6/04 11:22 pm
 
stantana
Junior tube assistant
Posts: 11
(3/16/04 6:45 pm)
  AC30 home built amp
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 Hello,

I have a AC30 GA 30 power transformer. It has 5 primary wires and 8 secondary wires. Please help me with testing the transformer to determine the correct hookup. How do I measure the voltages. I have a variac and meters etc. I completed the main board etc. I just need to figure how to hook up the tranny.

Thanks,

Stan
 
6G6
Junior tube assistant
Posts: 126
(3/16/04 7:09 pm)
  Re: AC30 home built amp
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 OK, I'm not looking at your tranny, just imagining it.

In my minds eye, I see either a black or green ground on the primary and a pair of red wires and a pair of blue wires.
One pair is for 120V, the other for 240V.
Pick one pair.
Connect it to a PT 5V tap if you can to keep the voltage down.
If you don't have a low voltage source you will have to use 120V (unless you are somewhere else, then 240).

Be careful. The seconday will have a higher voltage!

Now for the fun part. Find a pair the same color. Maybe green.
See what your voltage reading is. If it's fed 120, then it may be the 6.3V heater tap.
Measure it...carefully.
Try again with each other pair.
You should find :
A 5V pair. = rectifier heaters
A 6.3V pair. = all other heaters
A 450-500V pair. = B+
A center tap. = chassis ground
A 20-50V to ground. = bias tap

If you read half of what you expect, you have fed 120 into the 240 tap.

Colors may vary.

If you are able to use a 5V source, you will be safer, but you will have to multiply the secondary voltage by 24 to find out what it is.

Kinda like a gigsaw puzzle without a picture.
It makes perfect sense... after you get it together.

Oh and did I mention, be careful.

 
stantana
Junior tube assistant
Posts: 12
(3/16/04 7:59 pm)
  AC30 home built amp
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 Thanks,

There are 5 wires on the primary side:

yellow, red, brown, blue, and black. I hooked up power to the primary blue and black and measure the 2 gray wires together on the secondary and got 7 volts. Is that close enough. there is a 100 volt, 230, 115, 100, and 0 volt leads. I have a pdf schem I can share:  
 
stantana
Junior tube assistant
Posts: 13
(3/16/04 8:42 pm)
  AC30 home built amp
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Hello, here are the voltage readings for the power trans
secondary:

gray pair= 6.4 V

yellow pair= 5.3 volts

black and red pair HT B plus = 594 volts

white bias tap to ground= 91 V

green to ground = 97 V

I thinkin that white is the bias tap and green is the ground.

voltage was tweaked to 110 via variac

P.S. Used extreme safety precautions, including CPR trained wife to begin CPR if necessary.



What do you think.
 
6G6
Junior tube assistant
Posts: 127
(3/16/04 9:54 pm)
  Re: AC30 home built amp
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 I think you've sorted it out.
Nice to have a trained wife handy.
Ground is most likely to be either green or black.
The slightly high readings will go down some with a load on them.
 
stantana
Junior tube assistant
Posts: 14
(3/17/04 3:40 pm)
 AC30 home built amp
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Hello, I have another question and thank you for helping me sort out the tranny problem.

I need to place my hoffman type AC 30 board into a weber 6V30 chassis. However, I am at a loss where to place the board. There are tube sockets, trannys in the way. The chassis dimensions are: 13 1/2 by 3 inch turret board loaded.

Thanks,

Stan  
 
stan buczko
Junior tube assistant
Posts: 75
(3/17/04 8:27 pm)
 Re: AC30 home built amp
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 Here is a suggestion. You can make brackets to mount your trannys on the outside of the chassis and use sheet metal to cover the existing holes.

 
stantana
Junior tube assistant
Posts: 15
(4/6/04 10:00 am)
 Re: AC30 home built amp
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I have another question, I would like to build an amp with 4 6V6 output tubes. Could I use the existing AC30 hoffman circuit (punching out new holes of course) and use 6V6 tubes instead?

Thanks
 
 
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