DEACY AMP

[bigmuffpi]

Hi there,
i've got this pic of the original deacy pcb.

Those blue caps are probably electrolytics but i can't tell you anything about the four "metallized" caps.
On the right there are T1 & T2 transformers with a heat sink and two transistors over it (probably two ac128 for the output stage).
Some of you would know dentify the other components (resistors, other caps)?
Cheers!

[Rob Strand]

Check it out

http://www.vinylengine.com/phpBB2/viewtopic.php?t=13064

It's not exactly the same but I'm sure it's probably quite close. You should be able to match-up some values and even cross check the schem against your board.

(Your board seems to have more electrolytics caps.  The extra might be across the 9V rail or something.)

In these threads there's other schems,
http://www.diystompboxes.com/smfforum/index.php?topic=61336.0

http://freestompboxes.org/viewtopic.php?f=2&t=9198

Maybe a clone here,

http://fryerguitars.wordpress.com/2009/02/25/1-watt-amp-kit-drawings-and-schematics/

[zombiwoof]

By "metallized" caps do you mean the silver-colored ones?.   Those are obviously also electrolytics, as they have polarity markings on them.

Al

[Joe Hart]

Interesting. I have a perverse love affair with cheap, tiny, solid state amps. My favorite amp is a slightly modified 10W Yamaha practice amp with a single 8" speaker. I gig with it! Stick a mic in front of it and it sounds massive. Anyway I wouldn't mind building up a Deacy Amp.
-Joe Hart

[bigmuffpi]

Yes Zombiwoof, i mean the silver-electrolytic one.
Folk this is a pic of the original Deacy Amp made by John Deacon for Brian May.
I try to build a copy of this, so i'd like to know all the components.
Now i'm looking for a couple of Driver/Output transformers that may work for this circuit!
Here are the specs of the trannies:
Driver (interstage) transformer: 3.5:1+1 ratio, 20kohm-1 kohm CT
Output transformer:  3.1+3.1:1 ratio, 1kohmCT- 4ohm

I found a couple of Eagle transformers that may work but the output transformer is 300mW and i need at best 1W

[petemoore]

I try to build a copy of this, so i'd like to know all the components.
 Whether exactly the circuit BM ended up with [IIUC he tested some electronic equipment, tried tweeks here and there] is available or not, the circuit can be set up and *tweeked for guitar, as mentioned in the thread link, and seems plausible that this was done more than once before the 'final' design, the same is true here.
 Also mentioned were effects oboe' etc. as related to altering the bias, knowing the old transformer would tell more about how much the transformer specs/etc. are involved in the sound Vs. how specific it needs to be.
 First the circuit has to work somewhat before any of that can be worked through.
 Apparently some working Deacy is floating around, and there is interest [I saw what looked like new PCB], perhaps more info will float up.
 Meanwhile the transformer seems hard to locate.
 I haven't done blow the transformer tests so consider the cost of the 300ma. iron you mentioned, and outside work if:
 Building the circuit maybe?, set the transformer next to the 9v and try to decide if the cell would have enough 'uumph' to fry the former.
 Then test the circuit, Maybe pretest to see if it can be at least made to burp with ROTM PNP Si transistors first.
 Consider the input and output circuits of the transformer can be altered to reduce the ma. through the transformer.
 Altered response of course should be expected, but the circuit would be up and running and prepared for the suitable iron, should it show up.
 What happens in the other meanwhile ?
 If 'that' transformer can't be located, unless it was a tricky wind, can probably be fairly closely replicated, how close to 'center design' [there's logical 'match window' related to the Xformer windings, the only things to go on are 'was 4ohm speaker' and the circuit itself].
  Very interesting odd enough jobby [if it actually does the brass sections from guitar like that], type design to consider the designer may have gone 'offbeat from data sheets' so to speak to get it to do those things.

[brett]

Hi

Output transformer:  3.1+3.1:1 ratio, 1kohmCT- 4ohm

There is a fixed relationship between the turns ratio and the impedance ratio (ie. ratio^2).  Your 3.1 + 3.1 is correct, but the 1kohm is way out.  It should be 6.2 squared = 38.  I've used output transformers from about 32 ohms to 48 ohms in small AB transistor amps, all with good results.  In general, better heatsinks and more rugged transistors let you go lower with the impedance.
I wind my own output transformers (from wall wart transformers), but if you are willing to part with $5, you can get a Xicon output transformer (42TU048) http://au.mouser.com/catalog/specsheets/XC-600133.pdf.  I haven't used this one, but it looks perfect for this job (so it is weird how everyone gripes about no transformers for Deacy amps).  Although the datasheet quotes an 8 ohm load, it will work fine with a 4 ohm load.  Also, the rated output is 460 mW, but most output transformers can be driven harder than their rated output - you'll just get distortion.  That's a big part of the Deacy sound.
good luck

[bigmuffpi]

Ok, so i will buy one of this xicon 42tu48. Is there also a Xicon model for the driver transformer?

[brett]

Hi
The 42TM006-RC is a 20K:1K, but I'd definately consider the 42TM024-RC (10:0.5) because it has less DC resistance with the same impedance and turns ratios.
cheers

[bigmuffpi]

Ok, then ultimately the winning pair for my "Deacy Project" would be the 42TM024-RC as
Driver and the 42TU048 as output?

[petemoore]

  Ok, then ultimately the winning pair for my "Deacy Project" would be the 42TM024-RC as
Driver and the 42TU048 as output?
  Couldn't see actual price but it looked like a few buxx a 'pop' [knock on wood, no pun intended], proceeding with care at the output [more current here, 9v does x amount and that's it], looks like a low risk option.
  My guesses would be better or worse after some tryouts, I guess it'll work and work well, and the focus will then be on the speaker/amplifier as the big tonal influences [swapping trannies [upon availability] of suitable compatibility and competitive possibilities of course].
 

[bigmuffpi]

are some of you able to recognize the values ​​of resistors from this pic?

[valvusmusicus]

Hi All
Great thread
Just wondered if anyone had made a PCB foil they could share with the group?
Yeah, I know-if I really wnated one, I should design it myself!
But day jobs, lager and famillies take up alot of time!!

[Gordo]

Did anyone catch the price on the Fryer kit? 289 pounds?  What'd I break a friggin window???

[Ben N]

Did anyone catch the price on the Fryer kit? 289 pounds?  What'd I break a friggin window???

Heh heh. Here in Israel, "fryer" is slang for "sucker."

[DavenPaget]

Did anyone catch the price on the Fryer kit? 289 pounds?  What'd I break a friggin window???

What sorcery is this ?