|
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Decided to start this as a new topic. :)
Here's what I've found:
Most of the parts needed to assemble a Breadwinner/Deacon board are fairly easy to come by. The exceptions are going to be the inductor/power choke (it looks like a little donut covered with black rubber) and the switches.
First off, the inductor--the inductance of this thing is 1 henry. Not 1 microhenry, nor one millihenry, but 1.0 henries. Wow! Nothing even _close_ to that available from mouser or any other reasonable distributor. It looks like in order to reproduce the bw's inductor we have to roll our own. No biggie, just some added work. Inductors may be hard to come by, but cores, fortunately, are not. Easy enough to make a 1H inductor with readily available iron dust composite cores and copper wire, then seal them in rubber. Not cheap in terms of man-hours, but definitely possible.
The switches are another matter. There are multiple electrically identical switches available for the notch switch. Probably easy enough to find something that even looks and feels the same. I wish I could say the same for the pickup selector. There are electrically identical items, but I've yet to find anything that has a good sized toggle on it. I've dropped a line to the company that owns the company that bought the company that manufactured both switches in the first place to see if there are any stocks of them still available.
The rest of the components are all readily available. I'll let everyone know what I hear from the switch manufacturer, and try to work up some kind of pricing based on what the parts will cost plus some markup for the labor (I'd be etching, drilling, and populating the boards by hand, in addition to manufacturing the inductors).
Melmoth |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Okay, a quick update after talking to the always helpful folks at Ovation.
Switches are the one part they still have fair availability on. They're not cheap, but they're also not ridiculously expensive (try shopping for 3PDT stompbox switches sometime). No luck at all on the inductors, so it looks like I'll have to get cores and manufacture any I want to use. That's hardly the end of the world, but it _is_ a pain in the butt (imagine winding small guage copper wire around a pig iron donut the size of a quarter--now imagine that you've got to do it an EXACT number of times).
Ovation is sending me an original schematic, so hopefully I'll be able to determine the specs of the one unmarked transformer and find something to replace it.
Once I know about these factors I'll be putting together a test board layout. Once I've got it done, I'll post the pcb design, bill of materials and maybe some instructions for people who've never made a pcb before along with pricing for making a board for interested parties.
If anyone has data on the specs of the single transformer on the board, I'd be very happy to get them. |
|
| |
|
Joined:
December 2003
Posts: 13996
Location: Upper Left USA | Melmoth,
It is about time we get to have an obsessive compulsive Electronics person on the board! Long overdue! The thirty year old circuit boards are the weak spot in keeping these instruments going.
Would it be possible to recreate in a solid state what the board does?
Keep it up! |
|
| |
|
Joined:
January 2005
Posts: 640
Location: boulder | I'm with you all. It sounds ,uh,fun. No, I love to solder and build things. Finding time is usually the hardest part. Very cool idea and Nice effort Melmoth. Thanks, mike |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | MWoody,
Technically, the board is solid state with the exception of the pots, but I think I get what you're asking--could this be done in a smaller package with ICs or something. The answer is probably yes. You could, for instance, wire up a board using the opamp from a tube screamer instead of the FET preamp that the original used. You'd get a pretty good sound, too. The chip in question (usually a JRC4558D) is a dual op-amp which means you can do some interesting things with it--build in a switch to let the first stage overdrive the second, for instance or use both stages in parallel and provide a stereo output.
The sound, however, wouldn't be the same as the present electronics. I'm going to start by trying to produce a board as similar as possible to the original equipment and work out from there. The two things I'd most like to alter the board to allow are to add a rotary switch to replace the phase adjustment trimpot and allow on the fly adjustment between 4 or 6 levels of OOP including both pickups in phase with a bank of fixed resistors (although I think space for this is probably a bit limited--I might have to move the resistor bank onto a daughter board) and possibly to add similar adjustability to the notch filter.
If the parts aren't available it wouldn't be terribly hard to put together a circuit that would provide a similar FET boost using readily available parts. A preamp really isn't that complicated of a circuit. However, the BW/Deacon board is a bit more than just a preamp and some of the parts are pretty unique. Until we try to put together a new one we won't know how the modern components affect the sound.
As for being obsessive, I haven't done any of this stuff for about 20 years prior to deciding to buckle down and relearn all the project stuff I did as a kid. I've found it coming back faster than I expected, however, and have already managed to repair the switches on my Deacon, and am excited about the prospect of building new boards and mods.
Melmoth |
|
| |
|
Joined:
December 2003
Posts: 13996
Location: Upper Left USA | I can barely hang on to my Soldering Learner's Permit!
Good job! |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Woo-hoo! I have found a replacement toroidal choke in the right inductance!
http://www.electronicsurplus.com/commerce/catalog/product.jsp?produ...
All I need now is the specs on the transformer and we are ready to roll! |
|
| |
|
Joined:
March 2005
Posts: 1421
Location: Orange County, California | Mel,
Just a quick question, and you'll understand the question 1 second after I ask it. What is the DC resistance of that 1H indutor? I have in the past used a cheap readily availble high wattage wire-wound resistor in place of a purpose built inductor. If you have access to a good LCR meter, you can likely find something else that will work. the next question would be "why is it there"? Is it necessary for the circuit to function? Could you accomplish the same thing another way besides adding inductance to that part of the circuit.
Pocket-protector & hat with propeller by day, worship musician by night.. Has a nice ring to it doesn't it? |
|
| |
|
Joined:
December 2001
Posts: 7232
Location: The Great Pacific Northwest | I missed this thread earlier... I have all of the parts for the original circuits, unless you are just looking to build new ones. email me.
mileskb @ aol.com |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Miles: Do you know the specifics of the transformer on the board? All of the other parts can be purchased either new or surplus and electrically identical. The transformer doesn't appear to be marked (at least there are no markings I can see without removing it from the pcb. |
|
| |
|
Joined:
December 2003
Posts: 13996
Location: Upper Left USA | Breadwinner Site
You've seen this site, haven't you? |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Yep. Was the site that first told me what it was I had bought at the pawn shop when I was in high school.
http://www.doremi.co.uk/breadwinner/diag3.jpg
That would appear to be the deacon/breadwinner preamp, but the details next to the transformer symbol are illegible. I'm hoping the schematic from Ovation will have more details. |
|
| |
|
Joined:
November 2004
Posts: 1374
| I believe Brudev has the schematics for these boards and the legends for components in his galleries.
GH |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Again, yep. All of them except the transformer. It really isn't that weird when you look at audio transformers as a product. A lot of them were purpose made for specific applications. If we can't replace the transformer, maybe we can redesign the circuit to use a transformer with different specs. |
|
| |
|
Joined:
December 2001
Posts: 7232
Location: The Great Pacific Northwest | There are two methods for figuring this stuff out. One is to attempt to reverse engineer the circuit, the other is to dig out every similar transformer with similar physical attributes you can get your hands on and find one that works and sounds the best, or sounds like the original. Personally, I think the trial and error method works best and saves the most time in the long run. |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Well, John from Ovation is sending me a schematic, so maybe there will be specs for the transformer on it. I'll let you all know.
Alls I know for sure is that I just got the battery plate cover I needed on eBay and told Miles to go ahead and invoice me for the pickups. Living, breathing, shouting deacon, here I come. :) |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Okay, a quick update on the function of some of the items in the circuit:
The question was asked: do we need that inductor?
Well, the inductor is actually the core of the notch filter. Here's a page with a schematic for a simple band reject (notch) filter:
http://www.tpub.com/content/neets/14181/css/14181_51.htm
I'd point out that there is an error in the second illustration as the white area to the left of the shaded area should say "Frequencies Passed" instead of "Frequencies Rejected".
If you look at Brudev's schematic, you can see that when the notch filter switch is engaged the inductor (L1) is wired into the circuit with the notch filter engaged. It and the capacitors are tuning the center and size of the suppressed frequency band.
The transformer is in kind of a funky place. I'm not sure yet, but I think it may be there to condition power to the transistors, which, with 18v DC and 1970's transistors, was probably a really good idea. |
|
| |
|
Joined:
August 2006
Posts: 3145
Location: Marlton, NJ | Mel - can you recommend a good reference book for learning more about the electronics involved in this?
Mike |
|
| |
|
Joined:
March 2006
Posts: 1634
Location: Chehalis, Washington | So, once completed, will you be marketing this by chance? Or are you keeping it all for yourself? ;) |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | If you're just wanting to learn electronics theory and overall practice, _Electronics for Dummies_ is actually a really good introduction. If you're more specifically interested in amplification and effects as they're used in guitars, there are a lot of places that I'd recommend you peruse to get your feet wet before dropping any money on a text:
If you're interested in how guitar effects circuits work, try this page:
http://www.harmony-central.com/Effects/effects-explained.html
The effects explained page did a lot for me in terms of demystifying what a particular type of effect did and how the circuit which creates it works.
http://www.smallbearelec.com/home.html
Small Bear Electronics is a great company and the guy who runs it is super-helpful. He also is one of the only sources I'm aware of for buying germanium transistors already specced and matched for building fuzz pedals.
http://www.geofex.com/fxtech.htm
Here's a PILE of good articles from the geofex site including R. G. Keen's absolutely essential "Technology of the Tube Screamer." I learned a ton about this stuff by reading these. |
|
| |
|
Joined:
August 2006
Posts: 3145
Location: Marlton, NJ | Thanks! I'm planning ahead for future projects - the first is restoring my Preacher to it's original condition - no mods. After that I'd like to fool around a bit more. I'm sure I'll be bugging you alot in the upcoming months :-) |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Andrew - If (and keep in mind this is still an 'if') I can reproduce the original boards, I'll be making my pcb layout and bill of materials available free. It's not like I invented the thing, after all. That being said, if I can make a good replacement board, I'll certainly be open to building them for the solder impaired. |
|
| |
|
Joined:
August 2006
Posts: 3145
Location: Marlton, NJ | We should start up some Lunchtime Learning Sessions so the experts can impart their knowledge on the masses:
Mon: Transformers and Why We Love Them - Melmoth
Tue: 101 Uses for all that extra Veneer - MWoody
Wed: How not to bid on Ebay - CrimsonLake
12:00 in the large conference room.
Bring your own lunch. I'll bring the beer. |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Actually, the thing I can't get out of my head since I started working this is the image of those electronics installed in a Telecaster with a set of Seymour Duncan humbucking tele pickups. I suspect it'd make for an absolutely evil country guitar. What would you call that? A breadcaster? Has a good full gospel open brethren kind of ring to it. :) |
|
| |
|
Joined:
December 2003
Posts: 13996
Location: Upper Left USA | Righteous! |
|
| |
|
Joined:
May 2002
Posts: 1445
Location: Nova Scotia, Canada | Melmoth;
I wouldn't mind having a scan of that schematic when you get it. I'm not having any problems at the moment but you never know.
Wayne |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Wayne,
Will do. As soon as it gets to my mailbox it's going on the interwebs. |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Okay. I got the schematics from Ovation this weekend. They appear to be the same documents that are reproduced on the Breadwinner Fan Page. I'll make good (ie legible) scans of them and get them up on my googlepages tonight if I have time (it all depends what time I get done with work). The notation with the transformer symbol isn't unequivocal, but with the info there and some liberal testing of the board I have (which is working just fine) I should be able to figure out a good replacement. If it's just conditioning power for the preamp parts we're in good shape.
The other biggest problem is the need to find an appropriate dual potentiometer for the tone control. The stock one is dual ganged with two different values. I'm going to have to dig around to find something that works or else split it out to a separate neck and bridge tone control. I don't know how anyone else would feel about that. |
|
| |
|
Joined:
May 2003
Posts: 4389
Location: Capital District, NY, USA Minor Outlying Islands | I don't know if some of you recall, but a little while back Paul T mentioned that he was thinking about doing run of breadwinners in China. Me, I'd go for passive pickups. I know it wouldn't sound the same, but for me the mojo is in the shape. |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | Okay, here's the link for the breadwinner schematic:
http://gewalker.googlepages.com/Ovation_Breadwinner_Schematic.pdf
Unfortunately it doesn't do much to illuminate the details of the transformer. I've emailed the mothership to see if they have a copy of the referenced parts list. |
|
| |
|
Joined:
December 2003
Posts: 13996
Location: Upper Left USA | Cool.
What are all the squiggly line for? :rolleyes:
Where do you pour the mojo in? |
|
| |
|
Joined:
February 2006
Posts: 76
Location: Fairfax, VA | The mojo is put in at J1. :) |
|
| |
|
Joined:
August 2006
Posts: 3145
Location: Marlton, NJ | Melmoth - how is the project coming along? I've pretty much assembled the rest of the parts needed to put together a Breadwinner. |
|
| |
Breadwinner/Deacon replacement boards...