5F1 Champ Build

Sylas Wojo

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Hi, I'm trying to gather all of the parts to build a Fender 5F1 Champ amp (My first build). What do you guys use for Power and Output Transformers? I was following the mojotone build guide, and the 2 transformers they suggest are out of stock. It seems like buying all the parts separately is a lot cheaper than buying a kit, so I want to do it that way.
Your feedback will be appreciated.
( I'm only 17 so my electronics's knowledge is not super huge, go easy on me :) )
Sylas Wojciechowski
 

tubegeek

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Welcome!
Your cost analysis is correct ONLY if you can find all your parts at one or two sellers - shipping costs are relatively high compared to dome of the other parts. Resistors and capacitors aren't too expensive, but specialty hardware (handle, chassis, stupid stuff like the pilot light) will be more costly than you expect.

The bonus on buying your parts by your own choice is you can get exactly what you want.

There is s LOT of info on this site - experiment with the search function and you will find answers to questions you don't even know you have.

If you are new to soldering there is nothing more important to a successful build than developing that skill. Nothing EXCEPT safety. That's #1.
 

boredguy6060

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Boot Hill has sold more kits than anyone imo. It could be he is one of the two that are out of stock, but I doubt it.
Contact Dave @ Boot Hill Amps and he’ll answer any questions you have.

Good luck
 

avspecialist

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I like the Heyborer transformers, great performing. I hear a lot of good things about magnetic components and classic tone. The most expensive are the Mercury Magnetics. Some people love them som people think they are overpriced.
 

Sylas Wojo

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Welcome!
Your cost analysis is correct ONLY if you can find all your parts at one or two sellers - shipping costs are relatively high compared to dome of the other parts. Resistors and capacitors aren't too expensive, but specialty hardware (handle, chassis, stupid stuff like the pilot light) will be more costly than you expect.

The bonus on buying your parts by your own choice is you can get exactly what you want.

There is s LOT of info on this site - experiment with the search function and you will find answers to questions you don't even know you have.

If you are new to soldering there is nothing more important to a successful build than developing that skill. Nothing EXCEPT safety. That's #1.

I was going to build the cabinet and make a chassis to keep the price down. I already know how to solder so that should be a breeze... hopefully.
 

Sylas Wojo

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A lot of the different power transformer say they are for champ 5F1 amps, but some of them have different impedance and voltages, for example the Mojotone 759 Power transformer and the Mojotone 760 Power transformer both have slightly different output voltages, and the 760 has an extra wire. Do these differences actually matter? And what would I wire the one with the extra wire?
 

Lowerleftcoast

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A lot of the different power transformer say they are for champ 5F1... ...Do these differences actually matter? And what would I wire the one with the extra wire?
Good luck and ask away! But do also search TDPRI, you will find treasure here.
As TG says do some searching. I have read several posts that like the lower voltage taps for the 5F1. So yes the voltage makes a difference.
Amperage for the secondaries need to be rated high enough to satisfy the intended purpose. Although some of the old versions used a 40mA HT, generally the HT needs to be rated for a minimum of ~50mA for a 6V6 5F1.
If a rectifier tube is employed, the 5V secondary needs to be rated at 2A to 3A depending on the tube.
The 6.3V secondary should be rated for a minimum of 1A.
Higher ampere ratings are not a problem.

The unused wire is terminated on a terminal block or is caped off with heat shrink and tucked away.
 

Sylas Wojo

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As TG says do some searching. I have read several posts that like the lower voltage taps for the 5F1. So yes the voltage makes a difference.
Amperage for the secondaries need to be rated high enough to satisfy the intended purpose. Although some of the old versions used a 40mA HT, generally the HT needs to be rated for a minimum of ~50mA for a 6V6 5F1.
If a rectifier tube is employed, the 5V secondary needs to be rated at 2A to 3A depending on the tube.
The 6.3V secondary should be rated for a minimum of 1A.
Higher ampere ratings are not a problem.

The unused wire is terminated on a terminal block or is caped off with heat shrink and tucked away.

The Power transfomer Im looking at has a 5v secondary rated at 4amps, is that okay to use with a 5y3 rectifier tube?
 

corliss1

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Yup - that's plenty for a 5Y3. That's the amps *available* which indicates how much current can be supplied by that section of the winding, not how much the tube is going to draw.
 

Sylas Wojo

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Yup - that's plenty for a 5Y3. That's the amps *available* which indicates how much current can be supplied by that section of the winding, not how much the tube is going to draw.

Ah, makes sense, thanks so much. I think im going to go with the Mojotone Mojo759. It looks like it delivers lower voltage than the PT the comes in the Mojotone 5F1 kit, but I think it should be suitable for this build.
 

King Fan

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Welcome, Sylas. You're doing good research, and you're getting good advice here. Keep asking questions. Planning a build is the cheapest, *funnest,* and safest part!!! Don't rush.

I won't say the MOJO759 is wrong, but if it's me I might try to save a little money and simplify things with single-voltage 120 primaries, and I might be OK with a standard 325-0-325 HT. A problem that comes up fast with DIY sourcing is you're trying to stay with one or two vendors to save on shipping, and then you start to compromise on parts to stay inside their catalog. I've done DIY sourcing since my third amp build, but it's still really hard -- and still ends up being expensive due to shipping and errors. So if you're commited to DIY sourcing to save money, make triple sure you *do* get the right parts. One re-order, especially anything expensive, could easily push costs above a kit.

I'd still look at Boothill. Dave's costs are amazingly low, plus can save you a lot of money on shipping, and he'll send you a 'partial' kit -- one where hard parts (and easy parts, and tedious parts) have been done for you, but you're able to order in just what you want for PT, OT, and speaker (with Dave's advice and that here) and build your own cabinet.
 

Lowerleftcoast

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Yes the mojo 759 will work. Plenty of amperes available for the heaters and 75mA for the HT.

Right now I have heard some transformer vendors are out of stock so that makes things a little more challenging. As KF and others have said the shipping can kill a deal.
Do your shopping. Mouser and tubedepot are a couple other vendors.

Also you may want to look at the 5F2A vs the 5F1.

I have no affiliation with the companies mentioned above.
 

Sylas Wojo

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Welcome, Sylas. You're doing good research, and you're getting good advice here. Keep asking questions. Planning a build is the cheapest, *funnest,* and safest part!!! Don't rush.

I won't say the MOJO759 is wrong, but if it's me I might try to save a little money and simplify things with single-voltage 120 primaries, and I might be OK with a standard 325-0-325 HT. A problem that comes up fast with DIY sourcing is you're trying to stay with one or two vendors to save on shipping, and then you start to compromise on parts to stay inside their catalog. I've done DIY sourcing since my third amp build, but it's still really hard -- and still ends up being expensive due to shipping and errors. So if you're commited to DIY sourcing to save money, make triple sure you *do* get the right parts. One re-order, especially anything expensive, could easily push costs above a kit.

I'd still look at Boothill. Dave's costs are amazingly low, plus can save you a lot of money on shipping, and he'll send you a 'partial' kit -- one where hard parts (and easy parts, and tedious parts) have been done for you, but you're able to order in just what you want for PT, OT, and speaker (with Dave's advice and that here) and build your own cabinet.


I had a look at the 325-0-325 Transformer you mentioned above, but It looks like its output voltage is 650v, where as the mojotone 5F1 wiring diagram uses a much lower ~300volt output for the 5y3 tube rectifier. Would I have to step down the voltage, or am I looking at this all wrong?
 

Nickfl

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I had a look at the 325-0-325 Transformer you mentioned above, but It looks like its output voltage is 650v, where as the mojotone 5F1 wiring diagram uses a much lower ~300volt output for the 5y3 tube rectifier. Would I have to step down the voltage, or am I looking at this all wrong?

You are looking at it wrong. A 650 volt center tapped secondary through a 5y3 will probably put out 360 or so volts. But that's just a ballpark guess because it depends on of the current rating of the transformer and the current demand of the application its wired into. The closer you come to the maximum current rating of the transformer the more the voltage will sag and the lower it will be so it's impossible to know for sure based on the specifications most manufacturers provide. Classic tone often gives estimated voltages on their spec sheets but in my experience even those are unreliable.

As far as transformers and parts kits et cetera, you're getting good advice to look at Boot Hill. His prices tend to be very good for the kits he provides and they would be hard to beat unless you are leaving out some of those components. I think you said you're making the chassis yourself which will provide a small savings. The biggest savings you can have is on making your own cabinet which you said you are also doing so that's good.

Take a look at Weber and Antique Electronics Supply. Weber tends to have slightly better prices but they're shipping is kind of unreasonable in my opinion. AES has good prices and free shipping over $80 I think, and they often end up being the best place to buy amp parts for that reason. you should be able to get everything you need from either of those suppliers and I suspect that either would be significantly cheaper than mojotone at the end of the day.

As someone mentioned, the specialty amplifier specific parts tend to be some of the most expensive bits and depending on how much of a true replica you want to make, you can save some money by avoiding those. For instance a pilot lamp assembly with the jewel insert and bulb will end up costing you almost $10 by the time it's done but a led and bezel will cost $0.50. Similarly, vintage correct tweed, grill cloth and cabinet hardware will set you back, but if you are willing to look at other options you can save a bunch there too.

Lastly, think long and hard about what you really want to build. Your first build should be an amp you actually want not just a champ because people say that's a good first build. If you really want a champ, great but don't be limited to that amp because its what you are "supposed" to do.
 

Lowerleftcoast

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I would go for the lower voltage PT. I don't see much price difference in the few PT's I had a look at.
I think KF was suggesting just running higher B+.
 

tubegeek

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I had a look at the 325-0-325 Transformer you mentioned above, but It looks like its output voltage is 650v, where as the mojotone 5F1 wiring diagram uses a much lower ~300volt output for the 5y3 tube rectifier. Would I have to step down the voltage, or am I looking at this all wrong?

You've bumped up against a problem with the way manufacturers list their specs, and an issue with 50's-style tube electronics.

Settle in, this is going to take a second.

First: 325-0-325 is an AC specification. Within its current limitations, that manufacturer is telling you what the AC voltage (RMS voltage, not peak voltage) you can expect is going to be.

A #-0-# spec means that there is a two-part secondary with a center tap. This is suitable for full-wave rectification.

325 volts AC is a measure of the POWER, equivalent to a DC voltage of a steady 325 volts. That will come when a sine wave AC voltage is present with a PEAK voltage of 460 V, varying from +460, through 0, to -460, and back to 0, 60 times a second. (US: 60 Hz. If you are elsewhere, that may be 50 Hz.)

Now, how will we be USING this AC voltage? We want to turn it into DC. This is a rectification process. Our final DC voltage is going to be related to two things: the PEAK voltage we put into the rectifier, and the efficiency of the rectifier.

2020-style: use silicon diodes with high efficiency and minimal voltage drop, so you'll get something very close to a full 460V present at the output of the rectifier.

1950's-style: use a vacuum-tube rectifier, which will have a substantial voltage drop depending on which tube and how much current you will draw from it. Not always an easy juggling act to predict exactly. You'll get.... something... out the other end. As @Nickfl said, you can expect roughly 360 DC Volts at the rectifier output, on the first filter cap, with the arrangement under discussion.

Bright side: we don't always really care EXACTLY how much DC voltage we are getting because we are building a 300-400V tube amp, not a 3 or 4 V digital logic circuit. Score one for the 1950's. But the power supply voltage has implications for how we set up the power tube bias and that is a further subject for another 150,000 or so posts here.

Your mojotone ~300V is AFTER rectification and it depends on the rectifier and the AC output of the transformer. They are trying to save you some figuring, but not everyone wants that.

Further complication: some of the popular rectifier tubes use 3A @ 5V heaters and some only draw 2A @ 5V. So it's a reasonable idea to ensure you have at least a 3A rating on your 5V secondary, in order to have a wide choice of rectifier possibilities to play the juggling act with.

I'm sorry this is so complicated but this ain't no Raspberry Pi you're building here, with nearly-perfect low voltage regulators for the power supply and precision opamps for the audio amplification.

This is way more fun though. You can't get your pants to flap with a stack of op-amps.

I have attached a pdf from Hammond with some information on rectification which is kind of a classic.
 

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Sylas Wojo

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I had a look at the 5F2A, I think Ill go with that option, it looks like its the same as the 5F1, but also has a tone control knob. I noticed both the 5F1 and 5F2A have two jack inputs. In Rob Robinette's website, he labels them as 1hi and 2lo, obviously these are for guitar inputs, but what is the difference between the two inputs?
 




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