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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Tue Sep 22, 2015 6:11 pm
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After a little searching I found these:

Hammond PT
http://www.mouser.com/ProductDetail/Hammond-Manufacturing/291AX/?qs=itkJorDwoMKEQx0kN0KjKA%3D%3D

Hammond OT
http://www.mouser.com/Search/ProductDetail.aspx?R=1760Cvirtualkey54600000virtualkey546-1760C

These look like a match for the Tweed but I would appreciate it if someone would take a look before I pull the trigger.

I appreciate the help and advice. I'm 99% sure I could piece together a standard paint-by-number kit but you folks get what I'm after and I wouldn't try this without your help.


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Tue Sep 22, 2015 10:50 pm
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Both of these trannies look to be excellent choices for a tweed Princeton clone and the O/T's multi-tap secondary provides you with some options for differing speaker loads.

Arjay

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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Wed Sep 23, 2015 9:44 am
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It mystifies me why a faithful clone amp builder would consider anything but a Fender OT. It is the one part that breathes Fender into a reproduction.
In this case, the original Fender TF22905 is not only less expensive, but it outputs 60% more power.
The reason for the difference is that the multitap secondary takes four times the secondary windings than the single tap.
This requires reducing the size of the primary winding to fit on the same size bobbin. The smaller wire has higher winding resistance that limits the power. This also reduces the inductance of the winding, altering the performance, brightness, and bass saturation.
The convience of having a 8 or 16 ohm speaker is, in my opinion, sacrificing performance for something you don't really need.
Again, if you want it to sound like a Fender.......


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Wed Sep 23, 2015 11:53 am
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Tims, you can find OEM transformers for the tweed era Princeton? I can only find aftermarket models. The Hammond will be fine. There is no real need to have the OP hunt for the original Triads. This is a small single-ended amp.

If he were making a Super Reverb or Deluxe Reverb clone (or some such more $$$ push-pull model) --- I'd agree with you to look for original iron.

If anything, he could use Schumacher trannies for the blackface or silverface Champ. I can't find NOS ones, but used samples are available. I have found little difference when subbing Hammonds in for blown Champ trannies. Esp power trannies.


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Wed Sep 23, 2015 12:05 pm
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Were this my project I'd wholeheartedly agree that an original O/T (or one spec'd as such) would be preferable to a modern multi-tap design. But the gentleman was asking for viable options which I and others have provided. Ultimately though, the decision is his alone.

Arjay

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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Wed Sep 23, 2015 3:36 pm
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Certainly, any transformer can be used and will work and sound OK. If you really need the 8 & 16 ohm taps, go for it. You'll never notice what is missing.
But being a performance-oriented guy, the difference in wattage alone would make my choice obvious. I can find a number of speakers to make it all work.
The 125A35A was the sucessor to the Triad and was used extensively for Fender Champs and Vibrochamps for years. It is the closest thing to the originals that you will find in a new unit. I would hesitate to recommend a 50-year old tranny in new construction.

While aftermarket power transformers seem to make little difference in tone, my experience with aftermarket output transformers has been a series of disappointments.
None have performed as well as stock Fender OTs.
As you know, I don't do guitar listening tests, but voltage measurements across the audio spectrum at different power levels.
And the disparity between Vox originals and clones is shocking.

There is little in the way of actual information about true performance of transformers and this leaves consumers vulnerable to the hype. You can buy what you've been told you want, but for me, its all Fender.

One other note. If you do use a multitap unit, use the 4 ohm tap for the feedback loop


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Wed Sep 23, 2015 6:13 pm
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I appreciate ALL advice but let me see if I can do a better job of clarifying what I'm after.

The 5F2A was selected as more of a direction than an actual target. I can't remember if I have ever even heard one live so to say I have to have an authentic Tweed would not be totally correct. I picked the Tweed because many of the videos I've seen on the web come very close to the tone I'm looking for. And even then I have to allow consideration for the various mods, recording processes and compression used in the clips which is why I can't say it must be an absolutely pure Tweed.

My thinking, and I may be all wrong, is that if I start with a good Tweed foundation by carefully selecting solid trannys and caps I should be well enough in the tone-zone where I can "sweeten to taste" from there if necessary.

What I want to avoid is getting 80% of the way there only to find I used anemic parts elsewhere in the foundation. Does that make sense?

As far as the OT I have no preference for or against multi-taps unless there is a tonal difference, which I haven't been able to find yet. The plan is to build a head and use the 12's that I have in my Pro Reverb, which works great now thanks to this forum, while I test the amp and decide what to do next. The PR is great but way too loud the home.

I suppose I should have said I'm reaching for good clean and solid crunch without a lot of volume. Something like this could be very close to the tone I'm looking for.

https://youtu.be/u6qSYUwWOno?t=39s

Boot Hill doesn't offer an 5F2A but I can add get the 5F1 and add a tone pot.

Thanks!


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Thu Sep 24, 2015 8:10 am
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The link seems to have the "saturated OT-small single ended tone." A tone supposedly gotten from a tweed Champ driven to output distortion by Clapton, during the Layla sessions.

You need a good quality power tranny. Hammond EBD1290AX will do fine.

http://www.hammondmfg.com/pdf/EDB290AX.pdf


And a small output tranny. So that it can be driven in OT, by volume alone. Don't go for a heavy duty one, like the Mercury Magnetic. It will not be driven into saturation as easily. I'd recommend the Hammond 1760C. Since you are going to use a 12-inch speaker, being able to use an 8-ohm impedance will help your hunt for a good one.

http://www.hammondmfg.com/pdf/EDB1760C.pdf

Now, the speaker is very important. You prolly need a smaller 10-15 watt one. Not a 12-inch speaker with a huge magnet and voice coil assembly. The original blackface and silverface Champs had a tiny 8-inch onboard. These had a distinct OD tone. Adding to the fuzz. I'd look for an original Jensen (Chicago) P12R.

These Champs and tweed Princetons were all about single-ended overdrive in the output stage. Specifically, a tone derived from the under-built nature of the amp's circuitry. Keep to the simple components of the original amps and you'll be fine.

Good luck! Keep us posted. :D


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Thu Sep 24, 2015 8:21 am
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BMW2002Ti wrote:
Adding to the fuzz. I'd look for an original Jensen (Chicago) P12R.


+1

Probably the best speaker for that amp at any price.

Arjay

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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Fri Oct 09, 2015 6:41 pm
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This is starting to move forward, but slowly. I've acquired some old Raytheon and GE tubes that are supposed to score at or within 90% of NOS but finding good caps in one place is another issue.

I may find 1 or 2 Jupiter \ F&T caps here and there but not all in the same place. Does anyone have a favorite source for parts where I might have a better chance of getting all the caps in one place?

Also, the kit I'm using as a parts guide calls for a 22u\50v Nichicon, and I'm trying to avoid my self-imposed rule where I have 80% of original or vintage parts and end up with 20% of something else. If Nichicon are as good then I'll use them, but finding a 22u/50v in anything other than Nichicon has been hard. I think I saw a 22/500v F&T but will need to check my bookmarks.

My questions may appear really dumb to those with years of experience so if I toss out a Goober question here's why. I'm not an engineer by any stretch but I have what I would call a fairly basic set of AC\DC and soldering skills. I like analog and learned long ago that transistors can't touch vintage tubes in terms of sound, at least not the sound I'm searching for, but in my daily life I deal mostly with RF and data. AC\DC and Ohm's Law not so much. I still need to refer to a pie chart for that.


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Fri Oct 09, 2015 10:59 pm
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I've never found a single vendor that stocked every component I needed for a restoration or a rebuild. I can usually find F&T electrolytics and Allen-Bradley carbon comp resistors on Ebay, but for tone/coupling caps (Jupiter or Zoso), those usually have to be sourced individually through specialty suppliers. You might try tubesandmore.com or MCM for a more comprehensive inventory.

What type of RF equipment do you work on?

Arjay

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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Sat Oct 10, 2015 8:25 am
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Retroverbial wrote:

What type of RF equipment do you work on?

Arjay


Not radio\transmitter equipment per-say but a HFC network. I work in a cable system with 1300 miles of active plant delivering digital services using a mix of equipment that in some places is older than I am. It's interesting work. We went from an all analog forward design of 650Mhz to full digital system using QAM modulation for voice, data and video and it handles that just fine, except for ingress and impulse noise which is a battle especially during summer months. On the fiber side we provide dedicated fiber for banks, hospitals, cell companies and some military bases. We have a separate group to handle power supplies. My work is mostly on the transport side. I don't see or touch anything with more than 80 VAC and when I do it's all plug-n-play which is a big reason I know very little about live circuits compared to the experts in here.


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Mon Oct 12, 2015 8:41 pm
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I started looking at schematics for the 5F2a to make notes for a parts list and I'm finding what looks to be many subtle variations. Some show changes in the filter caps while another (Weber) is missing what I believe is the "death cap" from the fuse to ground. If so which one is correct, or does it matter all that much?

I started with plans to go with a kit since it includes everything anyway, but since I'm making tranny, tube, cap and speaker choices I figured I might as well bypass most if not everything in the "box-o-parts" kit if possible. I don't mind the money so much but $70 for a blank chassis has me vapor locked. I'm pricing aluminum sheeting to bend and drill one myself.

Again, this won't be a stitch by stitch Tweed clone but I want what made the tweed famous.. I mentioned at the top of this thread that I may be overthinking this, and maybe I am, but I really only want to do this one time and then, if necessary, I can tweak with small changes with the tubes or caps after I hear it.

Clean like this
https://youtu.be/w_MbfZ5a91Y?t=50s

And somewhat gritty and bell-like, like this.
https://youtu.be/w_MbfZ5a91Y?t=5m55s

I's not a true Tweed but close enough to get me there.

Thanks again.
Randy


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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Mon Oct 12, 2015 10:34 pm
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The "death cap" is entirely superfluous and should be deleted in the interest of personnel safety. Any properly designed power-supply circuit will bleed down through the ground conductor of a 3-wire AC cord if it remains connected to a correctly-grounded wall outlet.

Arjay

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Post subject: Re: Planning stage of building an 5F2A Princeton
Posted: Thu Oct 29, 2015 9:49 pm
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All the parts to build a head are in and the weather forecast for the weekend says we have a 100% chance of rain. Looks like a good time to stay indoors and get started, but I'm working with a budget and I'm also a lousy perfectionist with little patience so I know this is going to be a challenge for me.

My impatience began to surface about a week ago. I ended up with F&T, mojo-dijon, NOS rated Raytheon and Sylvania tubes, carbon comp resistors and Hammond transformers. I may not get exactly what I want but will hopefully end up in the general direction. Intentional or not, I expect this will be a learning experience so it's highly likely there may be some tone-tweaking with different tubes and caps after I'm done. Until I can get a cab and speaker I'll run it through the speaker(s) in my 65 Pro Reverb. I really like that old lady.

I also skipped the kit idea except for the purchase of a turret board. Good or bad, I decided to make this a personal build so the parts were ordered based on the 5F2a schematic, and I have fabricated a "C" channel chassis from a sheet of 1/16" aluminum ready to go.

Thanks for all the advice.


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