Woodward-Schumacher specs

[Colossal]

Go here: http://support.fender.com/schematics/gu ... ematic.pdf

The '57 Deluxe is running ~370V on the plates, and 320V on the screens, and it has a 250R cathode resistor. Cathode voltage is listed at 21.2. So, Fender is really doing that with new production tubes.

Well, at least we have an example of the exact same setup. Very cool find!

The load might be either 6k6 or 8K, but that doesn't matter for the idle point. With this hot bias it runs in class A up to about half-power.

I computed a bunch of different loads and your right, almost no difference.

BTW when you plot the load lines, the class B load line goes from Va-k at zero current to Ia = Va-k/(Zaa/4) at Va-k = 0. Then the class A load line has half the slope (Zaa/2 since both sides are conducting) and passes through the idle point at (Va-k, Ia).

I want to do a proper analysis on it; scale the screen curves to 330V, etc, but first just wanted to make sure I was in the ballpark with these assumptions about the amp operating as shown on the schematic before moving on. For the above, where you are saying plot Class B, then A portions, are you referring to procedure from Kuehnel (Power Amps, p.82, Fig 6-15) showing the composite load line?

Thanks for your help with this!

Dave

[surfsup]

I'll ask some peeps on the elevatormwho to talk to. What am i asking? Just thespecs of those three tx serial numbers?

[Colossal]

I'll ask some peeps on the elevatormwho to talk to. What am i asking? Just thespecs of those three tx serial numbers?

Yes please!

[martin manning]

For the above, where you are saying plot Class B, then A portions, are you referring to procedure from Kuehnel (Power Amps, p.82, Fig 6-15) showing the composite load line?

More like the next figure where he plots the class AB load line for a single tube from the composite curves.

You can plot the class A and class B load lines directly as Blencowe describes on his site (close enough for rock and roll!). Look over both the SE and PP articles, and note that he doesn't mention that cathode bias reduces the anode and screen voltages by a like amount, and so in reality an iterative solution is required to locate the idle point.

[Diablo1]

Philips lighting??? I work in their building...

Dude! Gather some intel!

Seriously, I have no idea why Schumacher would send me to Philips unless they somehow have their old records. Half the fun in researching these old amps are the snipe hunts

Philips lighting / Advance Transformer builds transformers for fluorescent lights and HID ballasts. I've visited their plant in Monroe WI many times. Did Schumaker outsource musical instrument transformer production to them in the past? I seriously doubt that they have built any MI transformers in the past few decades, I never saw any being produced and never heard any mention of that part of their business.

[Richie]

you might also look up some of the other chicago type amps, older--or in that range of year. gibson,supro,dano, etc.. Always seemed the gibson amps also had small underated transformers. Or maybe they just looked that way compared to others. But i know many are still going today and being played.
I don't think they ran voltages as high as the maggies. And some used a 200ohm cathode resistor.
The later fender amps i've seen some deluxe reverbs at 450 plate volts on 6v6s!

Also there are transformer places that have the gibson and valco replacement iron. You might look into those for some tech info data.

Most of the transformers in that era, were 115v or 117v listed. Same as the magnatone, was listed 117v on the schem.
The one model magnatone also has a weird set of stages or values in the power section. Like i had never seen used on any other amps, well mostly on the last preamp node.

[jcandmeirality]

Hi, im new to this forum and to amp making in general.
About a week ago in what be a state of madness I decided to build a clone of the Tonemaster Troubadour 214, basically the amp that Phil X uses in his youtube movies. I have attached the schematic that I am working from, which would be similar to the one that you may have used @Colossal.

Basically I have sourced most of the resistors/capacitors from online companies, and have arrived at the stage where I am looking at the OT and the PT for this particular amp build. I have read this information in the forum about three times trying to get my head around some of the details being discussed however I am lost in the lingo and I still do not know the correct transformers to choose.

Could you please let me know the model/brand/type of PT and OT that should purchase for this amp so that I can search online and get them shipped to Australia?

And one other question that I had was the dilemma of the mains power being supplied to the amp. It seems that the original magnatone amps used the 117v transformer, but how do I make this work when here in Australia the power is 240v any suggestions?

I am loving the experience and challenge of this project but know so little about building tube amps, so any help would be awesome!
thanks

Sam

[martin manning]

There is a Magnatone-Valco Yahoo group that may be a source of specs for this particular amp model. Without more information I'd think an export Fender Deluxe/Deluxe Reverb transformer set would work given that the power tube types are similar. There are a number of after-market replacements available, but maybe Hammond is a good choice since they are manufactured in Canada, and may have distribution in Oz. Here's a link: http://www.hammondmfg.com/guitarLine.htm Do you have a source for the varistors? They are not easy to find here.

[Colossal]

Hi, im new to this forum and to amp making in general.
About a week ago in what be a state of madness I decided to build a clone of the Tonemaster Troubadour 214, basically the amp that Phil X uses in his youtube movies. I have attached the schematic that I am working from, which would be similar to the one that you may have used @Colossal.

Basically I have sourced most of the resistors/capacitors from online companies, and have arrived at the stage where I am looking at the OT and the PT for this particular amp build. I have read this information in the forum about three times trying to get my head around some of the details being discussed however I am lost in the lingo and I still do not know the correct transformers to choose.

Could you please let me know the model/brand/type of PT and OT that should purchase for this amp so that I can search online and get them shipped to Australia?

And one other question that I had was the dilemma of the mains power being supplied to the amp. It seems that the original magnatone amps used the 117v transformer, but how do I make this work when here in Australia the power is 240v any suggestions?

I am loving the experience and challenge of this project but know so little about building tube amps, so any help would be awesome!
thanks

Sam

Sam,

My digging shows the PT to be 330-0-330 and the OT around 6k6-8k. I have nothing to substantiate this except historical coincidence, but Schumacher made OEM steel for Fender and Magnatone in those early days and the Radio Manual was the designer's friend at the time, so the PT/OT specs are similar to other classic amps of the era.

Magnetic Components and Mercury have parts in their catalogs that will fit the bill. In correctly sizing your parts, I would ask whoever you source from, tell them your target, rectified voltages. Make them work the problem backwards from the desired rectified B+ (around 375V). They usually know what the loaded and unloaded voltages will be for a given part.

Great amps and everyone should express their inner Phil X.

[jcandmeirality]

Hey thanks for the fast replies Thats great im going to start looking for where I can get the transformers today. Any idea on the price I should be looking at spending for each in USD? The Hammond replacements for similar amps sounds very interesting however I noticed that the Phil X custom 214 uses hand wound transistors just wondering if it would be worthwhile for me to source a brand that are the same but are hand made any thoughts? I found this website for replacement Transformers:

http://www.mercurymagnetics.com/pages/c ... natone.htm

These seem quite expensive, however they are hand made. If the original 214's were made with standard transformers that are similar to the Fender Deluxe/Deluxe Reverb then really shouldn't I be able to get that Phil X tone using the replacement parts, rather than hand made?

Do you have a source for the varistors? They are not easy to find here.

I did quite a lot of digging around while looking and found this information:

http://www.el34world.com/Forum/index.ph ... 50.20;wap2

Apparently the LITTELFUSE - V68ZA2P - VARISTOR, 3.0J, 40VAC resistors work great in Vibrato builds.On finding this information again I just realised that the varistors that I ordered were the
EPCOS - B72207S0400K101 - VARISTOR, 3.0J, 40VAC which are very similar however the capacitance is 900pF as opposed to the Littlefuse varistors, which are 600pF. This could be my undoing, I might have to reorder if they wont work well :S

Interestingly I just read the page after the one linked and someone suggested that magnatone are back in business now so maybe the original varistors will become available again?

[martin manning]

Here's another source of transformers: http://www.classictone.net/Fender-20W-D ... rmers.html These can be ordered through Triode Electronics in Chicago (the link is there), and they will ship to Oz. Note there is an upright-mount version of the power transformer. I wouldn't think Mercury's transformers are any more hand-made than other low volume parts. Many feel they are not any better, just over-priced.

Modern varistors are not the same as the ones Magnatone used. The originals are copper oxide (as noted on the schematic), while the modern ones are zinc oxide. There were silicon carbide versions too. The difference is in the shape of the current vs. voltage characteristic, with the older versions having a more gradual current rise. A faster rise is better for protection circuits so these newer, faster ones are seen as better. Magnatone amps have indeed been re-launched recently. If they are having special varistors made for their vibrato units I doubt that they would make them available. It would be nice to find out if the Littlefuse parts are actually an acceptable substitute. They are ZnO.

[jcandmeirality]

Hi so I have been doing a little more research on these varistors. Apparently a Varistor such as the ones used in the Magnatones can be cloned using a string of Zener diodes and have similar results!

http://dalmura.com.au/projects/Vibrato% ... ements.pdf

Let me know what you guys think about this alternative to varistors?

Sam