Voltages in stock 5E3?

[mbratch]

Anyone here own a stock vintage 5E3 (not a kit, not a new amp, no mods, but a vintage stock in good working condition)? Can you tell me what the plate (B+) and power tube cathode voltage readings are? And what rectifier tube you're using?

I'm very curious. I've seen so much information on what these things should be, could be, and varieties of settings in different kits. But I'm wanting to know what an off-the-shelf vintage 5E3 looks like for these measurements.

"Why is he asking this question?" you may ask. Well, I built a kit and like the tone. It has a PT that seems to be over-voltage of what is typical (the PT I have is 384-0-384). After several changes to bring it into spec (using zeners on the HV CT, and trying different values for the power cathode resistor) I discovered that the tone was somewhat flat when I had it within what I thought was spec. I realize tone is subjective, but I get that "Eagles" tweed tone when I leave the PT voltage alone and jack up the cathode resistor to around 470ohms, which puts the plate voltage at idle around 395V and power dissipation at around 12watts, which is a little high. So I'm curious what the real ones measure at, given modern wall voltages.

Thanks!

[slider313]

My '58 is running 365v from what I remember. I'm using a Bendix 6106. My Sylvania 6V6GTA's are running 39ma and 40ma. Most of my other sets run around 45ma. The Sylvania's give the amp a tighter response with more punch and clarity.

[sdgvintage]

part of the issue with stock 5e3 voltage is that in 1955 wall outlets put out about 100-110 VAC. Now you get between 118-125 vac. Which is about 10-20% higher which means yout b+ will also be that percent higher.
380-0-380 is what I believe what the secondary would be on an original triad if you give it 120vac.

You could look to getting a lower b+ transformer, something like 350-0-350 which would put you in the original 1955 B+.

[mbratch]

Originally Posted by sdgvintage

part of the issue with stock 5e3 voltage is that in 1955 wall outlets put out about 100-110 VAC. Now you get between 118-125 vac. Which is about 10-20% higher which means yout b+ will also be that percent higher.
380-0-380 is what I believe what the secondary would be on an original triad if you give it 120vac.

You could look to getting a lower b+ transformer, something like 350-0-350 which would put you in the original 1955 B+.

I was able to reduce the B+ using Zeners, down to 350V. But then I didn't like the sound of the amp any more (see my original post).

I'm aware of the wall voltage differences from back in the day to now. This all makes me wonder whether the Tweed sound we all currently know an dlove ios really wha tthe amps sounded like back then, given this fact.

[slider313]

Schematics for the 6G3 brown Deluxe show 365v. Schematics for the 5E4-A tweed Super, which was a dual 6V6 amp, show 380v.

[mbratch]

Thanks Slider313.

I'm interested in the 5E3 specifically. I suspect, if they had put the voltage on the schematic, it would be less than 365V, but that's an educated guess. The BFDR shows around 415V. Seems they kept cranking up the plate voltage as they went forwad with the design.

[slider313]

I believe it would be in the 340v-350v range similar to the 5E11 Vibrolux.

[mbratch]

Yeah that makes sense. I was hoping to get some real readings from someone with a vintage stock 5E3 so I could see the bias current and plate power dissipation at idle.

[SLBlues]

I have a Richter 5E3 and have been curious if it has been built to compensate between today's higher wall voltage of near 125V versus the 110V of the original 50's Tweed Deluxe. I would like run mine with a Variac to hear the difference between 125V and 110V input voltages. Interesting thread...

[GenoBluzGtr]

Not an answer to your question, but I recently picked up a 5E3 that was scratch built by Mike Yankie (Texas Tube Amps)...it was his personal amp. He self-sourced the parts, used a Heyboer PT and it has a NOS RCA 5Y3. The reading (using the Plate Voltage feature on my Weber Bias Rite) was 360V .

A friend loaned me his Clark Premium Beaufort so I could try some different speaker comparisons and I checked the voltage on his (with Mike Clarks proprietary PT that is wound to compensate for higher circuit voltages today) and it reads 305V! His rectifier is a NOS Sylvania 5Y3.

Quite a bit of difference. I can tell you that my tweed deluxe has a bit more headroom and volume, and sounds just a tad less smooth when pushed, but there are different tubes and those awesome paper-in-oil coupling caps in the Beaufort that could make that difference.

Also keep in mind that with the stock cathode resistor (250 ohm) there should be 20-25 Volts on the cathode, so the plate voltage to cathode voltage difference (in my case, 335-340V and for the Beaufort 275-280V) that acts on the current through the tube.

[slider313]

I just checked my readings: with a Weber Bias-Rite and the Bendix 6106 rectifier; 374v 38.4ma&40.4ma, with a GE 6087/5Y3GTB; 361v 36.9ma&39.1ma. The voltage readings include the cathode voltage.

[GenoBluzGtr]

Only 5 volts from the cathode to ground? I always thought there was more...

BTW, those Bendix 6106s are killer rectifiers... built to withstand a nuclear blast.

[slider313]

I originally put 5 but I believe it's between 5v and 10v. Oh, and my Bendix 6106 is mis-labeled as a 5AR4!!

[GenoBluzGtr]

I think you're right... it should be a 250 ohm resistor, if 40 mA of current is flowing through that leg it would 10 volts... right?

I*R=E ? .040 * 250 = 10Volts. makes sense.

[slider313]

Originally Posted by GenoBluzGtr

I think you're right... it should be a 250 ohm resistor, if 40 mA of current is flowing through that leg it would 10 volts... right?

I*R=E ? .040 * 250 = 10Volts. makes sense.

Right. And the actual resistor reading +or- would determine the actual drop.