The Amp Garage

Sorry, typo, I meant PT. That heater voltage seems rather low, can you recheck? If it’s correct, I suggest to investigate that further. The PT is the Hammond 291BEX which has a 240v primary: I assume that's why the overall voltages are a bit lower. Is there something I can do about it? I rechecked ...

What mains voltage is the OT designed for? If you’re unsure, the actual measured heater V AC, eg between 2 and 7 on an output valve socket, can be used to determine that. I'm not sure I understand the question, the OT is the tube amp doctor tweed deluxe replacement. Did you mean the power transform...

pdf64 wrote: ↑Tue Mar 14, 2023 12:16 am When taking voltage measurements, always include the mains voltage. It may be it was running 10% low.

Thanks for the tip! I took some measurements now and edited my former post. What do you think of the voltages?

Arrigo

And I’ve finally finished the assembly!

 It took me way longer than I originally thought, but since this has been my first real amp build I took my time and didn’t rush through it. Overall it was a very interesting learning experience, and I enjoyed the time I spent assembling it. Probably the leas...

I chose to go with the lower HV 290BX (US 120V primary). I ended up with a 375V B+1 and a plate voltage of 368V/368V on the JJ rectifier. Sounds great. That's cool! The 291bex is the 240v, updated version of your transformer. I should end up with similar voltages : ) In terms of "sag" and overall b...

You do not want to modify the chassis. 291BEX would most likely be fine, but if you want to go with the lower current higher voltage secondary (355-0-355 @ 115 mA, 238.1 ohms DCR), the 290BBEX is the one you want. The primary has options you don't need, but it can be wired for 240V, and the mountin...

pdf64 wrote: ↑Wed Dec 14, 2022 5:59 pm 237ohm HT winding; that’s more like it

I wish I had the knowledge to undertand these details... does it mean that the 291bex has the wrong specs for a 5E3?

Hello -- Been pondering whether adding to this thread would be helpful. Although Hammond markets their BFDR power transformer for a 5E3, in my albeit limited experience the Princeton/Champ power and their 5E3 output transformers are the better option: https://www.hammfg.com/files/parts/pdf/291AEX.p...

That would be a good choice to keep the B+ voltage down. What is your typical local line voltage? Typically around 240volts (235-244). I'm not looking to extract the last watt of power from the amp, quite the contrary. I was considering a transformer that "outputs" even lower B+ like Mercury FTDP-M...

Yes. I suggest not to think of it in terms if an ‘artificial centre tap’. Rather the goal is to make the heater circuit balanced with respect to circuit common, ie 2 x equal but opposing polarity 3.15V feeds, rather than the single ended 6.3V feed of the original 5E3 design. That can be done by con...

I just took a look at the innards of my Victoria 5112 amp, and I think it might have an artificial center tap: here it looks like they did it at the pilot light, by connecting a resistor to each side of the light and grounding the other ends to the on/off pot. It looks very neat, could I replicate t...

Hi everybody, lately I've been checking out power transformers' specs in search of the right transformer for the 5E3 I'm building. I've found that Hammond transformers are available here in Europe, and the model I was checking out is the 291BEX. Hammond advertises it as a deluxe reverb replacement, ...

So much to learn, thanks guys! I'm assuming you want to have 680p to ground when you pull the knob out, correct? That's not going to be possible using a SPST switch that closes on pull. Let's work in pF: 0.005u is 5000p, but you will probably find that 0.0047u or 4700p is what you can get. 680p in s...

which cap in the circuit you want to have on selector? this one to the ground= 5nF? if you want to increase the value, add then this blue connection, paralel. af.png if you want to reduce, then connection must be in series with 5nF Thanks bepone! I'd like to have the .005 as the stock value, and sw...

you can use it, just wire this switch in series with one cap, and 2 caps in parallel. one cap will have switch on-off , so you can select cap in-or out. other cap will be in circuit all the time. to avoid pop, when engaged , add 4.7Mohm (or so) over this switch. Thanks bepone! Will this wiring work?