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Discussion in 'Shock Brother's DIY Amps' started by newpain001, Feb 21, 2021.
In a 5E3, the two 6V6 will take about 80mA of power. The total power draw will be a little more.
Isn't that ok, just that the B+ might be slightly lower? It is advertised as a 5E3 PT.
Transformer companies are not very good at giving data. It seems to be more marketing than useful data.
I would say it is not OK to continually operate at over 80mA *if* the 75mA figure is the max rated output. A cathode biased 5E3 will be drawing over 80mA for the entire duty cycle. It is not fixed bias where it may run at 70% duty cycle most of the time and only peaking at 100% on occasion allowing cooling recovery time.
It may be the company states 75mA of current will drop the voltage to 330-0-330 and the Max current handling is unknown (to the consumer) but... what is the Max current handling number then? "Trust us".
I agree, based on the specs, it's in trust. I just emailed them so let's see what they respond, it would be helpful info.
Please share their response, it will be helpful.
Thanks for the detailed response.
I was also thinking about trying to source all the parts separately and found some parts list here https://el34world.com/Hoffman/5E3parts.htm and here https://hoffmanamps.com/MyStore/per...r&thispage=Amp_5E3Parts.htm&ORDER_ID=!ORDERID! but not sure if they are accurate and how difficult it will be to find all the parts online, including the chassis.
Looking at the transformers online, none of the companies specifies if the output transformer is 8K or not. I think it might be difficult to find good transformers (since I don't know the exact specs), but shouldn't be too bad for the other parts.
Found an interesting video about a 5E3 build from scratch.
Where are you looking at transformers? A lot of the sellers have a link to a PDF of a datasheet or spec sheet that shows the primary impedance and wire colors and sometimes transformer dimensions. Some don't though, Mercury Magnetics is notorious for listing descriptions about how they clone vintage transformers instead of listing technicalm details.
I checked Triode, Mojotone, StewMac, Ebay and few other websites if I am not wrong, only Triode provides specification docs.
According to these specs, this one at Triode looks like 8K, so maybe it's a good fit? But it doesn't seem to be in stock.
There is another one (Hammond) which is in stock: http://www.triodeelectronics.com/40-18088.html
But if I am not wrong, this is 6K: Spec: https://www.hammfg.com/files/parts/pdf/1760JB.pdf
When it comes to power transformers, I am not sure what to check, though.
Found these two from Triode's website:
Made by Magnetic Components Inc.
and this one which is around $30 more:
I'm preparing a for a thread that will be a collective brain dump on the subject of transformers, there is very little 'deep dive' info out there.
Companies that sell them have done reverse engineering on vintage models but don't publish the info.
For reverse engineer, here's what I'd do, dc resistance, impedance ratios, disassemble, count the winding turns, measure the core/laminates dimensions and wire thickness, I need to build a 1KHz tube audio signal generator to measure the inductance.
Last week I reverse engineered a small 10W OT from 1962 clone it, wound it yesterday and today I'll find out if it makes sweet geetar/farting noises (with my playing, probably both).
Don’t buy anything from Triode. That place will ship your amp part by part over the course of multiple months. You will then have to take inventory and email them when it’s inevitably missing something. I built a JTM45 for a friend and they sent multiple chassis and faceplates that didn’t even fit each other. One chassis took a 59 bassman power transformer! That got used for a spare parts build that turned out nice, but still, they were so aloof it wasn’t even funny at the time.
I built my 5e3 from parts I bought separately (mostly from Amplified Parts. since they had good prices on pretty much everything). Really not too hard- just use a spreadsheet of all the build materials and mark them off when you order them. Amplified parts lets you build a "project", so you can easily add all of your components and buy them at once. If you do it this way, you can get exactly the quality of everything you want (caps, resistors, wire, etc.) AND have leftovers since resistors typically come in packs of 5. This cost me about the same as a kit.
I bought a 5f1 kit from Boothill to build with my son (we were in a time crunch for a school project, and Dave who sells the Boothill kits is only about 20 minutes from me, so I could get it quick). It was a great quality kit, especially for the price and the convenience of picking up everything at once. The wire that came with mine seemed pretty thin, but has held up just fine.
Finally, I helped my buddy put together a 5e3 kit from Boothill. Same quality/convenience as my 5f1, and great for the price.
So, I personally enjoy picking and choosing all my parts individually (as opposed to a kit) since I get exactly what I want, but a kit from any of the vendors you mentioned will give you a perfectly great amp.
As to the sound of a 5e3? Well, there are 1000 threads on the TDPRI about that (and 1000 different opinions). Things like speaker selection, preamp tube choice (12ax7 vs 5751) and coupling cap values make a HUGE difference in the overall gain and tone of the amp that only you can decide if you like it. Personally, using lower gain preamp tubes and an efficient speaker lets me get a great (and plenty loud) amp that I can use for any purpose. Beautiful, thick cleans all the way up the dial, but easy to push into crunch with humbuckers, your guitar volume knob, or a clean boost.
I just received a reply from Mojotone regarding the current capabilities of their 330V-0-330V @75mA 5E3 PT, and am pasting it here with their permission:
The modern day 6V6 can draw up to 70ma of current at its absolute limit, when at 100% plate dissipation and 500vdc on the plate producing 14w. in a push-pull configuration. Fortunately the 5E3 does not run ridiculously high voltages, or It would eat itself in a matter of seconds. When we look at more manageable voltages of the original 5E3, anywhere from 360 to 400, everything starts to even out. Sure, the tubes are still running 85 to 90%, but it drops the current draw per tube (idle) in normal operating conditions including the sag drastically, because of the power supply inefficiency. This is accounting for sag in the power supply using a 5Y3, which is really the shock absorber in this whole equation. Initial current draw when a note is hit can run a tube up to well over 100%, but this is only for a millisecond, and then the dissipation drops. So, in short, yes looking at it on paper would tell you that every 5E3, or better yet, every cathode based Tweed amp should fail due to it's underrated output transformer, but Fender transformers were more-or-less over engineered to handle this. These transformers are so well built that you can actually use 6L6's in place of the 6V6's. Is it optimal? No, but it's just an example of how underrated these transformers are. Now, this brings us to the point of the stated current draw. We based our vintage transformers on direct tear-downs of originals, used those values for guidelines of what the transformer is capable of and then went to the drawing board to see how we could improve longevity. This included using slightly lower gauge wire in most cases to where we could increase limiting values but maintaining the overall footprint due to better materials and manufacturing than what was available 60 years ago. I can safely say that on average, our HV secondaries can handle up to twice the stated current easily without damaging the transformer itself. But, keep in mind doing this, the compression (or sag) will increase.
So..... 150mA then?
No clue, I'm just the messenger!