need to improvise..... dougs 5e3 to 6l6 and 5AR4

[bakerlite]

Soooo, fedex had to ground my shipment off tubes/rectifiers/transformer due to there being deoxit in aerosol form in the order - the company i ordered from should have known. I had earmarked the weekend to build a 5e3 esque amp for the gigs next week but its looking grim :(


Now i have to improvise..... and only with what i have to hand which is a 5e3 build without the PT, rectifier  and tubes.


But I do have s bucket of 6L6's , a 5ar4 , a mojo774 OT (super reverb/bassman/vibroverb) .  a beefier PT and a mismatch of filter caps....  and an empty weekend :)


so below is what I am suggesting as a work around :


couple of issues:


1)is the 7w cathode resistor gonna be enough? (I only have bags of 22r / 33r / 39r / 82r/ 47r and 4x 330R  in this size)
    --- I am thinking 4x 330R  in series (1220R) parralleld with 4x82R  (328R) to give a catode resistor value of 258 ohms, does that help in regards the wattge? 
2) Does the OT look matched enough?
3)worried about 354v and a 5ar4 giving too high a B+....  like something rdidulous like 490v at the first cap -could this be a show stopper?   

[HotBluePlates]

3)worried about 354v and a 5ar4 giving too high a B+....  like something rdidulous like 490v at the first cap -could this be a show stopper?

Does your power transformer have a fixed-bias tap? If so, copy the output stage and bias supply of the 5F4 Super (see the schematic link at the bottom of this page).

If you choose to use feedback, but are using a Deluxe chassis, you can leave out the presence pot; doing this, you'd copy the 5F4 circuit for V2A of your amp (the stage before the phase inverter).

It would be nice if you also had a choke to copy the power supply of the 5F4 Super.

The amp will be a bit different that a true Deluxe, and you should just wait for the right parts. Your choice.

[DummyLoad]

if you don't have a bias tap... i experimented with the circuit in the attached schematic so the values indicated are based on the results of those experiments.

with the use of this circuit, it is assumed that the PT being used does not have a bias tap, and that the rectifier configuration is that of a full wave grounded center tap with either solid state or vacuum rectifier(s).

--pete

[bakerlite]

Its amazing how helpful folks are here . especially towards people without the same level of expertise. Thanks!

I think maybe I was being a tad impetuous, I have so little free time that in my head there weren't nuttin' that'd stop me breaking out the soldering iron this weekend. But fresh start has it right.

I should just wait for the parts to arrive....
And hope that time  becomes available again soon.

Thanks again

[jojokeo]

I just re-worked a bunch of stuff on my Tweed Super Deluxe (it can run 5881/6L6s too but also has other bells & whistles). My PT is only 330-0-330 and my B+ is over 400VDC. My screens weren't too much lower. Since I was doing something else and it was a tad dark in my work area I noticed it was red-plating. Not really bad like something was horribly wrong but it caused me to re-make voltage measurements. Good thing too!
So it was running a Pdiss of 17.5 watts using the same 250ohm/10w cathode resistor. It took 450ohms to get it under control biased at 91.5%. While I was at it I put 1K/5w shared screen resistor in there also.
 
ps - before a show/gig it's better to spend those days leading up to it practicing your songs & solos rather than amp work.