CJ

Fender Blues Junior OPT
« on: April 22, 2018, 02:31:02 AM »
got a EL 84 based output on the operating table,  nothing wrong with it,  but some people take meds when they are not sick either, so wtf, over? jus sayin...  :D

15 watts into a 12 inch,  supposed to sound old school,

lams removed during pre-op, ready for open brain surgery, 

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

Re: Fender Blues Junior OPT
« Reply #1 on: April 22, 2018, 02:38:52 AM »
secondary leads,    two winds in parallel, no taps, 
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fender Blues Junior OPT
« Reply #2 on: April 22, 2018, 02:45:32 AM »
ripped the blu lead out doing a "pull test"  to check anchor strength, then realized we might need to know which wires go where,  pretty lame but nobody got hurt, just have to do some algebra, 

if Johnny has three apples, one red, one blue and one brown, and somebody steals the blue apple, how many apples does johnny have left?   :D

we hope that this is a simple coil,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fender Blues Junior OPT
« Reply #3 on: April 22, 2018, 02:57:28 AM »
secondary wind,  wire is pretty small, #25 or #26, does not need to handle a lot of power,

DCR is 0.4 ohms, usually you see around 0.2 ohms for the 8 ohm wind in a higher wattage amp,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fender Blues Junior OPT
« Reply #4 on: April 22, 2018, 03:04:06 AM »
down to the first layer,  figured out the coil geometry,   1/2 P  - S - P - S - 1/2 P

this is the next step above the P - S - P  and two steps above P-S

never seen P-S-P-S used before.

if you heat the coil often, you can rip right through the layer insulation without even removing it,

it is spring time, so we will put those paper chips outside for the crows,  the varnish will make for a waterproof nest,  :D
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Fender Blues Junior OPT
« Reply #5 on: April 22, 2018, 03:14:26 AM »
here is the print,

this is a nice sounding transformer, gentle rolloff, no rez peaks.

a little weak in the low end dept,

we calculate 29 K Gauss at 15 watts and 40 Hz, this is way over the 21 KG limit for 19 mil barn roof steel.

normal KG would be 19 KG flat out, which means 200 V-ac on the primary which only makes 5 or 6 watts of 40 Hz,

maybe that was what they were after to get that old blues sound,

we are going to stick as Tweed DeLuxe Triad #108  8K : 8 Ohms in  that Blues Jr and see if we can make that box rattle,

« Last Edit: April 22, 2018, 03:38:10 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

abbey road d enfer

Re: Fender Blues Junior OPT
« Reply #6 on: April 22, 2018, 01:06:44 PM »
we calculate 29 K Gauss at 15 watts and 40 Hz, this is way over the 21 KG limit for 19 mil barn roof steel.

normal KG would be 19 KG flat out, which means 200 V-ac on the primary which only makes 5 or 6 watts of 40 Hz,

maybe that was what they were after to get that old blues sound,
You don't need much response below 80 Hz for electric guitar; only pick attack and dive-bombs, which a typical Blues Jr. user is not adept.

Quote
see if we can make that box rattle,
I've used several Blues Jr.'s and I think they don't leave anything to be desired in terms of power and air-moving capabilities (in regard with form factor and weight).
I had to mod several of them, though, clipping out the infamous treble-sucking cap C35 (1500pF across Master Vol); 2.7kHz low-pass!
« Last Edit: April 22, 2018, 08:17:16 PM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

PRR

Re: Fender Blues Junior OPT
« Reply #7 on: April 22, 2018, 07:56:59 PM »
> 29 K Gauss at 15 watts and 40 Hz

Yeah, but that's 14KG at 82Hz normal guitar low-note. More than clean enuff for rock-n-roll.

Drop-tuners would normally opt for a more-guts amp than a Jr or be grooving on strained-bass tonez.

CJ

Re: Fender Blues Junior OPT
« Reply #8 on: April 23, 2018, 01:37:42 AM »
we went ahead and stuck a Triad 108 out of the Tweed DeLuxe on there, actually less inductance, but 4000 turns instead of 2240 of the Jr, and a full stack of 87 EI instead of a short stack of 75 EI, so the dive bombs will now work in this blues jr.

actually the guy uses it for a harp amp, so he will probably like this transformer with the gapped core = smooth inductance vs freq curve,

probably gonna leave the tone robber cap in there as there is nothing worse than a harp player with too much treble,

the amp sounds nice, hard to do an A/B on memory,  next thing it needs is a Cannabis Rex speaker, which were on sale two days ago,

working to dampen the reverb pan, there is a hi freq feedback problem with these amps coming from the pan that comes and goes,   fixed this before, you glue strips of 1/4 inch neoprene on the tank  and bag it.
« Last Edit: April 23, 2018, 01:43:18 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

abbey road d enfer

Re: Fender Blues Junior OPT
« Reply #9 on: April 23, 2018, 09:36:43 AM »
actually the guy uses it for a harp amp, so he will probably like this transformer with the gapped core
He may think different if he actually used it for a musical instrument.  :-*

Quote
probably gonna leave the tone robber cap in there as there is nothing worse than a harp player with too much treble,
There is nothing worse than a harp player, period.  :o  8)  ::)  :-[

Quote
working to dampen the reverb pan, there is a hi freq feedback problem with these amps coming from the pan that comes and goes,   fixed this before, you glue strips of 1/4 inch neoprene on the tank  and bag it.
Not a big issue anyway; next time he puts the amp in his trunk and drives, the spring breaks and the whining tone is gone.  :o I can't remember the number of spring tanks I had to replace in these Blues Jr.'s.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


mjrippe

Re: Fender Blues Junior OPT
« Reply #10 on: April 23, 2018, 12:44:47 PM »
There is nothing worse than a harp player, period.  :o  8)  ::)  :-[

Two words: electric bagpipes


 

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