plumsolly

Re: MK47 assembly - lots of pics
« Reply #20 on: October 20, 2010, 01:40:20 AM »
I think a Thiersch group buy was attempted/discussed a couple of years ago and if I recall correctly the price break was not enough to make it worthwhile.

Best, Ben



Re: MK47 assembly - lots of pics
« Reply #22 on: October 20, 2010, 04:28:54 PM »


Yeah, I was wondering what kind of price break (similar to Ben's) we could get from Thiersch, en masse...  ???

I didn't find any info on BeezNeez capsules price break. But if there's a appreciable volume discount how about K7 group buy?



Sredna

Re: MK47 assembly - lots of pics
« Reply #25 on: October 22, 2010, 03:11:39 PM »
It's working!   ;D


After initial problems with the 1uF MKT capacitor, it sounds quite nice also with a chinese K47 style
capsule.

The MKT had almost a total short, maybe 160V is underrated? Had some peaks of 120V during the finetunig of the PSU.

The PSU is very simple: 160VAC transformer, CRCRCRCRCR C=68uF R=500R 10W

The resistors are getting to hot to touch but not to melt plastic, the mic is warm and cosy...

So now waiting for a Beesneez capsule, Skylars housing, burning in the tubes, testing, testing, testing....

Thanks Max for this project!

Best,

Anders
Hmm... in which direction do the electrons actually go?

ioaudio

Re: MK47 assembly - lots of pics
« Reply #26 on: October 22, 2010, 05:53:04 PM »
The MKT had almost a total short, maybe 160V is underrated? Had some peaks of 120V during the finetunig of the PSU.

oh wow - sorry - i can send a replacement, let me know.
160 vdc should be all right (like the original), just bad luck with the cap.

-max

Sredna

Re: MK47 assembly - lots of pics
« Reply #27 on: October 23, 2010, 09:28:59 AM »
Now continuing with burning in of the tubes.

From the beginning they were quiet with occational pops.
Now, after maybe 6 hours, the pops are still there and are
most frequent at startup time.

Max, what are your experiences with these tubes?
Hmm... in which direction do the electrons actually go?

ioaudio

Re: MK47 assembly - lots of pics
« Reply #28 on: October 23, 2010, 09:56:38 AM »
let them burn in for at least 24 hours.
how did you solve the heater-droper *s heat flow to the housing?
which housing is in use? can you give some voltage readings?

-max

Sredna

Re: MK47 assembly - lots of pics
« Reply #29 on: October 24, 2010, 12:59:38 PM »
Burnin, burnin...  ;D
Still some snap, crackle and pops but getting better...

Im currently using a SE Electronics Z3300A housing, it's just temporary in the waiting for Skylar's housing.
The heater dropper was soldered with the legs slightly bent as a bow acting as a spring, it's
not that much pressure applied but the housing gets warm and cosy so it works.

Im also thinking about soldering a clip inside the housing tube or maybe install screw connectors on the
PCB and mount the resistor permanent inside the housing.

My readings:

Supply: 105V +/- 0.2V (Variations of +/- 1Volt over several hours, maybe house power variations?)
Heater : 34.8V (Between heater and dropping resistor)
Cathode: 1.3V (Between 27R resistor and pin2/7)
Plate: 43.6V (Obviously too high)
Capsule: 56.3V (At the voltage divider 2M/3M, cant get readings at the backplate)


The plate voltage is about 10V too high, checked the 100k and 30k resistors, they're ok.
Changed to a fresh set of tubes, getting about the same readings but plate voltage is now 50V!

What are your readings Max?

Best,

Anders



« Last Edit: October 24, 2010, 01:01:17 PM by Sredna »
Hmm... in which direction do the electrons actually go?


ioaudio

Re: MK47 assembly - lots of pics
« Reply #30 on: October 24, 2010, 01:53:39 PM »
your voltages are ok, including the plate.
do not mount the heater dropper on the transformer*s side.
two solutions: either drill&tap the base and mount the resistor or use some heat conductive glue.
-max


Sredna

Re: MK47 assembly - lots of pics
« Reply #31 on: October 24, 2010, 02:07:15 PM »
Ok, thanks! Then I can stop looking for Ra of VF14 ;)

Heater dropper is not on the transformer side. Why? (resistor is wirewound=inductor?)
 
Hmm... in which direction do the electrons actually go?

ioaudio

Re: MK47 assembly - lots of pics
« Reply #32 on: October 24, 2010, 02:11:24 PM »
we do not want to grill the transformer  ;)

Jim50hertz

Re: MK47 assembly - lots of pics
« Reply #33 on: October 26, 2010, 07:11:57 AM »
Burnin, burnin...  ;D
Still some snap, crackle and pops but getting better...


Still burnin' and noisy, or better?  :)
"Nasty, talking to a slightly deaf journalist, had claimed only that the Rutles were bigger than Rod."

Sredna

Re: MK47 assembly - lots of pics
« Reply #34 on: October 26, 2010, 08:17:52 AM »
Its much better but still some occasional pops now and then.

I also changed tubes and the new ones were considerably quieter
from the start and after a shorter burn time almost pop free.

Am now mounting the PSU in a proper enclosure so burn in is on halt but I feel confident
that out of the 6 pairs of tubes I have, Ill find at least one or two working pairs.
« Last Edit: October 26, 2010, 09:20:02 AM by Sredna »
Hmm... in which direction do the electrons actually go?

Jim50hertz

Re: MK47 assembly - lots of pics
« Reply #35 on: October 26, 2010, 08:31:54 AM »
Good news Anders.  :)

Seems like it's definitely worth having a stock of these around.  Thanks.

Jim
"Nasty, talking to a slightly deaf journalist, had claimed only that the Rutles were bigger than Rod."

Jim50hertz

Re: MK47 assembly - lots of pics
« Reply #36 on: October 29, 2010, 04:22:18 AM »

Psu - i am currently experimenting with choke / no choke.
The original NG psu was made in two versions - with and without the choke.
Triad 553-C-3X should be nice and cheap.


Hi max, any conclusions r.e. the choke/no choke experiments? 
"Nasty, talking to a slightly deaf journalist, had claimed only that the Rutles were bigger than Rod."

ioaudio

Re: MK47 assembly - lots of pics
« Reply #37 on: October 29, 2010, 08:07:29 AM »
yes:
1. the choke helps filtering crap from the mains and is a better solution for "poluted" places.
2. unloaded voltage does'nt rise as high as with the resistor-only circuit.

-max

« Last Edit: October 29, 2010, 09:31:59 AM by ioaudio »

Jim50hertz

Re: MK47 assembly - lots of pics
« Reply #38 on: October 29, 2010, 09:36:07 AM »
Thanks Max, I will go with that then... Do I simply omit the first two 1K resistors and sub the choke in?

"Nasty, talking to a slightly deaf journalist, had claimed only that the Rutles were bigger than Rod."

nashkato

Re: MK47 assembly - lots of pics
« Reply #39 on: November 01, 2010, 10:02:32 AM »
the triad inductor series offers different types.
max suggested the 10H , 500DCR , 50mA .
there are 7H / 10H , 240 / 270 DCR , 75 /90 mA inductors , too.

any comments on using another one than the 10H/50mA inductor ?








 

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