Federal Limiter AM864 thread

[NewYorkDave]

Actually, the high side to pin 2, low side to pin 3, and connect pin 1 to chassis. (But you knew that... just a typo, I'm sure). I agree, the centertap certainly isn't needed.

 

[Svart]

I was just making sure that there was nothing special, I've never used a trafo with B+ as the centertap before..

http://www.theopiumdenproductions.com/file-1.jpg

some progress, possibly usage this week..

 

[cannikin]

edit

 

[Joechris]

x is 6.2 V fillament...look at the transformer

 

[cannikin]

:grin:

 

[cannikin]

Need some troubleshooting help from you guys:

This is more of general Tube gear building issue but the Federal is a prime example:

what is the cause when the POTS sound scratchy? basically it sounds as if your trying to "tune in" a radio station - lots scratchy noise .... I have tried many different POTs because I thought it actually was a bad POT. but I have the same issue no matter what.... the scratch doesn't go away....so there's something else going on that I have no idea about... this happened with my LA2a too.

Lastly, I tried a Pad on the input didn't like what it did.. so I'm going to try an output PAD instead.... Any thoughts or words of wisdom?

Whatcha think?

 

[rafafredd]

maybe bad, leaky caps, and you are getting DC on the pot?

 

[enthalpystudios]

yeah dc on the pots is often whats up there.... i learned that recapping my bassman.

question i have however, is if you're working on something like the federal, maybe the circuit allowed dc on the pots? maybe especially on the pots that originally weren't out front. if thats the case, should a (correct) cap in series with the dc source stop it? is it as simple as a series cap, i wonder.

i dunno.

 

[cannikin]

Cool thanks For the info...

I'll check for Leaky caps - I used the Same Orange Drops for the two units that have this problem... so that might be it

For testing is it as easy as measuring the Pot for DC while its Powered up with VM?

Secondly, whats the Cure if that is in fact the Issue ( dc to the Pot)

 

[cannikin]

:grin: :green:

 

[NewYorkDave]

You want DC on that pot. Otherwise the circuit won't work.

By the way, "pot" is short for potentiometer. It's not an acronym like NORAD.

 

[cannikin]

:grin: :grin:

 

[enthalpystudios]

[quote author="cannikin"]Calling Tube Gurus --

rafafredd. enthalpystudios, PPR, NYD, CJ??[/quote]

NO!!! what are you saying... i dont belong there ;]

but i'm flattered.

but seriously, seriously, dont belong there....

thanks for believing in me though ;]

but hey which pot is this by the way? is it current control or threshold limiter?

i'm dumb. R8. read the post closer ;]

def should have dc on it.... and if it scratches, its probably fine, since it used to be in the back and needed a slotted screwdriver to adjust.

am i right in saying that it is a voltage divider used to vary the bias current on the tube that controls GR?

its good for me to look at this schematic, its still pretty much the first tube schematic i've really begun to unravel. really gotta build this guy!

just got turrets and the 'tool'

have to go to mcmaster carr (we have a huge warehouse about 20 mins away, desk service) for some garrolite (and a good deal, 33 bucks, on a stepped metric bit that hits 24mm at the top)

but then i'll be bustin out turret boards.

i'll figure this circuit out soon... i can feel it

hows it workin btw?

 

[rafafredd]

Please, don´t call me a tube guru... I´m nothing like this.

Let´s wait for the real tube gurus in here...

But, I would try a big wirewound pot there. You can find big 10W types, and try it. I don´t know if it would get rid of the scratches, but I would try.

 

[enthalpystudios]

fwiw, in addtion to rafa's suggestion i feel like I've read that conductive plastic high wattage pots can also help with this.... any truth to this?

 

[cannikin]

I ordered some PEC 2 Watt... expensive...
I'm also replacing the Orange Drops With Hovland MusiCaps... I'll let you know what I find out

 

[enthalpystudios]

please do... i've wanted to know if those hovlands are good are crap for quite a while.

i was gonna do my federal build with solens, just cuz sometimes you can get sweet deals on ebay and what not. have a few here, wouldnt need that many more values.

would love to hear an A/B sometime cannikin! really been wondering how this guy sounds. if you get a minute sometime that is

billy

 

[cannikin]

Hey B

I'll try and Post some stuff... just ordered everything for a Second Federal
Despite the Noise in the Pot.. I really like the sound of the unit.

 

[enthalpystudios]

good nuff for me

as if i wasnt going to build it already ;]

i really wish i could find a 2nd triplett dB meter...... this one looks the part real well, just wish i had a second... anything'll work tho, i suppose

 

[cannikin]

is there any way to get a VU working with this unit.. still don't understand the difference between VU and db

...time to search the internet