New Federal AM864 born

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DerEber

Well-known member
Joined
Aug 2, 2005
Messages
452
Location
München-Germany
Dear friends,

this is my first build of an complete unit and I am very happy.
When the Federal came up here I thought "this will be my first tube Limiter".
Now its 2011.

Federal1.jpg




Federal2.jpg




Federal3.jpg



I had ugly motorboating and now ended up limiting the Threshold-pot with some series
resistence. Threshold is going still going down to -14dBu.
I am having a 1:1 at the Input and padded the output with -12db, leaving +16dB gain.


thanks to all for your support and this great forum!

Stephan
 
Nice job Stephan!  - Looks great!  Congrats.  I dig the white jacket SK7s -  8)


What input and output transformers and chassis did you use?

Also, what are the mysterious looking switches/relays/circuit breakers?  mounted along the back?
 
Thanks,

for Input I used a 1:1 Malotki that was laying around.
The output is Edcor 4:1.

Where I bought the chassis.....?  I can´t remember. I did this in very small steps over many years now.
But I was lucky to find one that was not that deep. I must have the bill somewere  8)

The misterious looking things mounted along the back are simple pots. It´s the balance mod.
Somehow they are not that usefull for me. My tubes give same voltages at zero and -10db reduction.
Maybe I my meassurement is not correct. I meassured the Plate Voltage, correct?

I also leave the Ug2 pots counterclockwise. When touching one I get more distortion. When touching the other I get more gain. I don´t quite understand why changing Ug2 does not have the same result for bouth tubes. The unit seems to work fine, so I decided to leave it alone. But if someone can enlight me, I´d be happy.

 
Nice build, I bet it sounds great.

Curious about the capacitors hanging off the back panel.

I have an old AKG N12K power supply that uses a similar mounting system. Is this something you diy'ed or can you buy these caps with that threaded mount?

Mark
 
Biasrocks said:
Nice build, I bet it sounds great.

Curious about the capacitors hanging off the back panel.

I have an old AKG N12K power supply that uses a similar mounting system. Is this something you diy'ed or can you buy these caps with that threaded mount?

Mark

I can still buy them here over Germany. How long this will last, I don´t know.
Last time I ordered one like this for an old Radio repair I waited 12(!) weeks for them to arrive.
Maybe they need to manufakture them just for me.
Also the first caps I saw with the Phonenummer of the company on it  :D
 
DerEber said:
I can still buy them here over Germany. How long this will last, I don´t know.
Last time I ordered one like this for an old Radio repair I waited 12(!) weeks for them to arrive.

Any chance you could share where you got them and a part number?
 
Biasrocks said:
Any chance you could share where you got them and a part number?
The company is:
http://www.ftcap.de/seiten/de/home/home.php

I ordered them at Buerklin in Munich or you get them at mercanteo.de
 
Hello
I am in the process of building a Federal myself, and I wanted to ask how you achieve these 3 speeds? Are they release speed, attack speed or "presets" with attack and release? (I'd love to get presets )
 
thomasdf said:
Hello
I am in the process of building a Federal myself, and I wanted to ask how you achieve these 3 speeds? Are they release speed, attack speed or "presets" with attack and release? (I'd love to get presets )

It is presets.

As far as I remember I changed the C1..... or maybe C1 and R1 together.
Speeding it up will get you near "motorboating" oszilation problem.
I had a spare desk on my switch and I think while switching to smaller C1 I also swiched C5 for highpass.

So my fast  timings do not react on deep bass as much as the slow one.
I can see if I find detailed drwaings about what I did.

Getting a two deck switch for time would be wise. So you can experiment.

best,
Stephan
 
Hello Stephan

Thanks for your answer. I am interested in having a look at schematics or drawings / notes if you can find them!
Another question, how much voltage is going thru that selector? Which one did you use? I am having a hard time finding a sturdy one that feels solid in the end on which you would have 3 or 4 positions only and that could handle quite a lot of voltage...

Thanks!!

Thomas
 
Hey Thomas,

I used some Elma switch. I can´t figure out wich one now. the Info is burried in the bills somewere.
But I am quite sure it was Type 1 like in this pdf:
https://www.buerklin.com/datenblaetter/Datasheet_Rotary_Switches..pdf?ch=64190

speed 3 was original timing constantes.

speed 2 I substituted C1&R1 to 0,47 and 3M
                  C5 became 0,004
At least this is what I wrote on my schem.

speed1 I substituted C1&R1 to 0,22uF and 6,9M
                C5 is unknown here, as I soldered some different ones in serie/paralell and had a strange value in the end that worked even if it shouldn´t.

You should thy to make this components easy accessable, so you can experiment without taking the whole thing appart.

best, Stephan
 
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