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Topics - solidstate2199

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1
Hello, my Questions for this Project for people
With better understading of Transistor Phaseinverters.

I want to build a Standard Superlead Preamp in one of my
Solidstate 2199 SS Amps, but i want to build it with the tube
 phase inverter stage. The thing is, if i build a superlead and put
A ppimv inside it, why do i need the el 34 and the output transformer
If i cant play that loud to beginn with? The poweramp isnt working
Until it probably to loud.

So i want to build this unit for homeplaying and small gigs, 30 watt
Out of that old marshall ss should be plenty.

But i have problems understanding transistor pamps...
The 2199 has a socalled quasi complementary design..
Is it possible to inject the tube phase inverted Signals
Into this 2199 power stage and where?

Thanks the schematic i could upload or just check it
At drtube website.

Cheers


2
Tubes and Hybrids / Cooked Super Amplifier
« on: May 20, 2018, 07:45:20 AM »
Bought an old Superlead Style Amp, its not here yet.

One burned out EL34 Socket and what looks like the
negative feedback resistor is shot, plus collateral
to the surrounding parts.


There is a cable coming from the 16ohm speaker jack going
to that resistor so i guess it is the 100k seen on the schematic.

Can i suspect output transformer damage?

I make better pics when i have it here.


schematic
https://drtube.com/schematics/londoncity/dea100-early.gif

3
Tubes and Hybrids / blown filtercapacitor in 100watt. Why?
« on: March 01, 2017, 01:03:42 PM »
Hi Folks.

i bought a 1988 Laney AOR which works fine. Nice Amp.

One thing which caught my interest is that one of the 6 filtercaps
has been changed sometime ago.

As i open all my new amps to check the overall condition i discovered that
this capacitor must have really blown wide open because there were lots of
residue in the headshell directly under that spot.

What causes this? All other 5 L.C.R. caps looking fine without any dimples on top due
to age.

Im curious to what causes such an event. I guess too much voltage? (caps are 50uf/50uf 500vdc)

Thanks for your insights.

4
Tubes and Hybrids / Bias Question regarding Marshall 100watt 2203
« on: February 13, 2017, 06:36:19 AM »
Hi,

i bought a Marshall 2203 Clone.
100Watt, 4xEL34 3xECC83
It works flawless after thoroughly cleaning the dreaded Cliff-Type
Jacks (closing contacts).

The one thing that concerns me is that one of the EL34 looks way more
used than the other 3. After opening the Amp i discovered that the
loudspeaker-jack directly behind this particular tube-socket is slightly
melt, nothing drastic but it indicates that this tube has or maybe had some
sort of problem, it maybe draws more current was my first guess.
Or maybe the 1k5w screen grid resistor is not o.k.?
Note there is no sign of redplating or any other malfunction on this tube,
but all of the lettering is gone and i can see lots of little dents on the anode,
while on the other 3 the lettering is intact and there is absolutely no sign of
dents on the anodes.

These are original AEG (made by RFT, Eastern Germany) EL34 tubes, so i want
to keep those as long as they work.

I was checking the bias via the "Output Transformer Resistance Method".
My measurements as follows:

plate voltage: t1 - 440V (blue side); t2 - 440V (blue) ; t3 440V (red) ;
t4 - 440V (red) - !measurements were not stable, they varied between
439V to 441V over a period of 30 minutes, so i took the middle for all tubes!

output transformer centertap voltage: 440.5V ( varied between 440V to 441V)

voltage drop across half of the output x-former primary: 440.5V-440V= 0.5V

output x-former DC resistance measured with unpowered but warmed up amp:
red lead side=16.3ohms
blue lead side=17.6ohms

anode current blue side: 0.500v/16.3ohms=0.0307A or 30.7ma
anode current red side:  0.500v/17.6ohms=0.0284A or 28.4ma

HERE IS MY QUESTION! DO I HAVE TO DIVIDE THIS CURRENT /2 BECAUSE
THERE ARE 2 OUTPUT TUBES PER SIDE IN PARALLEL?

If so then this amp is biased very cold (27% red side, 25% blue side)

WHY IS EL34 NR.1 (t1, next to phase inverter ECC83) MORE WORN TO THE
EYESIGHT THAN THE OTHER 3? IT DOESNT GET MORE HOT THAN THE OTHER
ONES AT IDLE, MAYBE IT DRAWS MORE CURRENT UNDER MORE LOAD?

Any help welcome.
Thanks







5
Hello
i know there are one or 2 threads for the 2199 already, but i have some mod questions in
the future where i will use this thread..

I bought the 2199 some days ago, mainly for the speakers (G12K-85) and to use as a 2x12, because
i previously knew that these amps dont sound good. They are playable clean, and even then these models seriously lack presence. The build in overdrive...well i come to that later.

I played the Amp a little for testing purposes and there is an electronic high frequency oscillation.
Bassically on all 3 channels, on the normal not that much but just because this channel doesnt have much highs to start with. When i plug in the mix channel and turn the treble up past 6 and the bright gain up the amp starts to squeal like a dirty pig, the oscillation changes pitch and attitude when i change eq or gain settings. When nothing is plugged in , theres no oscillation, i read somewhere thats because the cliff jacks shunt the signal to ground.

Alright, i opened the piggy up today to find a siemens capacitor roaming free inside the amp housing.
Its C17. Question: on the photos you can see white gunk on 2 green electrolytics and the free space where C 17 belongs. Is this Marshall Factory glue or innards from C17? Why is the Amp still working
without that cap, what is it supposed to do, please understand i have no clue about electronics.

There is some circuit changing on the right side of c17, the leg of one resistor is connected to the one
beneath it and a tantal cap is piggybacked on top of it. I believe this mod is factory  because i found 2
pictures of 2199 innards on the web and there is the same modification made.

There must have been someone in there before me because 2 speaker wires which where
originally hardwired to the speakers where modified with a cliff jack mounted inside the chassis.
But i doubt that the cap was loose at this point. I dont really see any burnmarks at spot C17, maybe
on one side i dont know. Could the Cap be torn off while shipping? because the seller typically for
old stinky Marshalls only wrapped a little cardboard around and called it a day :duh

Also the schematic says C17 1000microfarad/ 25volt and the one found in the Amp saz 2500/35
but i suspect this is the Marshall factory C17 because i have other 2199s with the same cap.











Regards

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