Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on February 21, 2018, 01:39:58 pm
-
Hi, I have here two Stromberg Carlson monoblock tube amplifiers: 5Y4 rectifier, 2X 6V6's and a 6SQ7 . They are very old and have beeen modified to a certain degree. The model number is not indicated though on one block is stamped the number ''41' with unreadable character before, like a T but I'm not totally sure, stamped inside the chassis. I just can't find the schematics. One strange thing is that the power tubes pins 1 and 2 are strapped together to gnd...while the 8 is alone with a cathode cap. The power tranny is huge for 2 X 6V6's and has three center taps soldered to the chassis, I guess the third one is for the 5 V... Anyway, to make a long story short, I would need the schems first, I can't rely on what I see because of the mods performed before. Pics will follow.
Thanks for info if you have.
Colas
-
One strange thing is that the power tubes pins 1 and 2 are strapped together to gnd...
That was very common for an amp from that era. Pin 1 connects to the metal shell of the 6V6 and pin 2 in one side of the filament. The grounded metal shell acts as a shield around the tube and the grounded filament pin means you only have to run one filament wire to the tube.
...while the 8 is alone with a cathode cap.
Tube cannot possibly work with only a cap connected to the cathode. Look closely. I bet you will find a wire, or a output transformer lead, or the remnants of a resistor on pin 8. Pin 8 must have a dc current path to ground in order to function.
-
I have found a schem. (though it's not the model I have here) with 6V6's heaters wired one side to gnd along with pin no 1. I don't understand why both sides of the heaters supply seem to be tied to gnd ( look at the PT ).
Colas
-
To me it looks like the other side has got an arrow and letter F
-
Yes F from the filament secondary is going to pin "H" on all the tube sockets.. H = heater I suppose.
-
This site has lots of Stromberg Carlson info. Some of it requires an app called WinDJview to read it.
http://audiophool.com/MadeInRoch.html
-
I don't understand why both sides of the heaters supply seem to be tied to gnd ( look at the PT ).
I don't understand why you think they are both tied to gnd.
-
look at the pt, the heater supply shows an arrow connecting a white dot one one side to a white dot on the other side and to the ground what d'you think ?
-
look at the pt, the heater supply shows an arrow connecting a white dot one one side to a white dot on the other side and to the ground what d'you think ?
I think I want some of whatever you're smoking! :l2:
-
> heater supply shows an arrow connecting a white dot one one side to a white dot on the other side
Circle with a loop inside? That's a lamp. A two-6V6 radio *should* have four lamps so your friends know you paid a lot. (Two look dotted... maybe optional, depending if you got the fancy case or the extra-fancy case.)
-
it was giving me the impression that the first lamp was not a lamp but an arrow connecting the two sides of the filament supply to the gnd which was a nonsense sorry for this.
colas
-
It is a very ugly messy drawing with many confusing parts hidden in it.