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Topics - Vitrolin

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1
Tubes and Hybrids / Ibanez TSA30 Mains transformer
« on: March 13, 2016, 06:37:07 PM »
A friend has Ibanez TSA30, he was playing loud for a long time then it died..

He measured the primary side and seems as the internal thermal fuse has blown, so he asked me if i knew what the mains transformer for his Ibanez TSA30 was.
i tried google and only found this schematic http://gravinatubeamps.com/2014/08/02/ibanez-tsa-30-u-schematic/ that lack exactly what i am looking for.
so does anyone have a full schematic, have TSA30 you can open to take some measurements, or by some other reason know what the transformers secondary voltages are, the would bring a lot of joy.

2
Tubes and Hybrids / Performer/Roc-pro transformer
« on: February 18, 2016, 06:34:33 PM »
hey

Got a fender performer 1000, mains transformer blown.
From the schematic i can see secondaries 60VAC center tapped or 2x30VAC, but what would the current rating be?
The chassis says 300W but that seems excessive, any thoughts?


http://support.fender.com/schematics/guitar_amplifiers/Roc_Pro_1000_schematic.pdf

3
Amplifier Discussion / power amps and speaker impedance
« on: May 15, 2015, 04:31:32 PM »
hi
I have been wondering about what sets the limit for a power amps load.

example:
if a amp is rated minimal 8Ω and for some reason I want to load it with 4Ω.
lets say its a discrete push-pull with one complementary transistor set, could I then just add another complementary set, and related circuitry?
the above completely ignores that th power supply should be upgraded.

or is it the power supply current capability that limits the amps load impedance?

4
Tubes and Hybrids / Valvestate 8100
« on: October 27, 2013, 11:18:41 AM »
a friend gave me a valvestate vs8100 it did not work, i found out that the -15 volts were not there, i changede C61, C62 &  R101 they were looking suspicious. i now had +8 -6 volts or so. i replaced Zener diodes no change, then i removed TR8-9-10. and then +/-15 volts were on.
then i replaced them and it seemd maintain voltages.
i applyed signal and its output was not pretty. i then saw that problem was IC1. i took awhile since i started applying signal at input of IC8B and halfling my way back through the circuit.
but replacing IC1, it was shortet between + & - pins, it then was up and running.
so i dragged it to a fiends studio to see what i could do and try it with different speakers. it worked for a while, and i played around a lot with settings and then i wanted to try it with another cab, nothing but silence... voltmeter told me no +/-15V.
i tried some of the same procedures from last time but no luck this time and its pissing me off.

i hope someone have had a similar experience or maybe a usefull input.
 i attached a schematic

5
Amplifier Discussion / Amp power and supply?
« on: January 26, 2013, 08:56:16 AM »
hey
I have been wondering when building an amp how do i choose the correct transformer?
I guess first  i should start with choosing output power, lets say 120WRMS, then amplifier class since it says something about how effective it is, i think that AB is about 70%, not sure.
If so, then 120/0,7= 171VA supply?
How do you determine supply voltages, output power and speaker loads?

Voltages should bee high enough to put out 120W in 8R:
V=SQR(P*R)
V=SQR(120*8 )
V= 31V
but that's only RMS, The peak voltages are then:
Vp=VRMS*SQR(2)
Vp=31*SQR(2)
Vp=44V

I believe these are important considerations when designing an amp, im not sure if im on the right path here

6
Amplifier Discussion / Converting audio amp to guitar amp
« on: April 06, 2010, 04:40:58 PM »
hi i have a audio poweramp that i would like to convert into a guitar power amp and add a preamp, maybe tube based.
well the amp right now is a Yamaha A-320 the transistors are: SK A1104 and SK C2579, i have found a datasheet on the last one its a NPN, my guess is that the first i PNP and its push-pull amp.
i was thinking that maybe its that simple as to put a preamp before the volumepot, would be nice but propably not.
so... has any onemade a similar convertion or might have an idea that would be usefull.


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