INCREASE MAGNATONE 10A VIBRATO INTENSITY?
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INCREASE MAGNATONE 10A VIBRATO INTENSITY?
Any suggestions to increase the vibrato intensity on a Magnatone 10A? Amp has new tubes & 3 new electrolytic capacitors though the caps aren't in the vibrato circuit. I've attached the vibrato/reverb schematic from the Sluckey.com site. Thanks.
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Stevem
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Re: INCREASE MAGNATONE 10A VIBRATO INTENSITY?
Yes there is.
Looking at V4 you will see 3 caps going around counter clockwise from pin 6 to pin 7.
The thing to do is to replace another one of the .01 caps with a .02.
It would also pay to test the 270K resistor there on pin 6 to make sure it's has not drifted down in value.
You can also try replacing both .01 caps with .02 caps but the oscillation needed to make the Tremolo may not start up without a very strong testing tube!
Looking at V4 you will see 3 caps going around counter clockwise from pin 6 to pin 7.
The thing to do is to replace another one of the .01 caps with a .02.
It would also pay to test the 270K resistor there on pin 6 to make sure it's has not drifted down in value.
You can also try replacing both .01 caps with .02 caps but the oscillation needed to make the Tremolo may not start up without a very strong testing tube!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: INCREASE MAGNATONE 10A VIBRATO INTENSITY?
Check how tight the values are for the oscillator caps (.001 .001 .002). If good
try dropping the two 330k resistors feeding the 12dw7 cathode follower to 220k.
try dropping the two 330k resistors feeding the 12dw7 cathode follower to 220k.
Tube junkie that aspires to become a tri-state bidirectional buss driver.
Re: INCREASE MAGNATONE 10A VIBRATO INTENSITY?
As a quick check I would just put a jumper across those two 330Ks. Actually changing those resistors is more difficult that you would think.
The modulator tube V5 circuit could also cause weak vibrato so check all the components in that circuit.
Are you trying to increase the vibrato intensity because you think it's too weak and not performing normally? Or are you trying to "hotrod" to get an over the top effect? There is a simple mod that will greatly increase the oscillator output. It involves converting the grid leak biased oscillator to a cathode biased oscillator and using a red LED on the cathode. This mod is very simple on paper but may be difficult to actually implement due to the PTP wiring and the cone board circuits. Look at V4 and V5 on this pic to see what I mean...
http://sluckeyamps.com/magnatone/M10A_guts.jpg
I have no idea how the increased oscillator output may sound. I like the sound of my M10A just as it is.
There is a voltage chart on page 6 of my documents file that may be useful for troubleshooting...
http://sluckeyamps.com/magnatone/Magnatone_M10A.pdf
Re: INCREASE MAGNATONE 10A VIBRATO INTENSITY?
Great question: I am not trying to hotrod the vibrato but rather restore it to the intensity it was when I purchased it several decades ago. Thanks to everyone for their suggestions and I will get working on them soon.