Alamo Fiesta amp

cjlectronics · 12-07-2006, 03:22 AM

This is a small tube amo with a 12AU6 two 35W4's, and one 12AV6. From the circuit, it looks like the 12AV6 is the tube that drives the tremolo. I have replaced a 10uf/25vdc electolytic cap that is between the tremolo speed and intesity pots and a .05uf/400v cap that goes between one of the 35W4's and the 12AV6. Nothing has solved the no tremolo problem.

Any suggestions?

Thanks,
CJ

Amp Kat · 12-07-2006, 03:36 AM

You are using a foot switch ey ? Most of those won't work unless the jack is shorted. Can you see the photo bulb flickering when you turn the speed pot ?

Enzo · 12-07-2006, 04:00 AM

I am guessing that one of those "35W4" tubes is really a 50C5 or something. In particular, the one that .05 went to.

Get the schematic. Schematic Heaven has one, though it uses the older tube set - 50L6 and 35Z5. Bit ought to be close enough. Note the 12AV6 is indeed the trem oscillator. See the three 0.02 caps left of the grid? Replace those.

cjlectronics · 12-11-2006, 07:21 PM

Enzo, you're a genius! The three .02 caps that are part of the oscillator circuit fixed the tremelo problem.

There is no tremelo pedal jack on this amp. The tremelo works when the speed knob is turned CW.

Thank you Enzo and also Amp Kat for your assistance.

CJL

12-07-2006, 03:22 AM	#1
cjlectronics Supporting Member Join Date: May 2006 Posts: 182	Alamo Fiesta amp - tremolo not working This is a small tube amo with a 12AU6 two 35W4's, and one 12AV6. From the circuit, it looks like the 12AV6 is the tube that drives the tremolo. I have replaced a 10uf/25vdc electolytic cap that is between the tremolo speed and intesity pots and a .05uf/400v cap that goes between one of the 35W4's and the 12AV6. Nothing has solved the no tremolo problem. Any suggestions? Thanks, CJ

12-07-2006, 03:36 AM	#2
Amp Kat Senior Member Join Date: Jul 2006 Location: Baton Rouge,LA Posts: 1,062	You are using a foot switch ey ? Most of those won't work unless the jack is shorted. Can you see the photo bulb flickering when you turn the speed pot ? __________________ KB

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12-07-2006, 04:00 AM	#3
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,355	I am guessing that one of those "35W4" tubes is really a 50C5 or something. In particular, the one that .05 went to. Get the schematic. Schematic Heaven has one, though it uses the older tube set - 50L6 and 35Z5. Bit ought to be close enough. Note the 12AV6 is indeed the trem oscillator. See the three 0.02 caps left of the grid? Replace those.

12-11-2006, 07:21 PM	#4
cjlectronics Supporting Member Join Date: May 2006 Posts: 182	Enzo, you're a genius! The three .02 caps that are part of the oscillator circuit fixed the tremelo problem. There is no tremelo pedal jack on this amp. The tremelo works when the speed knob is turned CW. Thank you Enzo and also Amp Kat for your assistance. CJL

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