Tremolo all bunched up

trjones1 · 04-17-2008, 11:10 PM

Hi,
I'm Trevor, I've read about this forum over at diystompboxes.com and now I have a question that someone here might be able to answer

I have a Kalamazoo Model 2 amp (schematic: http://www.rru.com/~meo/Guitar/Amps/.../M2/schem.html). The tremolo sounds good, but the entire range of speed is bunched up in the first half of the knob's travel. Once you go past 12 o'clock the tremolo disappears and there is only clean signal. If you back the knob all the way down the tremolo eventually reappears. Does anyone have any ideas on what might be causing this? Thanks.

Don Moose · 04-18-2008, 01:22 AM

I notice that the speed pot is supposed to be a reverse-audio taper - if someone put in a linear or normal-audio pot it could do that.

Or it may be wired backwards - does the speed go UP when you turn the knob clockwise?

Hope this helps!

trjones1 · 04-18-2008, 02:29 AM

The pot works in the right direction (i.e. clockwise makes the speed go up). I'll check the taper of the pot, that could be it. I wish I had looked closer last time I opened the thing up. Thanks.

Enzo · 04-18-2008, 03:22 AM

I'd say leaky caps in the trem LFO. The old caps cannot charge and discharge smartly enough to maintain oscillation at higher speeds. I'd replace C5,6,7,8.

Are these original caps?

trjones1 · 04-18-2008, 04:21 AM

I believe those caps are original and probably could use replacement after all these years. Are these the type of caps that would benefit from using orange drops, or would any caps from Mouser do the trick? I'm new to the amp game and I haven't figured out which tricks are beneficial and which are just tricks.

Enzo · 04-18-2008, 05:43 AM

All they are are feedback caps in the oscillator. They are not in the signal path. I can't imagine how a 5Hz oscillator could "sound better" using one cap instead of another. It oscillates reliably or it doesn't. Any film cap should work well.

If the caps in the signal path meeded replacing, these would too. They are all in the same circuits, use the same powr source, and have lived the same life.

trjones1 · 04-18-2008, 03:36 PM

So you're saying I should just replace all the caps? I've already done the filter caps, I guess i could just do all of them.

ricach · 04-18-2008, 10:46 PM

I have one and I can at least tell you they're not supposed to do that. Not much help, I know, but if you need to compare readings, let me know and I'll help you out.

Enzo · 04-19-2008, 02:17 AM

A complete cap job on something that old would not be unusual at all.

04-17-2008, 11:10 PM	#1
trjones1 Junior Member Join Date: Apr 2008 Posts: 7	Tremolo all bunched up Hi, I'm Trevor, I've read about this forum over at diystompboxes.com and now I have a question that someone here might be able to answer I have a Kalamazoo Model 2 amp (schematic: http://www.rru.com/~meo/Guitar/Amps/.../M2/schem.html). The tremolo sounds good, but the entire range of speed is bunched up in the first half of the knob's travel. Once you go past 12 o'clock the tremolo disappears and there is only clean signal. If you back the knob all the way down the tremolo eventually reappears. Does anyone have any ideas on what might be causing this? Thanks.

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04-18-2008, 01:22 AM	#2
Don Moose Senior Member Join Date: Jul 2007 Location: Indianapolis Posts: 676	I notice that the speed pot is supposed to be a reverse-audio taper - if someone put in a linear or normal-audio pot it could do that. Or it may be wired backwards - does the speed go UP when you turn the knob clockwise? Hope this helps!

04-18-2008, 02:29 AM	#3
trjones1 Junior Member Join Date: Apr 2008 Posts: 7	The pot works in the right direction (i.e. clockwise makes the speed go up). I'll check the taper of the pot, that could be it. I wish I had looked closer last time I opened the thing up. Thanks.

04-18-2008, 03:22 AM	#4
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,303	I'd say leaky caps in the trem LFO. The old caps cannot charge and discharge smartly enough to maintain oscillation at higher speeds. I'd replace C5,6,7,8. Are these original caps?

04-18-2008, 04:21 AM	#5
trjones1 Junior Member Join Date: Apr 2008 Posts: 7	I believe those caps are original and probably could use replacement after all these years. Are these the type of caps that would benefit from using orange drops, or would any caps from Mouser do the trick? I'm new to the amp game and I haven't figured out which tricks are beneficial and which are just tricks.

04-18-2008, 05:43 AM	#6
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,303	All they are are feedback caps in the oscillator. They are not in the signal path. I can't imagine how a 5Hz oscillator could "sound better" using one cap instead of another. It oscillates reliably or it doesn't. Any film cap should work well. If the caps in the signal path meeded replacing, these would too. They are all in the same circuits, use the same powr source, and have lived the same life.

04-18-2008, 03:36 PM	#7
trjones1 Junior Member Join Date: Apr 2008 Posts: 7	So you're saying I should just replace all the caps? I've already done the filter caps, I guess i could just do all of them.

04-18-2008, 10:46 PM	#8
ricach Member Join Date: Jul 2007 Posts: 101	I have one and I can at least tell you they're not supposed to do that. Not much help, I know, but if you need to compare readings, let me know and I'll help you out.

04-19-2008, 02:17 AM	#9
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,303	A complete cap job on something that old would not be unusual at all.

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