Nostalgiatone 60’s no Tremolo (Solved!)

[Scott Bourgeois]

Pedal works but when the Tremolo is engaged no sound at all. LED pulses as it shoud. When kill switch is engage everything else works

 

[Barry]

First make sure the Volume pot (A25K) on the Tremolo is turned up past noon.

Since the Kill switch LED is part of the actual tremolo circuit the first thing I would question is the common anode connection. That should be a single, bi-color, common anode, LED. The hole pads are sized for a single lead in the center (anode) pad.

Also one side of the switch will not produce a tremolo sound as it is the kill side. But what you would notice, especially with the Tremolo Volume turned up, is a big difference in boost when engaging the Tremolo with the 3PDT foot switch.

[Scott Bourgeois]

I replaced the double LEDs with a bi color one and it works as it should but still no sound when Tremolo switch engaged at all when kill switch is on or off. A25k and B250k pots are at full.  Clean signal when tremolo footswitch is off. The Led flashes the tempo as it should when tremolo foot switch is engaged but no sound at all.  .

[Barry]

At this point I suggest an audio probe to easily locate where the problem is.

*** Build an Audio Probe

Whether that be the JFETs, transistors, bad soldering joint, or other items I cannot tell from pictures.

[Barry]

While an audio probe is the quickest, and best bet, you can also make sure to:

• Re-flow the Tremolo section of the circuit board.

I can’t tell if it is a trick of light but for example this transistor location looks questionable.

Like I said I would re-flow the entire Tremolo section. Also be careful not to stress the ribbon cable solder joints while moving things around.

• Verify that the combination of both transistors and JFETs are in the correct locations. If you subbed any values, double check orientations, etc..
• List voltages you are getting at each pin of the JFETs and transistors and be sure to make it easy to understand which pin, of which Q is receiving a specific voltage.

[Barry]

And one more thing I have just now noticed.

The backs of the showing potentiometers do not have covers.

If the potentiometers that are not showing are the same, (no protection), then you are likely shorting out the circuit against the solder joints.

 

From the first picture at the top this appears to be the case.

You need some sort of plastic cover.

[Scott Bourgeois]

Thanks Barry,

I am in the process of replacing the footswitch wires. I am aware of the potential of potentiometer backs shorting out the circiuit. I have them raised and have plastic covers on order.   Will be double checking components and all of the othere suggestions.

Thanks For your help

 

[Scott Bourgeois]

Got the tremolo working by replacing Q3 (2N5457 )but the tremolo effect is very faint or weak even at full depth

[Barry]

If Q3 was a bad FET you should probably replace Q5 with a known good FET as well.

The FET is very important and unfortunately there are a lot of bad FETs out there. Amazon and eBay are highly questionable. When I have them I always batch test first (hoping to get more in a month). You can find them from legitimate sources still, like stompboxparts.com

You may also use J113, J201, MPF102, and all have the same pinout. Make sure it is a reputable source.

Also you will notice what is going on, and where exactly, if you use an audio probe. It saves a ton of troubleshooting when you can hear exactly where to look.

FYI: I will have J201 in stack again, probably tomorrow. Hopefully, J113 as well, in a few weeks.

[Scott Bourgeois]

Solved!! Thanks Barry, I guess I’ve been lucky so far and not had faulty components on most of my other 50 + builds) . Q5 was defective, replaced it with a reputable J201.

 

[Barry]

A big, fat super, congrats!

Now make a separate post and show off that build and tell us all about it.

[Scott Bourgeois]

The tremolo works great but the depth pot has very little control. At zero it’s still “tremolloing” alot

[Barry]

As I recall now, you changed your 2N5457 out for a J201. While I would have thought this would work, and it does, after further investigation, it has a very high minimum channel resistance which won’t shunt the emitter bypass cap effectively. So, while it does work, it is probably the least suitable JFET for the job. I would suggest finding a more suitable JFET such as “Genuine” 2N5457, J113, 2N5486, or MPF102.

[Barry]

UPDATE 1: I tested this on my bench unit and confirmed this to be true. I substituted a genuine 2N5457 with a genuine J201 and while the Tremolo still works the Depth control is not as effective. I am looking into acquiring more suitable through-hole JFETs for this project asap. J201 is not a suitable substitution.

UPDATE 2: I can now confirm that J113 works very well and they are more readily available as through-hole.

*************************************************************************************************

UPDATE 3: One more trick I have had up my sleeve which I have not mentioned in the build document yet but if you look closely at all of the NostalgiTone PCBs that require JFETs you will see there is a place to solder SMD components. While it requires a fine conical point and a bit of skill it will future proof these builds for a long while to come.

see Q5 pads in image below (SMD will lay nicely on the top 3 pads which includes the square pad = Gate)

So for example:

The SMD equivalent of 2N5457 is MMBF5457, J113 is MMBFJ113, etc. Google.

[Scott Bourgeois]

Awesome, Thanks!

 

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