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Hello everyone. I’ve managed a few successful builds now, but this one has me stumped. Grateful for any assistance folks out there can provide.
Got everything set for the EA Tremolo v4 project, but when I powered it up and hit the switch no tremolo effect. LED lights and changes from red to green when engaged, but it does not flash/pulse when adjusting the speed and depth pots. However the level knob definitely affects the volume.
Did a search in the forum and found advice Billy provided (https://guitarpcb.com/community/topic/ea-tremolo-rate-and-depth-not-working/page/2/) regarding the LFO section. It sounds like that is the likely culprit, but that post was from an older version of this circuit that included the ‘kill switch’. I’m still a bit of a newcomer to this hobby and am unsure of how similar these versions are. What would be a good place to start troubleshooting? I’ve re-flowed the solder joins and checked voltages at the transistor pins (values below) and swapped in alternate 2n5457 and 2n5088, but still no dice. Hoping someone can tell me where I’ve gone wrong.
Note: Q1’s socket middle sleeve pulled out onto the transistor leg when I removed it. But get a voltage reading when reinserting, so I figure it’s still making a connection. If I’m mistaken, please let me know. Also a bit shaky with the DMM, so hopefully I’m taking these readings correctly.
Q1 (G = 4.52, S = 4.82, D = 9.52)
Q3 (G = 0, S = .01, D = 0)
Q2 (E = 1.09, B = 1.73, C = 5.75)
Q4 (E = .12, B = -.02, C = -.01)
The bypass LED is not intended to flash with the LFO rate when the LED is attached to the 3PDT daughterboard. (See page the bottom of page 2 of the build docs for version 4 of the EA Tremolo.)
D1 is part of the LFO circuit so the LFO won’t work without it installed on the main pcb
As Cybercow says you can’t use a 3PDT board with this build for that reason
Ah! Not sure how I missed that. Thank you both! Guess I’ll save that 3PDT daughterboard for the Mini Me Chorus
Thank you both again. Swapped in a new switch, wired it up and the tremolo is now working! No thanks to a socket that only holds onto Q3 after wobbling it a bit, but I’ll figure something out.
There is a bit of hum/buzz when engaged that you can hear with the throb of the tremolo. It quiets a bit when using a humbucker equipped guitar, but still there. Is there something I perhaps need to adjust, or is that just the price of admission for this circuit? I’m using a T-Rex Junior isolated power supply, but tried a one-spot style wall wort and got the same result. None of that noise when in bypass. Perhaps I chose the wrong type of component somewhere along the line?
In my experience, humbuckers and single-coils have a different impedances and will definitely sound different thru a LOT of pedals. The components all appear to be the correct type.
As for the trannies not seating well, I always use needle-nosed pliers to a bit of gentle wrinkle in the ends of the legs so they sit more firmly into those sockets. And once I know the circuit is working well, I lightly solder-tac one leg of each tranny to the socket. That ensures it will not fall out or come loose when dropped or other vibration.
And depending on any other pedals in a chain, high-gain pedals can bring up the noise floor of even the quietest pedals.
Most every modulation pedal I’ve built always seems to have a slight background noise associated with the LFO timing of the engaged circuit. But it is always minimal and not really hear while playing. If you can hear it thru the guitar signal coming thru, then there may be an issue somewhere. Double-check that LED and ensure none of it’s leg are grounded against the metal bezel.
Looks like putting a little bend in each leg of the transistor got it to seat and hold a connection much more reliably. Will get out the iron a bit later and try tacking it in with a bit of solder. Thanks Cybercrow! Definitely a trick I’ll use in future builds.
Would you recommend just soldering in the transistors (silicon ones, anyway) rather than socketing them? Or is that asking for trouble if I hold the iron on there slightly too long?
As for the slight hum, it’s not really all that noticeable when you’re playing. Just figured I’d ask while folks were kind enough to respond to my questions. Was going to give this to a friend of mine and wanted to button it up as best I can. No other pedals in the chain at the moment. But I’ll double check those LED legs. That’s probably a weak point, as indicated by my inelegant solution of electrical tape and blue tac.
Dr Seamus – using sockets or not is always a choice and rests with the confidence of the one in possession of the soldering skills and predetermining that the transistors are function and work correctly in the circuit. There are only a very few builds that I execute WITHOUT sockets. Very few. But every time I use sockets I will solder-tac at least one leg to the socket – OR – remove the sockets and solder the device directly to the PCB – but only AFTER I have verified the circuit is working correctly when it is stuffed into the enclosure. It depends on the build. I’m quite confident my soldering skills and still prefer to err on the side of caution on the beginning of builds.
Most devices can handle up to about 10 seconds of contact with a soldering iron tip. After that, all bets are off. Datasheets will often disclose temperature limitations on a device. I can get on & off a solder joint in under 5 seconds and sometimes in about 3 seconds. (Ergo my confidence level.) 😉
With LEDs, I sometimes get real persnickety (anal) and will do something like this . . . .
When the legs of an LED are not long enough to comfortably make the connection to its bezel (mounting point), I’ll put some shrink-wrap on the LED legs and add enough wire to make the connection.
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