Shruthi XT programmer, knobs and leds and assembly questions

I’m now a proud owner of a Shruthi XT kit from FCD72, but there’s a couple of customizations I’d like to make to the standard set of things that come with the kit.
First of all, I’m a bit of a knob fetishist, meaning that I don’t like rubbery plastic knobs, and rather have the something more old-school. The problem is, as Frank has explained, that the pot shafts are a bit too high for most pots and hence need to be dremeld down a bit.
Since I don’t have a dremel, nor a workshop where I can perform such an operation, and my wide already hates me enough for soldering in our living room (which is one with our kitchen, our studio and our library) I’d rather not do that.
Does anyone know some good 6mm shaft knobs that look something like these:
that work with the shafts, so that I don’t have to dremel them?

Question nr.2: I’ll have to de-solder the leds on the Shruthi, since they have been soldered for the transparent case, but the programmer frontplate is opaque (with the holes). I need to raise the leds a bit to stick out into the holes. Since I always made a big mess when de-soldering leds, do you have any special tip on how to do this?

I’m not in a hurry a friend of mine will do most of the assembly job, and neither I nor he have the time to get to it right now… but I can start sourcing the remaining parts and plan the thing properly :slight_smile:

Google can’t seem to tell me where to look for researching and buying XT controller kits. Can anyone point me in the right direction? I hope this question is not against Oliviers policy on this board Thanks, folks, for such an interesting forum.

No, this is not against any policy :slight_smile: You can probably post here

One thing to watch out for with 16mm Alpha pots - there seem to be a couple of designs out there with different ‘feel’.

I bought some 10K linear ones from Doctor Tweek that are noticeably ‘stiffer’ to turn than the ones I got from Rapid Electronics. Not a deal breaker, but perhaps useful to bear in mind.


That’s included !

Another question about alpha pot when you order Alpha Potentiometer 16mm 10k lin to musikding, Hex nut M7 x 0.75 Alpha are included with them ?

Great, thank you !

Shure, you just have to solder the ExpansionPort Wires directly to the 595, see here

On Earlier Boards (REV lower 0.6) Pins of the Output Expander will have to be soldered directly to the 74HC595. Its the right Chip under the ATMega seen from the bottom Side of the Control Board (don’t scramble the 2 74xxx chips, it wont work with the 74HC165).
Heres the PinOut:
Red=+5V(PIN1 of the OutPut Expander Port),
Black=CLK(Pin4) and

i would like to know if i can use Control Board v0.5 with shruthi XT programmer ?

Once you’ve soldered the LEDs and cut the legs it’s hard to lengthen them. The kit comes with new LEDs so you use those.

To remove the LEDs I do the following, remove as much solder as possible. Heat up one pad and push the LED to move that leg. Do the same for the other leg until it comes out.

Or use a large soldering iron bit and try to heat both pads at once and pull out the LED.

yep I was thinking about removing them completely and soldering new ones. I only have to find new leds, since I really like the white ones (but the kit comes with red ones).
btw. has anybody tried these for the leds: fresnel lenses for leds

@rumpelfilter: I’ve noticed those as well - should look good IMO, although might dim the LED very slightly.

I use opposite tactic when desoldering: i add more tin to the legs, that way tin stays liquid longer and it is possible to push/pull component out of the circuit. If there is temperature control in soldering iron it’s useful to turn it to max.
They used special desolder tips in my old workplace but i wouldn’t buy those for home. It’s so rarely when i need to use those and many different shapes would be needed… .

The opposite is right: If you have a temperature controlled Iron, turn the temperature down so you don’t damage anything. Your Strategie although is right putting that much Energy in the Solder joint that the hold Solder Mess stays liquid.

For this you’ll need a Processor controlled Iron with high Wattage, not these old school “Turn a knob to the right to make it hoter, just don’t trust the Scale” Thing. I recently bought a 60W Iron (if you read older Posts from me i sweared on my tiny 8W thingie) and this Beast keeps the Temperature constant wether you solder a SMD Diode or seal a Tin Can.

the tools I use:

spread a little soldering flux over joints then use a very hot soldering iron (750° F) and use the solder sucker to get the solder out.
If it doesn’t get it all, I’ll use the iron to push the leads out. If I still can’t pull it out, I’ll cut the LED off and pull the remaining lead out with a pair of plyers.

btw, I hate desoldering

@fcd, if worried about damaging anything, pull the IC’s out. Usually the passive components can handle it.

thanks for all the valuable tips! I’ll try the “add more solder then suck it away” technique :slight_smile:
I don’t have a really pro soldering station, in fact I don’t have a soldering station at all, but so far my iron has proven a valuable tool.

About those led lenses, anybody tried those?

about turning the temperature down in order to not overheat components i have to disagree with you fcd72.
i’ve had better results applying >400°C than with lower temperature. that way you don’t have to apply heat as long as you would have to with just 300 or 320°. it’s a good thing to add plenty of fresh tin, you can suck it out afterwards.
the higher temperature could be a problem if you have a self etched board with very thin/small solder pads and copper traces that can lift easily. but with decent pads / traces or any kind of industrial produced board there should be no problem.

Anyone tried making a solder sucker that attaches to a vacuum cleaner? :slight_smile:

also have to disagree re: turning heat down to de-solder - perhaps for homemade PCBs this is the case as rosch says, not to lift traces?

I generally set my iron on the hotter side of things in general, less time spent in contact with the surface results in less heat transfer to the rest of the components and nary a cold joint - fluid soldering iron technique is important though, I wouldn’t recommend an extremely hot iron to someone that hasn’t soldered at least a handful of circuit boards

have you ever soldered a battery, particularly a small disc battery for a vintage synth? same technique - you use an extremely hot iron to make sure the temperature spike is as brief and localized as possible, this way you are actually LESS likely to explode the battery, even though your iron is very hot

need to de-solder some LEDs myself, for nearly the same reason, and have been putting it off for months now!