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DIY Effects


JackLondon

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[quote name='Johnny Wishbone' timestamp='1499712337' post='3333104']
If you go for the Woolly Mammoth, be sure to warn the neighbours first!
[/quote]
:lol: I run a 500w TE stack as my practice amp (on very low to be fair) but in the conservatory and my neighbour is a big music fan and doesn't mind at all - sometimes asks me to turn up! And has been to a couple of our gigs.

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[quote name='ahpook' timestamp='1499713699' post='3333114']


That's good to hear - I've just ordered a Guma Vintage kit myself and the teeny-tiny transistors were making me worried !
[/quote]

I got my kit in October and have only just braved it! They are tiny but with a magnifier, pair of tweezers and pointed soldering bit it was a 2 minute job! The hints in the instructions are very helpful.

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[quote name='Johnny Wishbone' timestamp='1499719309' post='3333174']
I got my kit in October and have only just braved it! They are tiny but with a magnifier, pair of tweezers and pointed soldering bit it was a 2 minute job! The hints in the instructions are very helpful.
[/quote]

Thanks for the tip (ahem) - I'm concerned about the SMT J201s and their susceptibility to static...did you earth yourself up ?

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[quote name='ahpook' timestamp='1499763830' post='3333369']
Thanks for the tip (ahem) - I'm concerned about the SMT J201s and their susceptibility to static...did you earth yourself up ?
[/quote]

No, the only precaution I took was to leave them in their sealed pack until I was ready to tackle them. I still managed to drop one on the carpet all the same! :o

Edited by Johnny Wishbone
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[quote name='Johnny Wishbone' timestamp='1499765140' post='3333378']
No, the only precaution I took was to leave them in their sealed pack until I was ready to tackle them. I still managed to drop one on the carpet all the same! :o
[/quote]

:)

OK, my plans for sheets of tin foil, wire and various croc clips might be a bit OTT then !

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I work with smt pretty much every day, I've never actually seen an smt part (or any part actually) killed by static. ESD precautions are generally overzealous, and with good reason, but handling them with esd tweezers and just not licking them or rubbing them on the dog will usually be more than adequate.

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[quote name='bobbass4k' timestamp='1499769337' post='3333425']
I work with smt pretty much every day, I've never actually seen an smt part (or any part actually) killed by static. ESD precautions are generally overzealous, and with good reason, but handling them with esd tweezers and just not licking them or rubbing them on the dog will usually be more than adequate.
[/quote]

+1
Same here. Not saying it can't happen - and it may be more likely that an ESD hit could cause damage that causes a failure further down the line - 6 months ? 6 years ?
But unless you are experiency static shocks it's pretty safe for a DIY effort.

Guess I'll wandr back to the lab area now and Zap! some CMOS logic :blink:

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Guys, I've hit a brick wall in my search for wiring guidance on a bypass looper that I (foolishly, it appears) believed would be straightforward. Hopefully the collective wisdom of some experienced builders might be able to assist.

I'm wanting to build the following: a passive bypass looper with two loops in series, that has two footswitches. One footswitch selects loop A OR loop B, whilst the other selects both loops together (A+B ). Bright Onion sells such a device, but (a) it also has a master bypass, which i don't require, and (b ) I could build it myself for considerably less outlay.

With the exception of the aforementioned, I only seem to be able to find diagrams that do either A/B looping with master bypass, or just 2 series loops each with their own bypass. I dont really want to have to do the old "sideways foot operating 2 switches at once" dance, and what I want is obviously possible as it's been done. Can anyone devise a method for wiring what I'm trying to achieve?

Edited by Johnny Wishbone
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well i certainly wouldn't call myself experienced, and i'm not sure if this is wisdom or total nonsense.
loop a input jack to "on side" of switch 1
loop b input jack to "off side" of switch 1
connect both output sides of switch 1 to "on side" of switch 2
connect loop a + b jacks to "off side" of switch 2
connect switch 2 outputs to output jack
hope that makes sense

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for anyone thinking of doing a first build i can't recommend fuzz dogs pedal parts strongly enough
yes you have to do a bit of thinking but with the instructions and the pcb's
don't rush it even a total novice like me can end up with fully functioning pedals
1 blueberry boutique version and 1 exotic bb
no pictures yet, the blueberry got left naked and the bb well i experimented, could have been better but it will do

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Need a bit of advice folks !

I've started building the GUMA Vinatge kit ans have, with as much care as my shaky hands and bad eyes will allow, soldered the SMT JFETs in.

I've quickly checked the Gate - Source and Gate - Drain resistances and although I was expecting an open circuit, both chips are reading ~250K ohm.

Any idea if I've trashed the chips ?

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[quote name='ahpook' timestamp='1500369590' post='3337207']
Need a bit of advice folks !

I've started building the GUMA Vinatge kit ans have, with as much care as my shaky hands and bad eyes will allow, soldered the SMT JFETs in.

I've quickly checked the Gate - Source and Gate - Drain resistances and although I was expecting an open circuit, both chips are reading ~250K ohm.

Any idea if I've trashed the chips ?
[/quote]

Are the 250K readings with the JFets in the circuit ?

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[quote name='rmorris' timestamp='1500454186' post='3337811']
Are the 250K readings with the JFets in the circuit ?
[/quote]

That's all that's soldered in at the moment - I've measured the voltage drops as suggested by Julian at Schalltechnik (very helpful chap) and I get 0.7 Gate - Drain/Source and 1.3 D-S/S-D

The D-S/S-D are a volt higher than they should be so I suspect that I've overheated the transistors.

:(

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[quote name='ahpook' timestamp='1500454580' post='3337819']


That's all that's soldered in at the moment - I've measured the voltage drops as suggested by Julian at Schalltechnik (very helpful chap) and I get 0.7 Gate - Drain/Source and 1.3 D-S/S-D

The D-S/S-D are a volt higher than they should be so I suspect that I've overheated the transistors.

:(
[/quote]

How are you measuring the D-S voltage drop? It isn't as simple as it is for the, G-D/S, internal capacitance can skew the readings.

Try shorting source and gate and check the reading again, 1.3 sounds about right to me, as long as it's not fully short or open its probably fine. Like static, it's actually pretty hard to kill a part with heat. I'm not sure where this perception of smt parts as delicate faberge eggs comes from, but it's really not true.

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[quote name='bobbass4k' timestamp='1500461154' post='3337920']
How are you measuring the D-S voltage drop? It isn't as simple as it is for the, G-D/S, internal capacitance can skew the readings.

Try shorting source and gate and check the reading again, 1.3 sounds about right to me, as long as it's not fully short or open its probably fine. Like static, it's actually pretty hard to kill a part with heat. I'm not sure where this perception of smt parts as delicate faberge eggs comes from, but it's really not true.
[/quote]

I'm using the diode mode on my DMM.

Thanks for the reassurace - this is my first time working with SMD and it's a proper pain with my far-from-prefect eyesight.

Thanks for the tip about shorting the S-G connections - I'll give that a whirl.

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[quote name='bobbass4k' timestamp='1500461154' post='3337920']
How are you measuring the D-S voltage drop? It isn't as simple as it is for the, G-D/S, internal capacitance can skew the readings.

Try shorting source and gate and check the reading again, 1.3 sounds about right to me, as long as it's not fully short or open its probably fine. Like static, it's actually pretty hard to kill a part with heat. I'm not sure where this perception of smt parts as delicate faberge eggs comes from, but it's really not true.
[/quote]

+1
Sounds about right to me too.
And semiconductors - SMT or Thru Hole - are fairly robust when it comes to soldering.
Of course, it helps if you use a temp controlled iron and nice and hot so that iron only needs a short contact time with the component leg - especially if using Lead Free solder.

Edited by rmorris
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[quote name='bobbass4k' timestamp='1500461154' post='3337920']
How are you measuring the D-S voltage drop? It isn't as simple as it is for the, G-D/S, internal capacitance can skew the readings.

Try shorting source and gate and check the reading again, 1.3 sounds about right to me, as long as it's not fully short or open its probably fine. Like static, it's actually pretty hard to kill a part with heat. I'm not sure where this perception of smt parts as delicate faberge eggs comes from, but it's really not true.
[/quote]

OK, after shorting the G-S the voltage drop is still about the same.


Right then, I reckon that means things aren't as bad as I first thought.


:)

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[quote name='ahpook' timestamp='1500463880' post='3337958']
OK, after shorting the G-S the voltage drop is still about the same.


Right then, I reckon that means things aren't as bad as I first thought.


:)
[/quote]

Yep - I don't think there's a problem.
As Bobbass said failure usually open or short circuit - not intermediate value.
What is the jfet model number ?

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[quote name='rmorris' timestamp='1500471383' post='3338058']
Yep - I don't think there's a problem.
As Bobbass said failure usually open or short circuit - not intermediate value.
What is the jfet model number ?
[/quote]

Cool :)

They're MMBF-J201s

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[quote name='ahpook' timestamp='1500471646' post='3338062']
Cool :)

They're MMBF-J201s
[/quote]

Okay. Just checking that if there were something wrong they'd be easy enough to replace without having to get another kit of parts.
That series of jfet not so common in UK (to avoid shipping charges out of scale with the cost of a few small components) but Farnell have stock atm so should should be okay.
And your build is probably okay anyway.
Good Luck...

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[quote name='rmorris' timestamp='1500475993' post='3338106']
Okay. Just checking that if there were something wrong they'd be easy enough to replace without having to get another kit of parts.
That series of jfet not so common in UK (to avoid shipping charges out of scale with the cost of a few small components) but Farnell have stock atm so should should be okay.
And your build is probably okay anyway.
Good Luck...
[/quote]

That sounds right as the kit's from a German company.

I'll press on now, reassured by all the helpful advice.

Many thanks everyone.

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If you do have any issues with them let me know, I've got a big strip in the transistors drawer, I'd be happy to drop a few in an envelope (and an ESD bag of course...). I think you'll be fine though, before bitsbox started selling adapter boards for the SOT-23s I just used to solder leads then blob them in epoxy to use them as through-hole substitues... That was definitely not a graceful solution, but they all worked.

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[quote name='bobbass4k' timestamp='1500553282' post='3338653']
If you do have any issues with them let me know....
[/quote]

That's a very kind offer, but I assembled the kit this afternoon (about 4 hours all told I reckon) and it works a treat !

It is an excellent kit - really easy to put together once the SMD sweats were over.

Sound-wise I'm blown away - very much to my taste indeed.


There an optional SMD chip you can fit in place of the DIL Opamp which is meant to be less noisy and fatter sounding. That's a nice bit of practice soldering for me !

Edited by ahpook
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  • 2 weeks later...

I have been busy with a few things so didn't get around to ordering stuff until today. I now have a woolly mammoth clone kit plus assorted bits on its way to me. I can't wait to have a play and see how it works out. It's been ages since I have done anything more than just replace bits or do a simple rewire.

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