EA trem problem

GibsonGM · July 19, 2019, 02:58:44 PM

I hear you, Duck, and totally agree. The caps that are also attached absolutely can (and should!) skew the reading. Working with OP re. continuity testing...I'd actually 'beep' out source to the 10k resistor, then beep its other leg to ground to be sure. If that resistor is of another value, it sure could drag down Q4 enough to cause it to not work!

Clubb, are you following that? You should identify the source leg, make SURE it is going to the 10k, and make sure 10k is going to ground - with good solder joints...if the 10k is NOT 10k, you may replace Q4 only to find it still doesn't work...

Dclubb83 · July 19, 2019, 03:21:43 PM

Ok I'm not gonna lie. You guys are kinda losing me and a lot of this is going pretty far over my head. I'm trying to keep up, but I don't think I'm getting everything.

GibsonGM · July 19, 2019, 05:32:04 PM

When you build a kit, sometimes it's easy to accidentally swap resistors, and put the wrong one some place! So, if the source resistor at Q4 isn't 10k, it could cause problems (like, no sound). Duck wants you to make SURE you actually have a 10k there. Measuring source to ground might lie, though....capacitors also show up having resistance when you put a meter in a spot that is connected to them (it increases over time as you watch, generally).

That's why I didn't get too specific on you, ha ha. You could unsolder the resistor attached to the source, AT the source, then read that lifted end to ground, see if it's 10k. I hate the blue resistors, I can't read them for crap (old school I guess). That would separate it from C9, so you could be sure of the reading.

I still lean towards Q4 being dead, but that's a gut thing. You will 'get it' over time, LOL. Debug enough stuff, those 'tricks' will come to you! I'm trying to find a way for you to fix this easily...if you have another 5457, I'd say take out Q4, check that resistor, pop in the new one, done. But then you might mess up the pads on the PCB, so Duck is trying to see if that is REALLY necessary, or if it's just that maybe that resistor is the wrong value.

Dclubb83 · July 19, 2019, 07:58:17 PM

I checked that resistor, it is indeed 10k. Seeing as how this is only my second project and both have basically been kits, I do not have any spare parts. I am going to stock up on various components from Tayda soon and I'll definitely be sure there are some 2n5457's on there and I'll swap one out and hopefully that'll do it.

In the mean time I suppose I'll look over all of your guys' comments and try to make head or tails of everything that confused the hell out of me.. which was about 75% of it lol.

Thanks for all the help so far! You guys are great!

GibsonGM · July 19, 2019, 10:00:50 PM

Just be sure to come back with more questions, DC!

antonis · July 20, 2019, 05:42:37 AM

So, did we or didn't verify 10k from JFET Source leg to GND..

duck_arse · July 20, 2019, 11:20:09 AM

with all due respect, Sir Mike, I humbly submit that I actually wanted the opposite .....

Quote from: GibsonGM on July 19, 2019, 05:32:04 PM
When you build a kit, sometimes it's easy to accidentally swap resistors, and put the wrong one some place! So, if the source resistor at Q4 isn't 10k, it could cause problems (like, no sound). Duck wants you to make SURE you actually have a 10k there. Measuring source to ground might lie, though....capacitors also show up having resistance when you put a meter in a spot that is connected to them (it increases over time as you watch, generally).

we know his 10k is 10k, what I wanted was proof that the jfet was connecting to ground through that 10k. so put the black meter probe on ground somewhere [but not the resistor leg], and the red meter probe on the leg, the actual pin sticking out of the jfet, so we could be sure of all the solder connections and all copper the traces between. and because his 10k read exactly 10k in circuit, it got me thinking about what he was and wasn't measuring.

and apologies to you to, Dclubb83, for talking about you so rudely in the previous para.

Dclubb83 · July 20, 2019, 01:36:58 PM

Quote from: duck_arse on July 20, 2019, 11:20:09 AM

we know his 10k is 10k, what I wanted was proof that the jfet was connecting to ground through that 10k. so put the black meter probe on ground somewhere [but not the resistor leg], and the red meter probe on the leg, the actual pin sticking out of the jfet, so we could be sure of all the solder connections and all copper the traces between. and because his 10k read exactly 10k in circuit, it got me thinking about what he was and wasn't measuring.

This is what I did the first time, right? I had the output jack attached to the enclosure, I touched the black probe to the enclosure and I touched the red probe to the source leg (pin 2) of Q4 and I got a 10k reading. I thought it was a way of "2 birds"ing it. I could check the connection of pin 2 and also make sure everything was grounded correctly. Sorry if I'm doing a bad job of explaining stuff.

GibsonGM · July 20, 2019, 02:41:22 PM

Quote from: duck_arse on July 20, 2019, 11:20:09 AM
with all due respect, Sir Mike, I humbly submit that I actually wanted the opposite .....

Quote from: GibsonGM on July 19, 2019, 05:32:04 PM
When you build a kit, sometimes it's easy to accidentally swap resistors, and put the wrong one some place! So, if the source resistor at Q4 isn't 10k, it could cause problems (like, no sound). Duck wants you to make SURE you actually have a 10k there. Measuring source to ground might lie, though....capacitors also show up having resistance when you put a meter in a spot that is connected to them (it increases over time as you watch, generally).

we know his 10k is 10k, what I wanted was proof that the jfet was connecting to ground through that 10k. so put the black meter probe on ground somewhere [but not the resistor leg], and the red meter probe on the leg, the actual pin sticking out of the jfet, so we could be sure of all the solder connections and all copper the traces between. and because his 10k read exactly 10k in circuit, it got me thinking about what he was and wasn't measuring.

and apologies to you to, Dclubb83, for talking about you so rudely in the previous para.

I thought I asked him to do the same, and he did...I'm trying not to overwhelm the poor guy, he's new

"To use your meter for continuity, set to "ohm" (omega symbol) Touch probes together....you should get zero, or very very low, like .1 ohm. You can use this to see if points on the board are connected...you'll read that magnitude of number if they are! If not, you'll get oddball things...100s of ohms, 1,000s etc. You should read 10,000 ohms from the JFET source to ground, for example (check that; pin 2 on the thing, to ground)."

duck_arse · July 21, 2019, 10:11:00 AM

excellent. and apologies for harping. so, we can rule out a problem connection there. carry on.

GibsonGM · July 21, 2019, 10:35:02 AM

Nah, there's no harping here, buddy! Don't want to overlook one little thing that could be the key, and have him get all frustrated and give up!

Dclubb83 · August 01, 2019, 03:26:19 PM

Tayda didn't have any 2n5457's in stock.. so I grabbed a 2n5458.. threw in some sockets plugged 'er in and ITS ALIVE. Lovely lovely trem. Now this has only been tested with some audio from my phone through a Danelectro Honeytone, so I haven't actually ran it for real yet but it seems to be doing everything I want it to. You guys are the best! Hopefully I won't have to revive this thread with more problems in the future! Thanks for everything. Time to move on to a tagboard effects layout of a Super Fuzz for a friend. Wish me luck!

duck_arse · August 02, 2019, 10:20:04 AM

luck. do you prefer good or bad?

Dclubb83 · August 03, 2019, 03:06:18 PM

Haha it seems like I should have specified because I'm sitting here with no signal on this fuzz. I'm gonna see what I can do about debugging this guy myself. The Super Fuzz is one big ol fuzz circuit...

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EA trem problem