Hi yall
last night i made Jon Patons bear hug
and it's behaving oddly
EG when i power it up it make a very loud buzzing noise which quiet quickly goes.
The its loses all volume within about 30 seconds.
Its almost like as soon as one of the caps get charged up it stops working.
substitutions
Q3 No MPSA18 in stock so I used an 2N5089 as suggested by Mr Paton himself.
For D3 and 4 i used 1n60's
R4 used a 4k7 as suggested again by Jon.
didnt have any 1k reverse log pots so i used a 2k pot with a 2k2 resistor across lug1 to 3. Its all i could think of.
Heres the thread
I used the perfboard layout
http://www.diystompboxes.com/smfforum/index.php?topic=99892.0
voltages
battery 9.2v (after si Diode D1 voltage is 8.6v)
Vb 5.66
Q1
D 3.11
G 0.54
S 3.11
Q2
C 7.74
B 0.63
E 0.39
Q3
D 0
G 0.63
S 0
Heres some links to my dropbox pics
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#lh:null-Bearhug%20back.jpg
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#lh:null-Bearhug%20front1.jpg
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#lh:null-Bearhug%20front%202.jpg
i measured the DC voltage on input and output too just incase input 0v Output 3.26v is this normal or expected?
I think gate q1 should be about half v+, but I don't know what effect yr meter will have with that 10M gate resistor there. check your voltage at r5/r6, definatelty should be half V+ there.
wot value is that big green cap, where the 4u7 goes? wot voltage rating to make it so big?
I hate dropbox, and it's time for bed.
green cap is 4.7uf 100v
V bias is 5.66v at junction of R5 R6
sorry about the drop box i've yet to come to terms with embedding images
Night Duck Arse and thanks
1) I'm trying to figure out what's going on in the upper right of the back of the board. What is the tube jumpering over? There aren't any jumpers on the layout. Was your 10uF cap soldered into the row where the ground line was passing through?
2)
QuoteEG when i power it up it make a very loud buzzing noise which quiet quickly goes. The its loses all volume within about 30 seconds.
The behavior you're describing is what happens when the MOSFET fails to bias. Since your drain voltage is too low (by about 2-2.5V), and your source voltage is too high (by about a volt), that makes complete sense. This is also causing your gave voltage to be too low.
The good news is that you used sockets, which makes troubleshooting easier.
First: Pull out Q2. This will isolate the circuit from the rectifier.
Second: to eliminate the possibility that the FET is bad, you can replace it with a 470R resistor (or 1K, or even a piece of wire).
If you want to check that there's nothing wrong with your BS170, you can put a bipolar transistor in Q1. Go ahead and use one of the 5089s you have lying around (remember the pinout will be reverse). You should get LOUD and probably distorted signal. A high-gain transistor should bias somewhere at least close to the 5v range with the values used.
If you don't get loud signal, it's time to turn on the continuity setting of your multimeter and start checking all your contact points. Once you're satisfied that a part is connected to everything it's supposed to be connected to, then you start making sure it's NOT connected to something it SHOULDN'T be connected to (so just run the probe over all the contact points in the vicinity). While you're at it triple check all your resistor values.
If you DO get loud signal, double check the BS170. Maybe even flip it around in case for some reason yours have a reverse pinout. Use another one if you have it. Sometimes they blow up if they weren't in a static-proof baggie.
ive double checked the resistor values and all seem fine according to the chart calculator i consulted online
i removed Q2 and replace the Q1 with a bjt 5089 and it didnt lose volume or fade
i tried a couple of differant BS170 and the same old thing volume fade bad biasing etc
i removed Q1 and put the DMM on the sockets
D 8.64
G 0.83
S 0
I put the BS170 back in and put the meter probes on the Drain as i powered it up the voltages where nearer to what you said
D 4.5 ish
G 0.6
S 2.1
but after a few seconds the drains voltage falls back to 3.11v
and the sources voltage rises to 3.11
Stumped now????????
and the plastic sheathing is over the grd wire because like you said i put the cap in the path of it.
there is no jumper as such its just protectioni even removed it to see it it was the problem and same thing
I'm not sure if this has any bearing on anything at all, but I think there may be a typo in Jon's perf layout? If you look in the area of Q3 and read the three resistors to the right, they go 1M, 1K, 1K - which is what you have, Rich. But I think it should be 1M, 1M, 1K? (According to the schematic, there should be two 1Ms connected to the gate of Q3.) What do you think, Jon?
Edit: You might want to ignore all that... :icon_redface: I just re-read through the whole thread and it looks like the original perf layout on Jon's original post now reflects the Version B and/or C component changes. Long day. Time for bed! :icon_rolleyes:
yep i see what you mean.
I'll await Jons response before changing anything but i'll double check the old BOM too from Josh
Thanks for chiming in. All contributions are welcome.
Check my edit, Rich - posted simultaneously with yours. I'm talking b0ll0x again... :icon_lol:
Edit: If it helps, I have a vero layout that works!
I haven't had too much luck with vero but I'd sure like to try this compressor out for myself so yes please Bunny vero would be a welcome build for tomorrow
Cheers
Rich
Quote from: Kipper4 on August 16, 2013, 05:18:31 PM
I put the BS170 back in and put the meter probes on the Drain as i powered it up the voltages where nearer to what you said
D 4.5 ish
G 0.6
S 2.1
but after a few seconds the drains voltage falls back to 3.11v
and the sources voltage rises to 3.11
Stumped now????????
Yeah, that's bizarre and I've never encountered anything like it.
Anyway, if it works with a bjt, then the connections are right. I didn't see anything wrong in any case.
Try pulling q3, taking voltages again, then replacing it with a resistor or jumper. See if the voltages stabilize.
I'm wondering if there's a possibility one of the electrolytic caps is leaking.
A 2k pot with a 2k2 resistor? Can you explain to a noob how that works?
Best go read Geofx life of pots Jimilee.
In order to make a 1K pot out of a 2K pot i soldered a 2k2 resistor across from lug1 to lug 3 effectively halfving the pot value to a now measured 1k2 pot. I dont think it would magically turn it into a reverse log taper but the value was nearer to that desired by the parts list.
I hope this helps Jimilee
@ jon (is that the correct "attention, jon, question to you" syntax?)
on a working unit, what is the voltage at the gate end of the Q1 10M with and without the mosfet fitted? is this reading affected by meter resistance?
Quote from: duck_arse on August 17, 2013, 10:42:01 AM
@ jon (is that the correct "attention, jon, question to you" syntax?)
on a working unit, what is the voltage at the gate end of the Q1 10M with and without the mosfet fitted? is this reading affected by meter resistance?
With:
D 5v
G 2.5v
S 1.8v
Without:
D 9v
G 2.7v
S 0v
If it's any use, Rich, here's the vero:
(http://www.bouron.org.uk/marc/BHUGDIY.GIF) (http://www.bouron.org.uk/marc/BHUGDIY.GIF) (clickable)
Edit: This is using Jon's original "V1" circuit.
my voltage are nothing like that theyre as reported earlier.
Any idea which cap might be causeing a problem if any Jon?
My guess would be one of the ones attached to the Q1 either the 10uf above Q1 on the drain or the 47uf attached to the source of Q1
thanks for any hlep.
If i cant debug this i'll give the vero a whirl Mark thanks.
Have you check continuity on all the components associated with q1? There could be a bridge or something we can't see. You really can't trust your Reyes all the time.
I'm jiggered if i know Jon
i checked continuaty from everything attached to the mosfet and replaced a 47u cap and 2k7 resistor and its still behaving oddly.
loud hum on power up. works for a start then volume tapers off to hardly there at all and it sputters on its way out.
if i put my finger under the pcb to activate the mosfet the circuit works
it's driving me crackers.
Thanks for all the help.
Quote from: Kipper4 on August 17, 2013, 05:04:58 PM
if i put my finger under the pcb to activate the mosfet the circuit works
it's driving me crackers.
Thanks for all the help.
Check ALL your ground connections. Make sure the 2.7k is grounded especially. Reflow solder to stuff connected to the source.
I did some more checking and i cant figure it out yet i will. I'm having a day off from debugging the perf. Meanwhile i built the vero and its not exactly tonaly transparent infact i'd say its a lot more bassy.
maybe later when i get s=done at work i'll post some pics of it too
thanks
And I'm not getting any volume out of it. I thought it would give me a little boost for some reason.
The bypassed guitar is louder. Is this what was expected?
Quote from: Kipper4 on August 18, 2013, 01:06:59 PM
And I'm not getting any volume out of it. I thought it would give me a little boost for some reason.
The bypassed guitar is louder. Is this what was expected?
V1 isn't nearly as much boost as V2, but it'll still be about twice as loud (or more) as bypassed on lower compression settings.
Turn down the compression knob. Still not getting above unity?
Did you use 4.7K on Q1's drain, or 2.2K?
EDIT: I think it might help if you breadboard the first stage, the MOSFET booster part. You can use a 470R in place of Q3 (from the 47uF cap to ground).
Hi Jon
I used a 4k7 not the 2k2.
Just so I'm clear build the MOSFET booster that finishes after the 10nf and replace the q3 with a 470 to ground after the 47uf cap right.
Thanks
Here's the booster part:
(http://www.muzique.com/schem/mosfet.gif) (Check out Jack's project page here (http://www.muzique.com/schem/mosfet.htm) - great little booster, btw!)
If you take out the 10nF that leads out to the MPSA18, then you're pretty much left with Jack's booster circuit, except that the gain control has been replaced by the 2N5457 JFET in Jon's circuit. You could whip that out and replace temporarily with a small pot, just to check out the booster functionality.
I probed the booster section and im getting good signal at
the gate
the source
and initially the drain which quickly fade to practically no volume
i'm gonna whip out the 100pf and replace it and see if it make a differance.
the reason i say this is if i breach the grate drain connections i get a very loud signal and i suspect a poor qaulity 100pf
could this be it?
I'll build jacks booster later too just to try it. thanks Mark
Nope thats another fail.
This mosfet is going off bias very quickly.
Quote from: Kipper4 on August 19, 2013, 10:26:46 AM
I'll build jacks booster later too just to try it. thanks Mark
The reason I'm suggesting breadboarding it is because you've had the same problems twice now with two builds. Breadboarding it would allow you to remove and replace parts to determine (a) if something is wrong with some of your components or (b) if somehow a connection has been improperly made on both builds. If you breadboard the booster half and it works, then it's b. If you breadboard the booster half and it doesn't work, then it might be a.
Also, I'll PM you in a second.
i built jacks booster on a left over piece of perf and got pretty much the same results as found in the bearhug
ie a horrid buzzing while the mosfet settles then its a bit splatty which suggest to me its not biased right or the mosfet is blown.
The upside it doesnt loose volume or die on me but is unusable because it breaks up so badly.
I thought turn down the guitar signal. That didnt clean it up
turn down the gain pot. remained the same horrid break up just less volume.
i've got a few BS170s i havent tried yet (4) but they were all stored in the same bag so i suspect if ones bad then they all will be.
I'm getting closer
Thanks for all the help guys
Rich
i tried all the other BS170s and one sounds worse than the others but all seem to work despite the horrid buzz.
Sheesh this bosster has some serious gain.
Where too now guys any ideas?
Did you check the pin out? - BS170s and 2N700s are conveniently opposite to each other.
I cant think of a reason why the mosfet would become unbiased.
It sounds a bit like a cap charging and then causing a nuisance of itself. I don't think it will cause the symptoms you describe, but one other thing to try is the Zener - are you sure you have it the right way round?
You can test whether your MOSFETs are dead by making a very simple switch on a breadboard (it will work fine with 9V) -
https://www.google.co.uk/search?q=mosfet+led+switch&safe=off&client=firefox-a&hs=hs8&rls=org.mozilla:en-GB:official&source=lnms&tbm=isch&sa=X&ei=VkMSUurKAsbF7AbtzIHACw&ved=0CAcQ_AUoAQ&biw=1354&bih=890#facrc=_&imgdii=_&imgrc=1bJRXJSUZ9p2oM%3A%3BunMGhYRd5nLf2M%3Bhttp%253A%252F%252Fbrunningsoftware.co.uk%252FPictures%252FU-fig10.jpg%3Bhttp%253A%252F%252Fwww.edaboard.com%252Fthread244743.html%3B199%3B284
the zener has its cathode ( the end with the stripe on it IIRC) pointing to the gate
from source to gate
Quote from: samhay on August 19, 2013, 11:49:39 AM
Did you check the pin out? - BS170s and 2N700s are conveniently opposite to each other.
If you build Jack's booster roughly following the topology of the schematic (9V "up", GDN "down), then a BS170 would "face" left, but a 2N7000 would face right.
Quote from: Kipper4 on August 19, 2013, 12:01:40 PM
I cant think of a reason why the mosfet would become unbiased.
Me neither. Perhaps you need some anti-static bags for your MOSFETs? ;D
Quote from: Kipper4 on August 19, 2013, 12:48:25 PM
the zener has its cathode ( the end with the stripe on it IIRC) pointing to the gate
Yep, sounds right. Sure it's a zener? Daft question... :icon_confused:
Wanna see you fix this, mate. I've built both, and both do their respective jobs brilliantly. Hate to see you miss out! :(
Did i make a booboo because i notice that the top left hand corner 10ufs cap anode is not actually grounded in the layout
seen here
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20layout.pdf
should i have made a connection between the two grounds between the switch 2 position and the uppermost 4148 diodes cathode?
When i zoom right in now i can see the white connection behind the resistor and 22k and the diode cathode brb.
Switches the iron on.
Good spot, Rich! Yeah, you should be able to follow that white ground trace all the way from the top-left, across to the right, under the 22K (and forming one of the switch contacts), then down the right-hand side, before it heads west again (not forgetting the little return detour to the JFET).
Panic over it works a treat now and after only a few seconds trial i love it already.
Sorry guys my mistake.
Yay! It's working! But, um, I'm confused: What happened in the other layouts and the booster that your MOSFETs were distorting there? :icon_confused:
All the noise on start up is gone. It no longer sounds Dark and its got some serious squish if i want it.
Cracking design Jon
And guys Thanks for all the help over the last few days.
I dont like to be beaten.
The vero version one is still dark and only just boost.
I've yet to look it over seriously.
As yet Sir i have no idea why.
That switch is a stroke of genius by the way and its a long time since i've heard such an effective compression pot
You deserve a medal
Perhaps Order of the Pedal medal?
I'll have a word with the queen> Shes a family friend. :)
Quote from: Kipper4 on August 19, 2013, 02:05:26 PM
The vero version one is still dark and only just boost.
I've yet to look it over seriously.
The good news is, you're now very familiar with the schematic AND you have a completely working board to test every aspect against.
Also, I'm very glad you like it, and especially impressed and flattered by how determined you were to get it going!