fet boy

[3nity]

Matt you got a Function generator?
I would apply it at the input and check by stages with the Scope.
You should see wheres it coming from and whats causes it!

Hope it helps.

I'm still stucked with mines, i havent had time for nothing just working too much!

Jorge.

 

[fucanay]

No, I don't have one. I've just been checking this stuff with nothing attached. Could that be a problem?

Matt

 

[3nity]

I doubt it but the signal its better!

 

[fucanay]

Well, I hooked up a microphone and just scoped my voice. It was really cool to see the signal on the scope, but it changed nothing about what I'm seeing at the drain of Q1 and Q5.

I'm totally baffled at this point. Something is wrong with the circuit, but I can't see anything that simply changing parts or wiring would help.

Maybe it's time to just shelve them until someone with better skills than me figures out the problems.

Matt :sad: :sad:

 

[3nity]

With a mic plugged in you see a lot of things. not what you want

If you put a 1K you'll see a steady wave and from that you can see whats apart from the 1K!!

 

[fucanay]

[quote author="3nity"]With a mic plugged in you see a lot of things. not what you want

If you put a 1K you'll see a steady wave and from that you can see whats apart from the 1K!![/quote]

I did that from my laptops headphone jack last night. But I'm not really sure what I'm looking for. The wave was fuzzier than the flat line of DC that I have on the PSU, but it still doesn't help me solve anything.

I don't have enough knowledge to trouble shoot this past finding that there is a problem.

Matt

 

[lofi]

you have to trace the audio signal either in or out to the point where it goes tits. you got a decent camera or access to one? could you take some close ups of the boards (top and bottom)?

if so i will host them so we can all have a good look and maybe see something. the main problem here is that most of us arnt gurus and so are groping in the dark abit also.

but rest assured Matt, we will sort this!!!

Iain

 

[fucanay]

[quote author="lofi"]you have to trace the audio signal either in or out to the point where it goes tits. you got a decent camera or access to one? could you take some close ups of the boards (top and bottom)?

if so i will host them so we can all have a good look and maybe see something. the main problem here is that most of us arnt gurus and so are groping in the dark abit also.

but rest assured Matt, we will sort this!!!

Iain[/quote]

As far as where it goes ape shit, it's at the drain of Q1, and remains unchanged from there until it goes even more ape shit at the drain of Q5. Both of the 2N5457's.

Close ups of the tops can be found here: http://fucanay.fischerworks.com/diy/fetboy_in_progress/

These were taken before the changes to the grounding that were done earlier in this thread.

I don't have any of the bottom, but I have checked for bridges. And the fact that both channels behave identically, makes me think that there is something about parts selection that's wrong, not placement. Also, it's more than just me having this problem.

Thanks for the encouragement.

Matt

 

[Samuel Groner]

Can you take a scope pic with the according waveform?

Samuel

 

[lofi]

just taking kids to school, but do you get problems with only 1 board conected to the psu? i had similar with two 1176's when conected together but perfect on their own, cant read this threads last few pages as in a rush, so sorry if you have answered this before

Iain

 

[Svart]

I fixed mine.

Lets just say there was a short between the operator and ground..



I was looking for a circuit problem the whole time and it turns out I wired an XLR backwards...

Kids, just because you become an engineer doesn't mean you don't do stupid things. :green:

The pres work great!

 

[jrfred453]

I ordered a couple fetboy kits from PtownKid and I'm wondering if I can use a SSL9K PSU board to get the required 24v and 48v needed for the fetboys. What can I leave off of the 9K PSU? Just replace the regulator with a 7824?

 

[Svart]

you would have to move up in voltage rating on the transformer, replace the 7818 and leave off all of the negative voltage parts.

 

[3nity]

Hey guys i have problems with mine....i only hear a big hum when powered...?? and with the pot the hum goes loud or lower...??
Any toughts? electros got very warm.....i got a RS1 burned? any ideas?

 

[3nity]

The other one works fine but Q4 and Q8 gets very hot!
And it runs into oscillations very easily i'm happy cuz i can compare both now!

Cheers.

 

[3nity]

Alright i change Q2 and Q3 and voila!
They both sound but i have some tweaks to do before finishing the build!
small steps a day!

I have one question for you all: how warm the BD135 should get? my finger is burned when i touched them!

Thanks.

 

[Svart]

i swear these fetboys have been the most ^#I$&#&^#@ things I have tried to get built. I swear, everything that can go wrong with them has gone wrong.

So I got mine working the other day..

I decided to put them in a nice little box, with a nice little power supply.

I power then up at work and I see no problems.

I bring them home and plug them into a surge strip and POW!!!!

the hot and ground pins on the IEC cord MELTED to the contacts of the surge strip..

and I have NO idea why. The IEC plug goes through a fuse and to the transformer. The ground is to the chassis.

This WORKED on the desk at work. Nothing changed between there and here..

I tried another power cord and a different strip..

POW!!!!

Nothing is shorted between the line and ground, between any of the power supplies and ground, etc.

:roll:

 

[jarlehal]

I've joined the club of struggling fetboys. Got a couple of kits from Bryan and I'm putting one together now. Have a few questions..

The kits contain BD139-16 but I measured hfe, and the lowest one was 182. Most around 185. Do I have to get close to 20000 for the darlington pairs (mul) or will my pair of 185s do? (34225)

Got 20 of the 2n5457, but none of them got me to the 12v ballpark.. all resulted in 15v and above. Have to get a bunch of those I suppose.?.

When I have signal thru it, I have to turn the pot fully CW area to get any output. And there's not much gain. Any suggestions? Is this a result of the FETs dont match? I only feed them 24v, no 48v yet.

 

[3nity]

Do all the transistors are placed in the right direction?
Resistors? maybe?

PIX??
:thumb:

 

[Ptownkid]

Wow, i measured those 139's and they weren't that high...

You definitely need to get closer to 20,000 than that. I'll try and get some more.