Maestro Sample & Hold/Filter DIY problems...

[nirvanas silence]

First off, has any one built one from the layout given?  I built it and I can't get it to work and I'm checking the pinouts and they don't match.  Even after that its not working so I have alot of checking to see if the board matches up right.  ANy happen to know the appropriate voltages too?  My LFO and bypassed sound works fine so I think its a problem with the 3080Ts or the transistor pinouts.  Any ideas....

[Sic]

sorry bud, i just don't have the guts to try the S/H yet =/

[nirvanas silence]

Well when I get it done I'll be more than happy to help you if you have any questions.  I mostly curious if anyone has made it yet becuase some of the pinouts are wrong on the diagram I think.  I may be crazy, its 3:30AM here, but I think I am reading it right.  I'm gonna go crash for the night, homefully some more input by the morning.  Goodnight.

[Zero the hero]

The layout on GGG is correct, I've built it.
This circuit needs an accurate trimmers tuning. Make a search on the forum, others had similars problems.

[nirvanas silence]

I've played with the trimmers for about 10 minutes with no luck.  Turning the 10K gives me a quiet chirp occasionally.  I'm concerned that the layout says Q3 is oriented backwards.  I'm going to replace the 3080s since the trimmers probably aren't the problem.

[toneless]

The layout from GGG is 100% correct because many people
have build it...
I've tryed three times to build this fx but with no luck. I think I had
the same problems with you when turning on of the trimmers.
I ended up that the transistors were wrong....??!! I used BF245C but the
"Tonda" layout asks for BF245A. Anyway I don't know if this is a problem.
What trans are you using?

Next time I'll be more prepared 'cause I now have an audio probe!!!

Good luck.
Nick

[nirvanas silence]

Well the parts layout shows the emitter of Q3 going to a 22k, 100K, and 1M resistor.  The schematic shows that being the collector.  

I used BF245As I believe.  It must be a trimmer problem then.  Does anyone have a list of appropriate voltages?  I'm gonna replace the 3080Ts otherwise.

[Michael Allen]

All i can suggest is throw in a lot of sockets and then switch the tranny pins around and see if it helps. Print off the datasheets for the 3080 as well as all of the suggested transistors and the ones you're using and make sure you get the right pins in the right place.

[niftydog]

the parts layout shows the emitter of Q3 going to a 22k, 100K, and 1M resistor. The schematic shows that being the collector.

looks correct on both to me.  :?

I do, however, have two conflicitng pieces of information about Q1 pinout. One says it's EBC, the other says ECB. (looking at the flat side with pins pointing down, BTW)  Time to break out the DMM and check it out!

Tried audio probing it?

[nirvanas silence]

I'm starting to think I'm insane.  Look at the parts layout.  The emitter of Q3 goes through a 22K resistor then to the S&H/F switch.  In the schematic its the collector that goes through that same 22K resistor.  

I probed it and I get alot of distortion if have guitar hooked up to the input and probe the output to the output of the LM741 used as a gain stage right after the sensitivity control.  I also get alot of distortion at the gate of Q2 I believe.  No filter effect at all though.

[niftydog]

The emitter of Q3 goes through a 22K resistor then to the S&H/F switch. In the schematic its the collector that goes through that same 22K resistor.

no, definately not. You must have confused emitters and collectors on schematic symbols. It's a PNP, not an NPN, but the pin with the arrow is still the emitter.

Audio probe it systematically from the input, checking each node along the signal chain (Q1 and 2, IC1 and 2). Is the signal ok at the inputs and outputs of the 3080s?

I'm not that familiar with this circuit, but it looks to me as if that 741 isn't part of the audio chain; looks like it's part of the control of the filter...

[nirvanas silence]

When arrows are all over the screen you know it's time to sleep.

[niftydog]

funny, I was there just last night. Woke up this morning, change a 1 for a 2 and the 2 for a 1 and it all worked!!!

[Jason M.]

First off, has any one built one from the layout given?  I built it and I can't get it to work and I'm checking the pinouts and they don't match.  Even after that its not working so I have alot of checking to see if the board matches up right.  ANy happen to know the appropriate voltages too?  My LFO and bypassed sound works fine so I think its a problem with the 3080Ts or the transistor pinouts.  Any ideas....

Don't get discouraged. This is a unique and worthwhile project. Several people have built it from the layout at GGG, including me.

I tried searching the archives, but the project was introduced waaay back, when Aron's forum was at Ampage. Once the thread fell off the page, it was gone.

Make absolutely sure you know the pinouts of the transistors you are using and that they are oriented correctly. I used sockets for all the transistors.

Q4 is critical for the noise generator in the sample/hold mode. It MUST be a noisy transistor. I tried at least 20 2N3904's with no luck.
The first 2N2222 I tried worked like a charm.

Set the 100k trim to the midpoint of it's rotation and the 10k trim completely clockwise. If you look at the schematic, the 10k is a vol. control for the noise source.

The filter mode should work once the transistors are inserted properly.

Are you using two batteries or something else for power?

Good luck.

J.

[nirvanas silence]

Thanks, every transistor is oriented correctly and almost every combination has been tried.  I want to get the filter circuit working first.  I didn't etch the board so I'm checking for bad traces now.  This is the first time ever that I haven't been able to troubleshoot it in a few minutes which is why I think I have a fried 3080.  Also, I'm using a MAX1044 for +/- 9V.

[Travis]

Have you checked your MAX1044?  I have fried them by supplying just a bit more than 10V (10V is the max rating).  There is not much room for error.

If you are producing +/- 9V, take transistor and IC voltage measurements.  

It IS a known good layout.

[wui223]

mine wouldnt work. i use 2N5458 for Fet BC184 for the first fet/transistor.
I adjust the trimmer but nothing sound correct just plain guitar sound. how bout the noise transistor?

[soggybag]

The 10K trimmer adjusts the level of the noise. The 100K trimmer sets the range for sample and hold. I think it was suggested (to me) earlier to set the 10K trimmer to max and put the 100K trimmer in the center. Then turn the 10K down until you get the most usable range of noise adjusting the 100K a little to fine tune.

If you don't hear any your signal being filtered even a little bit, especially as you adjust the 100k trimmer, there may be something wrong with the filter section I might guess.