Maestro FSH1 from GGG problems

[dcjim]

Hello

DOA Maestro FSH1 from GGG

"DOA"= Dead on Assembly

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Schematic

http://www.generalguitargadgets.com/diagrams/fsh1asc.gif?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Parts layout

http://www.generalguitargadgets.com/diagrams/fsh1apl.gif?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

DIY board kindly etched by somebody from this or another forum probably about 5 years ago! It took me a while to get around to this project. Thank you whoever you are, I really don't remember. They did a good job.

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Parts

Q1 - Schematic specifies MPS5172, BOM specifies 2N5088. I used the 2N5088
Q3 - Schematic and BOM both specify 2N3906 which is what I used
Q4 - Schematic and BOM both specify 2N3904 which is what I used
Q2, Q5, Q6 - Schematic specifies 2N4303, BOM specifies BF245a. I used the BF245a

IC1, IC2 - Schematic specifies 3080T, BOM specifies 3080. I used CA3080E http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=160560321883#ht_500wt_768
IC3, IC4, IC5 - UA741CN used http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1094414&CMP=i-bf9f-00001000

I'd say I'm an intermediate beginner so I still get a bit confused with some component choices, the diodes

D1,D2, D3 - BOM specifies 1n4001. A search at Farnell gave two types, "standard" or "rectifier". I used these

http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1843694&CMP=i-bf9f-00001000

Finally, I saw multi-turn trimmers suggested in some build log but they seem to work out more expensive so I've used typical single turn presets. These types in fact

http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1141668&CMP=i-bf9f-00001000

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I made three modifications to the layout as link above

1. The BF245a JFETs were reversed as pins are the opposite of the 2N4303s

2. I couldn't source a 2M lin pot (although I now realise perhaps I could have used a 2M2 which I do have?) so I made the following substitutions (based on a post somewhere, possibly the build reviews for the Tonepad version, I can't remember exactly)

R28 was 2M pot, becomes 1M pot
R29 was 330K res, becomes 180K res
C10 was 0.15uF cap, becomes 0.33uF cap

3. It's powered by a charge pump not two 9V batteries in series. Circuit was from GGG

Parts layout (no schematic)

http://www.generalguitargadgets.com/pdf/ggg_ps_cpbp_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

I etched the board myself

As MAX1044s are a little hard to come by I'm using an ICL7660SPA for now which Google tells me is an equivalent (I understand the MAX chips are preferable as you can tie pins 1 and 8 to help eliminate the sound of the oscillator which can bleed into the audio path)

I'm confident the power supply is good as I get -8.14V across the ground reference and the bottom "-" pin and 8.26V across the ground reference pin and the top "+" pin for a 9V battery reading 8.3V

One area I do get confused sometimes is with all the jack socket, switch, power and ground wiring so here's what I have



Notes

1. Not sure what the empty pad above C2 is for ... ? I've looked at pics of other builds and it seems unused
2. At first glance it may appear that J1 is not grounded. It is as the sleeve is connected to the third pad from the bottom on the charge pump PCB which is connected to the ground pad below it

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So, that's what I've done and this is what it's doing in response ...

Naff all!

Well I can hear my input signal in bypass mode, hurrah! Otherwise all I get is a regular clicking sound in S&H mode, but not filter mode, and no guitar in either. The clicking is effected by turning the pots and trimmers; speed/intensity etc. So it's not completely dead but it's not much fun as it stands! Filter and S&H sections have left the building

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So here are my voltage measurements



(Or PDF http://web.mac.com/hardcoded/fsh1/volts.pdf)

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What I've checked so far

Orientation of transistors ... I will do it again (and again and again) but I really have done it about 5 times!
Checked continuity throughout circuit, all good, no duff joints
Checked all component values, they're correct
Had a go with an audio probe following the schematic (although not really sure what I'm doing). Signal stops abruptly at R16

I've also had a good Google

Most posts discuss either one or the other half dead (but not both) or best transistor selection for good noise source in the S&H circuit. I did find out about reversing the BF245a transistors from Googling which I've done and this is what lead me to check all transistors.

Perhaps I've fried some transistors flipping them around? Next thing I'm going to do is research how to check transistors are working. In the meantime if any of you lovely people spot anything it would be hugely appreciated!

Thanks
Jim

[dcjim]

Oh one other thing. U1 is I assume a wire/jumper? I have included it.

Also here's a pic of the build

[thedefog]

Do you have an audio signal on pin 6 of IC3?

Also, good thinking socketing this one. I had two bad CA3080's on mine as well as a bad 741 from god knows what early on during my first build. I also used BFA245s and had them reverse by accident to start, which probably cause the problems. I also had issues with ticking that never really went away, even with a LPF in place.

The tonepad layout is much nicer, replaces the CA3080 OTAs with an LM13600 and incorporates a MAXX1044 right onto the board. I'd recommend it if you decide to make another one of these in the future as I did.

[dcjim]

Do you have an audio signal on pin 6 of IC3?

Yes! Yes I do ... what next?!

[thedefog]

Do you have an audio signal on pin 6 of IC3?

Yes! Yes I do ... what next?!

Check Pin 6 of both IC1 and IC2. If you have output on pin 6 of IC1, then Q2 is probably bad.

[dcjim]

Bah!

I had it working and now it's bailed again! Had guitar going through it, not just test signal. Sounded lush. Funny thing is I think I did have signal on pin 6 of IC2. What I did notice for definite is that lug 1 of R15 had broken so I repaired that. That seemed to make it come alive. I left it and came back a little later to find it was dead again. I replaced Q2 anyway but still no dice. I don't have signal on pin 6 of either IC1 or IC2 now.

Bumclouds

[thedefog]

Bah!

I had it working and now it's bailed again! Had guitar going through it, not just test signal. Sounded lush. Funny thing is I think I did have signal on pin 6 of IC2. What I did notice for definite is that lug 1 of R15 had broken so I repaired that. That seemed to make it come alive. I left it and came back a little later to find it was dead again. I replaced Q2 anyway but still no dice. I don't have signal on pin 6 of either IC1 or IC2 now.

Bumclouds

If you had output momentarily, then you definitely just got a bad wire connection somewhere and your components are fine. Check continuity between your Pot/Switch lugs and where it connects on the PCB. Once you know they're good, it never hurts to put a dab of hot glue down on the top of the PCB to make sure they stay put. I acutally use Epoxy on the wires on the board if there is enough room to keep them from breaking loose.

[dcjim]

It was a duff CA3080! I bought a rare parts kit for a TR909 clone project I while ago and I wondered if it included a CA3080. Sure enough it did so I had a spare to swap out and bingo the beast came alive.

I was initially more interested in the FSH1 for the sample and hold section but the filter is really nice too. What is it, an envelope follower? The harder I play the more it opens up the filter yeah? Does the filter range pot effect the sample and hold section also? It's always a bit hard to tell what's going on when you haven't got a proper enclosure and things aren't labelled and you have to hold the pots to turn them.

So how did you get on with setting the trimmers? What do they control? I had a quick look and it seems quite tricky to get a setting that's good for both sample and hold and filter.

I think my transistor choice is Ok although it seems to choose lower frequencies more often than higher ones. I might socket the noise transistor and try several out. Also I think people have removed the clicking (which I have too) by experimenting with all the transistors.

What kind of epoxy do you use? I've tried a couple of brands but they're either too runny or too thick and it's difficult to get a neat blob.

And last but not least ... thanks for your help, much appreciated

[thedefog]

What is it, an envelope follower? The harder I play the more it opens up the filter yeah? Does the filter range pot effect the sample and hold section also?

Yep, it is, and it is pretty nice sounding. I've used it on a lot of other things besides guitars too. It was fun running drums through it.

So how did you get on with setting the trimmers? What do they control? What kind of epoxy do you use? I've tried a couple of brands but they're either too runny or too thick and it's difficult to get a neat blob.

Trimmer R27 controls the frequency/range of the S&H section. R26 controls the range of the filter. R26 does not affect the Sample & Hold and vice versa. Just use your ear to what suits you. There is definitely a small sweet spot for both of them.

I use JB Weld for epoxy, as it mixes up like a thick paste and is easy to be neat with. It takes longer to set as well, so you have a good hour or so to move it around if necessary.

There are some mods you can do to the GGG version that Moosapotamus has outlined to include a frequency range adjustment pot, as well as attack and decay controls for the filter. The Tonepad version includes these, but it isn't difficult to add them in if you want to have a little more control. I definitely recommend the attack and release mod, as it really adds more use to the Filter section. The resonance mod is okay, but not crucial IMHO, as well as the filter range pot.
http://moosapotamus.net/THINGS/fsh-1a.htm

[thedefog]

BTW, off topic, how was your experience building that 9090 kit?

[dcjim]

Thanks for the info. Yeah I quite fancy the attack and decay mods. The resonance was no good? Resonance is normally lots of fun on synths.

The pedal itself is only one half of this project as it goes. I've found this awesome looking enclosure for it that looks like something pulled from the flight deck of a Soviet era military transport plane! They're actually quite easy to come by although I'm not going to reveal my little secret until the pedal's done!

But it has like a hooded slot at the top of the enclosure. I've some 7 segment LED displays hanging around and when I'm not building guitar pedals I'm fiddling around with Arduinos and other microcontrollers. The LEDs fit perfectly in the slot and I thought it would look pretty cool if the slot had a row of them controlled by the Arduino. It might just be a big random number or a number that changes with the sample and hold section or maybe it displays numbers based on the pot settings. Dunno yet. Either way it'll be completely unnecessary, totally gratuitous and utterly brilliant eye candy! Well that's the plan anyway

The TR9090 ... wow ... well I haven't started yet. It's a huge project. It's not even a kit. There's just the boards and the EPROM chips with the sample data on and then I got the rare parts kit off of some guy on electro-music.com. I've started matching my BOM with Farnell order codes but that's as far as I've got ... ask me again in a year

[thedefog]

Thanks for the info. Yeah I quite fancy the attack and decay mods. The resonance was no good? Resonance is normally lots of fun on synths.

The pedal itself is only one half of this project as it goes. I've found this awesome looking enclosure for it that looks like something pulled from the flight deck of a Soviet era military transport plane! They're actually quite easy to come by although I'm not going to reveal my little secret until the pedal's done!

But it has like a hooded slot at the top of the enclosure. I've some 7 segment LED displays hanging around and when I'm not building guitar pedals I'm fiddling around with Arduinos and other microcontrollers. The LEDs fit perfectly in the slot and I thought it would look pretty cool if the slot had a row of them controlled by the Arduino. It might just be a big random number or a number that changes with the sample and hold section or maybe it displays numbers based on the pot settings. Dunno yet. Either way it'll be completely unnecessary, totally gratuitous and utterly brilliant eye candy! Well that's the plan anyway

The TR9090 ... wow ... well I haven't started yet. It's a huge project. It's not even a kit. There's just the boards and the EPROM chips with the sample data on and then I got the rare parts kit off of some guy on electro-music.com. I've started matching my BOM with Farnell order codes but that's as far as I've got ... ask me again in a year

That sounds pretty awesome. I need to mess around with my Arduino a bit more. Yeah, I usually love resonance on VCFs, but I wasn't crazy about it on the guitar. If you plan on using it on other things though, definitely do it.
I only asked about the 9090 because I seriously considered it myself. I've built a couple x0xb0xes as well as some modular synth stuff and a sound lab ultimate, so it was just the next logical step... Only I'm not crazy about the idea of being the guinea pig for such a daunting project. I did that with the Sound Lab Ultimate, but it was so well documented by Ray Wilson that there was hardly anything I could have done wrong.