The Engineers Thumb Debug

[Kipper4]

i built this today from Johns prefboard layout.
it was all going so well until i plugged it in.
i'll go to the debug page and report back asap

[Kipper4]

Here is the checklist to fill out:
1.What does it do, not do, and sound like?
the out put sounds like DC hum

2.Name of the circuit =The Engineers Thumb Compressor by Merlin B
3.Source of the circuit (URL of schematic or project) =
http://www.diystompboxes.com/smfforum/index.php?topic=97123.40

4.Any modifications to the circuit?   N
5.Any parts substitutions? If yes, list them.  A polarised cap 1uf (c4) i think
6.Positive ground to negative ground conversion? no
7.Turn your meter on, set it to the 10V or 20V scale.
Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 8.83v


voltages as follows:

Q1
C =1.09
B =8.27
E =8.09

Q2
C=8.9
B=0
E=6.62

IC1 (or U1)

1 8.22
2 4.12
3 4.17
4 0
5 4.17
6 7.86
7 8.22
8 8.85



IC2
1 8.24
2 8.08
3 7.88
4 0
5 8.83
6 8.07
7 8.24
8 8.84

IC3
1 1.1
2 0.9
3 8.06
4 8.07
5 8.1
6 0
7 0
8 0
9 0
10 0
11 8.86
12 0
13 0
14 0
15 0
16 0


geez i been planning this for weeks and this is frustrating .
I'll put some pics on my page and report back with the link
 

[Keppy]

Check the 1M resistor to ground off pin 5 of IC2. That pin should have about 4.5v, and if it doesn't none of your active components will be biased correctly.

EDIT: Also make sure there's not a solder bridge between the +9v track and that pin.

[Kipper4]

the prefboard layoutof Johns i used is almost at the bottom of the page on the above link

heres my photos

https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL#f:Engineers%20thumb%20back.jpg

i know the voltages are all wrong because i checked them agains Jdansti's on the page
what i can figure out is how come i have seeming got  voltage on the output

[midwayfair]

Looks like you have some problems in IC2. IC2 provides the 4.5V for the Vb. (All the pink wires in the layout are 4.5v). The voltage divider that accomplishes this is the two 1M resistors just to the right if the chip, connected to pin 5, one of which goes to ground and one of which goes to +9v. Check really carefully around that area

Double check continuity against the schematic for each part in the soldered board. Also, if you can post pics of both sides, I might be able to spot an error.

p.s. I continue to apologize for the jumpers making my perf layout hard to read.

What's Q2 doing? output buffer/boost?

EDIT: Connect 6 and 7 on IC2. They don't look connected in your pics and they have different voltages. Doesn't fix the pin 5 problem, though. Still looking. I have to get to practice, I'll check back when I get home.

[Kipper4]

there was a bridge which i thought i'd rectified until i put the DMM on it it now measures 2.98v at pin 5
have i got the wrong resistors in here or something. could that be the cause
colurs brown black green gold

[Kipper4]

dont laugh but i need to look for the end off my solder pump.
I left it primed on the bench and  the end shot off across the room when i was deep in thought debugging the ET build.
It scared the life out of me i nearly let out a bit of wee .i thought i'd blown the circuit and now i cant find the end of the pump so im trying to do it with solder braid.

[Keppy]

there was a bridge which i thought i'd rectified until i put the DMM on it it now measures 2.98v at pin 5
have i got the wrong resistors in here or something. could that be the cause
colurs brown black green gold

That sounds like 1M to me. You definitely still have a problem there though: ANY 2 resistors of identical value should give you 4.5v on pin 5 (give or take a few tenths depending on your battery).

dont laugh

Too late! Though I'm mostly laughing because that reminds me of stuff I've done.

[Kipper4]

i just double checked the colours and they're defo 1m and i cant understand why the voltages aint half here too. im gonna get the loop out and see if i cant see anything fishy again

[Kipper4]

sorry John Q2 is the diode and led set up thats not on the perf u did

[Kipper4]

just remembered i used a 1n4007 instaed of a 4001 too for the protection diode at 9v connection

[Keppy]

just remembered i used a 1n4007 instaed of a 4001 too for the protection diode at 9v connection

I think the only difference is the max voltage rating, which doesn't matter here.

[Kipper4]

thanks buddy

[Kipper4]

its working
i had to reroute the +9v a little and i made a mistake going from the 10 pf cap going to the wrong 1k resistor.
Can anybody tell me how to wire the switch up so i can use the indicator led please?

[Kipper4]

if you could do a sketch with i assume a 3pdt switch that would be great. I'm also assuming it will be using the input jack as a power on off switch. Right?

[midwayfair]

if you could do a sketch with i assume a 3pdt switch that would be great. I'm also assuming it will be using the input jack as a power on off switch. Right?

Edit:
1 4
2 5
3 6

Board input: 1
In jack: 2
Out jack: 3 and 4
Board out: lug 5
Base of Q2: 6

[Kipper4]

dpdt then thanks john
i guess this is a millenium bypass kinda thing

[deadastronaut]

^ yep..millenium bypass uses dpdt..


anyone made the 5 pot version of this...or dabbled with it?.

[midwayfair]

anyone made the 5 pot version of this...or dabbled with it?.

Yeah. Some of the attack and decay settings result in a "broken" compressor. I didn't find either useful ... if you shorten the decay, you get pumping. If you make the attack longer, the compression don't sound natural at all. Merlin notes that the threshold and ratio are redundant, which is what I found, too. The treble boost, however, is very useful and I ended up putting it on a dip switch inside my 1590A build because I pretty much never turn the switch off.

[deadastronaut]

ahh good to know, cheers jon.