Engineer's thumb isn't compressing much

[jtn191]

My Engineer's thumb isn't compressing much and is giving me less than unity gain when maxxed
I'm working on a vero build using this layout



voltages
IC1: 4.45, 4.40, 3.92, 0, 4.19, 4.45, 4.45, 8.86
IC2: 4.79, 4.45, 3.95, 0, 0.85, 1.98, 1.38, 8.86
began reading IC3 but ran out of time on my lunch break: 1.32, 0, 4.45...

I noticed pins 5,6, 7 of IC2 and voltages on the transistor were lower than what I've found in similar threads on forums (~4v)
I checked for shorts/mistakes but couldn't find any...think I got stuck with a bad BC327?

[R O Tiree]

If you could post some hi-def pics, well-focused, well-lit and BIG!! then maybe fresh eyes will be able to spot something wrong?

[jtn191]

[R O Tiree]

Check all resistor values - R3, R8, R10 and R11 should all be 1k - you have 10k resistors in those slots. There are some that are standing up and I can't see the bands, but they all need positive checking.

Check on the reverse side - some of the holes you drilled through to provide the track cuts are bigger than others - check with a DMM set to "continuity" that you actually did successfully break the tracks. Similarly, check that there are no solder bridges between tracks or across cuts in the tracks - easily done with vero.

[jtn191]

I double checked my 1k resistors and they measure/look the same as those in R11 etc. Most of the voltages look good, leading me to think it's Q1

[R O Tiree]

brown/black/black/red/brown is either 120 ohms @ 1% tolerance or 10k @ 1% tolerance, not 1k.

Look at R3 - 1k on the Bill Of Materials, and yet the colour bands tell me it's a 10k (or 120R):

The first 3 bands are just numbers in sequence, the fourth is the multiplier and the fifth is the tolerance:

Brown = 1
Black = 0
Black = 0
Red = 2
Brown = 1%

So, that makes 1, 0, 0, 10^2 = 100 x 100 = 10,000R = 10k, not 1k.

Of course, if you read it the other way, you get 1, 2, 0, 10^0 = 120 x 1 = 120R @ 1%.  This is the problem with 1% resistors, and why you should always check them physically with a DMM.

R8, R10 and R11 are the same - should be 1k from the BoM but you've put 10k resistors in there. R2 is probably the same, but I can't see it from your picture - it's standing up and hiding behind the red box cap, so that will need to be checked as well.

[R O Tiree]

jtn - I don't know if you caught my last post before the site crashed and we lost about 8 days' worth of posts? I saw the pic you posted of the resistor you took out at R2 and it looked like brown, black, black, brown, brown, which is 1k and you reported it as such, although you stated that the rings were brown, black, black, red, brown, which would actually make it 10k, not 1k.

OK, I'm really not trying to be funny or dismissive, here, but have you ever been tested for colour-blindness? People who are mildly red/green colour-blind have difficulty distinguishing brown shades from reds. It is for this reason that one could not be a licensed electrical engineer if you were colour-blind here in UK when I was growing up. I don't know if that's changed over the years... Anyway, sometimes the nozzles that spray the paint bands onto resistors get a splash from an adjacent nozzle, which can make orange look more like yellow or yellow look more like orange, and browns and reds can similarly get contaminated. What is certain is that the pic you posted on 4 June shows 10k resistors in R3, R8, R10 and R11. Remember, 5-band resistors have a slightly different de-code compared with 4-band ones, as you can see from my post of 7 June. Those I mentioned definitely look like 10k in your picture and there is only one way to prove that.

[jtn191]

I am actually color blind. So I don't go by color, I measure them with a dam out of circuit. I pulled the one in question, and it measures 1k...100% positive

[R O Tiree]

Which one? There are 4 in question, here...

[jtn191]

R2

[R O Tiree]

R2 was never in question - mostly because it was hiding behind C1 and standing up, so I couldn't see it. The ones I was interested in were R3, R8, R10 and R11. I marked them in this picture and posted it a while ago, but it got lost in the recent forum crash. They are marked in purple. You'll also see a light blue ring around a terminal of the switch(?) at top centre... that little rag-end of wire poking through the lug might be touching the casing of the switch, which might be shorting whatever that wire is carrying to GND. Best snip that end off "beyond" the lug and throw it away.