my lpb1 'tis not working

[Chris oej]

i've made a clone of a ehx lpb1. it wasn't working when i soldered it all together (true bypass was okay but completely dead once the circuit was engaged.

i've taken it apart and put it all into a breadboard to see if i could find the problem, but am having no luck.

i'm using a 2N5088 - readouts below:

battery - 9.84

C=9.78
B=0.9
E=0

Here's the schematic i'm going from:

http://www.beavisaudio.com/techpages/HIW/hiw1.gif

I'm using slightly different value resistors. i'm using:

R1= 470k
R2= 47k
R3= 10k
R4= 330r

I've seen alot of different schematics for the lpb1, and have read stuff from people using an almost identical configuration to this, so i thought that it should work fine.

does anyone have any suggests?

As always, any help is appreciated so much.

Thank you.

[R.G.]

i'm using a 2N5088 - readouts below:
battery - 9.84
C=9.78
B=0.9
E=0

The transistor is not working at all if the voltages are correct. Some possibilities are:
1. You might have measured that collector voltage on the collector resistor, not the transistor collector. That would allow the transistor to not be connected to the resistor by a bad solder joint, and the collector resistor would read the power supply minus some trivial amount. That would fit the observed.
2. You might have measured the emitter voltage the same way, on the resistor and not the transistor lead. If either the collector or emitter lead (or both!) of the transistor were open, the emitter would read that.

What you have going for you is that the base is at the right bias voltage.

Could be other things, but remeasure on the transistor leads, not the solder joints or the resistors.

[LucifersTrip]

...if you post a clear closeup pic of your breadboard someone may spot the error. As RG noted, it could be a bad joint...or wiring or soldering error....or you burned up the transistor when soldering (but don't know if you'd get .9 on the base)

I'm using slightly different value resistors. i'm using:

R1= 470k
R2= 47k
R3= 10k
R4= 330r

it may make little difference in this circuit, but in general there's no use in using different values if you have common values laying around that could get you closer:

470k in parallel with 47K = 42.73K
330r is series with 47r = 377r, 750r in parallel with 750r = 375r, 2K in parallel with 470r = 381r
330K in series with 100K = 430K
etc...

good luck

[Chris oej]

Hi guys,

Thanks for the suggestions. Here're some photos

http://s728.photobucket.com/albums/ww286/chris-oej/lpb1/


i tried out a wire bypassing all the components to make sure that it's not a problem with the soldering of the switch and it was fine.

I checked the transistor and resistors on my multimeter and they all seemed fine. Problems with the capacitors maybe? The don't appear to be polarised so don't think i can have them the wrong way round.

The values i posted were read from the pins of the transistor, and as it's on a bread board there's no soldering involved.

i'm sure i've made a completely schoolboy error somewhere.

Thanks for the help.

[deadastronaut]

i had a few minutes spare...this is how it should be wired...going by the schematic you posted..

don't forget to connect grounds together on board ok.. and input/out grounds too.....hope this helps ya!...

[Chris oej]

Hi

I tried the layout above. Sadly, its still not working.

I tested the transistor on the multimeter and it gave me a reading of 480 which then started counting down. Is this normal?

I tried to increase the resistance of r3 to get the voltage of the collector down. I put two 470k in series and got 5.1 volts on the collector. Still no sound.

I've noticed that a get a popping everyone I touch anything going to live. No sure if this is relevant.

Thank you all so much for your time.

[arma61]

Ciao

To be sure.... to be sure... I'd check the + and - bus connection, red circle and black line in the picture,  not all the breadboard are build in the same way.




Ciao

[deadastronaut]

ok try this then....i presume your breadboard connects in line vertically!!!!...

[DavenPaget]

Show us the underside of your bread*board .

[Chris oej]

Hi,

Deadastonaut - you were right with the first one, the breadboard connects horizontally. I checked it with an audio probe to make sure what connects where.

I've got a spare BC153L, might give that a go, to see if the 2N5088 is broken.

Thanks all

[deadastronaut]

cool....should be ok...

[Chris oej]

Tried the bc153l and still nothing. I think I maybe using the wrong capacitors. On the side of them try say:

WIMA
100/100-

And just 10 on the other side.

I have a feeling they might be 0.1 nf instead of 0.1 uf. Does anyone know for sure what they are?

Thanks

[LucifersTrip]

I tried to increase the resistance of r3 to get the voltage of the collector down. I put two 470k in series and got 5.1 volts on the collector. Still no sound.

the question is: how do you get NO sound if you have 5.1v on the collector. I'll take a quick guess that you have the offboard wiring wrong....Do you definitely have the jacks hooked up correctly?

edit: actually, what is the E & B voltage when C is at 5.1v?

[Chris oej]

After no luck i tried again with a different schematic and no variations on any of the values:

http://www.beavisaudio.com/bboard/projects/bbp_LPB1.pdf

Works a treat... except i've got the input and output on the wrong sides. D'oh!

[deadastronaut]

great!........