Hearthrob No Sound

[karter2000]

Hi all,

Just completed a Hearthrob Tremolo using a pcb from John Lyons.  Unfortunately, I'm not getting sound when the effect is on.  I get sound when bypassed (not even a faint sound).  I've checked all my connections and audio-probed the circuit, but nothing is standing out as to what may be wrong.  Voltages on the transistors are (using a 9.04v power supply):

Q1
C 0
B 0.67
E 0

Q2
C 2.63
B 2.02
E 1.58

Q3
C 9.06
B 1.26
E 0.66

Q4
C 0.68 to 1.97 (up and down)
B 0.66
E 0

Thanks for helping!

[GibsonGM]

Hi, can you post the schematic?

Just offhand, some of your transistor voltages look off.   Have a look at the board, be sure 1) the transistors are in there the right way, pin-wise and
2) that there are no solder bridges or loose solder joints anywhere - biggest cause of malfunctions on here!  Especially take a look around Q1's collector, you probably should have a decent voltage there.  Can't say more with no schem...

[karter2000]

Hi there,

The schematic is in this thread (not sure how to post pictures):

http://www.diystompboxes.com/smfforum/index.php?topic=71288.0

The Hearthrob is further down the page and based on the Schaller trem.

Thanks!

[karter2000]

Forgot to mention, I'm using 2n5089's

[GibsonGM]

OK, Q1 looks ok for now.  Pretty odd configuration, LOL.  Looks like Q3 & 4 are the oscillator, so they'll do weird things.

Thing to do (if you haven't) is use an audio probe, and listen to a signal from the input jack, and at C1, C2.  If you find a spot where the signal stops, there is a problem there.  If you get nothing at C2 (either side), then you have a problem with Q1 and/or its bias network of resistors.

I know it stinks, but if you have the bypass switching already in, you might remove it in order to individually test the input and output. If the switch is wired wrong (happens a lot!), you'll get exactly what you're describing.   That's why I test all my stuff BEFORE I add the bypass!   Then you know where the trouble is.  Just jumper-clip a jack to either end, both grounded to board ground, of course.   Jumper in your battery, and you're good to go.     Other option is to follow the signal thru the bypass switch with the audio probe, to be sure each is going where it should....the input or output could be grounded, etc etc.
See what happens!!   )

2N5089's are just quieter versions of the '5088, they are good.  Same pinout? I forget...
~MJP

[John Lyons]

There is only one transistor in the audio path so even if your trem isn't..."treming", you should still get clean signal.
Pop out Q1 and get Q2 working which is the transistor that you "hear" (clean signal when the circuit is engaged).
It may be a transistor pinout thing as mentioned.. Can you post a pic?

[karter2000]

There is only one transistor in the audio path so even if your trem isn't..."treming", you should still get clean signal.
Pop out Q1 and get Q2 working which is the transistor that you "hear" (clean signal when the circuit is engaged).
It may be a transistor pinout thing as mentioned.. Can you post a pic?

Thanks everyone, I'll check Q2.  How do I post a picture?

The weird thing is...when I audio probe the circuit I get nothing after R1 (47k).  I even replaced/removed the resistor and I still get nothing.  I guess that may mean Q1 or Q2 is not working.

[John Lyons]

yeah, pull out Q1 to test.
Q1 is like a switch which opens and closes
to create the tremolo sound along with the oscillator
parts etc. It may be "closed" and not passing signal.
Without Q1 you should at least have Q2 which is a
an amplifier but with little gain increase.
If you don't have sound with Q1 popped out then
Q2 might be off somehow.

[karter2000]

Okay, with Q1 popped out, I'm getting sound.  When I replaced it with another 2n5089, there's no sound again (also tried changing the orientation).  No idea why the sound is cutting out there.  I think I'm getting tremolo, as the LED is blinking (I've tapped it into Q4).

[karter2000]

Does anyone know the proper voltages leading up to Q1? ie after the 0.047uf cap, etc, etc

[karter2000]

Well...that was silly.  I got it working.  Turns out I used a 33k resistor in place of the 330k (R7 on schematic).  The package said 330k, but I must have never bothered to double check (note: never take package at face value).

At least I got some good trouble shooting practice!  Thanks again for everyone's help.

[John Lyons]

Cool, I was helping a guy trouble shoot a few builds and kept telling him.
"check the resistors with a meter before you pop em in." Only takes a few seconds vs
hour(s) to trouble shoot. Especially when your parts are of mixed sources

Glad you got it working!

[karter2000]

Yep, feel ready for that Dr. Boogie now!

Thanks again John for the great pcb (as always)!