Tycobrahe - Parapedal  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...

Re: Tycobrahe - Parapedal

Postby JimSalabim » 12 Jun 2015, 21:27

Alright, thank you!
This is the result:

U1:
Pin 1: 7.40 V
Pin 2: .503 V
Pin 3: 1.465 V
Pin 4: 00.5 mV
Pin 5: 1.485 V
Pin 6: 4.77 V
Pin 7: 1.92 V
Pin 8: 8.07 V

U2:
Pin 1: 00.4 mV
Pin 2: 00.4 mV
Pin 3: 00.4 mV
Pin 4: 00.0 mV
Pin 5: 00.2 mV
Pin 6: 00.2 mV
Pin 7: 00.2 mV
Pin 8: 00.3 mV
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 12 Jun 2015, 21:51

It looks like U2 isn't getting power.

I double checked your soldering....it "looks" ok.

Pull the ICs and check for continuity from the socket on the component side to the trace side of the IC pins.
(Continuity one lead on socket side of IC pin, the other lead on trace side of corresponding IC pin. Meter mode switched all the way to the right. Looks like your meter should make a sound when the two leads are touched together. (continuity)

If everything checks out OK...then check the voltages again...same thing pin by pin and then post.
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 12 Jun 2015, 22:29

The socket connections are fine.
But the voltages are still near 0, now also on the first IC!
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 12 Jun 2015, 22:32

Did you check the voltages without the ICs in the sockets?
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 12 Jun 2015, 22:40

Yes, same thing! No voltage at all pins.
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 12 Jun 2015, 22:48

Two things...

You have a cold solder joint somewhere in the power or ground path possibly one of the jumpers. Check all solder joints...even off board hardware...ie: DC jack and input jack.

Where sis you get the component parts list that corresponds with the layout?

I don't see a negative ground schematic.
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 12 Jun 2015, 23:03

OK, I’m checking all solder joints again (I already checked the continuity of everything right after soldering).
I used the parts from this GIF (second schematic)
http://www.geofex.com/FX_images/parapedal.gif
and the second layout from the PDF:
http://www.geofex.com/FX_images/newparapedal.pdf

I know the GIF shows a positive ground schematic, but the PDF shows a negative ground layout (at least that’s what it says). And the component parts should be the same?!

I put in the elkos and the diode in the direction of the PDF (second layout).

I used this wiring for true bypass:
Unknown.gif
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 12 Jun 2015, 23:59

At this point..I would hit all of the solder connections again.
There is a loose/bad connection somewhere which is the cause of the original problem...not working, no power to U2, and then no power to both ICs.
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 00:29

The problem must be somewhere else. I just tried two different diodes (a 1N4001 and another one which I can’t identify) and with both there’s voltage on every pin (except on the pins which lead to the ground). But still no sound. One time just hum, the other time nothing at all.
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 00:38

Maybe it’s correct that the layout says "D2" instead of "D1" and I just need a completely different diode? But which one would this be?
But since I don’t know anything about diodes, this assumption could also be complete nonsense :-) I don’t know …
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 01:15

Update: Took a new 1N270 diode, now there’s voltage everywhere too:

U1:
Pin 1: 7.53 V
Pin 2: .510 V
Pin 3: 2.90 V
Pin 4: 00.5 mV
Pin 5: 2.89 V
Pin 6: 4.83 V
Pin 7: 1.94 V
Pin 8: 8.16 V

U2:
Pin 1: 6.32 V
Pin 2: 2.85 V
Pin 3: 2.89 V
Pin 4: 00.8 mV
Pin 5: 2.88 V
Pin 6: 2.81 V
Pin 7: 7.45 V
Pin 8: 8.14 V

Still no sound …
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 13 Jun 2015, 01:23

Okay...

Those voltages look way better.

The best thing to do is use an audio probe to see where the signal stops.....then you will know what to target.

Here is the link for an audio probe:
http://www.diystompboxes.com/pedals/audioprobe.jpg

You have to build it. An old guitar cable and a capacitor is all you need.

Build this...and then I'll give you direction how tom use it.
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 13 Jun 2015, 01:25

You need an alligator clip as well but could get away with soldering a wire to ground and then to the shield of the guitar cable.
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 02:21

OK, got it!
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 13 Jun 2015, 03:13

That was quick...let me write out the instructions.
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Re: Tycobrahe - Parapedal

Postby armdnrdy1 » 13 Jun 2015, 03:25

Plug the 1/4" jack of the audio probe into a guitar amplifier. (with the volume turned low)
Plug a guitar into the input jack of the Parapedal.
Connect the ground from the probe to the ground of the Parapedal.
Power up the Parapedal and engage the effect switch.
Follow the schematic through the audio path touching the leg or pin of each component while strumming the guitar.
Start at the input jack and work your way into the circuit
The guitar signal should pass through the effect input and be picked up by the probe and sent to your amp.
You will hear the guitar as long as the signal is getting through to that point.
If the signal stops...you have an idea of where to look for problems. (wrong value resistor, bad solder joint, etc)
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Re: Tycobrahe - Parapedal

Postby Intripped » 13 Jun 2015, 03:40

jim, recheck resistors values, i've already spotted 3 wrong values from the pic you posted:

R14 sould be 1M, not 1k
R4 should be 1k, not 1M
R15 should be 1M, not 1k

For this message the author Intripped has received thanks:
JimSalabim (14 Jun 2015, 21:51)
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 03:48

Thanks! I plugged an iPod to the input jack instead of the guitar.
The following picture shows the result. This is the result of a test with the "unknown" diode again - the 1N270 stopped working again as soon as I started testing. So the signal could not pass the opamp anymore. Before the opamp it was the same result with both diodes.
The signal was getting very low already at C1 (10nF), then even lower and especially with much hiss at the end of R2 (47K). Then behind U2 there was only very very low hiss. At all other points there was nothing.
Bildschirmfoto 2015-06-13 um 04.24.12.png
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 03:49

Green: good signal
Yellow: very low signal
Orange: very low signal with hiss
Red: Only hiss (very very low)
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Re: Tycobrahe - Parapedal

Postby JimSalabim » 13 Jun 2015, 03:51

and it’s "behind U1" not "behind U2"
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