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 Post subject: Silver Pony II Help
PostPosted: Mon Dec 11, 2023 5:25 pm 
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Joined: Mon Mar 29, 2021 1:55 pm
Posts: 41
Hi All-
Built a Silver Pony II and before I boxed it I started testing it and nothing (just loud pop when I switch my test rig from bypass to effect).
Started troubleshooting with my test probe and Voltmeter and here is what I have so far. Clear input signal up to pin 3 of the 1st Op Amp and then no signal anywhere.
Weird thing is I measured voltage at IC's (3 TL072 & Charge Pump) and I am getting 9V everywhere... no voltage inversion at charge pump.
I checked across the 27K resistor by the +9V input diode (what looks to be a voltage divider circuit on the schematic and shows 1/2V on one side) and getting 9V there too.
I've attached some pictures of the board (note I removed the charge pump before I took the picture and swapped it out for another but no change .... but picture shows empty socket).

Thanks for any troubleshooting suggestions.


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 Post subject: Re: Silver Pony II Help
PostPosted: Mon Dec 11, 2023 9:09 pm 
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Joined: Tue Jan 02, 2007 1:24 pm
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Location: Albany, NY
scttwtr wrote:
Weird thing is I measured voltage at IC's (3 TL072 & Charge Pump) and I am getting 9V everywhere.

Are you saying that you measure +9V on EVERY pin of all four IC's?

When measuring the DC voltages, what are you using as the ground connection?

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


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 Post subject: Re: Silver Pony II Help
PostPosted: Mon Dec 11, 2023 9:28 pm 
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Joined: Mon Mar 29, 2021 1:55 pm
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Hi-

Yes anywhere from (+) 8.2 to 9.4v on every pin (all 8) of all 3 TL072's and the Charge Pump.
I used solder pad where the negative lead comes in from the power supply as ground. I also double checked using the pad where the negative lead of the battery would be connected and get same results. My power supply is a Boss brand wall wart and it measures 9.4v (matching most of what I measure around the board).
This has me stumped.

All the components are correct per build list. Only substitution I made was (3) 1N4002's instead of 1N4001 diodes which shouldn't matter.


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 Post subject: Re: Silver Pony II Help
PostPosted: Mon Dec 11, 2023 9:53 pm 
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Yeah, I think I understand what you're doing and that grounding doesn't work for measuring voltages in the effect circuit--you end up basically measuring your power source voltage everywhere you test. Instead of the way you're measuring, do this: First, make sure the sleeve tab of the Input jack is connected to the ground eyelet adjacent to the Treble pot connections and that the ring tab is connected to the ring eyelet where the DC jack connects. Then insert a cable into the input jack and use the SLEEVE of that jack as your ground connection. Re-measure all of your IC voltages with the original charge pump installed. I think you'll find that the readings make a lot more sense!

EDIT 12/12/23: Though I realized that what you were seeing related to not using the input jack to ground the power and effect circuits, I didn't fully understand why you would measure +9V throughout the effect circuit. So I asked "the boss," Keith/byoc. Here's his explanation:

The DC jack negative tab is not grounded until a mono plug is inserted into the stereo input jack--it's just 0V. But +9v will be applied to the circuit regardless of whether there is a plug in the input jack. Not having a cable in the TRS input jack circumvents its use as a power on/off switch and making the connection between the negative terminal and ground. The negative terminal is not part of the circuit until you put a plug in the input jack. The DC jack is, for all intents and purposes, its own circuit. And the pedal circuit also has no ground until there's a cable in the input jack--its "ground" is just floating in space. This floating ground is connected via the two voltage divider resistors in series to +9V. So without the ground being connected to 0V, everything is going to look like +9V when the black meter probe is referencing 0V. The DMM doesn't know that the two probes are on different circuits.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


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 Post subject: Re: Silver Pony II Help
PostPosted: Wed Dec 13, 2023 4:42 pm 
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Joined: Mon Mar 29, 2021 1:55 pm
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Duhvoodooman -

I million thanks :D !!
You were 110% right.
Switched ground and readings made total sense. Narrowed it down to a bad IC1 (TL072) which is why I was getting signal in but nothing coming out to rest of signal path. I've had pretty good luck with Op Amps but don't remember where I got these ones.

You guys on this board are the best and this pedal sounds great !!

I socketed all the diodes so now I will play around and pick my favorite sounds.


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 Post subject: Re: Silver Pony II Help
PostPosted: Wed Dec 13, 2023 8:30 pm 
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Glad to hear you got it straightened out. Enjoy the new pedal! :mrgreen:

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


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