synthchaser

Posted on January 10, 2018January 10, 2018 by synthchaser

Synthchaser #090 – Sequential Circuits Prophet 5 Factory Patches Demo

Demo of the 40 factory patch sounds from the Prophet 5 (Rev 3.2). This is not intended to be musical, just a demo of the sounds. I am far better at fixing them than playing them.

Buy this Prophet 5!

Sequential Circuits Prophet 5 Keyboard Synthesizer Pro Overhauled Rev 3.2 Excellent

Posted on January 7, 2018January 7, 2018 by synthchaser

Synthchaser #089 – Sequential Circuits Prophet 5 – Loading Factory Patches

Over the previous 6 videos, I repaired and restored a broken Prophet 5. Now that it’s all fixed up, in this video, I show how to load the factory patches into the P5 via the cassette interface.

Click here for a ZIP file, containing all 3 files of factory patches for the Prophet 5, compatible with Revision 3 Prophet 5’s.

Posted on January 6, 2018 by synthchaser

Synthchaser #088 – Sequential Circuits Prophet 5 Restoration & Repair – Oscillator Repair

OMG! The long awaited 6th installment of my my Prophet 5 restoration video series has finally arrived!

Last spring we mostly restored a broken Prophet 5, but I got busy with customer repairs and never finished it up. Today we’ll track down and repair one final problem with the P5… Seemingly random out of tune notes.

Posted on December 28, 2017December 28, 2017 by synthchaser

Synthchaser #087 – Oberheim OB-SX Restoration & Repair

Billed as a preset-only OB-X but sporting nearly identical voice cards to the OB-Xa, the Oberheim OB-SX is a pretty underrated synth. Here I give some love to a long neglected OB-SX by rebuilding the power supply, voice cards, and keybed, and repairing a few other problems I encounter along the way.

Posted on November 27, 2017 by synthchaser

Synthchaser #086 – ARP Pro Soloist Repair – Dead Presets & Broken Wow Effect

Repairing another customer’s ARP Pro Soloist. This one had very few patches working when it came in due to bad switches and a faulty VCA. Also engaging the Wow touch sensor effect would short circuit the keyboard and cause there to be no output at all.

Posted on November 16, 2017 by synthchaser

Synthchaser #085 – Four ARP 2600 Repairs

No, not repairing 4 ARP 2600s, making 4 repairs to the same ARP 2600…

In this video we bring life back to an ARP 2600 with 2 dead oscillators, dead sample and hold, and dead left speaker.

Posted on October 20, 2017 by synthchaser

Synthchaser #084 – ARP Pro Soloist Repair – Dead Touch Sensor, Dead Presets, Bleeding Notes

A customer sent in his Pro Soloist for repair because the touch sensor effects weren’t working and some presets sustained indefinitely after releasing the key. I also noticed several of the presets were dead. So we dive in and get this all fixed so he can get back to making awesome music with it.

Posted on October 18, 2017 by synthchaser

Synthchaser #083 – ARP Omni 2 Repair – No Output / Lights On, Nobody Home

Wrapping up the restoration of yet another dead ARP Omni 2, I hook everything up for testing & calibration, but there’s no output. Together we use some simple logic to figure out what’s wrong and fix the synthesizer!

Posted on October 18, 2017 by synthchaser

Synthchaser #082 – Sequential Circuits Prophet 600 Dead & Intermittent Key Repair

The Prophet 600 Panasonic keybeds often have problems with dead or intermittent key contacts. In this video I show you how to access the key contacts, and how to repair them for reliable long-term operation.

Posted on October 8, 2017September 25, 2023 by synthchaser

Cold Solder Joints

I was working on an ARP Omni 2 and came across a really bad soldering job. Someone had replaced the gating capacitors, but all of their solder joints were “cold solder joints”. What’s a cold solder joint? Well, first let me explain what a good solder joint is. With a good solder joint, both the pad on the circuit board and the leg of the component you’re soldering are sufficiently clean (both clean before soldering and from the flux in your solder) and hot for the solder to form a solid bond between the two parts you’re soldering. A good solder joint looks nice and shiny, like my work on this ARP Omni 2 below:

Now that we understand what a good solder joint is and how it’s made, we can understand that a “cold” solder joint is made when the two metals are not sufficiently heated or clean enough for the solder to truly bond between both metals. In a cold solder joint, the two parts may be stuck together, but may not have good electrical contact, and since the solder is really just a blob sitting on the surface of the pad or component, it’s very prone to crack or break off. You can typically spot a cold solder joint by its dull appearance, like I saw in the ARP Omni 2 below:

On the closeup photo you can really see the dull solder blobs just caked onto the pads and leads of the capacitors. And to no surprise, several of them just cracked off when I was going through removing and replacing all these capacitors.

Hopefully this explains what a cold solder joint is and how to spot one. To avoid making them yourself follow the following Synthchaser tips:

Clean all surfaces before soldering
Use flux cored solder
Make sure your soldering iron is at a high enough temperature (typically for synth rework I use around 700 degrees F)
Tin your soldering iron tip before soldering a part (apply a small amount of solder to the tip of the iron)
Position your soldering iron tip so it touches both the pad on the circuit board and the component and allow a little bit of time for both to get sufficiently hot
Feed the solder onto the component or the pad, not the tip of your soldering iron

If you find yourself melting the solder on the tip of the soldering iron, or “painting” solder onto the component from a blob on the tip of your iron, you’ll probably wind up with a cold solder joint.

Hopefully this helps, please comment if you have any other tips to avoid cold solder joints that I missed!