Bell Tone Synth Works

09/01/2026

We're hosting our sixth DIY Music Gear Repair Workshop on Sunday, September 13th! Bring a semi- broken piece of music gear of your choice and receive one-on-one coaching from us to learn how to fix it.
You can even bring something we don't usually work on: we will be welcoming mixers, pedals, solid state amps, eurorack modules and more in addition to synths and keyboards.
The price is $60 and registration is required as spots are limited. Visit the events page on our website (link in bio) to learn more and sign up!

08/28/2026

This week’s highlight:

Alison found a 1 day old kitten. Kittens this young need to be fed every 2 to 3 hours! With around the clock feedings and nourishing synth tones the kitten’s body weight increased by 33% in only 3 days! She’s now in the care of where she’ll be available for adoption once spayed in about 2 months.

We also got to install a few upgrades, in an 808 and a Juno-6.

08/21/2026

Josh (testing it out in the video) and Darian recently had the honor to work on four of Marshall Allen’s (of Sun Ra Arkestra) Crumar-Steiner Electronic Valve Instruments! The EVI’s handheld unit has 3 black switches that emulate trumpet valves and a rotary octave select canister with an additional “1/2 octave” switch mounted on the side. There is a piezoelectric disk mounted on the plastic wind chamber that responds to air pressure. Two of these EVI’s had broken wind chambers that needed to be re-glued, which we think happened during a performance! The synth itself is voiced by the CEM 3340 oscillator with the 4 pole SSM 2040 filter, a rare combination also found in the Crumar Stratus.

The 4 EVI’s required different levels of physical and electronic refurbishment. Two of them had previously been serviced but required new power switches and fuse holders. The other two were in very rough shape, and had had mice get into them so were completely disassembled to wash and sanitize everything. The 8 conductor cables that ties the handheld unit to the synth were also replaced. Matching switch caps were sourced for the 3 “valve” switches on 𝘗𝘭𝘢𝘺 𝘍𝘰𝘳 𝘛𝘩𝘦 𝘚𝘱𝘪𝘳𝘪𝘵. 𝘗𝘭𝘢𝘺 𝘍𝘰𝘳 𝘛𝘩𝘦 𝘚𝘱𝘪𝘳𝘪𝘵 also had some rusty areas on the control panel touched up. We also rebuilt the power supplies, replaced other important electronic components, installed new fuse holders, and replaced a power cable that had a missing ground pin.

These unusual instruments are both fascinating to work on and a piece of music history still being regularly played by the amazing local and interplanetary hero Marshall Allen 🪐

08/13/2026

06/12/2026

We are having showroom walk-in hours this Sunday 6/14 from 12:00 to 5:00 pm! Stop by and try out some of the fully-serviced vintage synths we have for sale. We have a variety of mono- and polysynths in a variety of price ranges... here are pictures of a few of the highlights:

Roland Juno 106
Akai MPC-60 (we have a 3000 too!)
ElectroComp EML-101
Moog Memorymoog
Yamaha CS-15
ARP SE-IV "Solina" String Ensemble

7000 Terminal Square, Upper Darby 19082 - main theater entrance!

03/15/2026

DX1 transformer revarnishing:
We recently finished working on this DX1, which is the most "premium" of Yamaha's FM synths. It has the brain of a DX5 (exact same synth engine), but is upgraded with features like a wood hammer action keyboard, rosewood body, and these fancy displays that do make it a lot nicer to use.
The worst problem this one had was something I've heard one have before, a horrible acoustic ringing coming from the small transformer in the switched mode power supply. This is the result of cracks and voids forming inside the transformer from its varnish drying out over time, allowing it to vibrate and resonate, and can happen to any old transformer.
Luckily, I have worked out a reliable, inexpensive method for vacuum impregnating transformers. Revarnishing them in a vacuum ensures that all these voids can be filled despite the surface tension of the varnish, as long as they are contiguous with the outside.
All that is required is a mason jar big enough to fit the transformer, a small vacuum hand pump (used for canning food), a clamp, silicone tubing and matching silicone grommets, and a second airtight container like a jar or valve bag.
With the tube to the second container clamped, the pump is used to remove all the air from the jar. When the clamp is released, varnish is siphoned over and you can actually see it being aggressively sucked into the transformer in a way that it wouldn't be without the vacuum. I pump a few more times after the varnish comes in to remove any bubbles that come over too, but I'm not sure it's even necessary.
Sometimes transformers are also heated before being re-varnished, but based on my research I didn't think it would be necessary for transformers this small + that have been kept dry + when a vacuum is being pulled.
The revarnishing was successful and the ringing is gone!
(I always get this song "Walk of Life" by Dire Straits stuck in my head, which is basically a boomer dad song that you hear at Home Depot. But there's a video of them playing it live and the d***y organ sound at the beginning is a DX1)

03/12/2026

We are having another DIY repair workshop to... celebrate the spring solstice (?) on March 22nd! At these workshops, you can bring a semi- broken piece of music gear of your choice and receive one-on-one coaching from our techs to learn how to fix it. You can even bring something we don't usually work on: we will be welcoming mixers, pedals, solid state amps, eurorack modules and more in addition to synths and keyboards. ..

the dead spider and web in the photo were actually found inside a mixer that was brought to our last session 😬
Visit our "Upcoming Events" page via the link in our bio for more info and to sign up. Spaces are limited!

03/12/2026

Restoring Don Buchla's personal Easel:
We're now spending our work days focusing on servicing their collection of Buchla instruments in preparation for their upcoming Buchla festival! Today we worked on two Music Easels, one of which is Don Buchla's personal "Weasel Easel." They were both in not very good working condition and are being fully overhauled.
By the end of the day today we had all modules of both working, but had to replace a lot of failed logic chips and op amps to get there. We've decided that on our next visit we will just go ahead and replace the rest since they have demonstrated such high failure rates (mostly A-series CMOS).
Another big part of servicing these Easels is cleaning CTS sliders, something we don't normally do anymore because we make our own adapters to use modern sliders, but for these museum Easels we wanted to keep them more original.
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The ~~mysterious incantations~~ at the end of the second video are just Darian reading from the schematic!

02/24/2026

Our new vintage synth sales showroom has been a success so far-- we're selling synths faster than we're getting new ones in!

If you have a vintage synth you'd like to sell through us, give us a shout! We offer consingment and also sometimes buy directly for cash depending on the synth and its condition. We still have plenty of cool synths for sale too, so check our listings on our website if you're in the market to buy.

02/05/2026

We have a very rare arrival here this week... A Clavioline! This single oscillator, tube-based electronic instrument was invented by French engineer Constant Martin and produced in France in the 1940s and 1950s, and sold in the USA by Gibson. This unit actually works pretty well... Miraculously well I would say, but still will be given a complete rebuild. Truly most components will be replaced including these "TINY CHIEF" capacitors, and it needs key contact and mechanism work too. It's so different from what we usually work on, yet not difficult to understand... Both unfamiliar and familiar at the same time.