Roland CSQ-600 Repair

CSQ-600

Overview In July 2019 I bought a Roland CSQ-600 Digital Sequencer in good external condition but not working 100%, and with the dreaded battery corrosion on the main PCB caused by the Roland Ni-Cad battery leaking. Whilst the previous owner had swapped a new battery in and kludged in 2 new wires for the failed traces, it was sold as needing repair, with possible RAM chip issues.

I bought my first secondhand CSQ-600 way back in the 1990’s and it also had PCB corrosion caused by a leaking battery. The PCB was so badly damaged that it was scrapped, as repairing was beyond my skills at the time. Fast forward 20 years and this second CSQ600 is going to be repaired to full functioning condition!

PCB Before Recap

CSQ600 History  Roland released the basic single track CSQ-100 Digital Sequencer in May 1979 and made over 2500 before introducing the more power 4 track memory CSQ600 a year later, which went onto sell over 2500 units into 1983 and the birth of MIDI. The CSQ-100 and 600 are micro processor based using an 8-bit Intel 8048 with a tiny 2k byte operating system, which went through 2 revisions.

The CSQ-100 has no battery, as there is no memory retention for the single 2114 RAM chip , so more of them have survived the decades. The leaking battery of the CSQ-600 has led to many being thrown away (such like my first one!), so they are harder to find.

In 1980 the CSQ-600 was for a brief year a powerful 600 note (analog CV) sequencer that was typically used with Roland’s CV and gate equipped mono synths of 1980 (SH-09, SH-1, SH-2 and 100M). In 1981 the mighty MC-4 arrived and was capable of 4 note polyphonic sequencing of the Jupiter 8 and Juno 60. In 1983 MIDI arrived and by then old fashioned CV/gate CSQ range was discontinued, with the basic sequencer features added into the mono synth (SH-101).

The CSQ’s languished in the unwanted category for many decades until the resurgence of analog synths and Euro Rack in 2005 onward. These basic sequencers regained some value and use, and a number of CSQ-600’s have been repaired from battery damage rather than being crushed. In 2019 their value had reached £150 – £400 in good condition.

PCB with Baking Soda

Repair Time The first stage was to open up the CSQ-600 and review the amount of battery damage. Fortunately the amount of PCB damage is relatively limited but the corrosion does not look to have been neutralised and the trace damage has not been attended to, just wires kludged in.

The PCB was removed and baking soda in a thick paste used to neutralise the battery acid, I left the paste on for 20 minutes and scrubbed the PCB with a toothbrush. In the end I did the whole main PCB.

The PCB’s in these sequencers always have excessive flux over the trace side of the PCB (see photo), which I also neutralised and removed with PCB cleaner, and then the whole PCB front and back cleaned in isopropyl alcohol.

With the PCB clean and dry I used a fibre glass pencil to remove the silk screen and corrosion on any affected traces, which included the damage near the battery but also further across the PCB. The bare traces were protected with water soluable solder and I used a flux pen to help things along. The two broken traces were carefully repaired with thin resistor wire, bent to shape and soldered onto both ends of the affected traces. The PCB was then cleaned again and dried for a few hours, before being put back in the case for an initial power up test.

PSU Old Caps

Recapping The power supply was re-capped, and the blue 40 year old electrolytic capacitors on both the power PCB and the main PCB replaced, along with any ceramic bypass capacitors. The replacement power supply capacitors are Panasonic:

• One 1000uF 16V EEU-FC1C102S
• Two 470uF 35V EEU-FC1V471
• Four 10uF 25V EEA-FC1E100H

I also replaced the 470nF and 1uF electrolytics using Nichicon UFW audio grade capacitors on the main board, as I had these in stock.

Initial Test TO BE CONTINUED!

.