Almost dead

Almost dead (Thursday 28 August, 2025)

Rebirth of my Crumar Bit 99 and Roland XP80

Today I handed over my Crumar Bit 99 (released 1985) and Roland XP80 (released 1996) synthesizers to Dutch Light & Sound Engineering (D.L.S.E.) for maintenance. Actually, I first contacted DLSE about 5 years ago to fix my Bit 99 but in the end, for multiple reasons, I never made the actual step. But now, also having a problem with the XP80, I decided it was time to move ahead before both synths would die.

Crumar Bit 99: fixing the keyboard and recapping

After 40 years (!) of duty, the keyboard of the Bit 99 stopped working some time ago. Likely, this is caused by oxidation of the key contacts as shown in Image 1 below.  The second problem is the synthesizer sounds rather thin (compared to what I can remember). This might be caused by electrolytic capacitors that are no longer within specifications (Image 2). So, just like a battery, a capacitor has two plates and some electrolyte and other chemicals that make up its composition.  The ‘recappers’ claim that after 15-40 years,  the electrolyte fails, reducing the capacitance value. Therefore, all or part of the capacitors in the Bit 99 will be ‘recapped’. However, it was explained to me that this might not give an improvement at all (read also this article). Thus, let’s see if theory becomes practice here.

Image. the bottom side of the keyboard. Each key is connect with the circuit board with a black metal rod. These rods should actually not be black but metal-like. The black probably comes from oxidation and/or filth that came into the Bit. This is the reason that the keyboard is not working properly anymore while it works fine through MIDI. Unfortunately, I cannot clean the rods myself since they are soldered to the circuit board.

Image 2. The bottom-board is where the sound generation takes place. Several electrolytic capacitors are visible. These will be replaced. 

What has been done with the Bit 99?

• Removed the keyboard. It was put together a bit strangely…
• Bus bars cleaned dry.
• When reassembling, it turned out that all sorts of things were wrong.
• It had been disassembled before and incorrectly reassembled.
• This caused a lot of unnecessary extra work during these repairs.
• The device was completely assembled incorrectly. It has now been properly reassembled.
• Test: Keyboard works again. Four TRS connections were broken—these were replaced.
• Output board, Voice board, and CPU board recapped.
• Battery replaced.
• Various tests: device seems to be fully in order.

Roland XP80: the Red Epoxy Problem

The problem with the XP80 is unrelated to its electronics but concerns what is known as the ‘Red Epoxy Problem’ (Images 3). A range of Roland synthesizers have metal weights glued underneath the keys to give it a semi-weighted feeling. Unfortunately, over the last few years an increasing number of these synthesizers have been reported that the this glue became liquid resulting in dripping glue from under the keys and weights falling out or blocking the keys, rendering the keyboard useless. This glue can even damage the print boards inside the synthesizer. My XP80 already lost several weights but I didn’t open it to see if the print board was affected. This problem can be fixed but takes considerable work as demonstrated in the video below.

In addition to this glue problem, the dial wheel will be fixed and the battery replaced. Depending on the states of the capacitors, these may also be recapped.

Image 3. Several images of the red epoxy glue and the key weights.

More information:

• Roland: Perishing Glue on Key Weights. (Sound On Sound Forum)
• The Red Epoxy Problem

What has been done with the XP80?

• Keys: Bad 1.
• Keys: Bad 2.
• Keys: Rinsed/dried.
• All electrolytic capacitors on CPU board replaced.
• Key weights glued. Keyboard assembled.
• Glue residue on bottom plate removed.
• Dial cleaned and re-lubricated.
• New battery installed.
• Test: OK. Reassembled.

References

• Crumar Bit 99 (Sound On Sound Magazine)
• Crumar BIT ONE, BIT 99, BIT 01: Little gems of expressivity (GreatSynthesizers.com)
• Roland XP80 (Sound On Sound Magazine)
• Roland XP80 (Roland Website)