Studer A812 Common Failures & Capacitor Replacement

1. Motherboard (Backplane) Interconnects

The A812 uses a complex motherboard with many press-fit pins and card edge connectors. Over decades, these connections develop high resistance due to oxidation and thermal cycling. This is very often the root cause of seemingly random, intermittent faults, crashes, and channel dropouts.

Solution: Before replacing capacitors, remove, clean (with DeoxIT D5), and reseat every single card and connector. This simple step solves a huge percentage of "broken" A812 issues.

2. Power Supply Capacitors

Failing capacitors in the power supply cause ripple, unstable voltage, and can damage other modules. The large filter capacitors are particularly prone to failure.

3. Electrolytic Capacitors on Audio Cards

The small bipolar electrolytic capacitors in the audio signal path degrade over time, causing distorted audio, loss of high frequencies, noisy output, or dead channels.

For all replacements, use high-quality, low-ESR, 105°C rated capacitors from reputable brands like Nichicon, Panasonic, or Rubycon.

Power Supply Units (PSUs) TOP PRIORITY

Board	Capacitors to Replace	Notes
A 812 500	All large electrolytic filter capacitors (10,000µF-22,000µF)	Most critical for clean power
A 812 501	All smaller electrolytics on regulator and control circuitry	Full recap recommended

Tape Transport Controller HIGH PRIORITY

Board	Capacitors to Replace	Notes
A 812 300	Every single electrolytic capacitor	Especially those near the microprocessor

Audio Path Cards MEDIUM PRIORITY

Board	Capacitors to Replace	Notes
A 812 200/220 (Repro Amp)	All electrolytic capacitors	Replace bipolar caps with modern film caps where possible
A 812 201/221 (Record Amp)	All electrolytic capacitors	Similar to repro cards
A 812 202/222 (Sync/Repro Switch)	All electrolytic capacitors	Fewer capacitors than amp cards

Support Cards LOW PRIORITY

Board	Capacitors to Replace	Notes
A 812 240 (Meter Driver)	All electrolytic capacitors	Fixes erratic VU meter behavior
A 812 320 (FDD Controller)	All electrolytic capacitors	If equipped, prevents FDD communication issues

1. Clean all connections - Reseat and clean every card and interconnect
2. Recap the Power Supplies - Most critical for stable operation
3. Recap the Transport Controller (A 812 300) - Solves most operational issues
4. Recap the Audio Path Cards - Restores audio quality
5. Recap Support Cards - For complete reliability