No red in monitor
- Tested the usual culprit, transistor in neck board, it worked fine.
- Followed schematic to find where red is handled from pcb to neck board and found a bad transistor located at Q203 (2SA562Y PNP Transistor).
- Replaced it and Red came back.
- However, colors were still muddy and not where they needed to be. Used my B&K 470 rejuvenator to clean the monitor guns and colors came back nice a bright.
Replaced Q203 (2SA562Y PNP Transistor) in monitor chassis
Right audio had bad crackle in sound during sound test. All speech was garbled.
- Swapped Pokeys – no change
- Used audio testing tool to test output from speech chip – audio is fine
- traced audio to AR board
- input audio is good
- output audio is bad – problem is in A/R Board
- Tested voltages and found a drop in voltage and isolated the problem to a bad capacitor (pulled suspect components and tested out of circuit)
Found a shorted glass ceramic capacitor on A/R Board on the right audio channel line. Capacitor located at C8 (.1uf 50v glass encapsulated ceramic capacitor). No more garbled speech
Right audio was very loud would not turn down with when volume was adjusted
- Tested volume pot located in the coin door and it worked, fine but suspected cold solder joints for the right audio channel due to fluctuations in audio when cabled were moved
- Re-soldered cables and audio volume worked correctly on both channels
Re-soldering of cables to volume pot located on coin door.
Links to documentation:
Monitor Manual and Schematics – Atari Monitor TM-281 4th Printing WG 19k4915 19in Med Resolution
Manual – Paperboy_TM-275_1st_Printing
Schematics – Paperboy_SP-275_1st_Printing