SPU AMPLIFIER TROUBLE CHART
(Continued)
See Section 254 |
| Trouble | Indication | Cause | Remedy |
Low Volume
(Continued) | No sound from one amplifier as shown when one monitor speaker is plugged in. | Power amplifier fuse burned out. | Replace burned out fuses. |
| Bubes burned out in power amplifier. | Replace burned out tubes. |
| Defective power amplifier unit. | Operate without the defective unit. |
| Poor Quality | Poor quality from more than one power amplifier. | Defective voltage amplifier. | Change to another voltage amplifier if available. If only one voltage amplifier is used, replace all tubes with matched pairs of new tubes. |
| Poor quality from one power amplifier, others O.K. | Defective power amplifier unit. | Operate without the defective unit. Check all tubes when convenient. |
| Hum | Loud hum heard from stage and monitor speakers. | Defective or burned out UX-281 tube in power amplifier unit. | Check for power amplifier causing the hum (using monitor speaker and jacks.) Replace defective UX-281 tube. |
| Loud hum heard from monitor speaker only. | Defective UX-280 tube (or Rectox unit) on monitor speaker. | Replace UX-280 on monitor speaker. Where the Rectox unit is used, turn off the AC power to the monitor and notify the RCA service engineer. |
| Noise or "Motor-Boating" | | Dirt and acid on top of the storage batteries. | Switch to the battery and clean the dirty ones. |
| | Gassing storage battery. | Do not use a storage battery sooner than one hour after charging except in an emergency. |
| | Loose storage battery terminal connections. | Clean and tighten connections. |
| | Poor ground connections on the projector. | Clean and tighten connections. |
| Low plate voltage readings at the metering panel of voltage amplifier. | Noisy or old "B" batteries. | Replace the "B" batteries. |
| | Noisy or old "C" batteries. | Replace the "C" batteries. |
| Whistling Sound | Whistling sound heard when the monitor speaker is plugged into one power amplifier and not when it is plugged into the others. | Defective or unmatched tubes. | Replace the UX-250 tubes in the power amplifier which whistles. If whistling continues replace the UX-281 tubes. See section 251. |
