Hobby Repairs

[channelmaniac]

Model: Amtrak N-Scale Locomotive
Symptom: Won't move. Buzzes then trips power pack breaker

This is a first for me as I've never worked on a train before.

Background: 11yr old son bought a used locomotive off of eBay. It didn't work upon arrival.

Removed shell from the engine. Removed 2 screws to take assembly apart. The assembly was 2 die cast metal halves with rubber washers between and plastic sleeves for the screws to insulate the halves. The metal wheels conducted electricity into each half of the assembly. The motor was wedged in the middle and had 2 metal tabs to make contact with each half of the assembly.

Motor tested good with a 9v battery. The gears transferring the energy from the screw gears on the motor to the drive wheels under the car were frozen in place. Removed the gears, cleaned the area with Q-Tips and alcohol. The plastic dust from the gears seized on the metal shaft. Carefully scraped the plastic from the shafts, cleaned the inside hole of the gears and reassembled. Tested the train with the 9v battery and it worked.

Train would not move smoothly on the tracks. Cleaned the metal drive wheels and re-tested successfully.

[channelmaniac]

Model: Kenwood TS-820 Amateur Radio
Symptom: Will not receive

Radio was as deaf as a post and wouldn't even receive the built-in 25KHz marker signals.

Checked the basics and found that the 9v power source on the AF-AVR board was dead and the 3.3v source was sitting at 2.5v. Replaced a bad 500 ohm pot and an open transistor in the 9v section. Adjusted the 9v and 3.3v sources to spec and the radio would receive on the 10M bands only.

Found the output of the VFO to be low. Adjusted the output to be .6v RMS as specified in the service manual. The radio would then barely receive the marker signal on most bands. Checked the PLL and the mixers. Checked the various signals in the VCO circuit and everything was good.

Tried to turn the band switch into Aux mode and it would not go. Checked the band switch on the COIL PACK board and found it was misaligned with the front panel. This caused the 1.8MHz band to use the 3.5MHz coils, the 3.5MHz band to use the 7MHz coils, etc. The 10M bands worked because they all shared a common coil. Realigned the band switch and the radio will now receive on all bands.

[channelmaniac]

Model: Klipsch RW12 Subwoofer
Symptom: Very low audio output

System is odd in that the power supply voltage outputs are variable and track the audio inputs. Without proper feedback, the power supply only outputs +/-4.2v to run the output circuitry.

Replaced 1 LM324 IC and 2 22uf non-polarized electrolytic capacitors on the Feature Board and tested.

[channelmaniac]

Model: Kalimar 2x Tele Converter for Olympus-OM
Symptom: Loose fit and rattles

Removed bent flange ring from back of converter, flattened it out, and remounted it to fix the loose fit. Removed the front ring and the inner lens assembly fell out. It was glued in place and the glue failed. Reglued the assembly into place, reattached the front ring, and tested.