I got a 500-T to fill out my 700-T, 550-T collection last week from another AK'er. He had gotten it as part of a 3 unit lot and wasn't sure about it's health/well being. Price was right, so it was shipped out here.
Well I finally got around to it y'day. Externally it's in good shape. No knobs, but I have a set from a 400-T parts unit that went on the 500-T. Typical Gold Foil missing but not a deal breaker except for those who must have it. Internally it had about 1/4" of dust on top surfaces which was removed with a brush, then it was sprayed down with CRC QD Electronic's cleaner. The Tuning V.C. was opened up and cleaned with CRC QD Contact Cleaner and buttoned back up. Brought out the DBT and Variac, and ramped it up on headphones and a dipole. 50-100-150W 3way bulb on 50W. Nothing. Checked the fuses and the main fuse holder had cracked at the cap, and the fuse was blown. Trip to Home Depot for fuses and replaced the Fuse holder. Tried ramping up again and had lights on it by 50V and no light on the dbt. Continued up to 120v and nothing on the dbt, with static on FM. As the tuning dial was all the way to 108mHz I dialed down the scale and got plenty of stations. The dial pointer is slightly off and needs resetting. Left channel was very weak but jumping the volume pot determined that the amps were working fine.
Started probing around the tone control board, and found that I could induce LEFT Channel to work. Bad caps. With some judicious pressure on the cap I could get it to stay on for about 5-10 minutes (long enough to check it out on both channels. MONO is definately weaker than STEREO, but MPX has some issues. LEFT SIDE Washes out the Right side and what there is of the right side is echoing, and somewhat distorted. Left Side is louder than Mono.
POWER SUPPLY CAPS after 45 minutes were all cool and operating voltages were all within 1% + or -. Bias was within 1volt, but with the bias pots on the amp boards being a weak point in the operation I left well enough alone.
To recap. It works, but it needs some help. This will be done after I get around to finishing the 400.
I'll get some pics up in the next couple days.
Larry
Well I finally got around to it y'day. Externally it's in good shape. No knobs, but I have a set from a 400-T parts unit that went on the 500-T. Typical Gold Foil missing but not a deal breaker except for those who must have it. Internally it had about 1/4" of dust on top surfaces which was removed with a brush, then it was sprayed down with CRC QD Electronic's cleaner. The Tuning V.C. was opened up and cleaned with CRC QD Contact Cleaner and buttoned back up. Brought out the DBT and Variac, and ramped it up on headphones and a dipole. 50-100-150W 3way bulb on 50W. Nothing. Checked the fuses and the main fuse holder had cracked at the cap, and the fuse was blown. Trip to Home Depot for fuses and replaced the Fuse holder. Tried ramping up again and had lights on it by 50V and no light on the dbt. Continued up to 120v and nothing on the dbt, with static on FM. As the tuning dial was all the way to 108mHz I dialed down the scale and got plenty of stations. The dial pointer is slightly off and needs resetting. Left channel was very weak but jumping the volume pot determined that the amps were working fine.
Started probing around the tone control board, and found that I could induce LEFT Channel to work. Bad caps. With some judicious pressure on the cap I could get it to stay on for about 5-10 minutes (long enough to check it out on both channels. MONO is definately weaker than STEREO, but MPX has some issues. LEFT SIDE Washes out the Right side and what there is of the right side is echoing, and somewhat distorted. Left Side is louder than Mono.
POWER SUPPLY CAPS after 45 minutes were all cool and operating voltages were all within 1% + or -. Bias was within 1volt, but with the bias pots on the amp boards being a weak point in the operation I left well enough alone.
To recap. It works, but it needs some help. This will be done after I get around to finishing the 400.
I'll get some pics up in the next couple days.
Larry
