Wurlitzer 1600 (518 amp) low volume
I am in the process of restoring a Wurlitzer 1600 with a model 518
amp. I re-capped the amp and replaced all resistors that had drifted out of tolerence. All tubes checked good with the exception of the 6J5 and 6L6's which have been replaced. All voltages checked within 10% of the values shown on the schematic. The problem is that the volume of the amp is quite low. At max volume, it is at about 1/2 the level that it should be. There is no audible sound at all until the volume control is at about the half-way position. There is no hum or distortion in the sound, it is just too low. I have tried the following: I have 4 different cobra cartridges and all sound the same. I have a spare set of tubes and replacing any or all of them makes no difference. Unplugging either of the output tubes makes no difference in sound output. In other words it doesn't matter which tube is removed, the output level is the same. Obviously, however, removing both tubes results no sound at all. Any ideas? I'm really stumped on this one. Thanks, Jonathan |
Sounds like a bad cathode bypass electrolytic cap in the front end of the amp.
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How about the mute switch ? I recently had a Wurlitzer 1700 with a broken
switch held in the closed position AND corroded contacts. This gave the same type problem you are having with yours. DPJ "Jonathan Day" wrote in message om... I am in the process of restoring a Wurlitzer 1600 with a model 518 amp. I re-capped the amp and replaced all resistors that had drifted out of tolerence. All tubes checked good with the exception of the 6J5 and 6L6's which have been replaced. All voltages checked within 10% of the values shown on the schematic. The problem is that the volume of the amp is quite low. At max volume, it is at about 1/2 the level that it should be. There is no audible sound at all until the volume control is at about the half-way position. There is no hum or distortion in the sound, it is just too low. I have tried the following: I have 4 different cobra cartridges and all sound the same. I have a spare set of tubes and replacing any or all of them makes no difference. Unplugging either of the output tubes makes no difference in sound output. In other words it doesn't matter which tube is removed, the output level is the same. Obviously, however, removing both tubes results no sound at all. Any ideas? I'm really stumped on this one. Thanks, Jonathan |
Thanks for all the input, guys. I found that the lower tonearm plays
at a much higher volume than the upper tonearm. I eliminated the switch that connects the correct tonearm to the main input cable via a jumper, so it looks like my problem is with the wiring between the upper tonearm and the switch. I would prefer to change the all the cables between the tonearms and the amp, but all of the shielded cables that I have around the shop introduce a very loud hum. Is there something special about the cable since this box uses a cobra cartridge? Has anyone found a suitable replacement for the heavy cable that goes to the amp as well as the smaller wires that connect to the cartridge? Thanks, Jonathan (Jonathan Day) wrote in message . com... I am in the process of restoring a Wurlitzer 1600 with a model 518 amp. I re-capped the amp and replaced all resistors that had drifted out of tolerence. All tubes checked good with the exception of the 6J5 and 6L6's which have been replaced. All voltages checked within 10% of the values shown on the schematic. The problem is that the volume of the amp is quite low. At max volume, it is at about 1/2 the level that it should be. There is no audible sound at all until the volume control is at about the half-way position. There is no hum or distortion in the sound, it is just too low. I have tried the following: I have 4 different cobra cartridges and all sound the same. I have a spare set of tubes and replacing any or all of them makes no difference. Unplugging either of the output tubes makes no difference in sound output. In other words it doesn't matter which tube is removed, the output level is the same. Obviously, however, removing both tubes results no sound at all. Any ideas? I'm really stumped on this one. Thanks, Jonathan |
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