Hello All,
Thanks to a fellow AKer, I now have in my possession a beautiful CR-420! I plan to restore this to use in my main rig so that I can move the HK 330c to the bedroom. The 420 came with a cut power cord, which I have replaced with a polarized one, but I wanted to get some insight before I dive in any deeper. I tied ground to the post that was also tied to ground on the schematic. Seems correct, yes?
I have yet to test the DC offset or bias, but I plan to do so tonight. I found info stating that bias should be set to 20 mV +/- 3 mV. I'm assuming that this needs to become under load, as with other receivers. Is that correct? If so, what is the preferred method for this?
Also, the tuning knob has A LOT of resistance when trying to change stations in either direction. The wheel attached to the tuning mechanism inside can be turned easily, and the string travels freely, but even without the string in place, the knob is incredibly difficult to turn. Any thoughts on what to do here?
After replacing the power cord and applying a liberal amount of Deoxit to the pots and switches, I hooked the unit up to test speakers. Sounds pretty great as is! Very detailed and clean... Save a constant rumble/crackle/distortion in the right speaker. It is only present when the speakers are selected. Level is constant, not tied to volume or source. The only thing that seems to have any effect is turning down the loudness control increases the volume of the kiss. It isn't loud enough to damage anything, and music at normal listening level nearly drowns it out, but I want to get this thing running in tip top. Could this be caused by the bias/DC offset? Transistors need to be replaced?
I plan on recapping this beauty with Elna Silmic IIs and Nichicon KGs, so I don't mnd swapping out anything else recommended while I'm at it.
Any suggestions and pointers are most welcome. I'll beside to document the whole process, if that'd be of interest.
Thanks!
Thanks to a fellow AKer, I now have in my possession a beautiful CR-420! I plan to restore this to use in my main rig so that I can move the HK 330c to the bedroom. The 420 came with a cut power cord, which I have replaced with a polarized one, but I wanted to get some insight before I dive in any deeper. I tied ground to the post that was also tied to ground on the schematic. Seems correct, yes?
I have yet to test the DC offset or bias, but I plan to do so tonight. I found info stating that bias should be set to 20 mV +/- 3 mV. I'm assuming that this needs to become under load, as with other receivers. Is that correct? If so, what is the preferred method for this?
Also, the tuning knob has A LOT of resistance when trying to change stations in either direction. The wheel attached to the tuning mechanism inside can be turned easily, and the string travels freely, but even without the string in place, the knob is incredibly difficult to turn. Any thoughts on what to do here?
After replacing the power cord and applying a liberal amount of Deoxit to the pots and switches, I hooked the unit up to test speakers. Sounds pretty great as is! Very detailed and clean... Save a constant rumble/crackle/distortion in the right speaker. It is only present when the speakers are selected. Level is constant, not tied to volume or source. The only thing that seems to have any effect is turning down the loudness control increases the volume of the kiss. It isn't loud enough to damage anything, and music at normal listening level nearly drowns it out, but I want to get this thing running in tip top. Could this be caused by the bias/DC offset? Transistors need to be replaced?
I plan on recapping this beauty with Elna Silmic IIs and Nichicon KGs, so I don't mnd swapping out anything else recommended while I'm at it.
Any suggestions and pointers are most welcome. I'll beside to document the whole process, if that'd be of interest.
Thanks!