05-23-2006, 05:44 PM
I have a 620 that has played well for several years. the original owner re-built all the cap blocks and i re did the electrolytics. Over the past year it has been having some problems. 1) the oscillator shuts down below about 600 khz. (kc for the purest out there) 2) when you turn the volume up about past half way it starts to sqeal like a little piggie.
I went in and checked and replaced all out of tolerance resistors, all but two actuallly. Checked all voltages, all with in close reason. I noticed that as I turn up the volume control the gain comes up smooth, then stops and as you advance the control it comes up fast. Then beyond that the squeal starts. Replaced the 75 and 42 with others from a working set and no change.
I think my problem with the oscillator shutting down is 150pf 250pf & 50pf micas so I am going to replace them. the biggest problem facing me is the sqeual. I have moved wires, checked resistance, voltages, etc. The radio works great at all frequencies above 600 Khz good volume and tone. but on the softer stations if you turn up the volume, Sqeal. This is the oldest set I have worked on, most are 39 and up. I must be missing something but I think I am too close to it. Any ideas would be welcome! Thanks in Advance.
I went in and checked and replaced all out of tolerance resistors, all but two actuallly. Checked all voltages, all with in close reason. I noticed that as I turn up the volume control the gain comes up smooth, then stops and as you advance the control it comes up fast. Then beyond that the squeal starts. Replaced the 75 and 42 with others from a working set and no change.
I think my problem with the oscillator shutting down is 150pf 250pf & 50pf micas so I am going to replace them. the biggest problem facing me is the sqeual. I have moved wires, checked resistance, voltages, etc. The radio works great at all frequencies above 600 Khz good volume and tone. but on the softer stations if you turn up the volume, Sqeal. This is the oldest set I have worked on, most are 39 and up. I must be missing something but I think I am too close to it. Any ideas would be welcome! Thanks in Advance.
