03-22-2013, 08:24 AM
I have a 90 chassis, the one with a single '47 output tube. I've been recapping this thing, and it's coming along pretty well, but there's one odd thing that I've noticed.
I keep having trouble with the '24 IF amp. Every once in a while it dies until I tap on it (the original one had an intermittent short in it, if it died and I tapped on it, it would come back, but I could see it arcing inside). What is interesting is, when the tube dies, or when I remove it completely, I can still hear the tuned in station in the speaker, although the volume control has no effect. I've tracked the signal paths and I find that all the bypass caps in the signal paths have already been replaced.
Both of the shields are missing. I have fashioned a shield around the IF amp, which seems to be very touchy, and breaks into oscillation at the drop of a hat, and this cleared up the oscillations.
Is it possible that I am going to have to locate the original shields in order to keep this 'ghost' signal out? I would not worry too much about it, but I'm thinking it may be out of phase and therefor cancelling some of the signal.
TIA
I keep having trouble with the '24 IF amp. Every once in a while it dies until I tap on it (the original one had an intermittent short in it, if it died and I tapped on it, it would come back, but I could see it arcing inside). What is interesting is, when the tube dies, or when I remove it completely, I can still hear the tuned in station in the speaker, although the volume control has no effect. I've tracked the signal paths and I find that all the bypass caps in the signal paths have already been replaced.
Both of the shields are missing. I have fashioned a shield around the IF amp, which seems to be very touchy, and breaks into oscillation at the drop of a hat, and this cleared up the oscillations.
Is it possible that I am going to have to locate the original shields in order to keep this 'ghost' signal out? I would not worry too much about it, but I'm thinking it may be out of phase and therefor cancelling some of the signal.
TIA
