06-29-2008, 06:23 PM
Update
Cap #23 is a .047 mf and tests very close to .05 mf so thats out of the way. Kinda sucks as it would have been a nice easy fix. I went through most components related to the RF section and found nothing. I confirmed the alignment and the osc section is trimmed correctly (high image) on all three bands . Just as a test I installed progressively smaller caps in place of the .05 mf (#23) and found a smaller valve caps help the problem though is not a fix. With a .005 mf the AM band RF trimmer works great. Performance and tracking is very good. The Police and SW bands are affected but the RF trimmers still are not peakable and tracking suffers on the police band causing poor performance.
It looks like the coil covers have been off the ANT and RF coils at one point in time. This leads me to believe this problem existed before the last guy worked on it. Question can the covers be removed while the coils are still wired to the chassis? I have a sneaky suspicion someone may have installed the wrong coil or done a rewind causing this problem.
I replaced the 75 tube and the intermittent problem was fixed. I did not try to re solder the grid cap as my father has way too many spare 75's anyway.
I replaced the volume control. The radio sounds way better with the correct part having a tap for the tone control and the correct tapper.
Cap #23 is a .047 mf and tests very close to .05 mf so thats out of the way. Kinda sucks as it would have been a nice easy fix. I went through most components related to the RF section and found nothing. I confirmed the alignment and the osc section is trimmed correctly (high image) on all three bands . Just as a test I installed progressively smaller caps in place of the .05 mf (#23) and found a smaller valve caps help the problem though is not a fix. With a .005 mf the AM band RF trimmer works great. Performance and tracking is very good. The Police and SW bands are affected but the RF trimmers still are not peakable and tracking suffers on the police band causing poor performance.
It looks like the coil covers have been off the ANT and RF coils at one point in time. This leads me to believe this problem existed before the last guy worked on it. Question can the covers be removed while the coils are still wired to the chassis? I have a sneaky suspicion someone may have installed the wrong coil or done a rewind causing this problem.
I replaced the 75 tube and the intermittent problem was fixed. I did not try to re solder the grid cap as my father has way too many spare 75's anyway.
I replaced the volume control. The radio sounds way better with the correct part having a tap for the tone control and the correct tapper.
Bill
It's not what you don't know that hurts you it's what you know that's not so.
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