Philco 620B alignment woes - Printable Version

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+--- Thread: Philco 620B alignment woes (/showthread.php?tid=1195)

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- wonderwrench - 06-29-2008

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.

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- wonderwrench - 07-06-2008

as asked above without answer
Question can the covers be removed while the coils are still wired to the chassis?

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- Ron Ramirez - 07-06-2008

Hi

Sorry, missed your question previously.

Yes, the coil shields may be removed without removing the coils. There are one or two nuts on top which must be removed; then, look underneath the chassis for four push-through metal tabs which must be carefully pinched together enough so that they will slip back through the holes. Once you look the coil shields over carefully, you will see what I am trying to describe.

You will have to do one hole at a time until you have all of the tabs released, then the shield will pull off from the top. Installation is the reverse of removal. of course.

You can also do this to IF shields on 1936 Philco models, if necessary.

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