I have an Pilotuner T-601 FM and like to use it,but,I don't believe it has AVC.Weak stations pickup fine and strong stations overload it,so I couple the ant loosely on strong signals.Am I correct on the AVC and how did older radios cope without AVC?

Hi,
It sounds like you narrowed the problem. Most likely culprit(s) are the decoupling capacitor in the IF, and possibly the reistor that is across it too. The cap should be about a .005Mfd. It would not hurt to look at the condition of the decoupling caps in the final detector stage too. These should be about the same value.

Older radios without AVC often had a "Local/Distant" switch that would either select between a high coupling factor, and a lower coupling factor between two of the stages (RF to IF, IF to IF, IF to first audio), or controlled the gain of one the IF, or RF stages.

: I have an Pilotuner T-601 FM and like to use it,but,I don't believe it has AVC.Weak stations pickup fine and strong stations overload it,so I couple the ant loosely on strong signals.Am I correct on the AVC and how did older radios cope without AVC?

:Thanks.I replaced the power supply filter caps and audio caps,but I wasn't sure about rf type caps and left the old ones in.They are little tube types and lead dress looked important.What is a good cap to use on these?I think the ant. was caped to the 120v imput also? : Hi,
: It sounds like you narrowed the problem. Most likely culprit(s) are the decoupling capacitor in the IF, and possibly the reistor that is across it too. The cap should be about a .005Mfd. It would not hurt to look at the condition of the decoupling caps in the final detector stage too. These should be about the same value.

: Older radios without AVC often had a "Local/Distant" switch that would either select between a high coupling factor, and a lower coupling factor between two of the stages (RF to IF, IF to IF, IF to first audio), or controlled the gain of one the IF, or RF stages.

:
: : I have an Pilotuner T-601 FM and like to use it,but,I don't believe it has AVC.Weak stations pickup fine and strong stations overload it,so I couple the ant loosely on strong signals.Am I correct on the AVC and how did older radios cope without AVC?

Hi,
Lead dress will be of some importance for the FM section, so your best replacement options are to use Mylar, or Polyester caps. Note which way the "-" sign is oriented, this is the outer foil, and can act as a shield (highly desired). If the replacements are not polarized, and you are not sure which is the outer foil, just assume the left hand lead as you read the information is the oter foil. At worst you pick up a little bit of noise. Polyester, and Mylar caps are smaller and than their old paper counterparts, so they should fit easily in the same space, and they are not expensive. Match the working voltage of the originals, or go a little bit higher. Make sure that you route the leads in the same manner, as the old leads and keep the leads as short as possible. Also take care not to melt the outer portion of the cap with your soldering iron, as this can ruin the cap by shorting it out.

If the antenna has a cap to the AC main, it may be using the AC lines in the house as the antenna system for FM. If the caps are disc type, or "postage stamp" type Mica caps, I would leave them for now. Only replace them if they are paper tubular types.

If you wish to retain the original apearance, often the paper tubes can be removed from the old cap and slipped over the replacement. Seal the ends with a "hot melt" glue gun, or candle wax- depending on color of the ends.

When all of this is done, you may want to "tweak" the alignment to get best performance. But, if it works acceptably after the new caps are in place, you don't "have to", but the results will be better. General guidelines for allignment may be on this site, otherwise the alignment procedure is approximately the same for AM, but you need to hit the "center frequency", for accurate channel seperation.

: :Thanks.I replaced the power supply filter caps and audio caps,but I wasn't sure about rf type caps and left the old ones in.They are little tube types and lead dress looked important.What is a good cap to use on these?I think the ant. was caped to the 120v imput also? : Hi,
: : It sounds like you narrowed the problem. Most likely culprit(s) are the decoupling capacitor in the IF, and possibly the reistor that is across it too. The cap should be about a .005Mfd. It would not hurt to look at the condition of the decoupling caps in the final detector stage too. These should be about the same value.

: : Older radios without AVC often had a "Local/Distant" switch that would either select between a high coupling factor, and a lower coupling factor between two of the stages (RF to IF, IF to IF, IF to first audio), or controlled the gain of one the IF, or RF stages.

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: :
: : : I have an Pilotuner T-601 FM and like to use it,but,I don't believe it has AVC.Weak stations pickup fine and strong stations overload it,so I couple the ant loosely on strong signals.Am I correct on the AVC and how did older radios cope without AVC?