This time, folks, I have news of a major setback \u2013 and an interesting discovery. First, allow me to tell you about the setback.<\/p>\n
Remember my test jig I threw together to try out the 37-116 RF unit I had intended to use as a \u201cstandby\u201d unit for this 38-690? Well, Murphy\u2019s Law seems to rule with this radio and anything having to do with it. I had previously noticed that it was playing, but at extremely low volume. So I made some changes to my 38-116 chassis test jig, and tried the whole thing together again.<\/p>\n
Not only was I hearing nothing at all now, but what I was hearing was the sick sound of sizzling somewhere inside the rebuilt 37-116 RF unit! This indicated that this RF unit was likely also burning a carbon track in a switch wafer. When it rains, it pours. So I won\u2019t be sending this RF unit to my friend. I resisted the temptation to take the whole thing outside and destroy it with my sledgehammer. Instead, common sense prevailed, and I simply set it aside.<\/p>\n
Pulling the 38-690 upper chassis back out later on, before I did anything else, I flipped the chassis over and did a resistance check between the end of resistor (64) which leads into the RF unit and ground. A properly working 38-690 would have read infinite resistance. But instead, the multimeter was reading 643 ohms!<\/p>\n
AHA! I was right \u2013 there is a partial short to ground inside the RF unit! To confirm this, I unsoldered the wire which carries B+ into the suspect part of the circuit inside the RF unit. I measured the resistance between the now disconnected wire and ground. Once again \u2013 643 ohms.<\/p>\n
I measured resistance again between the end of resistor (64), now disconnected from the RF unit, and ground. I found infinite resistance, as I expected. This confirms that the issue is inside the RF unit.<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
This time, folks, I have news of a major setback \u2013 and an interesting discovery. First, allow me to tell you about the setback. Remember my test jig I threw together to try out the 37-116 RF unit I had intended to use as a \u201cstandby\u201d unit for this 38-690? Well, Murphy\u2019s Law seems to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2599,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3454","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/3454","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/comments?post=3454"}],"version-history":[{"count":1,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/3454\/revisions"}],"predecessor-version":[{"id":3455,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/3454\/revisions\/3455"}],"up":[{"embeddable":true,"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/pages\/2599"}],"wp:attachment":[{"href":"https:\/\/philcoradio.com\/library\/index.php\/wp-json\/wp\/v2\/media?parent=3454"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}