{"id":7147,"date":"2021-01-31T12:32:00","date_gmt":"2021-01-31T01:32:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2021\/01\/31\/repairing-my-maplin-audio-waveform-generator\/"},"modified":"2025-07-21T22:24:33","modified_gmt":"2025-07-21T12:24:33","slug":"repairing-my-maplin-audio-waveform-generator","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2021\/01\/31\/repairing-my-maplin-audio-waveform-generator\/","title":{"rendered":"Repairing My Maplin Audio Waveform Generator"},"content":{"rendered":"

<\/a><\/p>\n

I picked this generator at the Kempton Park rally in London many years ago. I use it quite a bit, not only for circuit testing but also as an easy way to get my homebrew BITX rigs to send a signal so that I can adjust my antenna. I just plug this thing into the mic jack, crank in a small amount of 1 kHz audio, and I am ready to minimize SWR. <\/b><\/p>\n


<\/b><\/div>\n
It never gave me any real problems until last week. I opened it up and examined the circuitry for the first time. Lots of mystery chips in there. Fortunately they are all socketed. Thank you Maplin. <\/b><\/div>\n

<\/b><\/div>\n
Even without really knowing how each of the ICs work, it was easy to troubleshoot. See the schematic in the article that begins on page 21 in this .pdf:
<\/b><\/p>\n

<\/b><\/div>\n
https:\/\/worldradiohistory.com\/UK\/Mapelin\/Maplin-Projects-Book-48.pdf<\/b><\/a><\/p>\n<\/div>\n<\/div>\n
My Rigol scope showed a good signal going into and coming out of IC8, the LF351 op-amp. From there the signal goes to IC5 a 4066BE. But nothing was coming out of IC5. Thus IC5 was my lead suspect. I put in a quick order to Digikey. A couple of days and a few bucks later the chips (as always, I ordered several) were on my doorstep. Within a few minutes IC5 was replaced and the generator was as good as new. <\/b><\/div>\n

<\/b><\/div>\n
One annoying problem with this generator is that it has no automatic shut-off circuitry. So if I forget to turn it off, I soon have to buy two 9V batteries. Tony G4WIF suggested a simple timer circuit<\/a>. I may do that soon. Or, given that we are already on the IC dark side with this project, there is this: https:\/\/www.youtube.com\/watch?v=C4C2H_3BU3o&feature=youtu.be <\/a><\/b><\/div>\n

<\/b><\/div>\n
I recently find myself replacing a lot of chips in various rigs and devices in my shack. It seems that chips go bad more frequently than discrete transistors or even tubes. But maybe I’m just using older gear with older, more fragile chips. What do you folks think? <\/b><\/div>\n
<\/div>\n","protected":false},"excerpt":{"rendered":"

I picked this generator at the Kempton Park rally in London many years ago. I use it quite a bit, not only for circuit testing but also as an easy way to get my homebrew BITX rigs to send a signal so that I can adjust my antenna. I just plug this thing into the … Continue reading “Repairing My Maplin Audio Waveform Generator”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":7148,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[329,172,38,71,25,119],"tags":[],"class_list":["post-7147","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fishpool-tony","category-integrated-circuits","category-parts-suppliers","category-test-gear","category-troubleshooting","category-uk"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7147","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=7147"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7147\/revisions"}],"predecessor-version":[{"id":7149,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7147\/revisions\/7149"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/7148"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=7147"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=7147"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=7147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}