{"id":768,"date":"2018-06-26T21:51:55","date_gmt":"2018-06-26T20:51:55","guid":{"rendered":"http:\/\/www.wiredwood.co.uk\/wordpress\/?p=768"},"modified":"2020-08-23T17:36:54","modified_gmt":"2020-08-23T16:36:54","slug":"sony-tc-204sd-cassette-deck-motor-refurbishment","status":"publish","type":"post","link":"http:\/\/www.wiredwood.co.uk\/wordpress\/sony-tc-204sd-cassette-deck-motor-refurbishment\/","title":{"rendered":"Sony TC-204SD Cassette Deck. Motor Refurbishment"},"content":{"rendered":"

All seemed well with this cassette deck after I changed the belts and calibrated speed.<\/p>\n

\"\"
Sony TC 204SD<\/figcaption><\/figure>\n

Then, without notice after about an hour of use, it just stopped dead. Chic denied!<\/p>\n

<\/p>\n

Opening it up again I discovered that the motor had seized up. I could just about turn it by hand. Application of WD-40, followed by light lubrication helped a little. I was able to persuade the motor to start turning if I gave it a push. However, there was negligible power and there were “dead spots” where it was clearly receiving no power at all.<\/p>\n

\"\"
Sony TC 204SD motor removed<\/figcaption><\/figure>\n

This motor is controlled by an external control board. Studying the service manual confirmed that it was a pretty standard servo motor control circuit. Further research indicated that I would be able to get a replacement motor with built in speed control and replace the motor and circuit board with one of these.<\/p>\n

\"\"
Sony TC 204SD motor servo control circuit board<\/figcaption><\/figure>\n

I had a fall back position if all else failed, however there were two problems with this approach. The first was cost. Looking at about \u00a350 for a replacement motor, unless I went down the risky “used” route.<\/p>\n

\"\"
Sony motor in shielding can with 2 step pulley<\/figcaption><\/figure>\n

The second was the shaft diameter. 2 mm is common. 2.5 mm less so. I was going to be in for some extra expense or precision bodging to use a 2 mm motor with the 2.5 mm pulley. Changing the pulley as well is not an option because it is a two step pulley which accommodates both a square section belt and a flat one.<\/p>\n

I’ve got nothing to lose by having a go at fixing the existing motor. The first problem is getting inside it. A noisy electric motor and sensitive tape heads are not good bed fellows, so the motor is enclosed in a metal can to suppress electrical interference.<\/p>\n

\"\"
Shielding removed showing suppression circuit<\/figcaption><\/figure>\n

Careful examination revealed no obvious way in, so I resorted to attacking it with a blunt screwdriver and a hammer. To my delight the shielding can came apart quite cleanly. It was just a friction fit.\u00a0The first reassuring sign is the interference suppression capacitor across the motor terminals. Standard stuff. However there is also a suppression choke, which is beneficial, but often omitted to save cost.<\/span><\/p>\n

\"\"
Rotor, with damaged commutator<\/figcaption><\/figure>\n

I’m on familiar territory now. I am armed with a University education which included everything you want to know about electric motors and, more importantly, decades of experience taking model trains apart.\u00a0<\/span>Looki<\/span>ng inside we have a standard 3 pole DC motor. The black disc is a magnet which sends speed information back to the control board.<\/span><\/p>\n

\"\"
Rotor mounted in a Dremel drill<\/figcaption><\/figure>\n

The problem is the commutator. The rings are dirty, pitted and burnt. My tool of choice for fixing this is a glass fibre brush. I chucked the rotor in a Dremel to turn it while I applied gentle pressure with the fibre brush. A couple of minutes of this got rid of the worst damage.<\/p>\n

Clean everything and re lubricate the bearings before re assembling <\/span>the\u00a0motor and all is now well. Let’s hope it stays that way.<\/span><\/p>\n

P.S. for the belt change, see here<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

All seemed well with this cassette deck after I changed the belts and calibrated speed. Then, without notice after about an hour of use, it just stopped dead. Chic denied!<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15,11],"tags":[26],"class_list":["post-768","post","type-post","status-publish","format-standard","hentry","category-cassette","category-repair","tag-tc-204sd"],"_links":{"self":[{"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/posts\/768","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/comments?post=768"}],"version-history":[{"count":9,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/posts\/768\/revisions"}],"predecessor-version":[{"id":1687,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/posts\/768\/revisions\/1687"}],"wp:attachment":[{"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/media?parent=768"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/categories?post=768"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.wiredwood.co.uk\/wordpress\/wp-json\/wp\/v2\/tags?post=768"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}