Technics SP-25 rebuild - diyAudio
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Old 16th June 2017, 02:53 AM   #1
JimM is offline JimM  United States
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Join Date: Jul 2006
Default Technics SP-25 rebuild

Received my SP-25, and it does appear it is basically the same as a SL-1200, at least electrically.
Disassembled the turntable cleaned with soap and water sanded the rough spots with 400 wet dry and finished with 600 wet dry. Removed the transformer and built a CRCCRC power supply, unfortunately I didnít check the secondary A.C. which was 37.5 VAC and it took out one of my 3300uf 50 volt caps. Replaced them with some 100v caps with lesser UF values, my house voltage is 120vac, which is probably higher than the unit was originally designed for. If making this modification I would recommend 63 volt caps at a minimum. Currently output with the CRCCRC filter with 17.5 ohms resistance and 3.6k bleeder getting an output of 49.5 volts. Will see what it loads down to when I get the TT back together, as it is currently disassembled for painting. I think it is fortunate that I decided to remove and remote the P.S. as I donít think the 470UF 50v cap install on the original board would have survived for long. Thanks to 6L6 and others for the post on this modification.
Attached Images
File Type: jpg sp-25 as purchased.JPG (98.2 KB, 54 views)
File Type: jpg sp25 PS top.JPG (123.0 KB, 52 views)
File Type: jpg sp-25 plinth.JPG (120.3 KB, 52 views)
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Old 16th June 2017, 03:32 AM   #2
JimM is offline JimM  United States
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Join Date: Jul 2006
Paint prep sanded the chassis and platter rough spots with 400 wet dry and finished with 600 wet dry. Filled spots that didnít sand out without cutting into the metal with bondo glazing and spot putty, sand with wet dry 600. Ordered from Automotive Touchup, aerosol cans of base coat in the color of my Ford pickup, aerosol cans of high gloss clear coat, spray can of grey primer, prep solvent, and aerosol spray can trigger. Masked off parts of chassis and platter I didnít want painted then cleaned the chassis and platter with the prep solvent. Primed the parts with primer, sand with 600 wet dry between coats (ensure the coats are dry to the touch 15 to 30 minutes) I sprayed three primer coats. Sprayed 4 coats of base coat allowing dry to the touch between each coat around 15 minutes between coats. Wait at least 30 minutes then sprayed 5 clear coat allowing dry to the touch between coats. Dry time varies with temperature humidity.
Attached Images
File Type: jpg sp-25 top.JPG (253.9 KB, 54 views)
File Type: jpg sp25 topview closeup.JPG (242.5 KB, 53 views)
File Type: jpg sp-25 on cab.JPG (261.4 KB, 32 views)
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Old 16th June 2017, 12:49 PM   #3
Hiten is offline Hiten  India
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Join Date: Jun 2010
Location: India
Nice work.
Regards.
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