[Russtafarian]

I'm in the process of updating the power supply in a Technics SL1200 turntable.   I would like to increase current capability in case I decide to try some of the heavy mats and weights that are in vogue with the SL1200 these days.  I'm looking to do this for $30 in parts, not buy a $500 external box.  So far I removed the power transformer and put it in a separate box to get it away from the cartridge. 

The transformer box delivers 33vac to the power switch, rectifier and 470uf supply cap inside the TT. My plan is to keep the stock rectifier and replace the supply cap with a bigger, better cap and update the stock regulator with a quieter, higher current regulator.  The stock regulator takes 47vdc (33vac X 1.414) from the rectifier & supply cap and regulates it down to 21vdc.  From what I've read current demands are around 1 amp to start the platter and .25 amps to keep it turning.

I was thinking of using a LT1085 or LM317, but 47vdc sounds pretty high for those regulators.  Are there other regulators out there I should consider?  Thanks.

Russ

[mgalusha]

That is too high, the LT1085 has a max input/output differential voltage of 30V, 26V would be pushing it IMO. However, you can build a floating high voltage version. Look at some of the Maida regulator stuff that Google will turn up for more info.

http://www.national.com/ms/LB/LB-47.pdf

http://giaime.altervista.org/maida.html

I've built them to run up to about 330V with no problems. I have used MJE340 transistors with success.


Edit: Just looked at the LM-317 data sheet, the max input/output differential is 40V, so going from 47 to 21 should be OK but at 1A that 25W of heat dissipation you have to deal with.

[Russtafarian]

Thanks Mike.  When I saw 40v max on the LM317 data sheet I didn't realize that meant I/O differential.  Since that regulator will work I'll go with it.  To handle the heat dissipation I'll heatsink it to the aluminum plinth the same way the current regulator is.
 
I appreciate the help.

Russ