technics mod to 78rpm

[showdoc]

i have 2 turntables -

sl-1200 mk2
sl-1100a

am trying to find a mod to change either one of them to play at 78rpm

i know kabusa.com offers a switchable mod for 78 for the 1200, but they replace a couple boards and it's about $200

for what i'm wanting to do (convert some old 78's i have to cd's for my sister (and myself 🙂 i don't want to spend that much

i've seen a mod for a 1300, very simple - changing an 18k resistor by adding a 120k in parallel - bumps the speed up to around 78, but so far haven't seen anything for the 1200, or 1100a (keeping my eyes out for a cheap used 1300 to do the mod 🙂

i believe the 1300 mod actually adjusts the speed the sensors "think" they are receiving, thus speed up the turntable to compensate

i've been digging into the schematics of both 1200 and 1100 but i'm not quite as savvy as i'd like to be, and don't want to mess up something crucial and hose one of the turntables

it doesn't have to be "exact" - i'm assuming i could still use the speed adjust controls to tweak the speed after it's close to 78, just seems like changing a resistor to vary a freq or voltage somewhere would get me close to what i want

thanks in advance for your help
morelater
the show doctor

ps - hehehehe love all the high-end and homemade turntables etc... going on here - great stuff!!! 🙂

 

[bulgin]

technics mod...

Hi showdoc

I once changed the pot in a beltdrive Micro Seiki MB-18 semi-auto turntable to get the additional speed of 78 - 80rpm. In fact it is still in the tt and worked very well. OT, I also added a mono switch. Not sure if this would be feasible with a dd tt.

bulgin

 

[Netlist]

I would never record a 33 1/3rpm at 45rpm but I think it's worth a try to play the 78's at 45 and find a software program to adjust the pitch to the correct speed.

The ratio would be (1/78) X 45 = 0.5769

/Hugo