Conn ST-11 Strobotuner Mod Help

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Enzo

Member
Joined 2004
The clock only needs to be stable on a short term basis. Every time you use the unit, you start by calibrating it to the mains frequency. There is a setting on the front panel just for that. And by the time it is divided down for the motors, a few hertz drift would not be noticed. SO unlike some video source that must sync up to the world, they could get away with a "poorly designed" clock. These little units worked quite well.
 
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cos000

Member
Joined 2014
Hello to everyone.
I have a ST-11 bought from USA. I live in Italy and I have 230V 50Hz.
I've understood how to mod the tuner for 240V but my problem remain the 50Hz.
Does anyone know how to mod it in order to use calibration with 50Hz (transform it into a ST-12?

Thanks so much
 
E

Enzo

Member
Joined 2004
Do you have a schematic? Mine are miles away. Contact Peterson and ask if they have any such information. Last time I checked (a while ago) Peterson web site has a forum, and a section there where they discuss old Conn tuners. (Peterson bought the Conn assets when Conn went under.)
 
C

cos000

Member
Joined 2014
Enzo said:
Do you have a schematic? Mine are miles away. Contact Peterson and ask if they have any such information. Last time I checked (a while ago) Peterson web site has a forum, and a section there where they discuss old Conn tuners. (Peterson bought the Conn assets when Conn went under.)
Click to expand...

Hello
Thanks for the reply.
I have schematics of ST-11 which don't include 50Hz mod.
I know about that forum but it seems they have deleted it... I can't find it anymore...
Nevertheless, after one hour spent on calculations and thoughts, I think I solved it also with the help of post #17 of this thread.
I have to write it down and then I'll post my solution.
 
S

Souleyman

Member
Joined 2017
Hi there,
I've just got the ST-11 and very interesting about 50Hz mode too.
But I look here and some google results. No answers ((
Does anybody solved this thing with CAL mode?

Looking here on the table of Scooperman

Note .... Hz ...... Count ..... tw (ms) ..... Motor Hz ....... Motor RPM
C ....... 261.6 ..... 5D6 ....... 20.39 ........ 49.036 .......... 980.724
C# ..... 277.2 ..... 582 ....... 19.25 ........ 51.957 ......... 1039.15
D ....... 293.7 ..... 533 ....... 18.17 ........ 55.041 ......... 1100.83
D# ..... 311.1 ..... 4E8 ....... 17.14 ........ 58.328 ......... 1166.56
E ....... 329.6 ..... 4A2 ....... 16.19 ........ 61.771 ......... 1235.41
F ....... 349.2 ..... 45F ....... 15.27 ........ 65.469 ......... 1309.38
F# ..... 370 ........ 420 ....... 14.41 ........ 69.375 ......... 1387.50
G ....... 392 ........ 3E5 ....... 13.61 ........ 73.481 ......... 1469.61
G# ..... 415.3 ..... 3AD ....... 12.84 ........ 77.853 ......... 1557.07
A ....... 440 ........ 378 ....... 12.12 ........ 82.500 ......... 1650.00
A# ..... 466.2 ..... 346 ....... 11.44 ........ 87.423 .......... 1748.45
B ....... 493.9 ..... 317 ....... 10.80 ........ 92.617 .......... 1852.34
CAL .... 120 ....... 32E ....... 11.11 ........ 90.000 .......... 1800.00
Click to expand...
I've just understood that the CAL mode -- 50Hz or 100Hz or 200Hz or 400Hz possibly must be between G and G# notes but what exactly I don't know.
I've read this mod needed only four diodes moving but did not found what exactly.
Please help to find the solution.
 
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