Sound Technology SG1000A Special Modification Type 2995-9577

[Longnosegar]

I recently bought a ST1000A, and it has a Special Modification Type 2995-9577. It has an additional circuit board and a 8-9 wire connector in the back. Could this be a prototype? I emailed Sound Technology and Stan Curtis with no response. I didn't get any leads with it, and I am just waiting for a few parts so I can make the ST100 matching transformer.

1. What does this modification do?
2. I am curious if this modification will change anything related to FM alignment?
3. The Pioneer (SX-939) and Yamaha (CR-820) receivers I will work on both have 75Ω & 300Ω antenna connectors, is there a benefit to using 75Ω (ST105) vs 300Ω (ST100) matching transformers?

Thank you for any input.

 

[rcs16]

Probably some special function for a specific customers needs.
I could suggest to reverse engineer the pcb to draw up a schematic and figure out what it connects to in the schematics which we do have.
Emailing sound technology, interesting, where would you get their email address? I would have thought they folded before there was email, but I do not know for sure when they stopped their operation.
Try posting on DIYAudio as well in the test equipment section

Good luck

 

[Punker X]

Shot in the dark, wondering it's for some type of external modulation. Possible SCA or to use the generator as a low powered transmitter.

 

[gadget73]

I have actually run my stock 1000A as a low power transmitter. Its got L and R inputs and a position on the front for external modulation input. Wire it up and you get a rather good but low power FM transmitter.

 

[Longnosegar]

Probably some special function for a specific customers needs.
I could suggest to reverse engineer the pcb to draw up a schematic and figure out what it connects to in the schematics which we do have.
Emailing sound technology, interesting, where would you get their email address? I would have thought they folded before there was email, but I do not know for sure when they stopped their operation.
Try posting on DIYAudio as well in the test equipment section

Good luck

I had to pull the board out to do an inventory of the components,
Quantity Chip Description
1 RCA CD4016AE CMOS Quad Bilateral Switch
6 MCT2 Transistor Output Optocoupler
2 2N3970 N-Channel JFET
1 2N3414 NPN SILICON TRANSISTOR
1 2N3016 BJT NPN Transistor
I don't think these really spell out the function of the board. when received the unit, the meter glass was smashed to the face, and I thought it was a dummy meter, and the
plug in the back was for an external display. I fixed the glass and the meter is fine. My other thought was that it could be M3 modification since it seems to be mounted around the same place.
I will check out diyaudio.com.
The company still has a website, and even offers service and calibration of old units, but the website seems to be from the 1990's www.soundtechnology.com/service.html

Thanks for the info.

 

[chazix]

stock 1000A as a low power transmitter

Does a stock ST do the pre-emphasis that's used for conventional broadcast FM? I'd be kind of surprised if it did.

 

[gadget73]

it just modulates whatever you put in, so to make it sound truly right it would need to have that added to the input signal

 

[DDickey]

I recently bought a ST1000A, and it has a Special Modification Type 2995-9577. It has an additional circuit board and a 8-9 wire connector in the back. Could this be a prototype? I emailed Sound Technology and Stan Curtis with no response. I didn't get any leads with it, and I am just waiting for a few parts so I can make the ST100 matching transformer.

1. What does this modification do?
2. I am curious if this modification will change anything related to FM alignment?
3. The Pioneer (SX-939) and Yamaha (CR-820) receivers I will work on both have 75Ω & 300Ω antenna connectors, is there a benefit to using 75Ω (ST105) vs 300Ω (ST100) matching transformers?

Thank you for any input.

Did you ever find out what this mod does? I have an ST1000A with the same mod and I'm clueless