audio-talk

The correct setting is in the service manual. Show us what you are getting.

Hi Nick, there must be something wrong, I have connected exactly as the manual said. I have taken a photo of the connections. I am still getting two saw tooth wave forms. See photos.

THat would point to a short somewhere or a fault somewhere around the sample and hold area and R186. Maybe a failed TR151.

Hi Nick, just looked at the circuit diagram and found the R186 that is supposed to be a 150K resistor. will check it tonight. also the TR151, 152, 153 & 154, they are a JFET?

Yes, its the sample and hold that implements the phase lock. the pulse samples the ramp at the position it is at the time, and that held value is then used to provide the phase lock signal to the turntable.

Hi Nick, Tested the resistor between S & T, reading is 147.7K. Also tested the scope probes, just in case there was a short in them, they are both fine.
so it looks like the TR 151 could be faulty. Will check it tonight. Testing JFets is a little different to std standard transistors, is that correct?

Yep, though TBH, I would just get a replacement and replace it.

Hi Nick, I can do that, I purchased a full set of replacement transistors, so if you ever need any.

Hi Nick, replaced TR 151 with a 2SK30a, still getting identical waveforms. I was looking at the circuit diagram and test points S & T are adjacent to TR153 & TR154, could any of these be the culprit? I will test around them and see what happens.

Yep maybe also check for a short somewhere. Trace back from the gate if that meet and see if the pulse appears.

Lots of smily faces, Nick, you wont believe it, I got it going with the right wave forms. The only thing that needed adjusting was 78rpm, 33 and 45 both locked on perfectly. What I did, was replace TR121, TR128, TR151, TR152, TR153 & TR154. the whole sample and hold setup.

Mate, how do I ever thank you for your time and patients? you are a true legend, thank you, thank you, thank you.

Kindest Regards

Wolfgang Felber

Just a couple of photos to show the wave forms, hopefully they are OK in your eyes.

Brilliant, you did the hard work, I just typed some words. Very well done. Those waves look perfect.

Just to add, I think this thread shows the great thing about the sp10Mkii design. Unlike every other DD turntable I know of, its all done using discrete parts and some off the shelf logic (that’s still basically available). So as you have shown its all repairable.

Yup, great effort there Wolfgang, well done!