Show Off Your Linear-Tracking Turntables

Got a Goldmund Studio with T3F tonearm. Won't track a record because the belt is not moving when the motor turns. Whether this is a tired belt or a mechanism that is more work to move than the belt can supply, I have to determine but figure it is the belt.
Possibly needing a new belt but that size is NLA.

I guess I'll get some pics.
 
IT'S BAAACK!!!!

My PX-3's tonearm stopped tracking several, probably 15 years ago. Button functions had started acting intermittently at first and then totally dead. Very frustrating as I've owned this TT since new in the early 80's and it had been rock solid. I looked for advice online but none of the symptoms were quite like ones people were describing. I started down the path of restoring and flipping the rubber belt...and that led nowhere as the issue was with the belt's motor drive mechanism being stuck. My debug skills and time to work on it were non-existent, so into the corner it went until a few weeks ago.

I obtained the limited service guide, which had a detailed schematic ... verified the photosensors seemed to be doing their job, apparently a common failure item. I drilled into the cad cell sensor circuit as the arm was not advancing into the record grooves. I measure transistor voltages and compared to the schematic ... some were close while others were way off. Cross-referenced the old Japanese transistor part numbers to current products, figured I might as well do the diodes, replaced the push-button switches and electrolytic caps. Turns out 4 of the transistors I measured with odd values, so they were suspected as they had apparently gone out of spec, since they did not come up as dead.

Back in business!

Went ahead with doing all of the transistors, diodes and electrolytic caps, and then calibrated the DC balance and Tonearm Angle adjustment.

Works perfectly now!
IMG_9484.jpeg
 
e30m3mon said:
IT'S BAAACK!!!!

My PX-3's tonearm stopped tracking several, probably 15 years ago. Button functions had started acting intermittently at first and then totally dead. Very frustrating as I've owned this TT since new in the early 80's and it had been rock solid. I looked for advice online but none of the symptoms were quite like ones people were describing. I started down the path of restoring and flipping the rubber belt...and that led nowhere as the issue was with the belt's motor drive mechanism being stuck. My debug skills and time to work on it were non-existent, so into the corner it went until a few weeks ago.

I obtained the limited service guide, which had a detailed schematic ... verified the photosensors seemed to be doing their job, apparently a common failure item. I drilled into the cad cell sensor circuit as the arm was not advancing into the record grooves. I measure transistor voltages and compared to the schematic ... some were close while others were way off. Cross-referenced the old Japanese transistor part numbers to current products, figured I might as well do the diodes, replaced the push-button switches and electrolytic caps. Turns out 4 of the transistors I measured with odd values, so they were suspected as they had apparently gone out of spec, since they did not come up as dead.

Back in business!

Went ahead with doing all of the transistors, diodes and electrolytic caps, and then calibrated the DC balance and Tonearm Angle adjustment.

Works perfectly now!
View attachment 74831
Click to expand...
I love my PX-3 it sounds wonderful and just fun to watch it work. Still using the original cart, what do you have in yours?
 
e30m3mon said:
IT'S BAAACK!!!!

My PX-3's tonearm stopped tracking several, probably 15 years ago. Button functions had started acting intermittently at first and then totally dead. Very frustrating as I've owned this TT since new in the early 80's and it had been rock solid. I looked for advice online but none of the symptoms were quite like ones people were describing. I started down the path of restoring and flipping the rubber belt...and that led nowhere as the issue was with the belt's motor drive mechanism being stuck. My debug skills and time to work on it were non-existent, so into the corner it went until a few weeks ago.

I obtained the limited service guide, which had a detailed schematic ... verified the photosensors seemed to be doing their job, apparently a common failure item. I drilled into the cad cell sensor circuit as the arm was not advancing into the record grooves. I measure transistor voltages and compared to the schematic ... some were close while others were way off. Cross-referenced the old Japanese transistor part numbers to current products, figured I might as well do the diodes, replaced the push-button switches and electrolytic caps. Turns out 4 of the transistors I measured with odd values, so they were suspected as they had apparently gone out of spec, since they did not come up as dead.

Back in business!

Went ahead with doing all of the transistors, diodes and electrolytic caps, and then calibrated the DC balance and Tonearm Angle adjustment.

Works perfectly now!
View attachment 74831
Click to expand...


I have tested many transistors. Even if they pass the diode junction test, they can have ZERO gain..
 
Wheel-right said:
I love my PX-3 it sounds wonderful and just fun to watch it work. Still using the original cart, what do you have in yours?
Click to expand...
For now, I reinstalled the Ortofon MC10 cartridge that I bought new with the turntable (back around '81 or '82). Flip-down dust shield removed for better clarity. It was my first MC type, and I believe it was Ortofon's entry-level MC at the time. It came with the matching transformer that seemed to work well with the PL 2000-II that was paired with the 400-II and formed the core of my system at that time.

I should also note that the speakers I used back then were also made by Ortofon, their top of the line at that time, Model 445 that boasted a pair of 8" woofers, mid and tweeter - as well as 2 aperiodic ports for the woofers. The drivers were made by Scan-Speak, a relatively newcomer at that time, so I have been told. I still have the speakers in use in the garage system ... still sound fine, but pale in comparison to the a/d/s/ L1230 that are on the main system now.

Attached some pictures of the teardown and repair...note the rubber belts were in very good shape, so I flipped them over as they had some "memory" bends from the spindles. Also reconditioned the rubber with "Gummy Pfledge" ... BMW guys know about this magical stuff!

Glen is working on a cool phono preamp for MC and MM cartridges ... he gave me the motivation to reopen this old turntable. Onward to building the same preamp he has started!

IMG_9486.jpeg
 

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e30m3mon said:
For now, I reinstalled the Ortofon MC10 cartridge that I bought new with the turntable (back around '81 or '82). Flip-down dust shield removed for better clarity. It was my first MC type, and I believe it was Ortofon's entry-level MC at the time. It came with the matching transformer that seemed to work well with the PL 2000-II that was paired with the 400-II and formed the core of my system at that time.

I should also note that the speakers I used back then were also made by Ortofon, their top of the line at that time, Model 445 that boasted a pair of 8" woofers, mid and tweeter - as well as 2 aperiodic ports for the woofers. The drivers were made by Scan-Speak, a relatively newcomer at that time, so I have been told. I still have the speakers in use in the garage system ... still sound fine, but pale in comparison to the a/d/s/ L1230 that are on the main system now.

Attached some pictures of the teardown and repair...note the rubber belts were in very good shape, so I flipped them over as they had some "memory" bends from the spindles. Also reconditioned the rubber with "Gummy Pfledge" ... BMW guys know about this magical stuff!

Glen is working on a cool phono preamp for MC and MM cartridges ... he gave me the motivation to reopen this old turntable. Onward to building the same preamp he has started!

View attachment 74833
Click to expand...
fascinating!!!
 
My beautiful PL-L1000 stopped tracking. It was intermittant at first, but eventually even the rotary position failed to move the arm. I hoped it wasn't the CdS cell in the arm carriage, but realized that it had nothing to do with the rotary movement control. I tore it apart and dismounted the circuit board, got all the cap values from the board- not the parts list or schematic- and replaced them. I never thought there was such a thing as a non-polarized electrolytic- I always thought that electrolytics were polarized by nature!

Works perfectly now, except one thing- misses the edge of the record by about 2mm. The wiring harness isn't long enough to connect the front panel controls with the top cover disconnected to adjust the pots. I can live with that, just can't depent on the automatic start when I press the button.PL-L1000 BOARD_sm.jpg
 
Parts list for the PL-L1000 / PL 8000 series two if anyone else decides to do the same. Provided to save time for others...
For $20.68! Saved the expense of a new TT!
 

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laatsch55 said:
I have tested many transistors. Even if they pass the diode junction test, they can have ZERO gain..
Click to expand...
I second that motion...
I finally found a decent Transistor Tester, a Sencore TF-151A. I had to change out the electrolytic capacitors. There are better transistor testers out there (I think the TF-166 has more bells and whistles), but this one does test Gain in a High and Low range (Power and Signal transistors). Most of my measurements are for comparison and matching, so the absolute values are not that important to me. I have discovered several "bad" transistors that might have passed the diode junction tests or were not showing a direct short to the casing.
So much better than swapping digital VOM leads.

The fun part is measuring some original Phase Linear XPL909 NPN transistors. They typically measure 10-30 Gain, compared to the ONSEMI MJ21196G, which always measure a very consistent 50 +/- 5 Gain. But I occasionally find a XPL909 with a gain of 9 or 4, or 2!
Again, these are the numbers from my Sencore, not absolute values.
 
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