My Pioneer PL-400 turntable is not maintaining speed, it will work sometimes, then when he operates for a while the speed will increase. I suspect capacitors mainly because the turntable was built 40 years ago in 1980. I has a couple odd capacitors that I want to check with the experts on. One is a .47uF tantalum, C5, that runs from one of the buffer amps in IC2 to ground. Any reason I couldn't replace that with a film capacitor? The IC's use ceramics to decouple and a couple for timing, C14&C15, around the crystal, X-Tal. Could I replace those with film capacitors? The last one I have a question about is C8, an electrolytic 1uF, 50V, could that be replaced with a film cap? I suspect cost in 1980 drove the selection of the caps and space for the tantalum cap, but pretty sure I can find a cheap small film cap that would work, if the tantalum wasn't selected for a specific purpose.
View attachment Scan20200815131635-0.pdf
View attachment Scan20200815131635-0.pdf
First, concern yourself with the speed pots - VRxx's
Use a good contact cleaner such as Deoxit in them, work them back and forth a number of times, and spray again, repeat.
They get dirty over time.
Observe any change, if good, you're done.
If no change, THEN worry about ripping out capacitors.
Use a good contact cleaner such as Deoxit in them, work them back and forth a number of times, and spray again, repeat.
They get dirty over time.
Observe any change, if good, you're done.
If no change, THEN worry about ripping out capacitors.
the speed pots are trimpots on the circuit board and locked with paint. I did check them with an ohmmeter and they read a very consistent reading without changing. I will measure them again, write down their reading and give them a cleaning. Then I should be able to return them to their original value.
I originally thought it had something to do with the speed select switch. I did clean it with Deoxit and thought it fixed it, but it didn't. It is one of those intermittent problems that can drive you crazy. I am not an electronics tech, but have taught automotive technology for 35 years.
Testing the contacts of the speed select switch is an easy task.
The contacts should read 0 ohms when closed, and repeated switching should result in the same reading each time, without fail.
The contacts should read 0 ohms when closed, and repeated switching should result in the same reading each time, without fail.
If you really decide to replace the pots, it might be better to adjust the correct speeds afterwards with the use of a stroboscopic disc or a smartphone app, for instance the RPM calculator.
Best regards!
It's not the trim pots or the speed select switch. After sitting overnight it works perfectly for about 15-20 minutes, then slowly starting speeding up, then goes crazy spinning so fast it gets out of balance.
I bought all the caps to replace the originals using the same types of caps and the crystal for less than $20 at Mouser.
The manual describes using an oscilloscope to set the speed system, I'll do that after replacing all the parts.
I bought all the caps to replace the originals using the same types of caps and the crystal for less than $20 at Mouser.
The manual describes using an oscilloscope to set the speed system, I'll do that after replacing all the parts.
That sounds like it could be temperature related. Make sure all mechanical fasteners are tight, and look for any iffy solder joints.
Agreed, already checked all that, re-flowed any iffy looking joints, cleaned all connections with Deoxit.
I have located the bad part. The Pioneer PD1003 chip has went bad, shorted internally, dropped input voltage to 2 volts, took the chip out input voltage came back up to expected 10 volts.
Anyone know where I can find one of these chips? I have searched online.
They were used in PL-300, PL-400, PL-500, PL-600 and PL-L1000 turntables and in the CF-F1250 tape deck.
Anyone know where I can find one of these chips? I have searched online.
They were used in PL-300, PL-400, PL-500, PL-600 and PL-L1000 turntables and in the CF-F1250 tape deck.
Found an interesting technical article you might be interested in https://www.google.com/url?sa=t&sou...FjABegQICBAB&usg=AOvVaw1edYod7By-F85Y0smGt1Ls
I've seen that and it's a last resort, I didn't like his feedback numbers and am worried about getting a fake or none working chip.
Was hoping someone on here would have a non-working model sitting around.
I'll try the ebay connection as an absolute last resort.
Was hoping someone on here would have a non-working model sitting around.
I'll try the ebay connection as an absolute last resort.
Thanks, that's the article that helped me diagnose the problem. I'm also considering building a circuit to frequency divide down to the two frequencies I'd need for 33 1/3 operation only.
Could this be the same chip? If so, there are numerous available on the internet. https://www.google.com/url?sa=t&sou...FjABegQIBRAC&usg=AOvVaw1VmfEt4I0Qo3zKP_OX8UrS
I am also facing exactly same problem like you with my JVC LF-71 DD TT 🙁
Once it cools down and I turn it on it run at right speed for 10-15 min and later starts spinning like mad😱
I am sure its not the issue with speed control circuits or loose connections etc.
and I think problem lies within motor circuit and wanna fix it but the thing is I just have basic knowledge of electric components, could you please guide me how you found out that the issue is in IC?
My TT motor is DD DC servo and have similar kind of IC like yours(NEC VC1029) so how could I test if it working fine?
kindly advice.
Attaching snap of the motor circuit:
Attachments
I have no idea without a service manual and schematic of the circuit.
You might want to take a look at the attachment a couple posts above, it describes how the Pioneer systems work and your looks kind of similar. I do know Pioneer let other vendors use their technology
You might want to take a look at the attachment a couple posts above, it describes how the Pioneer systems work and your looks kind of similar. I do know Pioneer let other vendors use their technology