Sharp vz 3500 Turntable problem

[Flamgewarble]

Hi all, I see someone else has had this problem but it doesn't seem to have been resolved in the thread.
I have a sharp vz3500 with the vertical turntable, I am having trouble with the arm tracking, basically, it doesn't but ff rw etc. All work, it's just when you're playing a record the arm isn't tracking, I have tried a couple of different belts on the arm motor but that's not worked, any ideas? I know there's a little LED sensor on both of the arm assemblies but I can't imagine they have both failed. Any help would be greatly appreciated as it's the last bit of the puzzle, I have got everything else working

 

[flavio81]

You should ask a moderator to move your post to the Turntables sub-forum, this is the Introduction sub-forum.

 

[avionic]

Welcome aboard Flamge

Please read this thread before you post; The Introductions forum is for INTRODUCTIONS

If you are new here please read the AK rules to avoid problems here. Also if you have questions search out the appropriate forum to ask your questions in. Thank you very much. Mike

www.audiokarma.org

 

[squirrelnest]

Welcome to the forum from Virginia.

 

[jbrainey]

Hello and welcome to Audiokarma.org!

 

[Hyperion]

Welcome to AK!

 

[Flamgewarble]

Thanks for the warm welcome, it looks like someone's moved this for me, sorry, just learning my way around the site.

 

[maxhifi]

First of all, download the service manual, I found it online easily.

The tracking error circuit is shown in detail in the manual. It looks like both phototransistors are in parallel, and whichever one is receiving light is providing an error signal to the jungle control IC through a transistor. To troubleshoot this effectively you will need to make measurements at the IC to make sure it's actually getting an error signal, then figure out if the motor driver is working right. It looks like quite a complex circuit, and a defect in any part of it could render it non functional, so it is difficult to troubleshoot remotely. Most of it is shared by both arms though.

You also want to have a look over the mechanical side of things and make sure any replacement belt isn't too loose or too tight, and that the arms can move freely and nothing is binding.

I have never worked on the Sharp plays both sides turntable but I do have a Sansui which is similar, and it was a bit it a chore to make it work properly. The main defect of this kind of turntable is noise from the record flopping around and being undamped and unsupported. I used mine a ton though and loved it, hopefully yours will also come to life.

 

[Flamgewarble]

Hi maxihifi, thanks for the reply, I have the service manual which I need to study and see if it makes sense to me, I'm not the best at fault finding, everything so far has been mechanical and belts, it's doing the same thing on both sides which, to me suggests it's unlikely to be the sensors and more likely to be further down the line, as you say, something more circuit board related.
The motor works fine as you can ff and rw.
I will update with my findings if I get anywhere.

 

[maxhifi]

Hi maxihifi, thanks for the reply, I have the service manual which I need to study and see if it makes sense to me, I'm not the best at fault finding, everything so far has been mechanical and belts, it's doing the same thing on both sides which, to me suggests it's unlikely to be the sensors and more likely to be further down the line, as you say, something more circuit board related.
The motor works fine as you can ff and rw.
I will update with my findings if I get anywhere.

Just be persistent, and methodical. Look at every pin on the big control IC and think about what voltage value they need to be for the turntable to work. Also consider that any reed switch or micro switch could also be a cause of trouble

 

[Flamgewarble]

After putting this aside for a few weeks I went back to it today and discovered a capacitor with a snapped leg, then spent some time studying the circuit diagram to find out where it had come from, which was much easier once I'd printed it out, I don't recommend trying to study it on your phone, lol, anyway, I think I have worked it out and have soldered it back in place, tomtom

 

[Flamgewarble]

Tom Tom?! My phone had a senior moment then, so, tomorrow I will put it back together and see if I got it right.

 

[ranf1970]

If possible, I think it would be better to replace the capacitor than just solder the snapped leg.

 

[Flamgewarble]

If possible, I think it would be better to replace the capacitor than just solder the snapped leg.

Hi ranf1970, that's a good idea, I will see if I can order some later.

 

[Flamgewarble]

Well, I replaced the capacitor and it's still doing the same skipping thing but now forward and back functions have slowed down to a snails pace, any ideas?