NSM City 1 record selection fault

[graham8rdx]

Hi Hi everyone,thanks for letting me join...
 could someone please suggest why the MO relay would loose drive current and open immediately after the carriage moves out from the parking location? If I then manually hold the MO relay closed the carriage will then proceed to travel to the selected slot and continue to load and play the record ... is there another signal responsible to maintain the drive to keep the MO relay closed once the carriage has moved off from its home stop?
hope you don’t mind my direct questions and thank you in advance for your reply
kind regards Graham

[jukenorman]

Hi Graham,
Possibly the operating switch BS is faulty? You haven't said whether you're equipped with documentation but some quite poor quality manuals can be found at
nsmjukeboxmanuals.yolasite.com/manuals.php which would be good enough to idemtify the location of BS but not great for schematics. You can find info on contact cleaning in the stickies.

Norman.

[graham8rdx]

Thanks For your reply Norman,
Unfortunately I don’t have any schematic for the NSM .. I had found the repository you mentioned on the Internet but there only seems to be diagrams and parts lists but no circuits...
Is the switch you speak of the scan button located on the motor drive board? Or something on the carriage itself?
By the way if I hold the reset button down on the volume box the MO relay closes and the carriage moves and the selection completes in the same way as me manually holding the MO relay closed !
If I can trace the source of the signal that should be energising the MO relay after the carriage has started its move to select a record I would be close to finding the fault
Again thank you for your reply Norman

[graham8rdx]

Ahhh... found the switch BS on the carriage... I will check it’s operational tomorrow... should this deliver current to the MO relay or should it deliver drive power to the carriage motor once it has left the home position?
Kind regards GrahamK

[graham8rdx]

Looking at the BS switch measurements all seems in order... although one position has a slight contact resistance ( between 2 and 3 ohms)...
Should the carriage also have a Reed switch in parallel with one side of the BS switch? Or is that on the later version of the carriage?
Kind regards Graham

[jukenorman]

Hi Graham,
I think your best bet is to make up a little lamp tester with a battery and light bulb and test the BS switch using the lamp. Measuring contacts by resistance (especially with a digital meter) is fraught with problems and is well documented all over this forum. And if you're getting 2 or 3 ohms with a meter, it almost certainly points to the switch.

Norman.

[graham8rdx]

Hi Norman, you were bang on with the BS switch.... turns out the normally closed contact in the switch is open circuit... I ve ordered a replacement micro switch

Thanks for your help
Kind regards GrahamK

[graham8rdx]

Hi Norman, selection and play is all good now... however I have low level sound with some distortion on left channel... if I swap over the preamp pcb’s the problem moves to the right channel... do you have a schematic of the Amplifier preamp pcb?
Thanks in advance Graham

[jukenorman]

Hi Graham,
I don't actually have a lot of NSM documentation. If your amplifier pre-amp is the same or similar in layout to the one in the ESII service manual (page 62) on the NSM manuals site in the second post, then I have a diagram.

Norman.

[graham8rdx]

Yes Norman, that is the same PCB with 2x d4007 inverter integrated circuits
Thanks GrahamK

[jukenorman]

Hi Graham,
I have a paper copy that I can send you if you message me your address. There is no need to return it.

Norman.

[graham8rdx]

Thanks for looking at this Norman,
Btw how is your 1493? I’ve rebuilt 2 of these over the years and know Rockola well...
Could you possibly take a photo of the preamplifier part of the diagram and message it to me?

[jukenorman]

Hi Graham,
I have sent your diagram by post, you should now probably delete your address from a public forum. Also check your private messages.

Norman.