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My DIY Audio Scope so far (will update)

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Wurly1

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Here's a tricolor meter project i made some 3 years ago for a jukebox.
red is for bass, green for mid and blue for high.
I'm thinking about using the same technique and use color to separate front from rear instead of bass vs treeble.
What do you think?
 

Jim the Oldbie

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Wow, is that an NSM jukebox? My first real job in high school was working for a local guy, fixing pinball machines and his fleet of NSMs scattered around the county. Haven't seen one of those carriages in over 40 years...
 

Wurly1

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Wow, is that an NSM jukebox? My first real job in high school was working for a local guy, fixing pinball machines and his fleet of NSMs scattered around the county. Haven't seen one of those carriages in over 40 years...
Yes i bought NSM carriage parts and my goal is to design new control circuits from ground up using TTL logic, transistors and relays and put all this in the smallest coolest cabinet.
I managed to make it work and select correctly few times but i had to put this project aside. Since retirement is just around the corner I intend to resume work on it in 2021 and maybe use a raspberry pi to provide touch screen control. I still have to learn to code with python do.
 

Jim the Oldbie

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That sounds like a fun project! If I may stray from the topic just awhile longer: Does your carriage have the core memory or the motorized pin selector underneath?

(Your LED meters look bitchin' by the way.)
 

Wurly1

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That sounds like a fun project! If I may stray from the topic just awhile longer: Does your carriage have the core memory or the motorized pin selector underneath?

(Your LED meters look bitchin' by the way.)
Thank you for the LED meter comment.

The record tray does not have any selection pins, when the carriage is moving, two opto-couplers fed through a comparator and counter tell the record positions of the carriage. The position is then compared to the memory containing the selection information (1 = play, 0 = continue). the mechanism in the carriage have a selenoid which when energized, toggle into "load and play the record" at the end of the record, the mechanism return to scan mode. At the left end of the record tray there is a pin than physically toggle a switch on the carriage thus reversing the carriage from left to right. The same thing happen on the right "Home" position.

 
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Jim the Oldbie

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Thanks for the additional video, that really takes me back.

That rack & carriage looks very similar to the ones I used to service, but also a bit different. The optical seek system must be a newer development, or did you DIY that part?

As you may know (and if I remember correctly), back in the late '60s/ early '70s, NSM used a real magnetic core memory for record selection, using tiny ferrite cores & wiring just like the computers of the day. But after a court loss to Seeburg, who was using the same type of system, NSM had to revert to a motorized sliding pin arrangement under the rack, which was a step backward technologically.

That's the reason I asked about yours - the mag core setup relied on a faint 1 uS pulse from the cores to detect the selected positions in the rack, and might have been more of a challenge to DIY, heh.

As for the topic: I've been wanting to throw together a simple analog quad "vector-steering" circuit to use on the front end of an old dual-channel CRT scope I no longer use at work. But awhile back it occurred to me that I no longer have an easy way to connect something like that to my system! Everything is digital right up to the power amps, with separate analog outputs for each woofer, tweeter & midrange coming out of a pair of miniDSP nanoAVR-HDAs (see avatar).

I'll have to keep any visualizations in the digital realm, since that's where the audio lives for the most part. Not that I'm complaining - I absolutely love the sound - but things sure ain't as simple as they used to be!

Oh well - another reason to get back into coding, which I've missed.
 

Wurly1

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As you may know (and if I remember correctly), back in the late '60s/ early '70s, NSM used a real magnetic core memory for record selection, using tiny ferrite cores & wiring just like the computers of the day. But after a court loss to Seeburg, who was using the same type of system, NSM had to revert to a motorized sliding pin arrangement under the rack, which was a step backward technologically.

That's the reason I asked about yours - the mag core setup relied on a faint 1 uS pulse from the cores to detect the selected positions in the rack, and might have been more of a challenge to DIY, heh.
This is from one of their last models using ortofon cartridge.
I removed the front tone-arm protective harness, that make it look much different.
The sensor module was part of the carriage. There's two sensors close to each other and a rotating disc making one turn every time the carriage advance one position. when the carriage goes in one direction, sensor 1 pick up the pulse signal before sensor 2 and if sensor 2 pick up de pulse signal before sensor 1 it means the carriage goes in the other direction. All i had to do was to normalize these pulses using NE555 and then decode these pulses with logic gates to generate pulse on the up or on the down pin of a counter.
Simple in theory but a bit challenging.
I like using older technologies like TTL logic and static memory.
That's what i studied back in early 80's at college.
A lot of fun finally! lol
 
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