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Consumer Scopes?

watchnerd

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#1
While searching for a vintage phono pre / tape head amp, I discovered that way back in the day, McIntosh made consumer scopes.

I know why you'd use a scope in the lab, but why would these have been sold to end-user consumers? What were they used for?







 

Blumlein 88

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#2
I never heard of these before. Marantz made a tuner or two that had scopes in them for optimum FM performance. You could see multipath and see if your tuning were dead on. It frequently drifted in the old days.

I found this:

http://marantzpassion.blogspot.com/2012/08/the-mcintosh-mi3-performance-indicator.html

I know a few tuners used to have o-scope outputs so you could do the same with an external scope. I once had a Heathkit oscope which was small for a tube unit, and low bandwidth, but plenty fine for this purpose. I used it for that and trouble shooting. Picked it up for $10 at a yard sale somewhere.

I guess this is just the same idea optimized for audio in a pretty case. Use for FM, use for testing, use for checking vectorscope like imaging of stereo signals.

http://sportsbil.com/mcintosh/Scope/MPI4/MPI4_own.pdf

Owners manual here. You kept it connected so you could see how your system was performing including phono, FM, and power amp. Combine with test record signals and you could do a system check at any time. I guess you could use a switchbox, and something like the $79 DAC and a computer for the same purposes today if you wished.
 

watchnerd

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#3
I never heard of these before. Marantz made a tuner or two that had scopes in them for optimum FM performance. You could see multipath and see if your tuning were dead on. It frequently drifted in the old days.

I found this:

http://marantzpassion.blogspot.com/2012/08/the-mcintosh-mi3-performance-indicator.html

I know a few tuners used to have o-scope outputs so you could do the same with an external scope. I once had a Heathkit oscope which was small for a tube unit, and low bandwidth, but plenty fine for this purpose. I used it for that and trouble shooting. Picked it up for $10 at a yard sale somewhere.

I guess this is just the same idea optimized for audio in a pretty case. Use for FM, use for testing, use for checking vectorscope like imaging of stereo signals.

http://sportsbil.com/mcintosh/Scope/MPI4/MPI4_own.pdf

Owners manual here. You kept it connected so you could see how your system was performing including phono, FM, and power amp. Combine with test record signals and you could do a system check at any time. I guess you could use a switchbox, and something like the $79 DAC and a computer for the same purposes today if you wished.
I was thinking it could be used to check cartridge azimuth on an LP system...
 

watchnerd

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Yes, the manual covers that.
Yep, just found that! Thanks for the link to the manual.

Could be a pretty fun toy...

This makes me think that one of the biggest benefits of analog is that it's so finnicky and flawed it gives you a whole raft of things to play with, tweak, optimize, etc.

Except for room correction, digital really gives the user nothing to do, so they end up being drawn to magical tweaks for the sake of something to play with.
 

NorthSky

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#8
Wow, educational read.


Design
"The R-390A is a general coverage radio receiver capable of receiving amplitude modulated, code, and frequency shift keying signals. Its tuning range is from 500 kilohertz to 32 megahertz, in 32 one-megahertz bands. The circuit is the superheterodyne type, double conversion above 8 MHz, below which triple conversion is used. It employs 26 vacuum tubes(6AK6 x 3, 5654 x 2, 12AU7/5814A x 2, 26Z5W x 2, 3TF7 x 1, 6BA6/5749W x 6, 6C4/6100 x 3, 6DC6 x 1, 0A2 x 1), a larger than normal count for most general-coverage receivers. The receiver weighs 85 pounds and can be operated on 120 volt or 240 volt supplies. It fits neatly into a 10.5 inch-tall standard 19 inch equipment rack.

Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front-end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing. Each major area of the receiver is contained in easily removable subassemblies, and these can be repaired or replaced as needs be. Though the R-390A is mechanically and electrically complex, alignment and servicing were designed to follow simplified procedures published by the Signal Corps."
 
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watchnerd

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#9
Wow, educational read.


Design
"The R-390A is a general coverage radio receiver capable of receiving amplitude modulated, code, and frequency shift keying signals. Its tuning range is from 500 kilohertz to 32 megahertz, in 32 one-megahertz bands. The circuit is the superheterodyne type, double conversion above 8 MHz, below which triple conversion is used. It employs 26 vacuum tubes(6AK6 x 3, 5654 x 2, 12AU7/5814A x 2, 26Z5W x 2, 3TF7 x 1, 6BA6/5749W x 6, 6C4/6100 x 3, 6DC6 x 1, 0A2 x 1), a larger than normal count for most general-coverage receivers. The receiver weighs 85 pounds and can be operated on 120 volt or 240 volt supplies. It fits neatly into a 10.5 inch-tall standard 19 inch equipment rack.

Tuning of the R-390A's radio frequency and intermediate frequency front end is synchronized by means of an ingenious mechanical system of racks, gears, and cams. When the front panel tuning controls are rotated, this system raises and lowers ferrite slugs in and out of the receiver's tuning coils. This ensures that all front-end circuits are tracked, meaning all circuits are tuned to the correct frequency to maintain excellent selectivity and sensitivity. The receiver's construction is modular for easy servicing. Each major area of the receiver is contained in easily removable subassemblies, and these can be repaired or replaced as needs be. Though the R-390A is mechanically and electrically complex, alignment and servicing were designed to follow simplified procedures published by the Signal Corps."
Isn't moving slugs around how all pre-quartz tuners worked?

I remember seeing the guts of a vintage receiver and was shocked how mechanical it was.
 

Blumlein 88

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#10
Isn't moving slugs around how all pre-quartz tuners worked?

I remember seeing the guts of a vintage receiver and was shocked how mechanical it was.
Some used variable capacitors.
https://en.wikipedia.org/wiki/Variable_capacitor


I used one as a tuner for LP cartridges in a circuit once. Worked pretty well. The capacitance in the phono leads would alter cartridge response. You could use this to tune the result within reason.
 

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