Author Topic: Help identifying the model number  (Read 882 times)

cmark115

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Help identifying the model number
« on: November 30, 2016, 03:46:39 PM »
I bought this mid 60's Motorola for my son.  It works well and sounds great.  The ID tag on the back is cut and the part with the model # is missing.  I'm just trying to find out the exact model so we can get manuals, etc and can date it.  I will attach pics and give you the data that I think I have figured out so far.

It's a "Custom 20", according to the control plate.  It has tube amps, the vibrasonic feature and the woofer is behind the center wooden panel.  I think its a 1963-64 era model. 

Any help is appreciated.

orotone

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Re: Help identifying the model number
« Reply #1 on: December 01, 2016, 09:29:46 AM »
A google search of "Motorola custom 20 console" brings back dozens of hits and pictures including various model numbers, etc.  I believe the cabinet is made by Drexel. There are a few youtube videos of Motorola consoles that may help as well. https://www.youtube.com/watch?v=L08NvT9gdqg or https://www.youtube.com/watch?v=bcC-L__Cz-s

cmark115

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Re: Help identifying the model number
« Reply #2 on: December 01, 2016, 10:05:55 AM »
Thanks!  Any leads help!  I've been hunting ebay and youtube and all kinds of sights looking for a match.
The closest I have found are these two, both with similarly size cabinets and inner controls that vary in the cabinet style.[http://mrsnicholsonhome.com/2015/10/07/1960s-motorola-custom-20-stereo/] or [https://www.youtube.com/watch?v=MJU1CnLl1ZY], but neither list the model number.

What I think I know is that Motorola introduced the vibrasonic feature in 1962 and that it ceased utilizing tube amps after 1964, so I think that is the date range.


Motorola Minion

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Re: Help identifying the model number
« Reply #3 on: December 01, 2016, 01:41:43 PM »
Correct date range. There is a 1963 catalog in the downloads section, tab at top of page.
I have 1963 and 1964 Motorolas with the exact same AM and FM dials but a different control layout. The model number would certainly begin with SK followed by a two or three digit number

The tuner-preamp and amp chassis numbers begin with an HS and the date might be stamped "8M64", etc
Tubes - Magical - Tubes

Dave

cmark115

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Re: Help identifying the model number
« Reply #4 on: December 06, 2016, 02:57:35 PM »

Dan,

I don't see the exact model in the 63 catalog.  There are a couple of models that are close; base cabinet looks same size but different finishes or center panels, etc.  The Touraine is one of them. 

I do know that the amp is HS1239B made in Oct of 63.  Not sure where to go to find out exactly what this is.

Mark


Motorola Minion

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Re: Help identifying the model number
« Reply #5 on: December 06, 2016, 04:02:08 PM »
The model may be an SKR-something as it is a 1964 with radio.
The 1964 Motorola catalog has the final year's tube models. I would personally buy and upload should on show up on epay. ::)
Tubes - Magical - Tubes

Dave

HiFiFun

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Re: Help identifying the model number
« Reply #6 on: December 09, 2016, 06:02:48 PM »
Mark,
I found your power amp chassis HS1239 in Sams Photofact # 707-9 from mid 1964 publication.
It is a hybrid transistor/tube console. Vibrasonic circuit included in the photofact.
It is a three channel stereo, with distinct bass channel for woofer.

There are four Motorola models listed in the photofact:
1. Model SK145
2. Model SKR145(tuner)
3. Model SK163
4.Model SKR163(tuner)
5. V-M record changer VM102RC

HiFiFun

cmark115

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Re: Help identifying the model number
« Reply #7 on: December 12, 2016, 02:36:33 PM »
Thank so much!   That is very helpful.  I have my record changer tag with the model number, which is a V-M make.   I didn't realize that the amp was both transistor and tube.  I did notice from the outputs that it was three channel.

I will dig around and see if I can match it up to the models you listed.

Mark

HiFiFun

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Re: Help identifying the model number
« Reply #8 on: December 12, 2016, 06:51:33 PM »
To clarify, the transistor circuit is in the FM tuner circuit.

HFF

Motorola Minion

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Re: Help identifying the model number
« Reply #9 on: December 16, 2016, 12:52:09 PM »
Very interesting that Motorola employed transistors first in the tuner and did not introduce them first as audio pre-amps-outputs like RCA and Zenith did. I suspect that your tuner performs a bit better than the tube cascode units in earlier Motorolas. In my opinion, the tubes drifted a bit over hours of operation though were selective as a Zenith.

There were many models and variations of Motorolas, judging by the different Sams sets in the 600-700s, probably due to variations like the tuner, preamp, verbaphonic and non-reverb layouts. The variety from Motorola seemed to drop off while Zenith, Magnavox, RCA and even Admiral increased their product lines (and power output levels) after going transistor.

See if yours has the preamplifier stages on a separate chassis from the amp and tuner. Many Motorola consoles did this so the same amp chassis could be used in case a tuner was not included all the models.

Magnavox in comparison had a different amp for phono-only models. An example is AMP175 versus AMP185 for the phono-only model.
It seems logical the source selector and controls would AT the 12AX7 preamp stage instead of cables to the controls from the amp or tuner chassis. 
These are just plain fun to work on but you need to patiently take it ALL  :P out and make notes how the cables are routed.
Tubes - Magical - Tubes

Dave

TC Chris

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Re: Help identifying the model number
« Reply #10 on: December 16, 2016, 06:55:47 PM »
I was thinking the same things about how odd to have transistors first in the tuner.  That was the last use of tubes--the Nuvistor--for many devices.  As I understand it, they were lower-noise and handled overload better than early transistors.   I've got an early all-transistor Fisher 600-T receiver, a curbside find (together with a Garrard Lab 80 changer).  I took them  home and plugged the receiver in and heard only hiss.  I was a bit discouraged, then the hiss dropped and the FM tuner worked.  Afterwards I looked and found two Nuvistors in the front end.  They took a few seconds to warm up (hiss time) until they were conducting (FM heard).

By the way, within 1/2 mile of my house I've found that Fisher and a Sansui all-tube 1000A receiver (it has transistors in the phono preamp), both at curbside.  Also a Heathkit console. 

Chris Campbell

electra225

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Re: Help identifying the model number
« Reply #11 on: December 16, 2016, 07:14:52 PM »
I have an SK-176-W from 1965.  I still have the original bill of sale, owners' manual and all the literature and packing materials original to the set.  Mine is a bit later than the one featured, but is a pretty stout performer for a small and relatively inexpensive console stereo.  The redeeming features of mine outside of its documentation is the Drexel cabinet.  The literature with mine tells " the eight-tube chassis gives the performance equal to the finest solid state sets."  Mine has a hybrid chassis, with tubes in the front end and solid state components serving in detector, limiter and FM detection duties.  Mine has a 12AX7 pre-amp and 50HN5 audio output tubes.  Probably someplace around 5 watts per channel.  The FM stereo tuner is less prone to drift than my Magnavox tube tuners are.  Mine has the two large seperate knobs for AM and FM and the four small controls in a quad much like the one pictured.  I have the same amp and changer in a table model stereo as well, an SK-98-A.  The VM changer has a very light tone arm and is easy on records.  My console has a bad cartridge that may be unobtanium.
If it ain't broke, call me.  I can break it....

Ken Doyle

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Re: Help identifying the model number
« Reply #12 on: December 16, 2016, 07:47:08 PM »

I've found that Fisher and a Sansui all-tube 1000A receiver


That's a gem!  Overhaul it and enjoy it.  Separate bass and treble for each channel, and a real hi-fi AM tuner section.  The output transformers are famous for their quality.  One of these days I have to dig mine out the basement and overhaul it.  The Sansui 1000A is one of the most respected receivers of the late tube era.

TC Chris

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Re: Help identifying the model number
« Reply #13 on: December 16, 2016, 10:21:38 PM »
For the Sansui, replace all those evil oil capacitors!  Mine had been discarded because somebody replaced all the tubes, including the 7591 outputs, and then one of the outputs self-destructed.  They apparently didn't want to throw good money after bad so they set it on the curb.  I threw a bit of money and work into new caps.  I found an extra, not matching 7591 in my tube stash and it was AOK.  Online sources suggested that the oil caps were a common failure mode, and mine demonstrated that it's true.

Chris Campbell