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Messages - Motorola Minion

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1
Music / Aretha Franklin
« on: August 17, 2018, 08:08:54 AM »
As we have lost one more great talent, I was fortunate enough to hear the Queen of Soul cover "Long and winding road" in a way Paul and the Beatles probably never imagined. I had just missed her cover of "walk on By" unfortunately. So I'm looking on youtube now and imagining how it would have sounded.

Her vocal range was all the more sweet and nostalgic heard through a 1965 "last of all tubes" Zenith Console as I boxed in the speakers. Being one of the last all-Beatles songs, it was always bittersweet anyway, yesterday it was more so :'(

2
Motorola / Re: Motorola Stereophonic SK107 - Phono with Vibrasonic
« on: August 16, 2018, 12:35:17 PM »
It is just too hot, muggy and awful to enjoy my old car sitting next to it, I manage to make progress on this junior Motorola Stereophonic. All I need is a good fan and some fantastic sounds to be happy in the garage these days.

It's been belting out Henry Mancini's greatest hits LP and Three Dog Night CD. It sounds with these extreme music genres like it should too ;) The chassis, Both preamp and amp have been recapped, cleaned and tested. Its nice to NOT have a tuner in this compact model but it was an option suffix-FM.

After plugging in the tubes and powering up, I measured power supply and tube voltages to find all within a small range of spot-on with the Sams schematic. I installed a terminal strip between the 6BQ5's and 6V6's which allows easy measurement of output tube cathode voltages and confirming resistor values without removing the chassis, held down with 10 bolts. The 6V6 pair for the bass/vibrasonic channel is about 20 volts and each of the single-ended Mullard-sourced 6BQ5/EL84 were a bit higher than listed at 8.25 and 8.5 volts. Mullard and Amperex tubes are considered valuable mainly due to longevity. Many of the original 6BQ5 used in Zenith and Motorola plus a few Maggies were either "made in great Britain (or Holland)". USA mfrs made great 6V6 and 6L6 but a difference with a 6BQ5 is noticeable with the ear and confirmed with a meter: European-made EL84's have higher quiescent cathode current set-points. I can expound further once I restore my 3 RCA's that all use 6BQ5, bothe single-ended like this and push pull, in a Fisher Electra 7 using a 481A amp and a Magnavox Symphony with the 9300 amp. .

After playing some demanding orchestral tracks on the record changer (borrowed from my restored Motorola using a Sonotone 9t cart) and through the radio (using the stereo input option), using a classic Rock CD - The cone tweets sound great, but I wonder what subbing in some Mag Kilocycle horns would sound like. 8)

This console is the entry-level stereophonic yet almost as rowdy as my two bigger Stereophonics both using 6 x 6V6 and a 12" or 15" woofer. Specs say EIA 20 watts for the little guy and 51 watts for the bigger ones. 

The loudness is great at 3-4, staging with wide open sound - but as you pass 7, the Bass needs to be dialed back from 8 to 6, or else the 10" woof gets saturated. The vibrasonic effect barely worked until I saw a shipping pin still in place to keep the reverb tank springs from moving. I was wondering what that long string from the reverb was. A tage was at the other end. It was gone but I bet it stuck out of a back cover hole and instructed you to "pull out the string" after the console was delivered.

This console was never serviced, yet working as most are found. This will be confirmed when I start working on the 1200 series V-M changer. For now, im using my other changer while I work on it. Im waiting a week to do that for more Zoom-spot turbine oil to come in the mail.

For now, the cabinet is really dirty so I have to do that in the meantime - Ill post that easy clean-restore-a-finish and wax next.

3
I have two spare Magnavox transformers. One from an AMP-142BC.

4
Magnificent Magnavox / Re: A tuber I am considering. Comments??
« on: August 14, 2018, 01:07:32 PM »
Persistence pays off....sometimes but I have CL replies routinely ignored even though I ask "when can I come look" Some folks must be afraid to meet a potential customer :-\


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Magnificent Magnavox / Re: Magnavox Stereo Theater 1MR418M restoration
« on: August 10, 2018, 03:01:39 PM »
Greg,  You have an "FM stereo" position on the selector switch in addition to the "tape" , correct?  My 57-03 mag preamp-tuner only has "stereo" inputs for tape or phono.

6
Sightings / Re: 1963 RCA
« on: August 10, 2018, 10:25:01 AM »
So the RCA tuners drift?  I thought that was a Magnavox exclusive.  Is that a tube tuner?  Stereo or stereo compatible tuner?  Does it use an stereo decoder (multiplex adapter) of some kind?

See tag for my 3VF516, its an FM stereo tuner on one chassis. I have not played with it yet, as I have a more entry-level 1961 VCR244 "Living Stereo" RCA console to work on first.

The 6C9 is also in an Admiral tuner which has a hard time with its AFC, so I don't use it even though my key stations are below 91.9 Mhz and also happen to be stronger than their adjacents.

I agree with Greg about Mag tuners, the AFC action has to wide of a range for today's crowded band. Maybe RCA is similar, but I would expect a bit more sensitive. The design is certainly different.

Matter of fact, the 1963 Zenith I'm finishing up is working great and its plenty sensitive just like the Motorola tuners that use the German-made pull-string tuners employing the 6BQ7A. 

7
Zenith Solid State Discussion / Re: Different problem
« on: August 07, 2018, 12:29:51 PM »
Steve has looked at the schematic and so have I.  I can speculate that if you cannot get one of the #1819 indicators lit, one of the SCR's may be defective.

The circuit seems to be designed so that if the lamp is bad, a 10K resistor in parallel with it will allow about 2 ma of current to maintain the SCR's conduction.

One thing that jumped out at me was the card edge connectors that connect this PCB (switching module). If these could be pulled off, cleaned with deoxit and reinstalled,  trouble might disappear. Also, if the SCR for FM was swapped with AM or tape with phono, you'll find them defective. Also, a 1mf cap in each SCR anode circuit could be the problem.

Based on Steve's MM2670 description, my Z966 also has the same amplifier. Maybe the touch selectors were introduced on 1970 and later models. I bet not many high-end Zenith consoles made after your 1971. :-\

8
I want to preface this by saying that often, changers seem to work fine mechanically. When they don't, you need to mean business, so get down and dirty!

For oiling spinning metal parts, Zoom-Spout turbine oil must bein every record player toolkit. 3 in 1 type and sewing machine seems like appropriate vintage oil to use BUT it is generally sloppy and attracts dirt. Less is better, always.

I used to HATE doing record changers during the 80s, preferring the carried-in 9" to 20" TVs. The TV road tech pulled the changers from consoles and brought back to the shop for us bench toads, and as you can guess, peak season was October-December.

Doing changers was fun - like taking out the trash, so our service manager had a no-fail 8-step method we used on BSR, Magnavox and RCA units pulled from consoles and brought back to the shop by the road tech. "Just do it" I was often told when I verified it was operating correctly, and already looking for a new stylus (often in vain) in the dusty parts drawers.

Lubriplate or white lithium grease ( aka GC's Phono lube) is mandatory for all sliding parts. Go in ONCE with your best stuff and you'll own the repair. Just do it all, forgetting anything will make you repeat those annoying processes.

Isopropyl alcohol (IPA) and alternately, lacquer thinner, Q-tips and shop towels are all that is needed to clean off dirt-encrusted grease. it also does a great job on motor capstan "stepped shafts" plus the inside of the platter along idler track

Rubber-Renu is highly reactive oil of wintergreen and seems to work on most but NOT ALL idler pulleys to remove glaze. Only slightly more effective than IPA. If the pulley has deep fissures in the rubber, it probably overheated when the player motor was left on when it stalled, basically finishing off any chances for a lasting revival. Bite the bullet and replace it.

Bottoms-up work first

1- Mandatory motor maintenance - mark positions of every nut, 6-32 screw, washer, spacer and bearing bracket before you take ANYTHING apart. Soak those bearings first with IPA, using a cotton swab to pull the gunk out. Soak next with Zoom Spout or similar super-thin stuff.

2- Clean the changing mechanism with IPA and shop towels, and yes, you must take cycle gear-wheels off shafts or sliders out completely. Sliders on V-M players are tricky but you will not be successful without a thorough disassembly - cleaning and lube. trip levers that slide must be cleaned and having another player along side to compare whats out of place or bent cannot be understated.

Topside last

1- Pull off the platter from spindle. RCA's need a snap-ring pliers, Mags and BSR use a C-clip and V-M's use a small plastic O-ring and grooved center pin. Most are easy but on BSR's - spindle grease turns into JB weld, and must be soaked with lacquer thinner or worse to get it loose, spin-able and removable. I have yet to try "weasel piss" (WD40 or PB blaster) as it is hard to limit overspray.

2- Take idler pulley off and give it the business with IPA and oil the shaft/spring washers. Check alignment with the motor shaft thru all speed settings. If it does not land in the middle of a step, motor mount grommets are flat/gone OR if solid, it may be improper idle shaft washer placement.

3- Move center pin in/out, up and down while dousing with IPA to get ALL the crud out that causes it to drop two records or operate sluggishly. The tiniest bit of oil is all this part needs.

4- Platter spindle cage/ball bearings and washers need a thorough soaking and de-gumming, here we had success with lacquer thinner also. Pay attention to sandwiching the bearing between TWO thin washers. They like to stick and drop off during disassembly. To keep from hunting parts like those washers and center pin balls (V-M) that bounce off the bench, do your disassembling in a dishwashing tub or big cafeteria tray to catch anything that cuts loose.

5- The grand finale included checking speed with strobe disc under light from incandescent or fluorescent on magnetic ballasts. Try all record sizes/rpms and verify it worked on the 45 adapter, run through all cycles and at 78 (or 45) rpm to distribute all the oil and exercise every operation.

It always worked, no call backs, all the more reason to love Magnavox and RCA changers in particular.
About 5 years ago, I had to re-learn the whole process for Voice-of-Music changers, used in all my Motorola and Zenith tube sets.

I may post a thread on V-M by itself, renowned as rugged YET labor intensive to disassemble and re-assemble :P.

9
Would this fit in a 1964 Fisher or Sylvania I have where Garrard AT60s reside?

10
Zenith Solid State Discussion / Re: Different problem
« on: August 03, 2018, 08:16:57 AM »
Is your selector "switch" a touch-pad that employs a "solid-state" or CMOS chip to switch between tape-phono-am-fm, etc?.

This could be as easy as a replacing a socket-mounted IC chip, but Ill look up the Sams schematic to be sure.

If its the pushbutton type like the lower-priced B920/30/40 series, its only a matter of leaning the contacts and cleaning/lubing the pushbutton levers and sliders.

The tape motor will run if power is on regardless of whether the selector is there or no.

Only the phono position should transfer total power control to the record changer lever.   

11
Fisher / Re: 1955 the fisher electra in ebony cabinet ~ k-15 chassis
« on: July 26, 2018, 12:05:55 PM »
Great looking Fisher, appears a bit more loaded than later custom electras. I have two myself, a CE 7 last all-tube 1964, and an E492, full SS.

The Brilliance and Presence adjustments are very interesting to see in the age of mono, but do not mount on the chassis obviously. What are these connected to? ???

12
I have not finished putting together my 1962 Normandy with that 93-series amp and 57 tuner. I am hoping to make mine a better amp before I do. So...

I read some of your other posts about the 6EU7 being troublesome but otherwise electrically the same as the 12AX7.
Would you consider replacing the 6EU7 sockets (there is one in the tuner as well) and rewiring to use the 12AX7 instead?

13
Zenith / Re: 1964 Zenith console with drop-in tuner
« on: July 18, 2018, 09:20:43 AM »
After doing the soak and set on the originals, the mushy sound is gone ;D! The tone controls and bass boost operate as intended. I greatly underestimated how good the original speakers are and how tailored this amp is to drive them. The replacement speakers I got will have to be used in another project. Their specs, if accurate, were lost on this amp.

Now to how the speakers were "fixed": What I did was spray water onto both the cones from the front, being careful not to let the water run past the voice coil felt pad, then flipping them over and wetting the cone thoroughly from the back.

A local radio guy that posts on Videokarma clued me and several others into this trick. I have used on several speakers to date and I think I know what de-formed the cones.   

Most consoles live in a nice house but then moved to garages, basements and worse than that, out-buildings and barns. Rarely are they found in attics like old radios, heat does other nasty things to old rubber and plastic.

The speaker is mounted in such a way gravity is acting on the coil/cone assembly. Humidity causes the paper cone to deform and "droop" pulling the voice coil out of alignment.

What the wetting procedure does is make the cone pliable, then drying/setting with speaker in a vertical plane and allow the voice coil and spider assembly to "fall" back into alignment..

14
Zenith / Re: 1964 Zenith console with drop-in tuner
« on: July 18, 2018, 09:04:02 AM »
The FM tuner is now working as well as it ever has, no drift and stereo light on. The 6JK8 was substituted with a 6BQ7A/6BZ7, which works the best overall.

I tried other dual triode tubes used as RF amp/osc and most worked: 6BK7, 6AQ8/ECC85 that the Germans and Fisher used.
The 6AQ8 tested OK yet it did not produce a strong signal and the tuning had to be moved about .3 Kc, as an oscillator, differs in operating characteristics from the common 6BQ7. 

With no static from silver-mica disease on AM or FM :D, I can finally put this in the cabinet and re-visit the speakers.

 

15
Chat / Re: Just Missed The ZOT!
« on: July 16, 2018, 01:45:15 PM »
......  With the antenna reconnected last evening, I got many actual shortwave stations, over and above the domestic harangue stations.  I got Radio Romania for the first time.

No way a digital receiver with the same antenna would have survived. Thanks for the cautionary tale.

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