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Tube Amp - Capacitor Cross Reference?

either someone didn't spring for the MPX, or it wasn't actually available. The official standard wasn't settled until April 1961, though it was known to be coming before that point. If this was made before then, it wouldn't have shipped with an MPX because officially it didn't exist at that point. Afterwards it was probably an optional thing. Not everyone lived where FM stereo was a thing, so maybe it wasn't an option that people cared about. FM wasn't the main radio system until the 70s anyway.
 
Thanks for the info, Gadget. I going to leave things as is, but if I ever find a deal on a compatible MPX, I can always add after the fact. Besides the actual Motorola MPX units, would a tube MPX unit from the likes of Knight or Bogen with the MPX RCA input and the L-R channel RCA outputs possibly be options, or would I really need to stick with one from Motorola to be compatible?
 
honestly a solid state one would probably be a better solution. Tube MPX units are kind of fussy, and if its not stand-alone it would have to plug into a socket someplace on the tuner that you'd need to know the proper connector for along with where it puts what voltage to see if its compatible. I have one robbed out of a junked 70s Pioneer receiver for my console.
 
Yep, I was scratching my head! But, since the model is from one of the first years of FM stereo, maybe the original owners just waived off on such extravagance, like Gadget suggested.

Speaking of head scratcher, I had a dummy moment today (which is fairly common for me). I cleaned the record changer motor today, just to see if it was “alive” and worth continuing work on. The phono power harness comes from the tuner vice the pre-amp, and while I turned the pre-amp setting to “Phono” I neglected to .... wait for it ... shut off the tuner. So, nothing happened when I turned on the record changer. Checked the voltage coming from the harness on the tuner, and barely anything. Wired the changer motor directly to power and it worked great. Finally, it dawned on me to turn off the tuner. All of a sudden my voltage meter showed plenty of power coming from the harness. Plugged it into the changer and the motor came to life. I’m so used to integrated, solid state components, it didn’t dawn on me to shut the darn tuner off first. :rolleyes:

So, despite a little ignorance causing some panic today, it was actually another successful day. I still have to go through and clean the rest of the record changer, but I’m happy to report it’s alive and looks promising! Also, replaced all of the #1847 bulbs with LEDs...so nice. Got warm white to keep things original looking.
 
cademan said:
Okay, that one is weird! :crazy:

:biggrin:
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Not that weird. Its a stand-alone board. 12vdc and signal in, and you get L, R, and a stereo indicator lamp out. Just needs 2 pins jumped for stereo enable, or it can go to a stereo/mono switch.
 
gadget73 said:
Not that weird. Its a stand-alone board. 12vdc and signal in, and you get L, R, and a stereo indicator lamp out. Just needs 2 pins jumped for stereo enable, or it can go to a stereo/mono switch.
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Nono, I know that, I was referring to his unit which seems completely different than most 3 channel Motorola's I have had and have seen in my life time!
 
This one seems to be the bare bones model. The other SK models in that time period seem to have reverb and slightly larger right and left channel speakers, especially if you got one with the high-end Drexel cabinet (those are darn purdy). Those models probably came with the MPX chassis, too?
 
While I’m waiting for record changer parts, I decided to tackle the cabinet this weekend. As I mentioned before, this isn’t the higher end Drexel cabinet. The top and sides actually had a very thin laminate (not wood veneer), which I sanded off. The wood underneath the laminated surfaces is cabinet grade plywood, and the other wood trim is a softer type wood. Each took the stain a little differently, so I went darker (walnut) to try to even things out. Did I mention I hate wood finishing!! Plus, it was rainy and humid today. Good grief. I’ll be doing the polyurethane throughout the coming week.

Looking forward to working on the record changer and getting this part of the job behind me.
4-D3-D565-C-39-A1-46-D3-ABF0-E446-ABE1-FE5-B.jpg
 
gadget73 said:
Cabinet looks great. I like that a lot more than the original color.
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Thanks, Gadget. I let the stain sit a little too long on the top and it is staying a bit tacky in spots, so I have some fixes I need to make, but I think I should be able to correct things. Yesterday’s humidity didn’t help things.

To contrast with the darker finish, I have a simple, lighter colored grill cloth (I think a replica for Vox guitar amps) that I am hoping looks nice. It’s slightly darker than the grill cloth I have on some AR speakers on my basement system, which I really like. Looking forward to getting past the staining and poly part of this job.
 
I haven’t had as much time in recent weeks to work on the console as I would have liked, but I was finally able to get the grill cloth, speakers, and trim hardware installed in the last couple days. I’m hoping to get the components (sans record changer) back in the cabinet tomorrow along with the lift top. I received parts to rebuild the record changer about a week ago, and I hope to tackle that in the next week or so. Appreciate all the help I have received here to get to this point.

JP

Grillcloth.jpg


Speakers.jpg
 
Back, again!

A couple questions. I’m being defeated by the clips used to mount the VM record changer back into the cabinet, and I didn’t take pictures of them before I pulled the changer last month. Does anyone have a stupid simple guide or pictures to get the screw properly attached to these clips:

Clips.jpg


Second, I was playing the system today for the first time since reinstalling the speakers with the new grill cloth (pictured in my previous post). The grill cloth is a replica for Vox guitar amps, and it has almost a vinyl/rubber-like texture woven into the fabric. When the bass is turned up much past 3-4 and the volume is below halfway, the fabric vibrates quite noticeably at the opening in the wooden mounting board for the center channel woofer. Other than at those openings, the fabric is glued down and stapled quite tightly. The speaker is not the original Golden Voice ceramic 12” (had a bad cone), I placed it with an Alnico 12” that came out of vintage Lafayette. Any ideas on what could potentially be done to stop the loud vibrating...short of changing to a different kind of fabric?

Thanks,
JP
 
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they shouldn't have to come off, they will just flip up to go out. Pulling them is kind of a PITA, putting them back on isn't much fun either. I'd do this out of the console otherwise its just pure hate.

anyway, slide them back on, then stick a screwdriver under the tongue of the clip to get it to slide past the screw. Pull the screwdriver and the tongue should drop down and hold in place.
 
Thanks, gadget! So, I can get them on like you described. But then the problem is that there is about 3/4” gap between the cabinet and the clip ... i.e. the clip doesn’t hold tight to the cabinet. Could it be that the spring shocks on that the changer sits on are compressed? The foam insulation that was in the springs completely disintegrated when I pulled the changer.

I thought I remember the clips being tight to the cabinet. I’ll take some pictures if my description is lousy.

EDIT- Picture showing clip installed

Clip-on.jpg
 
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Its supposed to float for isolation. The clips are there as a transport lock, back the screws out until the clips pull against the cabinet and it sucks the changer down to keep it from bouncing around when being moved.
 
Well, son of a gun! Thanks for clarifying, Gadget. I think that is what the previous owner had done, and that is why I remember the clips being tight to the cabinet.

Now, I need to figure out that grill cloth issue.

I also put a scratch in the pre-amp faceplate tonight. While it’s just cosmetic, I’m pretty bummed about it, and I think my only option, other than leaving it, is repainting it (you can see it in the photo below left of the treble knob). But on the positive side of things, after completing the record changer rebuild last weekend (while watching some great tutorials on YouTube), it seems to be working like it should!

VM.jpg
 
Well, file this under “you can’t fix stupid.” The reason I am getting the vibration from the “grill cloth” is I installed Tolex wrap and not grill cloth. The wrap was mixed in with the grill cloth on the site I purchased it from, and I wasn’t smart enough to know the difference. I still have two more yards of it left to remind me of my shame. :rflmao:

So, it looks like I will be pulling the speakers back out and re-wrapping them with actual fabric this time. I really like the look of that darn Tolex, so I am hoping to find something similar. I’ll chalk it all up to a good learning experience if I ever do another one of these.

But for any other “newbs” out there reading this, Tolex ain’t grill cloth. Save yourself a $50 mistake!!
 
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