Author Topic: Help finding information on a Motorola SK71MA console  (Read 807 times)

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #15 on: October 25, 2018, 05:43:44 PM »
Schematic from amp label

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #16 on: October 25, 2018, 05:44:25 PM »
Schematic from tuner label

Motorola Minion

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Re: Help finding information on a Motorola SK71MA console
« Reply #17 on: November 05, 2018, 12:44:29 PM »
How do you recommend I clean the sockets and plugs? Deoxit?

Yes, the plugs and tube pins can be less-expensive contact cleaner but the controls and switches should be DeOxit, as they need a lasting lubricant along with the needed cleaning.

I will look up your tuner but the amp is already in the downloads section http://vintagehifi.net/index.php?action=dldir;sa=details;lid=289
Tubes - Magical - Tubes

Dave

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #18 on: November 23, 2018, 12:18:39 AM »
So while the family is recovering from the overabundance of food, I took some time to finally disassemble this monster.

It looks like I have the following models:

Amp: HS-960A
PreAmp: HS-961B7
Tuner: HS-997B

PS, the download you linked too was the one I uploaded, so good to know I do have the proper schematic for my amp lol....

I have some pics on my other thread (linked here).  I'd rather not repost here as well, so go take a look there.

I'm planning on de-oxit all the RCA connectors and possibly replacing the RCA's that are there with something a bit better, but nothing super exotic.  I also am betting I need to replace a fair amount of the amp tubes as they look quite bad.

If someone can point out to me the parts I need to look to replace on the schematic, or on the actual underside of the amp it would be much appreciated.

Also if anyone has the schematics for the Tuner and Pre-Amp that would be appreciated.

I plan to make a "project binder" showing what I've done on the amp and then laminate the pages and leave it inside the console so if someone ever opens it back up they can see the work thats been done.

Kinda like a hidden time capsule.

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #19 on: November 23, 2018, 01:24:01 AM »

Bill

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Re: Help finding information on a Motorola SK71MA console
« Reply #20 on: November 23, 2018, 07:21:02 AM »
That one should sound pretty good when done with your rebuild.  It you don't have a tube tester, see if you can locate someone that can test the tubes for you.  Replace tubes that are shorted, and try the weak ones before you discard them.  Weak tubes can sometimes sound just fine.  RCA connectors should be fine after cleaning.  De-oxit the tube sockets and all the controls, basically everything you can think of.  Replace ALL capacitors, and check all resistors and replace them if way out of tolerance or bad. 

I hope this helps?  If anyone else has suggestions please jump in!

Bill


EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #21 on: November 23, 2018, 08:19:46 AM »
Thanks Bill.  I dont have a tester but a good friend of mine rebuilds tube amps (and all things vintage) for a living.

I was planning on testing the tubes with his tester and also having him help me figure out which parts to order and replace.

Hes got a 6 month wait list but I plan on having him replacing things since Im not very good with ansolder iron and Id prefer not to learn in this unit.

If nothing else I can get parts ordered over time in advance so it delays the lag time.

Im also likely replacing the RCA cables with some better ones I have just because the old ones are in the signal path and Id prefer to replace them.

I have some MIT cables from a buddy super cheap that meet the criteria.  If not then then likely some Blue Jeans Cable LC-1.  Not sure if Im doing that for the turntable or not since I dont plan on actually using it beyond making sure its functional (spins) and has been cleaned up.

I will be pulling the drivers later this week if I get more time so I can clean and inspect them all.

Im also gonna research what other options I might have, at least for the low range driver.  Maybe something a bit more efficient, or with more throw.

The other drivers have soldered on parts so unless they need replacement Im leaving them alone.

All that said, I welcome thoughts and advice from you guys as you know more about this than I do.

Lastly any help with tracking down manuals for the pre-amp and tuner would be most appreciated.

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #22 on: November 23, 2018, 01:00:51 PM »
I added a ton more disassembly pics this morning at the other thread.  The link below will take you directly to that post.
http://forum.polkaudio.com/discussion/comment/2458013/#Comment_2458013

Bill

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Re: Help finding information on a Motorola SK71MA console
« Reply #23 on: November 25, 2018, 08:01:09 AM »
As someone who likes to preserve things,  I would not change out cables, until you have all the chassis rebuilt and hear how everything sounds.  If you want to us the hi-tech cables for the stuff you are adding that's ok.  I also would not change out the woofer until you have the rebuild done.  Companies did a good job matching the components they used, to get the best sound they could in a piece of furniture.  Please, listen before you change anything.

Bill


EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #24 on: November 25, 2018, 08:35:07 AM »
Bill:
No worries on that one.  Replacing costs money so I prefer to start with the gotta do, and later on try the what if.

The RCA cables are really corroded and dont appear to be anything special.  The internal wiring otherwise will remain as is.

I plan to replace the RCA to the radio and to the reverb unit but leave the TT ones alone as they appear better built.

Either way before replacing drivers I would give it 6 months of listening before deciding and Id still keep the factory stuff.

From my brief minutes with it working, nothing will be replaced drive wise.

Bill

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Re: Help finding information on a Motorola SK71MA console
« Reply #25 on: November 25, 2018, 03:46:25 PM »
 :) :) :)

Bill

electra225

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Re: Help finding information on a Motorola SK71MA console
« Reply #26 on: November 25, 2018, 07:34:13 PM »
Someone has spent too much time on AudioKarma....... ;)
I don't need Google.  My wife says she knows everything.

EndersShadow

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Re: Help finding information on a Motorola SK71MA console
« Reply #27 on: November 27, 2018, 07:21:57 PM »
Someone has spent too much time on AudioKarma....... ;)

If your talking about my reference to MIT cables, I got em for 20 bucks from a buddy, so I didn't spend a ton on em, and I already have em, so why not.

And Blue Jeans cables aren't exactly top tier audiophile kind, but they work quite well.