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Sanyo 920 cleanup


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#1 caution

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Posted 01 January 2018 - 10:43 PM

Finally cracked this fella open last week after a long wait to investigate some issues. The missing switch cap I already replaced was rattling around inside! So, spare switchcap.

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There were a lot of screw problems. The back, the frame, the preamp, and the deck all had either stripped heads, stripped holes, in the wrong locations, missing insulating washers, not originally from the unit, or just straight up missing. So I spent the first day sifting through my screw collection and finding correct replacements for all of them based on service manual data.
 

I had expected the belts to need replacement since the deck was dead, but they were new. Just too big. One fell off and was why the deck wasn't running. Swapped them out with correct sizes and everything works fine. The idler tire and pinch roller were a little crusty so I sanded them down a bit and are nice and rubbery again.

On plastic stuff, a cabinet screw post had to be rewelded, and I replaced a missing dial string pulley. Very strange as they put back the little axle for it. At any rate, it's not essential to function, but helps keep the string straight as it comes off the tuner shaft. I found one with the same diameter but had to grind down one side to make it identical, and bored out the hole a bit to fit the axle.

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I noticed a pair of 33-ohm resistors along the bottom edge of the preamp that didn't look factory, and sure enough they're not in the service manual nor on pics of other 920 boxes. So I removed them. No difference so far that I can tell. They were pulling the base of a pair of transistors on each channel to ground, but didn't seem to make any sense what they were trying to achieve.

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Someone (maybe Sanyo?) also messed with a few of the air core inductors on the tuner board. FM tunes in very strong, but I'm not sure about the other bands, it may be fine.

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Sanyo soldered the motor wires, so I added a connector to them to allow the deck to come out.

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Sanyo also used a couple of lousy connectors for chassis-to-frame connections that you slip a tinned end of a wire into, but is nearly impossible to come back out without the use of a pick, so I may replace those with better ones.

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Next up: figuring out why the deck only records the left channel.
 



#2 T-STER

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Posted 02 January 2018 - 12:32 AM

These are one of my favourite boxes, no scrap that, my number one favourite box so it is great to see this one getting a proper going through. I look forward to part two, it may help inspire me to fix my dead one.

#3 Northerner

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Posted 02 January 2018 - 03:21 AM

Wow that sure had been messed with! Good luck with the rest

#4 Hurb

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Posted 02 January 2018 - 03:40 AM

Missed getting one a few weeks ago.... Still pissed off about that! Good job!!



#5 Northerner

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Posted 02 January 2018 - 03:57 AM

Missed getting one a few weeks ago.... Still pissed off about that! Good job!!

Could be worse...you could’ve had one then sold it to T-ster lol 😂

#6 Dbzerk

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Posted 02 January 2018 - 08:33 AM

Nice one.
Always love reading your write up caution!

#7 Reli

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Posted 02 January 2018 - 11:59 AM

Sanyo tuners often lose their ability to lock onto stations, so maybe someone was trying to fix it.  The FM chip however is typically the problem.



#8 Hurb

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Posted 03 January 2018 - 03:29 AM

 

Missed getting one a few weeks ago.... Still pissed off about that! Good job!!

Could be worse...you could’ve had one then sold it to T-ster lol

 

 

LOL! Feeling much better now!! 



#9 JVC Floyd

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Posted 03 January 2018 - 08:04 AM

I love the 920 if for no other reason its the only box I ever made money on lol. Pretty much sold itself for 5 times what I paid but I only paid 40 bucks for it and I didn't even have to work on it .

#10 Transistorized

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Posted 03 January 2018 - 11:17 PM

Aren't we all busy working away at saving boxes. A busy year so far :-)

 

I am going to take a guess as to why it doesn't record on but one channel. Probably suspect record bar (if it has one) or possibly function switch (would try stereo to mono and see if the head will write both tracks in mono). After that I'd be scratching my head but I know you can find the issue



#11 Northerner

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Posted 04 January 2018 - 02:36 AM

I love the 920 if for no other reason its the only box I ever made money on lol. Pretty much sold itself for 5 times what I paid but I only paid 40 bucks for it and I didn't even have to work on it .

Lol I’m the exact opposite, it’s literally the only one I made a loss on. I usually buy fixer uppers and always make a strong profit on eBay. But I bought my 920 serviced and working so it wasn’t a bargain, then I sold it to Tre for less because he’s a mate :-)

#12 T-STER

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Posted 04 January 2018 - 12:18 PM

 

I love the 920 if for no other reason its the only box I ever made money on lol. Pretty much sold itself for 5 times what I paid but I only paid 40 bucks for it and I didn't even have to work on it .

Lol I’m the exact opposite, it’s literally the only one I made a loss on. I usually buy fixer uppers and always make a strong profit on eBay. But I bought my 920 serviced and working so it wasn’t a bargain, then I sold it to Tre for less because he’s a mate :-)

 

Ow i feel bad now, i wasn't aware you made a loss  :sad:

 

If it makes you feel any better it is by far my most treasured possession and i would never sell it....



#13 Northerner

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Posted 04 January 2018 - 01:30 PM


I love the 920 if for no other reason its the only box I ever made money on lol. Pretty much sold itself for 5 times what I paid but I only paid 40 bucks for it and I didn't even have to work on it .

Lol I’m the exact opposite, it’s literally the only one I made a loss on. I usually buy fixer uppers and always make a strong profit on eBay. But I bought my 920 serviced and working so it wasn’t a bargain, then I sold it to Tre for less because he’s a mate :-)
Ow i feel bad now, i wasn't aware you made a loss :sad:

If it makes you feel any better it is by far my most treasured possession and i would never sell it....
More to life than money :-)

#14 caution

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Posted 04 January 2018 - 01:56 PM

Thanks T and Si yeah it certainly has its little issues here and there, but with beauties like this you take all the time you need to get it right  :yes:

And thanks Dbzerk! Did my M70 parts ever show up?

Good to know about the tuner Reli, I'll have to check closer on the state of the bands and see if there's anything still out of whack.

 

Transistorized that's sort of what I was thinking, either that or the function switch. I am attacking those record bars next, actually there's two of them in tandem. I just purchased a bottle of Deoxit in a needle dropper, so hopefully that keeps it inside the switch and not all over the board! I was already just soaking the end of a Q-Tip with the aerosol can, but even dripping those into a switch tends to run out and onto the board.



#15 Van Presence

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Posted 04 January 2018 - 03:40 PM

Wow. The plug for the deck is a genius idea. I got mine to that point, just to look at the deck. Only to realise it couldn't fully come out. I'll send you mine to do too. Ha
Could you post pictures of the bits you had to take off to change the belts. I'd like to get mine running when I attempt to get belts.
I'm also missing 1 of the blue ribbon bits for my parts box. Any idea how/what to replace?

#16 caution

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Posted 05 January 2018 - 02:58 AM

Hah thanks VP, yeah I used a connector I scrapped from something else and used a pick to finesse the sleeves out. Snipped off the old wires, soldered the motor wire ends on, and popped them back into the housing. I never pull the connector bases off boards during a scrap, just the wires with the connectors on the ends. So, I used some snap-to-size .1" pitch header pins. I lucked out, the motor wire board holes were .2" apart.

 

Actually I do have an intact blue ribbon, from a selector switch in an old Soundesign receiver I tore down.

 

You don't have to take anything off the deck to replace the belts. Just remove one of the end screws on the rear bracket and wiggle that side up a bit, it gives you just enough room above the flywheel to slip off both belts.



#17 Lasonic TRC-920

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Posted 05 January 2018 - 04:26 PM

Man, you sure do dive deep into the electronics. These are fantastic looking boxes. Maybe one day I'll stumble across one.

 

Keep up the great work!



#18 SLO

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Posted 07 January 2018 - 08:18 PM

Man I wish I had the technical skills of some of you guys. I can clean the shiat out of a box really well, but this type of stuff is amazing to me.

Great work Eric, I also hope to add one of these 920's to my collection someday, although my wife would say otherwise haha