rx 5080 tuner and line in failure

I have 2 old rx 5080. (my and my brother's old machines from when we were kids). well, last year, the line in on his quit working, and this year, i somehow messed up the tuner on mine.

I was going to open up his to check solder/etc around the jacks on his... but the tuner on mine I'm not sure I would be able to do anything with.

searched the site and have seen comments on the tape players on these, and some notes on taking them apart.

anyone got a good illustrated guide to opening one of these up... or at least step by step so I don't mess it up?

I assume the phillips head screws are jis standard, not us (i tried using a phillips on one, and it wants to jump out... common sign of jis. or... are the things just nastily loctited in?

Welcome Velvet! These are pretty simple machines. There are philips screws that hold them in. Simply remove them and everything should slide right off. Be sure to release wires where neccessary before pulling the halves apart.

As far as tuners being screwed up we'll need more detail as to what it is or isn't doing.

so they are phillips, not jis? ok.

yeah, i know i was being vague with the tuner. basically, while using it in a dim tent, I turned it one way to it's end of travel, and turned more. tuner bar still moves, and nothing feels out of whack, but the tuner no longer tunes in am or fm.â™ 

VelvetHammer said:

yeah, i know i was being vague with the tuner. basically, while using it in a dim tent, I turned it one way to it's end of travel, and turned more. tuner bar still moves, and nothing feels out of whack, but the tuner no longer tunes in am or fm.â™ 

Click to expand...

Can the tuning wheel pop off the rod on a varcap?

don't know about that.. i'll study. got the line in machine apart.... I should take pics so others know what's going on

fairly disgusting inside

I'm going to open up the tuner one now. the line in one I can't see anything blatantly wrong... but those jacks are buried under the tape mechanism, and at the back of the circuit board... so it's real tough to see. i don't know if i want to attempt to try and dissasemble to the point where i can remove the board and get at them.

going to have to read up on cleaning measures on this site, at least get the dust out, spray the pots with cleaner, etc while i have it apart.

VelvetHammer said:

I'm going to open up the tuner one now. the line in one I can't see anything blatantly wrong... but those jacks are buried under the tape mechanism, and at the back of the circuit board... so it's real tough to see. i don't know if i want to attempt to try and dissasemble to the point where i can remove the board and get at them.

going to have to read up on cleaning measures on this site, at least get the dust out, spray the pots with cleaner, etc while i have it apart.

Click to expand...

DeOxit might help on the line-in if the switch is dirty or very slightly corroded.

ok... pics...


on the one with the bad line in... see the solder on one of the jacks looks like so.


I'm thinkin' that ain't right. Probably have to get a bud with better solder skills than mine to clean it off and resolder. really don't want to have to pull that whole board out to do it....


on the tuners. nothing in the mechanical stuff looks wrong. pulleys, strings, etc seem to function well. also learned it doesn't matter how far you spin the knob, it can't affect the electronics because the string will slide on the tuning knob shaft.

the working machine's tuner looks like so


the non-working machine looks like so


obviously, the ancient rubber band that once held the wires in place melted/deteriorated... not sure how etc.
i thought maybe the problem is those tiny wires can not cross each other in some way, so i gently pushed them like so


that had no effect.
btw... when i say tuning doesn't work... when i move the indicator up and down the tuning scale, i never get anything resembling a radio station... just static.

i also eyeballed the antenna on the box, but nothing looks goofy there. thought about hooking a wire to the external antenna screw to see if that might work.

Fatdog said:

VelvetHammer said:

I'm going to open up the tuner one now. the line in one I can't see anything blatantly wrong... but those jacks are buried under the tape mechanism, and at the back of the circuit board... so it's real tough to see. i don't know if i want to attempt to try and dissasemble to the point where i can remove the board and get at them.

going to have to read up on cleaning measures on this site, at least get the dust out, spray the pots with cleaner, etc while i have it apart.

Click to expand...

DeOxit might help on the line-in if the switch is dirty or very slightly corroded.

Click to expand...

And unless you are tecnically savvy, I'd be VERY carful with the tuner mechanisms. They are sensitive and unless you have the equipment, if not out of whack, it will really be screwed. So be very careful...

oldskool69 said:

And unless you are tecnically savvy, I'd be VERY carful with the tuner mechanisms. They are sensitive and unless you have the equipment, if not out of whack, it will really be screwed. So be very careful...

Click to expand...

ya, at this point, I'm not touching diddly.

VH, when you turn the tuning knob, take a look at the variable capacitor. Do you see any movement in there?

I also noticed this:



I wonder why Panasonic did this two different ways??

Fatdog said:

VH, when you turn the tuning knob, take a look at the variable capacitor. Do you see any movement in there?

Click to expand...

No. I looked at the working one as i moved the knob, and i can see the components inside moving as the string moves the needle. on the broken one, that thing does not move.

is there anyway to "bump" it? don't know if they can get stuck over time, or if I could have bottomed it out by overturning the knob when the travel should have stopped.

VelvetHammer said:

Fatdog said:

VH, when you turn the tuning knob, take a look at the variable capacitor. Do you see any movement in there?

Click to expand...

No. I looked at the working one as i moved the knob, and i can see the components inside moving as the string moves the needle. on the broken one, that thing does not move.

is there anyway to "bump" it? don't know if they can get stuck over time, or if I could have bottomed it out by overturning the knob when the travel should have stopped.

Click to expand...

If the big, plastic wheel is moving (like in the picture below)



and the varcap has no movement, I would say something has definitely come loose somewhere.

It might require additional disassembly to get in there. Perhaps a screw or gear was popped out of place.

Seriously, trying to figure out the varcap and other issues...diodes etc...or the RF amp...if you don't have the experience...

Lots to think about here and without the test gear...you're running a track meet in a swimming pool.

If you've got some of this and know how to use it...go for it...



If not...I'd get some hands on help. FM tuners are not as simple on the surface as they seem to be. I am not knocking the help trying to be offered, but others here like Superduper and TMR will agree.

fully understand.

I'm honestly just wondering who's left in our area that would still work on old stuff like this.

Hopefully, it will be something simple like a slipped gear. Otherwise, yeah, you're up the creek.

Sounds like a mechanical issue so nothing electronic to diagnose. Fix the mechanical issue and problem solved. First thing I would do is turn it around and turn the wagon wheel by hand to see if it works. If not, then the wagon wheel might be stripped or screw loose. If not, then the cap shaft might've snapped in which case, toss it out. You aren't likely gonna find another varicap and even if you do, the entire shebang will need to be realigned which is big $$'s, more than an RX-5080 is worth. It's parting out time.

As for the differences that fatdog pointed out, those are both caps. On one, they used an aluminum one and on the other, a ceramic one. A cap is a cap so they can be used interchangeably but I'm suprised to see those two contrasting components because typically, ceramic caps have far smaller values than electrolytics.

Fatdog said:

Hopefully, it will be something simple like a slipped gear. Otherwise, yeah, your up the creek.

Click to expand...

that was my thought.

I took the pulley off the top to eyeball movement, etc.

I'm fairly certain either a gear is slipped inside the varcap or some other mechanical issue. nothing i could do seemed to make the assembly want to rotate again.

I put the pulley back on (think I'm ready for the Grand Nationals in Cat's Cradle), and I'm going to stop messing with it.

I'll have to decide if I'm going to look into paying someone to fix it... or just treat it as a sound system for an mp3 player, etc.

I'm going to show the line-in solder job to the electronics repair guy at work to see if it's something he'd touch or not.

Refreshing and reflowing the solder can't hurt. But the line in failure might not necessarily be from poor solder joint at jack. Do you see any obvious mechanical issue with the solder connection? You can test it with a VOM to see if it's getting proper connectivity. The amber stuff is merely rosin (fluxing compound) and doesn't affect anything. That will clean right off with some isopropyl alcohol.

i'll have our tech check it electronically. I posted the pics because when i look at all the other solder joints up there, they are clear as a bell, no rosin like that.