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Nakamichi 580 no audio at RCAs & headphone jack

Ok. Looks like I'm really being a moron again...
S**t happens sometimes :(

The problem wasn't actually with defective or different spec 945 devices (except that last Amazon batch of defective crap). The problem was that the technician was defective!

These transistors for the lights have crazy splayed pins! Using ones for the adjacent lamps I'd just pull & plant without really looking at the pins. But using others, including new ones, I'd of course have to position the pins. I was doing that wrong! :(

The good and bad pin positions are in the photo. Notice one leg is crossed if correctly positioned.

What threw me off is that the functions still worked fine. Only the dim lamp.

Thanks to dankik for posting about the KSC945. That made me think of pin positioning today!
 

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Looking at the lamp/switch circuit on the Control Switch board:
  • It looks like the PAUSE lamp gets its power from the same source as PLAY, so it should only light IF the PLAY lamp is on
  • When you have the PLAY lamp lit, the DC goes through D601 and PL601 and gets grounded through the PAUSE switch
  • The only other destination for the signal is Kpau* for the pause circuit
  • Is the dim PAUSE lamp on all of the time or only when PLAY is also on?
  • Check D601.
1789485675608.png
 
Fixed!
Now the 580 is (finally!) basically done!
It still needs cosmetics. I also recently noticed some very minor right channel distortion during playback. It also probably needs better calibrations with dedicated test taped. But overall it's doing great now!
 
Wait!
Oh wow!
The lamp is actually STILL on!
But it's on so dim that it's not really noticeable...
Almost looks like the shutoff sensor bulb is shining through it!
 

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dankik said:
Looking at the lamp/switch circuit on the Control Switch board:
  • It looks like the PAUSE lamp gets its power from the same source as PLAY, so it should only light IF the PLAY lamp is on
  • When you have the PLAY lamp lit, the DC goes through D601 and PL601 and gets grounded through the PAUSE switch
  • The only other destination for the signal is Kpau* for the pause circuit
  • Is the dim PAUSE lamp on all of the time or only when PLAY is also on?
  • Check D601.
Click to expand...
It's on all the time. Even with stop lamp off.
 
Definitely shouldn't be stealing ICs from the RM-580!
The PCB is extremely fragile and pads lift very easily!
But "you do what you gotta do." ;)

At least it still (kinda) works with TI 4011BE instead. :)

But the remote only works at 2-3" distance (that's INCHES not feet). That really defeats the purpose of a remote!
 
gnexus said:
It's on all the time. Even with stop lamp off.
Click to expand...
I don't see a stop lamp on the schematic? Looking at the board layout, I only see 3 lamps: PLAY (LL602), REC (PL603), PAUSE (PL601).
Is your board different that what is shown in the SM? Are we talking about the 480 or 580?

1789490391215.png
 
RM-580 remote fixed!
Finally! That project was very difficult to do without proper diagnostic equipment... :(

It now has a new TI CD4011BE, new caps, and all new very fancy Amazon no name Chinese 945 transistors!

Works now from across the room! :)
 
dankik said:
I don't see a stop lamp on the schematic? Looking at the board layout, I only see 3 lamps: PLAY (LL602), REC (PL603), PAUSE (PL601).
Is your board different that what is shown in the SM? Are we talking about the 480 or 580?
Click to expand...
Sorry for any confusion.
It's the 580 with the lamp issues. A 480 has no stop lamp...

This is the 580 thread. So discussions should really be limited to that deck to prevent confusion. I tried, but...

I'm looking now at the 480 SM. That control PCB is same as your photo. So not applicable.
 
So on the 580, you still have a problem with the PAUSE lamp on dimly? Is it only on when the PLAY lamp is also on or all of the time?
 
dankik said:
So on the 580, you still have a problem with the PAUSE lamp on dimly? Is it only on when the PLAY lamp is also on or all of the time?
Click to expand...
The PAUSE lamp problem was transferred to the FF lamp a while back after i fixed the shorted wires and when I swapped Q413 for the FF 945 transistor. Much better there because then the deck is not in mute!

So then a dim FF lamp was the issue...

Now. After getting the 945 pins correct, the FF lamp is still on but INCREDIBLY dim (see photo). It's nearly unnoticeable. You probably couldn't even see it anymore with the front panel installed except maybe in total darkness. So it's no longer a big deal. But it's still on...

Gonna try a different transistor. Again...
 
A new Chinese 945 finally completely fixed the issue. :)

But, in absolute darkness, there was still some light from the shutoff lamp shining through the back of the FF lamp. Had to put some black RTV on the back of the rubber lamp holder to block the light from the shutoff lamp. Now it's totally dark. :)
 
The ancient 580 is now doing very good!

Now need to check for full erasure and see if still any very minor right channel playback distortion.

And cosmetics... this deck was rather beat up even when I first got it long ago. Also kinda hate that capstan runs constantly when powered on. So it's mostly just been in storage. But sounds excellent now! :)
 
Yes. It still has bad right channel distortion at full output level. :(

Think it's the output level pot even though it has already been disassembled & cleaned. Hate doing that! It's still quite scratchy now on the right channel only.

The distortion is only past about 70% output. That's why I didn't notice it earlier.
 
A recording of a CD from a high end CD player now sounds identical to the CD itself! So it now has the same sound quality as a 480 when properly calibrated. Pretty impressive! The new capstan belt and sanding the capstan hubs eliminated any noticeable W&F.
 
NO erasure! :(

That makes two decks with that issue...

Have 0.1 ohm resistors hopefully arriving tomorrow to check the erase circuits.
 
Disassembled the output pot and cleaned it again. The right side is very difficult to clean because the shaft is staked permanently to the plastic wiper. Did the best possible but still has minor "scratchiness."

So swapped it with the input pot. Better!

But distortion is still there on right channel at higher output levels...
 
Oh hell! That sucks!
Thanks very much for noticing that! :)
I read it wrong! Works fine for output, but probably would have blown the recording input had I tried it...

So MORE work and STILL scratchy pot on output :( and even more soldering to do...
Anyway, at least now know the pot isn't causing the right channel distortion. So getting somewhere.
 
Sure enough it says 100k on the input pot!
Somehow didn't even notice... :(

So might as well disassemble the 50k pot again while it's off. But it's dangerous to do multiple times because the ears can break...

This time trying different technique of "pressure washing" it with contact cleaner since previous attempts didn't resolve the problem.

Too bad new pots aren't easily available.
 
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