Pioneer CTF-1000 revisited

Posted this at AA in the Tape Forum 'cause they were complaining how dead it was... got no responses there?! I was trying not to bother y'all again about this particular deck, but guess I have to. Ahh, well...

I have recently acquired a physically beautiful Pioneer CTF-1000 cassette with some performance "issues". Now, I understand the mechanical issues relating to tape handling on this deck (some fine advice at AK related to this)... but it seems that there's also an electronic problem of some sort that kind of surprised me.

Here's the deal. After a minute or so of play, the line-level output of the deck just sort of fades away (rather rapidly) to nothing. The VU meters are still bopping, and there is output at the front panel headphone jack, but nothing from the line-level outputs (either set) on the back. Turning the unit off and then back on brings the line-level output back briefly. Sounds like a component is heating up and changing value (or OVERHEATING and just "packing it in"). The strange part to me is that the headphone output is still there when the line-level output dies. I'd have thought that the output preamp would be shared between the headphone and the line outs (perhaps with buffer added between the preamp and the headphone jack to assure adequate drive), so this strikes me as a rather odd problem.

Anyone know of the likely cause for this problem? I have no schematic for this guy (although I do have the manual).

Thanks for your attention!

The problem is the muting transistors on the output are being turned on. this may be caused by a dirty switch in the transport, or it may be a problem with the logic. The reason the headphones work is they probably come before the muting circuit. To verify this, put the Source / Tape switch in Source. If you have output now, it's the muting. You may need a schematic for this, but try the following:
Near the output jacks there may be 2 transistors. These should be the muting transistors. Near the transistors there may be a wire going to the transport. Follow the wire and see if it goes to a switch. If it does, clean the switch with 400 grit sandpaper and flush with contact cleaner to remove debris.

That's a beautiful pair of Marantzes in your avatar. Care to share the details of those beautys?

(I've always thought that the vintage Marantz was among the most attractively designed audio equipment. That blue/black/silver look is about perfect. And, if they are like the Marantz I used to own, they sound even better than they look.)

The tuner is a model 125. The integrated amp below it is actually a Kenwood Model 600, a wonderful dual mono design that was made to go with the 600T tuner which I don't have.
The 125 is a great tuner, though, it is my favorite of the 3 tuners I own.
I too like the styling of the old Marantz, the blue and silver, there's nothing like it today.

Thank you Doctor! I will evaluate this when I get a chance. Didn't have any input hooked to the deck when I tested it, but of course that can be taken care of.