Akai 280D-SS stuck in record mode.

[SeriousSam]

I recently acquired a vintage stereo system in lightly used condtion. It consists of a Garrard Zero 100 TT, Pioneer CS-77a speakers, Pioneer QX-949 receiver, and Akai 280D-SS reel to reel. I paid the handsome sum of $105. This included a tote box of tapes and all of the original owners manuals.
The Zero 100 works somewhat, the speaker tweeters need new surrounds and the receiver works perfectly so no major problems there. My real problems concern the 280D-SS.
Problem#1
When I press the FWD button to play a tape, the tape does move at the proper speed but the record light comes on without pressing the REC button and appears to be in record mode. Information that was on the tape is certainly being overwritten. The FF, and REW work fine (when they work). I have checked the record button to make sure it is not stuck in the "on" position. It is not.
Problem #2
Sometimes the transport buttons don't work at all. When I press them, none of the relays fire and I only get a dull glow from the indicator lamps. The tension arm switch is in play and functioning, but my 24vdc supply has dropped to around 8vdc. I can come back to it after a while and it starts working again with the voltage returning to 24vdc.

I pulled the System Control Board and did the rivet fix as well as pulled the relays and checked them for function. The relays were fine and I installed them in different positions so as not to mask a relay problem I might have missed. On re-installing the board, I got the exact same results.

I'm thinking I might have a leaky cap in the 24vdc supply line (if I can figure out how to get to it) but beyond that I'mm pretty clueless.
If anyone has any ideas, please chime in.

Thanks,
SS

 

[westgate]

first thing i would consider is cleaning the buttons and switches by squirting some deoxit into the backs of them. they may have oxidized.

and while you're at it, clean (and keep clean) the heads and guides with at least 91% isopropyl alcohol on q-tips.

 

[SeriousSam]

The switches all check for proper continuity in the off and on positions. The heads have been properly cleaned. The problem still exists.

 

[vinylguy4]

This probably will not help, but I'll spout out a wild guess.
Does the 280DSS have the round plug in the back? There is a multipin socket on the back that either needs the remote plugged in or the 'filler' plug.
Sometimes the plug is missing.
If no plug, can use some jumpers instead. Jumper socket 1 and 11, also jumper 5 and 6, that is what my old notes say.

vinylguy4

 

[SeriousSam]

The remote filler plug was in place, but on the off chance it was bad I replaced it with jumpers. The problem is still there.

 

[mtgc]

There is a chance you have a stuck contact(s) on your control panel. You said you tested the unit and it had continuity, but did you use de-oxit or equivalent to clean all the switches? If you didn't, then do so and see if this solves the problem.
Another possibiltiy is a stuck relay. Check the main and aux boards for relays, take off the protective covers (carefully!!!) and give each a shot of de-oxit and work the relay back and forth (again carefully!!!) to make sure all the contacts make and break in the proper manner.

MTGC (Michael)

 

[SeriousSam]

I removed all of the relays from the system control board removed their covers and applied deoxit to all of the contacts. Before re-installing them, I checked all of the electrolytic caps and semiconductors for shorts and found TR108 shorted emitter to base. This had the same effect as pressing the record button while simultaneously pressing play. This would also explain my 24vdc line falling to around 8vdc. The replacement transistor arrived from Mouser today and was installed along with the relays.
That fixed the problem!

I can now listen to the tote full of tapes and I think its going to be quite a walk down memory lane.
Thank you all for your time and suggestions.

SS