Akai GX280D-ss Quad Deck, REV and Speed Problems

[R to R Guy]

I am new here and have a few Quad items buy mainly vintage audio from the 70's. I am needing help already with a Quad RTR! I recently picked a Quad Akai GX 280D ss tape deck, dead but started working upon cleaning the 2ch/4ch switch and others. It now which works fine at 7 1/2 ips and forward but lacks REV and 3 3/4 ips which I have been attempting to fix.

Two problems remain.

Problem 1: No REV

I have resoldered the past thru connectors with wire inserts. I have cleaned the contacts on the two REV relays. I checked the transistors and TR 111 showed bad. It is the one TR mainly involved with the REV. I went ahead and and changed TR1 and TR111.

I plugged in the circuit board and after pushing the tape recorder ON button only, the tape started running in REV, with no light on REV button, but a light on the FWD button! None of the buttons work including the stop. I tried this several times, same result. I unsoldered TR111, plugged in the board and everything works except REV as before. I tried reversing C and E on TR111 and the deck runs in only REV but STOP button works. So what I have is operation is normal except no REV with TR111 in (although bad operation) or no REV without TR111 installed.

Any body got some ideas to solving this mystery?



Problem 2: 3 3/4 ips speed is too fast

I had changed out TR209 when I had no 3 3/4 ips speed and now have 3 3/4 ips speed back but sounds speeded up or too fast. I made a timing tape by measuring 225 inches of tape and marked with a Sharpie. With 225 inches of length, 3 3/4 ips is exactly 60 secs and 7 1/2 is exactly 30 secs.

I timed 3 3/4 ips speed and found it to be at 43 secs, too fast. I should be 60 sec. Additional info 7 1/2 ips is right on 30 sec.

I located L1 inductor, which is used to adjust 3 3/4 speed, found out which way to turn and using a non conducting tool, increased the speed by turning L1 until I got to 56 secs and ran out turns at 6 turns. Checked 7 1/2 ips before and it was right on 30secs but a check when L1 was maxed out at 3 3/4 ips and 56 secs, 7 1/2 was 32 secs. So I backed L1 back 6 turns and have 7 1/2 ips back to 30 secs but 3 3/4 ips is back to 49, back to ground zero with 3 3/4 too fast.

Any ideas what to do next?

Thanks for your attention and help.

Charlie

 

[cupboy]

Apply sensing foil to your tapes (on the back side) and it should go into reverse on it's own. Have you tried that?

 

[R to R Guy]

Cupboy

I tried a adding foil sensing tape and it still did not reverse. Thanks for the reply.

Charlie



Update Problem #1: NO REV

I came up with a work around.

Since it works well except for REV with TR111 out and works only in REV with TR111 in, I did the following. I installed TR111 with the e and b leads. I wired a spst switch between the c lead and the socket hole on the the circuit board (c lead goes to the REV relays on the board).
I installed the switch on the back metal panel where I can easily reach it when operated in the vertical position.

Now I can have REV with TR111 in service and have all other operations with TR111 out of the circuit.
The RTR will not automatically switch between FWD and REV with use of the foil sensors but I do not do that anyway (too many tapes to mess with adding all that foil).


Problem #2: # 3/4 speed too fast.

No progress but still looking for answers. There must be a working but bad component somewhere. Also looking for a resistor or coil to add to circuit that will cut that speed down.

Charlie