Hi. my machine has suddenly developed an issue, when playing the sound alternates in and out, both channels. No sound for near 1 second then sound for 1/2 second very predictably. I push the reverse button I get the same thing. Has anyone heard of this before? Thanks
Problem With Akai GX 210-D
- Thread starter KMcCarthy
- Start date
Hello, welcome! I'm not sure what could be the specific cause of your problem, but there are a few things you can do to narrow the search. If it were me I would:
a). try a second tape just to be sure the problem isn't recorded on the tape.
b). change the playback speed, if the tape is recorded at 7.5ips try 3.75ips and see if the dropout interval decreases or stays the same. This will tell you if the problem is related to the transport rather than something electronic.
c).if the rate of dropping out remains the same regardless of the speed then the problem is in the electronics and it is common to both channels. This might point to a problem in the power supply.
I hope this is somewhat helpful.
a). try a second tape just to be sure the problem isn't recorded on the tape.
b). change the playback speed, if the tape is recorded at 7.5ips try 3.75ips and see if the dropout interval decreases or stays the same. This will tell you if the problem is related to the transport rather than something electronic.
c).if the rate of dropping out remains the same regardless of the speed then the problem is in the electronics and it is common to both channels. This might point to a problem in the power supply.
I hope this is somewhat helpful.
Thank you tapepath, I have tried a different tape but I like your other ideas. I will try when I get home later.
Update on the issue, yesterday I tried to diagnose this issue and found that the unit played flawlessly for 90 mins, when I first started it it cut out a couple of times, then perfection. Tried again today an the issue is back. Played normally for about a minute then back to cutting out in the same in-out cycle. If this is a power supply issue, is it DC, I would imagine the lights and motors are AC? They are fine, reels moving as normal.
Usually problems that are intermittent are caused by loose connections. I would suspect a power supply lead to the audio circuitry since both channels are affected. A service manual would be a good idea at this point. It can tell you how to disassemble the chassis from the cabinet and where the internals are located.
Another possibility could be the muting circuit (described on page 15 of the service manual) connected with the auto-reverse function. As an experiment you could try removing transistor TR5 which, when activated, shorts the signal to ground. Then see if that channel remains on. Keep the playing volume fairly low if auto-reverse is activated since muting will be off.
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I checked voltage in and out of the power supply board, both very close to what's on the print and not oscillating, just steady. As far as the 2nd part of your answer, do you mean unsoldering the transistor from the board?
Correct, the deck activates a muting circuit when the auto-reverse function happens. The muting circuit turns transistor TR5 on so it conducts the audio signal to ground, shutting it off. There could be something causing a false triggering of this muting circuit, so if this transistor was removed there wouldn't be any muting. If you're reluctant to remove the transistor you could place a volt/ohm meter set to "ohms" across one of the channel's outputs and ground. If the audio shuts off the meter should read "0" ohms when it happens indicating that the muting circuit is being falsely triggered.
I did a test by putting a meter across the end of an rca plug connected to the output jack in the deck. Interestingly it seems to be doing the opposite of your suspicion, it alternates between open and a measurable resistance when a tape is playing. Another interesting thing was that I see a resistance ounce like a heartbeat even with no tape playing and the meter attached but only on the channel with the meter hooked up. Not sure what that means.
I'm sure, I could see the meters bouncing just as they do when connected to the stereo and audio drops out cyclically, however I didn't have the cables connected.
Not sure what to suggest at this point. For me troubleshooting a problem begins with trying to figure out how I would make the problem happen. In other words I try and imagine how I would get a tape deck to periodically stop producing audio and then switch back on again seemingly randomly. Tape decks that have auto-reverse add a complexity to the usual playback process and this is what drew my attention to looking at the schematic. The odds are high that this is where your problem lies. Maybe removing the shorting transistors? You can always put them back if it doesn't solve the problem.
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