I'm trying to sort out some problems on an Akai GX286.
I've cleaned it up a bit, it was all pretty grimy inside and showing its age. Boards are a bit sticky, and cleaning with alcohol leaves a cloudy white residue once the liquid evaporates. I don't know much about very old boards or what is causing that, so I'm not sure if I can do much about cleaning in a way that's going to help the board. I've taken out only the touch panel board and the system control board so far, and there's no evidence of corrosion on electrolytics, nor do any of the transistor legs look corroded.
This decks uses 2SC945s, from what I've read there's no particular issue with them (unlike the well known issue with 458s). I'm assuming therefore that there's no rush to replace those. Also, the LD3141 IC is not used in this deck - looks like the only IC listed is STK024, on the power amplifier board.
The main problem I need to fix before I can consider any others is that the machine will suddenly stop or go into reverse or fast wind during playback. This has been happening for a long time, according to the person who gave me the deck.
Just as a project, though quite a long term one, I may go through the machine board by board and do cleaning and possibly replacement, along with other necessary renewals or repairs. The deck was cheap when it was bought so I'm willing to experiment a bit and hoping to learn a few things as I go.
Is it likely that replacing electrolytics, tantalum caps and transistors would really help with the playback issue though? I may do a cap replacement later, and I'm putting together a list of all caps on all boards for when that day comes, but I am guessing there would be other things I should be looking at first, like touching up the solder connections on the underside of the boards. Any suggestions on that or other things I should be doing?
I have cleaned all switches I could find, oiled the pinch wheel bearing, and done the pinch wheel solenoid position adjustment according to the service manual. I haven't checked the pinch wheel pressure with a spring scale, as the wheel has to be off to get the deck open, so that'll have to wait until I close everything up again. There's a brake solenoid adjustment in the service manual, I haven't got to that yet. Also no adjustments to the brakes, as I've never done that on a deck yet and I don't want to mess that up - or not yet, anyway.
I've cleaned it up a bit, it was all pretty grimy inside and showing its age. Boards are a bit sticky, and cleaning with alcohol leaves a cloudy white residue once the liquid evaporates. I don't know much about very old boards or what is causing that, so I'm not sure if I can do much about cleaning in a way that's going to help the board. I've taken out only the touch panel board and the system control board so far, and there's no evidence of corrosion on electrolytics, nor do any of the transistor legs look corroded.
This decks uses 2SC945s, from what I've read there's no particular issue with them (unlike the well known issue with 458s). I'm assuming therefore that there's no rush to replace those. Also, the LD3141 IC is not used in this deck - looks like the only IC listed is STK024, on the power amplifier board.
The main problem I need to fix before I can consider any others is that the machine will suddenly stop or go into reverse or fast wind during playback. This has been happening for a long time, according to the person who gave me the deck.
Just as a project, though quite a long term one, I may go through the machine board by board and do cleaning and possibly replacement, along with other necessary renewals or repairs. The deck was cheap when it was bought so I'm willing to experiment a bit and hoping to learn a few things as I go.
Is it likely that replacing electrolytics, tantalum caps and transistors would really help with the playback issue though? I may do a cap replacement later, and I'm putting together a list of all caps on all boards for when that day comes, but I am guessing there would be other things I should be looking at first, like touching up the solder connections on the underside of the boards. Any suggestions on that or other things I should be doing?
I have cleaned all switches I could find, oiled the pinch wheel bearing, and done the pinch wheel solenoid position adjustment according to the service manual. I haven't checked the pinch wheel pressure with a spring scale, as the wheel has to be off to get the deck open, so that'll have to wait until I close everything up again. There's a brake solenoid adjustment in the service manual, I haven't got to that yet. Also no adjustments to the brakes, as I've never done that on a deck yet and I don't want to mess that up - or not yet, anyway.
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Hello Bohuweno your tape deck has several automatic features including this automatic condition applied when-
The sensing pole reverses the tape direction during playback mode .
Automatic reverse is affected when the sensing FOIL ( affixed to the INNER side of the magnetic tape ) comes in contact with the sensing pole .
If you have the older model its fixed to the OUTER edge of the tape surface ---obviously a weak design fault they rectified .
Check that out first before doing anything else as it will need to be fixed .
The sensing pole reverses the tape direction during playback mode .
Automatic reverse is affected when the sensing FOIL ( affixed to the INNER side of the magnetic tape ) comes in contact with the sensing pole .
If you have the older model its fixed to the OUTER edge of the tape surface ---obviously a weak design fault they rectified .
Check that out first before doing anything else as it will need to be fixed .
You should sign up over at tapeheads---lots o' AKAI experts there who can help:
Reel To Reel - Tapeheads Tape, Audio and Music Forums
Reel To Reel - Tapeheads Tape, Audio and Music Forums
Thanks for the suggestions.
Duncan2, for the moment, I have only tested the deck with tapes that have no foil. Wouldn't that mean there's nothing that would trigger an error with the sensing pole?
Dotneck335, I had a look at Tapeheads today, you're right, quite a bit of information about Akais there, and also I think in some old DIY Audio threads. From what I've read so far, I'm still not sure if the general opinion is that the 945 transistors should be replaced with KSC1845s, but leaning more towards doing it anyway if I'm going to be doing electrolytic replacement.
It looks also as if my problem could be caused by the relays (TECK-36) on the relay board, so there is some advice on cleaning the contacts, which may solve the problem, but also a few recommendations that it might be better for the long term to just remove those and replace them with hermetically sealed modern equivalents, which are (they say) easy to find.
Duncan2, for the moment, I have only tested the deck with tapes that have no foil. Wouldn't that mean there's nothing that would trigger an error with the sensing pole?
Dotneck335, I had a look at Tapeheads today, you're right, quite a bit of information about Akais there, and also I think in some old DIY Audio threads. From what I've read so far, I'm still not sure if the general opinion is that the 945 transistors should be replaced with KSC1845s, but leaning more towards doing it anyway if I'm going to be doing electrolytic replacement.
It looks also as if my problem could be caused by the relays (TECK-36) on the relay board, so there is some advice on cleaning the contacts, which may solve the problem, but also a few recommendations that it might be better for the long term to just remove those and replace them with hermetically sealed modern equivalents, which are (they say) easy to find.
The 2SC945,s are 100ma + as opposed to 50ma in the kSC1845,s among some other specs of differences but I noticed the signal feeds to them look like low value electrolytic changing them to film capacitors should be an improvement .
Before I do any replacement of parts on PCBs, I wanted to get the boards somewhat clean. I haven't been able to do anything about the white residue though. It disappears while there is liquid coating the board, but returns quickly as the board dries. Wiping dry with a rag doesn't seem to get better results.
So far I've used distilled water, isopropyl alchohol (76%), and then went for a longer cleaning with the board immersed in a sink of water with some soap added. I used a soft toothbrush and a paintbrush for the water wash, then rinsed it off several times before drying. There's really not much difference in results though, because the white residue returns as it was before. The attached photo is after the sink wash.
Any ideas what to try next to get rid of the white crud?
So far I've used distilled water, isopropyl alchohol (76%), and then went for a longer cleaning with the board immersed in a sink of water with some soap added. I used a soft toothbrush and a paintbrush for the water wash, then rinsed it off several times before drying. There's really not much difference in results though, because the white residue returns as it was before. The attached photo is after the sink wash.
Any ideas what to try next to get rid of the white crud?
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To answer my own question, the solution (or not, as it were) seems to be 100% IPA.
I received a 1L bottle of the stuff yesterday. One going over with that and the hideous looking board in my photo is back to a lovely shade of green. Very relieved, as none of the other cleaning processes worked for me. Now I know what to do, I can move on to more of the boards. If I get around to it, I'll post a better quality photo of a board before and after cleaning. The difference is amazing, and the process is pretty fast too.
I received a 1L bottle of the stuff yesterday. One going over with that and the hideous looking board in my photo is back to a lovely shade of green. Very relieved, as none of the other cleaning processes worked for me. Now I know what to do, I can move on to more of the boards. If I get around to it, I'll post a better quality photo of a board before and after cleaning. The difference is amazing, and the process is pretty fast too.