Akai GX-4000d playbackj
- Thread starter Young46
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No it's on the storage post.
Yes the pinch roller is a little hard and shows minor cracking. I cleaned it with a coffee filter and got quite a bit of residue. I have it torn down so I haven't had a chance to test it after cleaning the pinch roller. No doubt the roller needs to be replaced. This unit has a cooling fan that must have been installed by a previous owner. I can't find anywhere that this unit came with a fan.
Make sure the capstan drive belt is on the 60hz step of the motor pulley and not the 50hz step. The 60hz step is the smaller of the two.
dhnash
Super Member
I second KevinJS's comment about Terry's Rubber Rollers. He will make your old, hardened, glazed or cracked pinch roller look and work just like new for $35 plus shipping. I have used his service many times and have never been disappointed.
http://www.terrysrubberrollers.com/
http://www.terrysrubberrollers.com/
Hello and thank you for your reply and help. I apologize to all who have responded with suggestions. I had to have emergency gallbladder surgery and have been feeling bad for several weeks now so I have not been ignoring anyone it's just that I have not had the energy to work on the unit and respond to the replies.
Yesterday I sanded the pinch roller and cleaned the residue off of it. I haven't had the chance to get the rubber rejuvenator yet but will try to find some next week. After sanding the roller I put it back on and played it for awhile. It seemed to help although it did not solve the problem. I also cleaned everything in the tape path.
Thank you for the reply. I have a question about the "smaller" pulley. The motor pulley has a small and larger diameter pulley. The flywheel also has a small and large diameter pulley however the two don't line up i.e. small to small, large to large. They line up larger diameter motor pulley to smaller diameter flywheel pulley and smaller motor pulley to larger diameter flywheel pulley. Right now the belt is on the larger diameter motor pulley and smaller diameter flywheel pulley. Is this correct or should it be on the smaller diameter motor pulley and larger diameter flywheel pulley?
Thanks dhnash and KevinJS for the info. I will contact him next week.
Thank you, yes the switch is in the correct 60hz. The "button between the reels? Which button are you referring to?
That's why it is running too fast, it's set up on the wrong pulleys. Smaller driving pulley = slower final drive speed, larger driven pulley also = slower final drive speed. Large drive pulley and small driven pulley = faster final drive speed (think of a 10 speed bike to picture the ratio and result). Try it with the belt on the small motor pulley and large flywheel pulley, that should be the correct position for 60hz operation. Also if this deck came from overseas and was used at 50hz then you need to make sure that the 50/60hz motor capacitor switch is set for 60hz.
Thank you, I will try what you suggest. Now that I have the unit torn down and have the pcb's accessible are there any caps and transistors that I should replace?
Well, yes and no. Akai decks use Hitachi 2sc458 small signal transistors in the record and playback sections of their amplifier boards and that particular transistor doesn't hold up very well. If the record and playback functions are working fine then you may want to just leave it alone and enjoy it. Personally I always replace any and all 2sc458's with commonly available ksc1845 transistors whenever I have an Akai deck torn apart for service just as preventive maintenance but that's just me. I've had dozens of Akai decks of all models and years come through here with problems caused by those transistors so if I'm in there I just do them (I buy ksc1845's 100 at a time, they are good for many applications).
Problems caused by failing 2sc458 transistors can include weak or no playback in one or both channels, weak or no record in one or both channels, squealing sounds, crackling or rushing wind noises in record or playback, jumping or unresponsive VU meters, garbled playback or recording, increased noise floor and background hiss etc.
People often blame the Taiyo-Yuden SIP package (an early style chip package) for amp problems in these decks but believe it or not the old SIPs are pretty reliable and don't really seem to fail all that often. I've really only had one deck with bad SIP chips (an M-10) and I think it was hit by lightning because both SIPs were bad and other stuff was blown out too.
Caps I generally leave be unless they are causing an issue but that's kind of a controversial subject. Personally over the years I have found many more issues caused by failing transistors than by failing capacitors but I'm not going to get into that.
Thanks. I am familiar with the ksc1845 having used them in various Pioneer receivers. I will order some from Mouser and replace the 2sc458's while I have it down.
corpblues
AK Member
Thank goodness for this thread. I am cleaning up a GX-4000D for a friend. I checked that it played or thought I did, before spending a day cleaning it up. It cleaned up great and appears to be in excellent condition. It is factory marked on the back it was set to 220/50, but while I had it apart I found it had been changed over to 120/60. However, after cleaning it up and putting it back together I noticed it ran too fast.
(note : don't use a classical tape when testing as it might not be immediately obvious if running fast. Any voice recording is immediately obvious.)
After recenting being down this same path with another deck, I thought it might be pulley related. So searched AK and found this chain.
After moving the belt to the small pulley on the motor and big pulley on the flywheel it plays properly. However, there is also a metal drive belt guard that has to be loosened and moved to the left and retightened. The metal gaurd is obviously designed to be adjusted for the 60 or 50 mhz position as it has slots. If you don't move it, the belt will rub moved to the other mhz position.
(note : don't use a classical tape when testing as it might not be immediately obvious if running fast. Any voice recording is immediately obvious.)
After recenting being down this same path with another deck, I thought it might be pulley related. So searched AK and found this chain.
After moving the belt to the small pulley on the motor and big pulley on the flywheel it plays properly. However, there is also a metal drive belt guard that has to be loosened and moved to the left and retightened. The metal gaurd is obviously designed to be adjusted for the 60 or 50 mhz position as it has slots. If you don't move it, the belt will rub moved to the other mhz position.
