238 noise

[Caveman]

Had motor board recapped. Before recapping had a speed issue and noise issue. Speed issue fixed noise still there only on playback across all 8 Trks.

No noise on way in, no noise monitoring during recording only on playback. Heads clean I don't use nr. It's a loud buzz not motor sound as far as I can tell I used pitch to speed and slow noise stayed same pitch and level. It's too loud to deal with later or eq it out.

Any ideas where to look would be greatly appreciated, not a ground hum either. High pitched.

Thanks

 

[SkywaveTDR]

Some noise like this has to be evaluated on the bench as I can not just guess what it can be. Everyone is looking for a fuse type fix but there are fewer and fewer fuses used these days and the old method from 50 years ago does not work . It hasn't now for a long time. Either you are I will need to have a look at the power supply and the needed grounding that is done. Maybe there are some electrolytics that have decreased in size as well. Could be a bad solder joint or a lose ground screw?

 

[Caveman]

Sam, thank you. I was trying to get this thing ready for an acoustic band but 238 is just not being good for me Im gonna have to use a 38. Are you still backed up for next 20 years? My local guy is good but not as finicky as you and Id love to get this 238 in shape for me to keep and use around here. It can be lots of fun if working properly. Has a nice little punch too around 200htz.

 

[SkywaveTDR]

Well as the holiday approaches I have gotten a few units out like a A3300SX, A2300SD, 122 Mk II and I have many decks open an in process. Yes there are 3 238 units here that others can not fix here also. I don't expect at 62 that I will last 20 years so I suspect that in a full time scene I will get this stuff out in less than 2 years. I do have Dan my cassette deck associate who works on Nakamichi and another guy wanting to help. This might pan out to be of use.
Otherwise I could have a look at it and see what kind of problem you have. Most the time hum on all channels is a simple fix but we need to locate what is causing that. I have resoldered some 238 power supply boards. None of this stuff was made to aerospace or mil specs. Sometimes I wonder with wave solder that I see if it even reaches consumer level. Still most of it I can fix. Stuff like Dolby S with no schematics or documents well I don't have the time to deal with that.
I hate SMD as it causes more failures the longer they use that junk. I get rid of those kinds of caps.

 

[Caveman]

Ill resolder first before sending out, I can do that at least. Thanks it gives me something to look at, Ill change out filter caps too while in there, maybe Ill get lucky.
Ill get on it right after holidays and report back here maybe it'll help others. I have one channel out on playback now too, faulty rca jack or solder joint so Ill try and address that while Im inside. I know old unit but lots of run and I actually like what it does to the sound. Funny how we wanted transparency and digital is pretty transparent and I don't like it lol

Thank you very much for pointing me in a direction. I don't have the dolby s I have the dbx but never use it. Id rather eq any hiss out. ;-)

 

[SkywaveTDR]

Very good. Many problems on well made stuff is rather minor in nature. Make sure to recap that motor board or you will be sorry you let that go. This is one I did a long time ago and they don't have stability problems or failures.

 

[Caveman]

motor board was recently recapped had noise before recap thought it was the caps but still had noise. Pulling channel boards going to switch see if my trk 7 issue is on board go from there. Thanks again Sam