Fostex G24 24 track recorder Help?

G

glenn taylor

New member
Hi guys I just bought a Fostex G24 24 track recorder. Finally had some time to load some tape on it and check it out. The functions like rewind, fast forward,play and record all work. What I need help with is I can't get any input on most all of the channels. Channel 12,14, 24+ another few show a bit of level on the leds,but for the most part nothing. Has anyone worked with this machine? I tried sliding the 1st 4 channels out and cleaning the connections. Still nothing in line in or will record? GT.
 

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No....just CPR.

The cards in the Dolby S machines just seem to go bad much moreso that the earlier Dolby C versions. I've got a G-16 with Dolby C, and all the cards still work after 23 years. I even have a used back-up deck, and all the cards work in that one too.
 
Gt,

I had a G16S few years back, basically the some machine. The cards started going bad. You might try switching one that is dead with one that still has some life and see if the problem follows the card. Are you sure your mixer is putting a good signal out? You might also try and change the channel outs from mixer (if one is in the chain).

Ron
 
The channel outs are working. I tested by feeding the two outs to other channels on my board. They work fine.
Wow bad cards? I heard a bit about some of these machines had bad caps. I wonder what is going bad on the cards.
I am not sure where to start? GT.
 
glenn taylor said:
The channel outs are working. I tested by feeding the two outs to other channels on my board. They work fine.
Wow bad cards? I heard a bit about some of these machines had bad caps. I wonder what is going bad on the cards.
Click to expand...

If you're lucky, it's just the capacitors. But often it's the Dolby IC itself, which AFAIK is fatal because the ICs probably aren't available anymore. Unless you're really lucky and it is a capacitor problem, I your only options may to either try and figure out how to bypass the noise reduction by studying the schematics (but then of course you'll have no noise reduction) or to get some compatible Dolby C cards and use those instead.
 
jpmorris said:
.... or to get some compatible Dolby C cards and use those instead.
Click to expand...

AFAIK....with the Fostex G-Series...you can't just swap Dolby S cards with thosr from a Dolby C machine.
I know when I first got my Dolby C, and like a year or two later they came out with the S version, and I kinda felt short-changed, so I asked Fostex if there was a way to upgarde my deck to be an S version....they said NO.

Of course, now I'm glad it wasn't possible and/or that I didn't go out and get an S instead. :)
 
jpmorris said:
If you're lucky, it's just the capacitors. But often it's the Dolby IC itself, which AFAIK is fatal because the ICs probably aren't available anymore. Unless you're really lucky and it is a capacitor problem, I your only options may to either try and figure out how to bypass the noise reduction by studying the schematics (but then of course you'll have no noise reduction) or to get some compatible Dolby C cards and use those instead.
Click to expand...
There is a noise reduction in or out switch on the back panel. So turning this switch to the out does not take the dolby with the possibly bad part out of the machines circuit? GT
 
It would just switch NR off...but I believe the Dolby circuit/chip is still tied to the rest of the card ciruit...so no, that won't solve your problems.
 
miroslav said:
It would just switch NR off...but I believe the Dolby circuit/chip is still tied to the rest of the card ciruit...so no, that won't solve your problems.
Click to expand...

I still think that given the schematics you could bypass the chip, but it would take board-level modifications. In terms of replacing the capacitors, are they through-hole or SMT on these machines?
 
It's been awhile since I had my hands inside my G-16 (been working with the Otari MX-80 the past year).....but I think they are through-hole...though it matters not, since finding new/good S-chips for the Fostex is like finding diamonds in used kitty litter...and I've dumped a lot of kitty litter in my time, and none of my cats ever shit a diamond....not even a lousy Fugazy! :D

AFA a bypass modification...it may be possible for a strong electronics tech...but I think way more work/effort that anyone will want to tackle, which is why most people just look for a second deck to cannibalize.
 
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miroslav said:
It's been awhile since I had my hands inside my G-16 (been working with the Otari MX-80 the past year).....but I think they are through-hole...though it matters not, since finding new/good S-chips for the Fostex is like finding diamonds in used kitty litter...and I've dumped a lot of kitty litter in my time, and none of my cats every shit a diamond....not even a lousy Fugazy! :D
Click to expand...

I was thinking about the capacitors rather than the chips, I think the ICs are SMT. But it occurred to me that we might be too quick to point at the Dolby codec - it might be that they're fine and the audio path has choked on the way into or out of the IC.
It might be worth recapping one of the cards that is partially working and see whether it comes up to full functionality. If it does, it might not be the Dolby at all.
 
Well...it's possible...but just a short time ago there was someone here with almost the identical issue...and he tried swapping a few caps, moving cards around, and a few other things...and it didn't do anything for the dead cards...and yes, they were Dolby S too.
 
I talked with a repair place in Chicago. The guy said most likely it's a $300 fix. He wouldn't take a stab at what he thought was wrong,but said it was a pretty easy fix. "Not the caps" he said. Man........ I tried putting a hot signal all the way across the machine today. Playback show very little close to no signal. The channel arm lights are orange when I push the record.
I assume this is correct for this machine. GT.
 
It's not my money, but $300 seems pretty reasonable given that he's probably going to have to mess with all 24 cards.
 
Yes I am thinking about sending the machine up there to Chicago to get fixed. However repair guys have given me a good price on the phone and once the equipment is in their hands they say it will cost more. Which is ok with me. Before I send it I want to try a few more things. The noise reduction might be the problem. It seems like a global thing.(if this is the right term). I have 1 week until I have to have some heart surgery so I am killing time,but will send it out if I have not fixed it once I am out of the hospital. GT.
 
Does anyone know where I can get a service manual? For starters I'd like to check the voltages and see if they are ok. I also tried playing back a tape recorded on another machine and got nothing. So the playback for sure is not working. GT.
 
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