Hi everyone, I'm hoping that someone here maybe able to help? I have a Fostex G24S which is suffering from the dreaded leaky capacitors on several of the R/P amp boards.I have got the service manual for the G16/G24.My problem is that my boards have a different part number than the one shown in the manual.The manual lists the boards as part number:8251878 but the boards that are fitted are part number:8251897.These are not illustrated in the manual I have.I do not know in what year this machine was produced but it seems that it may be a later or earlier version of the one detailed in the manual.I was wondering if anyone can point me in the right direction to obtain the proper schematic for my machine? Any information would be gratefully received.regards Mike
Fostex G24S-Schematic for r/p amp
- Thread starter mikero55
- Start date
sweetbeats
Reel deep thoughts...
Have you compared the schematic or PCB layout in the manual to your board? I wouldn't get hung up on the part number of the assembly...that could change year-to-year with only minor or nil changes to the assembly itself.
And anyway if it just recapping that you need to do can't you just replace for like values of what's on the board right now? Don't need a schematic for that.
And anyway if it just recapping that you need to do can't you just replace for like values of what's on the board right now? Don't need a schematic for that.
Thanks for your time and quick reply.......perhaps I should have been clearer.My problem stems from the fact that the boards have all had at some time had a partial recap and I would have liked for my own peace of mind to check that this was done acurately.
Interestingly, although the boards are obviously the same shape and size as the manual.....the component layout is significantly different. Regards Mike
Interestingly, although the boards are obviously the same shape and size as the manual.....the component layout is significantly different. Regards Mike
sweetbeats
Reel deep thoughts...
Hm. I just looked in my G24S manual and it is likely the same one you have.
If I was in your shoes I'd turn to the schematic in the manual and start tracing through and comparing the circuit topology to your card.
I bet you'd find that circuit-wise it is nearly identical. Often times revisions are related to component layout.
Try checking the caps you have against the values in the manual and see how different they are. If some are greater in value chances are you can just replace with like value.
If I was in your shoes I'd turn to the schematic in the manual and start tracing through and comparing the circuit topology to your card.
I bet you'd find that circuit-wise it is nearly identical. Often times revisions are related to component layout.
Try checking the caps you have against the values in the manual and see how different they are. If some are greater in value chances are you can just replace with like value.
Hey Sweetbeats
Nice to see you in the Fostex section. I was just looking to see if anyone had info on an issue. Maybe you can help me. My G24S shows no life in the meters. Nor do I hear any sound from the prerecorded tape. I used to hear it and the meters worked fine. I am puzzled. I can't believe all cards are not working all at once. It must be something else. I don't want to take out the cards simply to do a 'tire kick' and slip them back. Nor do I want to tamper with the heads. I have demag the heads, still no change.
Hope someone has some thoughts on this puzzle.
Nice to see you in the Fostex section. I was just looking to see if anyone had info on an issue. Maybe you can help me. My G24S shows no life in the meters. Nor do I hear any sound from the prerecorded tape. I used to hear it and the meters worked fine. I am puzzled. I can't believe all cards are not working all at once. It must be something else. I don't want to take out the cards simply to do a 'tire kick' and slip them back. Nor do I want to tamper with the heads. I have demag the heads, still no change.
Hope someone has some thoughts on this puzzle.
sweetbeats
Reel deep thoughts...
I'll tell ya what others would say...
1. Check your fuses and don't go with just a visual check...pull 'em out and check 'em with an ohmmeter.
2. If the fuses are all good then its time to isolate the power supply and check the voltage on all the power rails.
3. If there was a fuse or two that were bad and it/they keep blowing when you put new in its a more complicated problem.
4. If the rails are all good on the power supply its a more complicated problem.
It starts with checking the fuses and checking the power rails with the power supply isolated.
1. Check your fuses and don't go with just a visual check...pull 'em out and check 'em with an ohmmeter.
2. If the fuses are all good then its time to isolate the power supply and check the voltage on all the power rails.
3. If there was a fuse or two that were bad and it/they keep blowing when you put new in its a more complicated problem.
4. If the rails are all good on the power supply its a more complicated problem.
It starts with checking the fuses and checking the power rails with the power supply isolated.
Thanks Sweetbeats
Okay I will do what you suggest. But I have to admit I find it hard to believe it has anything to do with the fuses. (hehe! My famous last words). There is no other indicator of failure anywhere else. The machine works! But....I will start there cos I have no other option given. I think your experience speaks volumes, so I will let you know how it goes. First though, I'm going to speak to Mr. Ohm's about his law. hehe!
Okay I will do what you suggest. But I have to admit I find it hard to believe it has anything to do with the fuses. (hehe! My famous last words). There is no other indicator of failure anywhere else. The machine works! But....I will start there cos I have no other option given. I think your experience speaks volumes, so I will let you know how it goes. First though, I'm going to speak to Mr. Ohm's about his law. hehe!
sweetbeats
Reel deep thoughts...
So, wait...
Are you sure you have the source selected to sync or repro?
Also, you may want to start a new thread.
Are you sure you have the source selected to sync or repro?
Also, you may want to start a new thread.
Hi Mikero:
Hello Mikero:
I really feel the same, and indeed, if not actually changing the capacitors'll fix the problem. What if I am sure, is that really the problem is in the r/p amp of my FOSTEX G16s, as two of the cards work, the change of position, and are OK, I need only solve the problem of the other! .
Have you done any repair or replacement of capacitors? What do you recommend?
In relation to the schematics, in my case, I have also in the service manual 8251878 and 8251897 in the machine. I started to make it up as recommended Sweetbeats, Make it visually and comparing.
If someone in the forum can help me, I'll be extremely grateful..
Hello Mikero:
I really feel the same, and indeed, if not actually changing the capacitors'll fix the problem. What if I am sure, is that really the problem is in the r/p amp of my FOSTEX G16s, as two of the cards work, the change of position, and are OK, I need only solve the problem of the other! .
Have you done any repair or replacement of capacitors? What do you recommend?
In relation to the schematics, in my case, I have also in the service manual 8251878 and 8251897 in the machine. I started to make it up as recommended Sweetbeats, Make it visually and comparing.
If someone in the forum can help me, I'll be extremely grateful..
miroslav
Cosmic Cowboy
I heard from a very reliable source (Steve Puntolillo - Sonicraft.com) that the Dolby S versions had issues with the Dolby S chips, and they are prone to eventual failure and not repairable or replaceable as there are none to be found anymore unless you get another Fostex S machine for parts that has working chips.
I use to feel somewhat shortchanged because I bought my G16 in the first year or two of production, so I have one of the Dolby C versions, and I always wished I had the S...but Steve said I was lucky to have the C version as those Dolby chips never failed.
Apparently...if the chips fail...that's it with the card on that channel.
I use to feel somewhat shortchanged because I bought my G16 in the first year or two of production, so I have one of the Dolby C versions, and I always wished I had the S...but Steve said I was lucky to have the C version as those Dolby chips never failed.
Apparently...if the chips fail...that's it with the card on that channel.
Must be one somewhere
Hi peeps. I have two of these annoyingly lovely G16S machines. Both have different R/P cards. I'm looking at a 8251897 and my other machine has the earlier cards with the Dolby daughter board. Neither of these cards is mentioned on the 3 versions of the manual I've downloaded....
Somewhere on the planet MUST be the right version. We need to find an ex-fostex engineer.
Meanwhile does anyone think that if a cap shows signs of heating (i.e. a discoloured case) this could be a clue to its demise.
Not sure what to do about the earlier cards although the machine works ok with the Dolby switched off. I read somewhere that the Dolby chips on these were very dodgy.
Gaz
Hi peeps. I have two of these annoyingly lovely G16S machines. Both have different R/P cards. I'm looking at a 8251897 and my other machine has the earlier cards with the Dolby daughter board. Neither of these cards is mentioned on the 3 versions of the manual I've downloaded....
Somewhere on the planet MUST be the right version. We need to find an ex-fostex engineer.
Meanwhile does anyone think that if a cap shows signs of heating (i.e. a discoloured case) this could be a clue to its demise.
Not sure what to do about the earlier cards although the machine works ok with the Dolby switched off. I read somewhere that the Dolby chips on these were very dodgy.
Gaz
miroslav
Cosmic Cowboy
I've tried my G-16C a couple of times with the NR off, and it was OK, not bad in any significant way...but I think it has a better overall sound quality with the NR on.
Luckily, the G-16 decks with Dolby C are apparently not prone to the breakdown issues that the Dolby S chips had.
You can hit it harder with the NR off to try and make up some S/N...but then you can only go so far with low frequency stuff as it will just overload and not really compress like on bigger format decks.
The Otari 2" MX-80 I got recently came without NR (not counting the built-in crappy HX Pro, which I don't use)...so I was concerned a bit about S/N, but I can hit it so much harder than the G-16, and it just takes it without a hint of overload...and it sounds nice and clean.
Anyway, I think you can still get a lot of work out of the G-16 even with the NR off...just watch that low end, and you can also boost some upper high end going in, then just roll it back on mixdown, and that should help with the S/N.
Good luck!
musicbizzy
New member
I have the same problem.
My machine is a G16S with the 8251897 101 ONE CHIP DOLBY S BOARD which was their latest production card.
The R/P card/board in the service manual was a 3 chip design and earlier production and #8251878 001.
If you or anyone has a copy of this production change schematic and board component layout, I would
certainly want to purchase a copy.
Thanks,
Musicbizzy