Fostex G16 service manual

WarmJetGuitar

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Does anyone of you have a service manual for the regular G16 without the "S" or even better a straight up solution to our issue?

One of our G16's won't erase properly on all tracks and our tech who's usually a wizard can't figure out how to sort it. He's been looking for a service manual all over the web and was only able to find it for the S version. Can you help me out guys?
 
Just to be clear...your model G16 is the Dolby C, and not the Dolby S version...?

I have the service manual for the C...at least I don't recall if it states one or the other...I think it's just says Service Manual G16, but I'll have to check later today...I'm not at my studio.
At any rate, I think I got it from Fostex before the S version came out...so it would be for the Dolby C.

I have not specific answer to your problem, and I don't know if the service manual will help solve it.
It's been awhile since I calibrated my G16 using the service manual, as I stopped using it 3 years ago when I got my Otari MX-80....but even so, I don't recall that there was a lot of extra troubleshooting info in there, like for your situation. It was mostly the calibration/set up stuff and schematics.
 
I only have the G16S service manual as well, but I'm certain the Dolby C version and S version are going to be the same when it comes to erasure and bias circuits, as you switch NR off to adjust them anyway.

If all 16 channels are failing to erase properly, there are two things I would look at. The first is mechanical... adequate tape tension/contact with the erase head, and position of the erase head. Is it aligned correctly? And the obvious gunked up dirty head of any kind, R/P or erase. Anything that interferes with tape to head contact is going to reduce performance.

The second thing to look at (in any multitrack) is the main Erase/Bias PCB. Each of the 16 R/P Amp cards has its own erase and bias circuitry and adjustment points, but there is a main erase/bias PCB that feeds all of the R/P cards. You could have some component failure there or even further back to the power supply that feeds the main erase/bias circuitry. It could even go all the way back to the main power supply for the deck. At any rate it has to be a broader issue because The likelihood of all 16 R/P cards failing in that way all at once is zero.

These machines are getting on in years, so things do fail, but just a little tip I try to pass along when these things come up. If you're using +9 class tapes, like ATR, SM900, GP9, etc, on these machines you're going to burn the above circuitry up a lot sooner... because your pushing them to the bleeding edge. Don't know what tape you're using or what tape a previous owner may have used, but just thought I should throw that bit of info in for good measure and for future reference for anyone else that may come across this thread. Fostex recommends 456 for those machines and to keep these things running well into the future that's what we should be using (or bias compatible, SM911, SM468, 3M 986, etc)
 
Oops... I almost forgot to mention one of the more common mechanical issues: Is the tape lifter fully retracting after going from rewind or fast-forward to reproduce mode? If not of course it's going to be interfering with tape to head contact by pushing the tape away from the heads ever so slightly. If it were more than ever so slightly you wouldn't be able to record or playback at all, but ever so slightly is enough to screw up your erasure spec, which should be 70dB down or more..
 
I would consider what Beck is telling you before you do anything else.

AFA the service manual, looking at the one online for the G16S/G24S...mine simply says Service Manual Model G16 (there is no mention of C or S).
The copyright date for the manual is 1990...so it's most likely pre-S machines.

OK...here is the ONLY specific reference to the Erase calibration procedure:

*******************************************************************************************
4.3.6 Erase Current Adjustment

1) In adjusting the erase current, put all the 16 tracks in record mode.

2) Rotate all the 16 tracks of the ERASE LVL pot (R207) fully CW.

3) To adjust TRACK 1, for example, hook the hot side of the oscilloscope probe to TP-6 and ground clip of the probe to GND pin.

4) Set the core of T-1 (ERASE ADJ) so that voltage at TP-6 reaches the peak level point.

5) Then adjust ERASE LVL (R207) so that the voltage at TP-6 is 85mVp-p or 30mVr.m.s. (-30dBV).

6) Calibrate tracks 2~16 in the same way.


4.3.12 Erasure Measurement

1) Put NR ON/OFF switch to OFF.

2) To adjust TRACK 1, for example, apply a 1KHz, 0dBV (1V) signal which is 10dB higher than the reference level, to INPUT jack 1 and put TRACK 1 in the record mode.
Partially rewind the tape to retain a section of the 1KHz signal and then record over the remaining section without any signal at the input.

3) Rewind to the start point of the recording, playback the tape and insert a 1KHz bandpass filter between OUTPUT 1 and the level meter to measure the output.

4) The level ratio between the 1KHz recording and the no-signal recording is the Erasure figure. It is considered as a normal condition if Erasure is higher then 70dB.

5) If it is off the spec, increase Erase current about 10% by the procedure of Section 4.3.6.
Monitor the Erase current waveform on the oscilloscope at adjusting and set the core just before the waveform begins to deteriorate.
A higher current will heat the Erase head and result in damage to the tape. And check the Head touch condition of tape.
*******************************************************************************************

That's it...there are no other references to the erase head or any erasure issues.
Hope that helps.
 
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There's some valuable advice there guys, thanks a bunch.
And yeah, it's the version with Dolby C. I'll send this thread to the tech and I'm sure he'll get it running.
 
Hey guys... the G16C is still causing headache. Does anyone of you have the whole manual in digital format?

Our tech is watching this thread. The problem is that the erase head won't go any further than 12 milivolt and it's supposed to go to 85.

I'll give a virtual round of beer to anyone who can help us sort this issue, got a session this weekend.
 
I will scan my copy of the G16 Dolby C Service Manual for you.

I saw your post a few days back, and then I just forgot about it until you PM'd me....sorry.

I don't need/want any money for it.
Pass it on..post it on websites...whatever.
I'm kinda surprised that Fostex doesn't provide the Dolby C version service manual on their website, but then, it's 25 years old. I guess they didn't want to bother scanning/providing it since they switched to the Dolby S version after only 2 years of the C version production.

It might be a PITA to scan some of the schematics pages, since they are fold-out, larger pages, but I think the scanner at work is large enough to do single sheet scanning of the larger pages...but I can't just feed the whole thing in...it's one page at a time, and all the pages are double-side content.

I'll post it back here in this thread when it's done...tomorrow or the next day.
 
What a PITA!!! :D
It took me like 8 tries to get the whole manual scanned in.
Our networked scanners at my day job scan directly to your email account...but the email accounts have a limit on the attachment file size. :facepalm:
So I was trying to scan it first in one shot, but it was way to big for the email. Then I messed around with different resolutions 2-3 times, still too big...then I broke it up into 4 chunks...then 8 chunks....then finally 12 chunks, and that worked.

Here's the link...I combined the chunks into a single PDF file.
Also...there is no page 94/95...there never was. I think it was a typo by Fostex when they put the service manual together.
I've had the manual safely tucked away for years, so it hasn't seen a lot of handling, and I don't think the page fell out...but I'll double check tonight. If I find it, I will scan it and add it...but I'm 99% sure that there never was page 94/95.

Fostex G16C Service Manual
 
I dont even have a fostex, but I thank you for your work. Sounds like quite the undertaking. ☺
 
Wow, thanks a million Miroslav - thats extremely generous of you, you truly saved my ass with this one. Owe you a huge favour.
Man, I love this forum! People like you make a major contribution in keeping proper recording alive and well.
 
I'll be visiting Denmark this summer...get that spare room ready.... ;)

Post back if you get anywhere with the G16 repair.
 
Yeah, drop by Århus for beers and coffee on us :-)
Havnt had the time to deliver the beast for repair but will happen soon, just need to transfer a tape for some mates who wanna mix in the digital domain.
 
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