Fostex R8 Calibration issues...

[Dertodesking]

Hey guys,


This is my first thread so bare with me.

A couple months ago i fell in love with tape. So i decided to introduce some r2r into my studio. I bought a Fostex R8, and then an other for spare parts. Change all the parts that were'nt up to snuff, cleaned and demaged-it. bought some reels of RMGI LPR35 and taught i was good to go. Unfortunatly, being the way i am, i wanted to make sure that everything was in order before i start recording. So i got myself a calibration tape from MRL. I ordered the 21J403 which is a 15isp, IEC, 355nWb/m tape.

So i started the calibration process, which, let me tell you isn't so easy on that machine. Ok, i'll admit it's my first time, but the service manual is badly written and confusing. So here's what i did so far:

- I could'nt check the speed and flutter since i don't have the test tape or the equipment.

- I adjusted the phase and the azimuth

- Calibrated the Input and Meter level

- Calibrated the Reproduce level

- Checked the frequency Response

Now when i get to the Bias section everything gets confusing. First the service manual says to check for Bias leakage, which i did for the Repro section but not for the Record section. I just can't find the test point #5 that they're talking about.

Then we move on to, Section 4.3.6 ''Erase current adjstment" in wihich they ask me to "Set the core of T-1 so that voltage at TP-6 reaches peak level". I'm really confused but the whole "Core of T-1" and how do i make it reach peak level.

Last but not least, my real problem hehehe. Section 4.3.7. Bias Current Adjustment. All the manual says is:

"Put all 8 tracks in the record mode. Hook the oscilloscope probe hot side to TP-1, and ground clip to GND. THen set the BIAS LVL pot,C101, at approximately 300 Vp-p over the peak point.

That's all fine, easy enough to do but, the manual suggest to use Quantegy 457, so my guess is that's the set up for that type of tape. If wan't to use either some RGMI LRP35 or SM911 what then? I think, but i'm not sure that SM911 as to be set up at 3db overbias (i might be wrong there). How do i make a proper reading of the bias level i'm setting. This machine is pretty non-standard. It's only got 2 heads so i can't monitor the repro head while the machine is in record. And the VU meter does'nt do that fun little thing where the needle rise t'ill it peaks and then you can set your overbias.

Sorry for the super long thread...

Hope somebody has the knowledge i seek....

I know it's not the best machine in the world but i gave it a lot of love already and would love to see it run like it did 20 something years ago.

Thank you!

 

[Thrust]

You might get a brtter response in the analog forum.

 

[mixsit]

Gadds, flash back. Guess I had the '80, striping SMPTE on trk8, but never got in to it that deep.
Good hunting. Shure someone will chime in..
Cheers

 

[A Reel Person]

I'm gonna go off memory and maybe opinion here or there.

Set the core of T1: T1 is a "toroid". A Toroid is a winded wire coil in circular form, often times with a magnet in the center. It's an inductor, basically what they're referring to. Hopefully you can find the location by using the manual. Setting the core would be adjusting the center magnet with relation to the toroid windings at large. Hopefully there is an adjustment tool slot to facilitate adjustment. Common inductors would be designated with an "L" and typically be contained in a little "can" type packaging. T1 is probably a larger inductor that's not contained in a canned packaging.

Then,... comes the "niceties" of working with a 2 head deck. For bias, all of the "adjust for xxx volts on test point xxx" business is to accommodate the fact that there is no "read after write" on a 2 head deck, as is on a 3 head deck. Setting bias voltage for xxx volts on 457 is a succinct method, and 457 should be bias compatible with SM911 and "close enough" for LPR35,... so just go with it!

The alternative would be to "record/rewind/playback/adjust/repeat" method,... for bias, which would be impractical and prohibitive to attempt. However, after bias you will set Record Level and will use just that method. It is quite tedious and time consuming, so gather your thoughts, calm down, don't panic, and devote as much time as necessary to accomplish that task. To estimate 12 hours of fiddling to get all 8 tracks recording up to proper levels would be reasonable, IMO. I've been there and done that.

Sounds like you've made good progress so far, so give it some time and effort and you can see it through!