Fostex 80 heads adjustment/relap/ etc.

[Blue Jinn]

Have two model 80s, one w/ extreme uneven head wear (trapezoid) and one which has the guide(?) roller cap threads stripped, (who knows how that happened) and I am assuming a broken capstan belt (capstan won't turn) LEDs seem functional on both though.

Does anyone know an easy way to remove the head blocks from these? I'd like to send the 80 heads to JRF for a looksee.

Also, the SM doesn't really discuss zenith adjustment, just azimuth and height. I'm assuming the two screws that hold the head in place can be adjusted to correctly get the zenith, but how do you measure this? I've read something about about putting grease pencil or chalk on the head and then making sure it gets rubbed off all the way. Any other thoughts?

(Also picked up an A8 which has some head wear, but looks like pretty even head wear. Will see how it cleans up, has some Ampex 456 goo on some of the tape path. All the VU lamps are working too. Bought from second owner, who didn't use it too much, kept the original box and styrofoam though, so that says something.)

I'll try to post some pics of all of this as it transpires.

 

[Blue Jinn]

Followup:

Well, the A8 cleaned up pretty well, heads look decent. Was squeaking a bit, but ran some tape across it ff/rew/play etc etc. All functions seem to work, like it just had to wake up from a long (per seller 10 year) slumber....

As for the 80s, the parts machine (with the better heads) -- doesn't sound like the capstan motor is even turning on (listen for it while engaging one of the tension arms -- so motor maybe. Havn'et pulled either apart yet.

Also, one of the tension arms was bent slightly on the "better" machine (worn head machine) these aren't the most stout little guys, bent it back into what looked like straight, or straight enough....

 

[Blue Jinn]

Reviving my own thread here. I did stumble across this Tape Recorder Alignment which discusses a means to check zenith. I am (finally) getting a 'scope this Friday. Guy's going to deliver it too. I still haven't dug all the way out of the mess yet but close, and I still haven't fixed the Otari, and I still haven't taken down the parts 80, and I still haven't fixed the Quadra (needed the scope first so that doesn't count) and I still haven't eaten lunch. Other than that it's all cool.

 

[miroslav]

I still haven't dug all the way out of the mess yet but close, and I still haven't fixed the Otari, and I still haven't taken down the parts 80, and I still haven't fixed the Quadra (needed the scope first so that doesn't count) and I still haven't eaten lunch. Other than that it's all cool.

Thanks for the progress report.

 

[sweetbeats]

I still haven't gotten to "all cool".

 

[BradL8068]

Blue Jinn
Usually azimuth is the only adjustment that is a single screw. Height, zenith, and wrap are usually a function of mounting the the head in the block and frustrating and interactive.
( get the zenith right and you have screwed the height) So it usually takes experience to get these all in line so the azimuth can be adjusted.
This youtube video explains the different type adjustments.
Azimuth and Head Adjustment terminology - YouTube
The simple answer to your question yes grease pencil. You put a light coat on the face of the head and play garbage tape. A wear pattern will show. If it is a rectangle you are good.
if a trapezoid you are bad. but adjusting that will effect height. so you need to go around in a circle until they all match. If your heads are already worn in a trapezoidal pattern you may never get it to look good.
SO while adjusting the mounting screws the goal is to get the height so the tape travels centered over the head AND smoothly through the guides, zenith so the tape doesn't ride up or down, wrap for peak high frequency, and azimuth for proper phase alignment. It can be a few hours of He** even if you have done it before. If you want to try yourself it can lead to a sense of pride IF you get it right. If you don't it can wreck your machine until someone fixes it. That's the long answer BUT if you send the FULL head block to JRF I expect they can do all of this for you when relapping the heads.
Most machines (except cassettes) have just a few screws that allow the whole head block and guides to be removed in one shot. A matter of fact it is impossible to adjust anything but azimuth on Studer machine while the heads are mounted on the machine. Though I have done all these alignments on a MCI ( a bear but I was trained at the factory)
Brad

 

[wkrbee]

If the head has a trapezoid wear pattern,the "tilt' is off.this could be because it was never set up correctly at the factory,I've seen a few 8 trk .5 " machines,(hang over Monday),or maybe the chassis is bent?

 

[A Reel Person]

My recollection is that...

On the Fostex A8/A2, which I've inspected, and assuming here the M80 is the same in this regard,... the heads are hardwired to the audio section by a point to point soldered wiring harness. There is no clever disconnect, no connector, no way to get those heads separated from the rest of the unit except to desolder the wires from their mount point.

It's been a long time. I could be wrong, but I don't think so. YMMV.

 

[Blue Jinn]

On the Fostex A8/A2, which I've inspected, and assuming here the M80 is the same in this regard,... the heads are hardwired to the audio section by a point to point soldered wiring harness. There is no clever disconnect, no connector, no way to get those heads separated from the rest of the unit except to desolder the wires from their mount point.

It's been a long time. I could be wrong, but I don't think so. YMMV.

I think you are correct, although I also think if you dig far enough in the machine you can desolder from one of hte main boards without having to swear too much.

 

[Blue Jinn]

Blue Jinn
BUT if you send the FULL head block to JRF I expect they can do all of this for you when relapping the heads.

I am pretty sure that is a service they offer when you send hte whole head block. FWIW, I had a spare MSR-16 head relapped by him a few years back, very nice to deal with. I haven't taken either of these machines apart yet, so I am not sure exactly how much of a PITA it would be to swap the entire head block down to the main card it connects to. I'll have to look at hte service manual first. I'll certainly post back if/when.