Bottlehead Forum

General Category => Technical topics => Topic started by: ironbut on September 28, 2012, 09:14:15 AM

Title: Measuring magnetic heads?
Post by: ironbut on September 28, 2012, 09:14:15 AM

After reading a post on another forum regarding the measurement of inductance of tape recorder heads (playback and/or record) I tried to search for the best method of doing this. During my "surfing" I found that deviations from stock inductance can also be used to indicate head wear.

I can't quite remember where I saw it, but I seem to remember that folks use an inductance bridge for doing these measurements.
Well, I don't have an LC meter or an inductance bridge but I do have a bunch of tape recorders and headblocks so I thought it might be an interesting project to do measurements on them.
So, for the most part, I'd be looking at ranges of 100-800 mH and I'd like to get pretty reasonable accuracy.
What would be the best method?
Buy an old bridge or build one specific for the range I'm interested in?
Or are the current LC meters better or just as good?

BTW, I'm just at the "what if" stage and I'm hoping to get a better understanding of inductance out of this little exercise. So any books or sites you guys can recommend would be great!

Title: Re: Measuring magnetic heads?
Post by: Paul Joppa on September 28, 2012, 11:01:42 AM

First thing is to find out at what frequency, and at what signal level, the inductance should be measured. For components with a magnetic core, the inductance is a more or less strong function of these parameters! Then you can look for a meter that works at those frequencies and levels.

I have not done that search, so I don't know the answer - if I did I'd post it!

Title: Re: Measuring magnetic heads?
Post by: ironbut on September 28, 2012, 02:00:53 PM

Thanks Paul. Exactly what I needed to know.
I was kinda floundering around for the right questions to ask and hoping that you'd give me a little direction.
Now I know just the guys to pester!

Title: Re: Measuring magnetic heads?
Post by: Jim R. on September 29, 2012, 05:34:10 AM

Steve,

Would that be MRL? JRF magnetics?

One of these days when all other projects are done (yeah, right) I'd like to start poking around in my two r2r decks, though I have no idea where I'd put them :-).

-- Jim

Title: Re: Measuring magnetic heads?
Post by: ironbut on September 29, 2012, 09:20:09 AM

Hi Jim,

Yup. John French is #1 on my hit list and I'll probably bump into Jay McKnight at the AES convention in a month.
I'll start by doing some searching in the AES archive. It's amazing what you can find in there!