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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Wed 27, 2019 8:27 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 11698
Location: Powell River BC Canada
see the following:
Attachment:
pentron  q iii.jpg
pentron q iii.jpg [ 243.57 KiB | Viewed 422 times ]
Attachment:
pentron quik kit q.jpg
pentron quik kit q.jpg [ 154.69 KiB | Viewed 422 times ]
Attachment:
pentron q ii.jpg
pentron q ii.jpg [ 173.8 KiB | Viewed 421 times ]

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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Wed 27, 2019 5:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Canton,Ohio.United States
Hey Jim
No problem there because I am only demagnetizing the heads. the heads that I am installing. They will be in my hand. Tape not even near it.

Steve
That process of head demag is like demagnetizing a tv screen tube. It will be easy with heads in hand first.
That book mag was interesting. Also the address on the mag just happens to be a town about 70 miles away from here.

Now those pictures of the kit show standard type heads which mine aren't even close. There is no gap to speak of. They just have 2 different types of metal. The top is silver colored and the bottom half is copper colored and that is where it records. No spring adjustments either. I may put the set in tonight or tomorrow. I assume the recording metal is what they refer to as the pole piece. I will let you know. But I think I would need that kit if I tried the nortronic heads. Info is great!!


John


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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Thu 28, 2019 9:38 am 
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Location: Tucson, Arizona U.S.A.
The little rectangles they show in those drawings aren't the gaps; they are the pole pieces. The gap is very small. You may need a magnifier to see it.

Also note that the heads have to be demagnetized periodically in use. Some manufacturers recommend something like every 10 hours of run time. Some folks recommend demagnetizing any time before you play a valuable tape. A tape that has been damaged by a magnetized head cannot be restored.

Also demagnetize any steel parts that contact the tape including tape guides and the capstan.

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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Thu 28, 2019 4:28 pm 
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Location: Canton,Ohio.United States
Good points Jim.
Never thought it had to be done so often.
I did put a set of used heads in last night. Aligned them the best I could and it sounds a lot stronger. Wow, were the heads I took out worn! These heads have a squared off "U" shape of surface the width of the tape. Those pieces were loose and shouldn't be so I pulled one out. I took apart the head and it looks like these were designed like an old headphone set. Each end of the U went inside of a slot in the coil.. The long part of the U pressess on the tape.
That piece is two tone color . Copper color on top and silver on bottom. Looks nothing nothing like a head today.

John


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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Thu 28, 2019 6:11 pm 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
Early machines like the Wecor had replaceable pole pole pieces
(just like phono needles) The were sold in small bags as I recall.



The difference between degaussing a color TV and a tape head is this:.

If you make a error by interrupting the current flow to your coil, close
the kinescope, you leave a color splotch on the screen. Then you just start
over.

If you induce a large spike in 1 Henry inductance with coil of hundreds of
ohms of very fine copper windings, you may cause it short out. A strategy
might be to connect a resistor across it.

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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Thu 28, 2019 11:36 pm 
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Quote:
If you induce a large spike in 1 Henry inductance with coil of hundreds of
ohms of very fine copper windings, you may cause it short out. A strategy
might be to connect a resistor across it.

Even if you don't damage anything, you can leave the head magnetized worse than it was in the first place.

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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Fri 29, 2019 12:04 am 
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Location: Canton,Ohio.United States
Guys
You make it sound like its better to leave it alone!lol If I try it, I will do it at a distance. The way Steve said.
That would be nice if thats how you fixed one of these heads. That U piece sits in slots, and I guess the slots have to be pressed tight against them. Then how far they are in makes a difference, I am sure.
As I type, i am listening to a tape being transmitted to a pocket radio in the room I am at. These tapes I am using are recorded from A.M around 1980, but on a Hi Fi recorder. A Roberts Stereo . So I am only using track 1 and 4.
It sounds pretty good now, even though its pretty primitive. For backround music, just fine. I also think it may improve once a few tapes go thru since I am sure they weren't used for last 30 years!

John


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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Sun 31, 2019 1:52 am 
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Location: Canton,Ohio.United States
Mr radio Technician Steve
I have a question about the great info you gave me. I bought a tape head 3000 from the Nebraska Surplus. It is not even close to the correct size on the Pentron head. So, I looked at the mounting kits. they fit all, except the 3000 series. Then I saw at the bottom Quik-kit 77 which is for the 3000 series. It says its exact same as Kit 74 but made for 3000.
Am I on the right Track? (no pun intended). With that picture they show, I am not sure how it will mount to the recorder, but I will give it a try!


Also, in an earlier post , you were saying some recorders have built in degausers. Are these what were known as Crossfield heads? Like a Roberts and Akai recorders have.? just curious


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 Post subject: Re: Tape Recorder Head question
PostPosted: Mar Sun 31, 2019 3:36 am 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
If you can post a photo of the head assembly in the Pentron, it would help.
I do not have Sams CM 4 which has your model.

Cross field system by Akai /(Roberts) is not self demag. It induces bias
through the tape with a separate head. I had thought it was similar to
the patent by Marvin Camras , but an Akai engineer imbedded in the department
I ran years ago did not seem to agree.

I think the Revere/Wollansac auto demag hinges on bias rise and decay
during r/p transitions.

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VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
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 Post subject: Re: Tape Recorder Head question
PostPosted: Apr Tue 02, 2019 12:34 am 
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Location: Canton,Ohio.United States
Hi Steve
I knew sooner or later, I'd get a request to post a picture.lol I never have yet. I was looking at how you do it and see its to shrink to 256K. I'll have to figure it out. In the meantime, I did get the used heads set and put them in. Aligned it pretty good and its playing ok.
I can tell you this that the 3000 head is not a drop in replacement for sure! It had to be mounted somehow. The originals have a screw in the back of the head that when loosened drops in a slot on a metal plate behind the heads.
Thats the adjustment up and down. That plate is part of a bracket that has 2 screws for forward, left and right.

In the first picture you sent me on how to replace a pole piece and align a head. Those are similar and have the replaceable pole pieces you were talking about. But I have no springs and the mounting screws are in a different spot.Otherwise it is close. That must have been a later Pentron. I can say, dad's was the first year. The knobs are unique and ours does not have the switch on the volume control to shut off the motor only.

John


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 Post subject: Re: Tape Recorder Head question
PostPosted: Apr Tue 02, 2019 7:00 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 11698
Location: Powell River BC Canada
quote:

I can tell you this that the 3000 head is not a drop in replacement for sure! I

Nortronics never claimed that heads were a direct drop in because tape
recorder manufacturers had their own designs for heads. The whole era of home
tape recording was like a 'sound camera'. It wasn't intended to copy and just
transcribe phono records. The artists had been fighting over that since sheet music.

Attachment:
Nortronics general i.jpg
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Attachment:
Nortronics general ii.jpg
Nortronics general ii.jpg [ 141.1 KiB | Viewed 328 times ]

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VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: Tape Recorder Head question
PostPosted: Apr Tue 02, 2019 5:31 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
As far as safely demagnetizing heads.....or anything really.......just make very sure you do not power up or down the demagnetizer anywhere near the device, or any metal really. That way you’re sure not to damage anything

...edited 4/3 to fix what the spell checker "fixed"

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Last edited by Barry H Bennett on Apr Wed 03, 2019 12:20 pm, edited 1 time in total.

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 Post subject: Re: Tape Recorder Head question
PostPosted: Apr Wed 03, 2019 12:09 pm 
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Location: Fernandina Beach, FL
Barry H Bennett wrote:
As far as safely demagnetizing heads.....or anything really.......just maybe very sure you do not power up or down the demagnetized anywhere near the device, or any metal really. That way you’re sure not to damage anything

Pretty simple advice and exactly correct and important. To demagnetize tapes and tape heads etc. I start with moving in a circular motion whilst energizing te device. Move closer and demagnetize the item, and then back away moving in circles still. I don’t remove power until far away, more than a foot.

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