Wow it actually works
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Wow it actually works
I finished rewinding my 1-d head as an 8 ohm head. Thank you Markrob for the instructions. I haven't actually tried cutting a record with it but I hitched it up to a speaker output on my stereo and it was very loud. I will try cutting one of the laquers I bought from dour Saturday.
I did not make new bobbins though--I was getting a little impatient--but I fixed the old ones and rewound with 8ft of 30 gauge wire like Markrob said. The wire I finally found is probably as old as the head it self. I still can't believe it works as well as it is. It took a long time to "gap it"--you need to make sure you don't get any of the wires stuck in the gap. Initially I used "whiteout" to hold the wires on the coil just incase I needed to unwind them for some reason. After everything was all set I used a very small amount of super glue to hold them.
Here are some pics--not very good as usual but you can kind of see the coils, the wire, and the head all back together.
http://hermosillo.es.craigslist.com.mx/wan/1033087905.html
As I went through the head it came across as though the head had gotten wet as some point (most likely why it was blown). The two small plates that "sandwhich" the rubber damped were rather corroded and the little screws did not catch much. Hopefully this will not affect anything down the road.
Anyways, I will let you know how the test cut goes tomorrow.
I did not make new bobbins though--I was getting a little impatient--but I fixed the old ones and rewound with 8ft of 30 gauge wire like Markrob said. The wire I finally found is probably as old as the head it self. I still can't believe it works as well as it is. It took a long time to "gap it"--you need to make sure you don't get any of the wires stuck in the gap. Initially I used "whiteout" to hold the wires on the coil just incase I needed to unwind them for some reason. After everything was all set I used a very small amount of super glue to hold them.
Here are some pics--not very good as usual but you can kind of see the coils, the wire, and the head all back together.
http://hermosillo.es.craigslist.com.mx/wan/1033087905.html
As I went through the head it came across as though the head had gotten wet as some point (most likely why it was blown). The two small plates that "sandwhich" the rubber damped were rather corroded and the little screws did not catch much. Hopefully this will not affect anything down the road.
Anyways, I will let you know how the test cut goes tomorrow.
Tim
I set up the head today and did some test cuts. They were very loud! I was fooling with the volume on the amp but I really don't know what I am putting into the head. Can anyone tell me how I can put in a VU meter? You just put it in parallel right? Before I could not see any movement in the grooves but now I can!
Tim
- cuttercollector
- Posts: 431
- Joined: Sun Jun 11, 2006 4:49 pm
- Location: San Jose, CA
Glad you are getting nice loud cuts now.
You could get a rough comparison by listening to the cut material against a typical record to see if you are in the ballpark.
In fact you could play a good record as your source and cut it then compare the two. That will reveal a lot!
Putting a VU meter directly across an 8 ohm cutter drive signal would probably give you close to meaningless results. If it reached "0" at the point that the head was cutting at some standard level it would be coincidence.
Some points to ponder -
Have you got the eq so it is correct for playback?
At what level does it distort?
How much power will the head handle before blowing up?
At least put a pot in series with the meter (heavy duty 1W? perhaps 1000 ohm?) so you can adjust "0" for the point of audible distortion, and it also might be a good idea to fuse it (1/4A?) before you blow it up !
You could get a rough comparison by listening to the cut material against a typical record to see if you are in the ballpark.
In fact you could play a good record as your source and cut it then compare the two. That will reveal a lot!
Putting a VU meter directly across an 8 ohm cutter drive signal would probably give you close to meaningless results. If it reached "0" at the point that the head was cutting at some standard level it would be coincidence.
Some points to ponder -
Have you got the eq so it is correct for playback?
At what level does it distort?
How much power will the head handle before blowing up?
At least put a pot in series with the meter (heavy duty 1W? perhaps 1000 ohm?) so you can adjust "0" for the point of audible distortion, and it also might be a good idea to fuse it (1/4A?) before you blow it up !
All I am using right now is a 1970's Lafayette stereo to power the head. I wanted to come up with a way to get a rough idea of the volume. When I turn the pot the cut is not very loud, but at a certain point it really gets the head moving. If I go up a little higher is does distort. I don't really want to find out what level it blows at; at least not intentionally, although it really isn't that bad to rebuild. I like the pot with the vu meter and the fuse you suggested. I will make a box with terminals a meter and a fuse this week. All I really want is something to give me a rough idea of where I am with the volume.
Tim
Hi,
Glad to hear you got the head re-wound! One thing you may not have known is that you should add a 2 ohm 5w resistor in series with the head. This is needed to make the low freq turnover happen at 500 hz. per the RIAA specs. It also makes the head 8 ohms at 1 Khz. I measured mine to be sure I was in the ballpark. You will lose a bit of loudness, but as you can see, the head needs very little power to get decent modulation.
The corrrosion you are seeing is also on my 1C and 1D. I think this is because the two round plates that couple the rubber damping are brass and the lower one was soldered to the threads of the aramature. Back in the day, they tended to use acid flux to prepare the surface and over time, this reacts badly to the metal. I think this may also be the reason these heads are found open. The small gauge coper wire soldered to the terminals seems to rot because of the use of the acid based flux. I think it will be really hard to blow up the head with new windings. 30 ga. wire needs to see several amps to fuse. The head will distort long before that happens. The good news is that now that you know how to tear into the head, you will be able to repair it in no time.
I'm still experimenting with my Presto heads. I am not able to get he nice light band test reults shown in the 1D manual. This has to do with the damping, I'm sure. Mine has a peak in repsonse at about 6Khz with a Q of 3 or so. I can compensate with EQ, but I'd like to get it to behave more like the specs. Perhaps that never really happens with the 1D in the real world. Has any body here been able to get a nice flat response usign the Preso heads? Any ideas on damping material and/or methods?
Glad to hear you got the head re-wound! One thing you may not have known is that you should add a 2 ohm 5w resistor in series with the head. This is needed to make the low freq turnover happen at 500 hz. per the RIAA specs. It also makes the head 8 ohms at 1 Khz. I measured mine to be sure I was in the ballpark. You will lose a bit of loudness, but as you can see, the head needs very little power to get decent modulation.
The corrrosion you are seeing is also on my 1C and 1D. I think this is because the two round plates that couple the rubber damping are brass and the lower one was soldered to the threads of the aramature. Back in the day, they tended to use acid flux to prepare the surface and over time, this reacts badly to the metal. I think this may also be the reason these heads are found open. The small gauge coper wire soldered to the terminals seems to rot because of the use of the acid based flux. I think it will be really hard to blow up the head with new windings. 30 ga. wire needs to see several amps to fuse. The head will distort long before that happens. The good news is that now that you know how to tear into the head, you will be able to repair it in no time.
I'm still experimenting with my Presto heads. I am not able to get he nice light band test reults shown in the 1D manual. This has to do with the damping, I'm sure. Mine has a peak in repsonse at about 6Khz with a Q of 3 or so. I can compensate with EQ, but I'd like to get it to behave more like the specs. Perhaps that never really happens with the 1D in the real world. Has any body here been able to get a nice flat response usign the Preso heads? Any ideas on damping material and/or methods?