Tube Amps / Music Electronics
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|5/16/2006 4:19 AM|
|Dave Stephens||Warning Scotch 235 black paper tape DON'T USE|
I got two big free sample rolls of this stuff, it looks right, very authentic looking. I wrapped some P90s in it and tonite before I shipped them off ran the pickps through the Extech LCR meter. Something seemed wrong as my 8.2 K coil was reading 7K. I thought uh oh, coil short. The Extech seemed to confirm this as the AC resistance was really high like 28K more than double what it should be. I thought coil short for sure. Unwrapped the tape and before destroying the coil measured the DCR and the inductance, suddenly everything was back where it should be. So I put my ohmeter leads across the tape and it was really conductive, so much that in the pickup range it was reading 2 or 3K. The tape is so conductive shielding the two coil ends with it and wrapping the coil with it actually dropped the pickup from 8+ down to 7K.
This stuff is NOT suitable for wrapping coils. If you use you may get a fairly good DCR reading, my other coil measured OK, but again the AC resistance was way high, you'll get a dulled down muffled pickup. BAD NEWS.
So the search for black paper coil wrapping tape continues for me. The Stew Mac stuff is somewhat acceptable but on exposure to air the adhesive turns real goopy and sticky mess. Looks good but some of it is mildly conductive as well. About all that leaves thats really safe to use is the 3M fabric tape.
Anyone found a good source of black paper tape that works yet? This stuff ain't IT.......Dave
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|5/16/2006 7:54 AM|
Maybe this is a reason to use my teflon tape trick. It will insulate the coil from whatever conductive properties may exist for what is a cosmetically appropriate outer layer.
|5/16/2006 12:24 PM|
The stuff Wolfe was using seemed really nice...not sure if he wants to share his secret though? Wolfe?
|5/16/2006 6:52 PM|
Using teflon, well you'll still have a conductive wrap around your coil which is going to create eddy currents, you'll lose some high end. I'm amazed how conductive this stuff is, I bet if you stuck two ends of it in a wall socket it would blow the circuits. Bad stuff. Yeah I saw some of that Tape on Wolfe's tele bridge a customer sent, so I could match it up polarity wise with the neck pickup I made. Looks good but I wonder... Truth is if you have $500-1000 3M guys will make anything you want. I'm going to see if I can find an email contact for them and see what they could do, maybe a bunch of us could go in a a box full. Dave
|5/16/2006 8:57 PM|
On 5/17/2006 12:52 AM, Dave Stephens said:
The issue is that while it can short adjacent turns of wire, it is too resistive to make a good shorted turn by itself.
The US site doesn't say this, and gives a better data sheet: <http://solutions.3m.com/wps/portal/3M/en_GB/Industrial-Adhesives-and-Tapes/IATD/Document-Centre/Datasheets/?PC_7_0_DG9_root=8LDH4KRS0Wgv&PC_7_0_DG9_output=html&PC_7_0_DG9_gvel=K3NJX3DN0Zgl&PC_7_0_DG9_vroot=N1R8HNDBQDge&PC_7_0_DG9_node=JDR12NVMVDbe&PC_7_0_DG9_theme=iatd_portal&PC_7_0_DG9_command=SalesPortalPageHandler>.
Anyway, the larger problem may be that 3M will stop making it.
|5/22/2006 7:39 AM|
I was going through some old boxes of photo gear, and found a roll of Scotch 3M 235 Photographic Tape that I bought in July 1982 (I date-mark things like tape). The adhesive is all dry now, and doesn't stick, but the tape is not at all conductive, on either side.
|5/17/2006 3:55 AM|
|Wolfe Macleod||3m will make anything - and reply to Greg Simon|
I believe I mentioned this quite awhile ago, about the 235 being conductive. I raised holy hell here about it and that 3M won't bring back the #4 tape.
I've contacted 3M many times about this, and they won't do custom runs for anything less than about $250,000. They they'd do it for $1000, I'd do it in a heartbeat. I'd do it tomorrow, in fact.
I am no longer using the 3M tapes. Nor am I using the Japanese "Union" Tape that StewMac is selling - because it is also conductive. And they went bankrupt. I have several rolls if anyone wants it - free.
In response to Greg...
When I met with Seymour at the last NAMM show, I mentioned the name of the tape I found. He was rather shocked, and knew what I was talking about.
As for the secret...sorry guys. I hate to be an ass, but on this one, I have to. I drove myself crazy for well over a year searching constantly for this stuff.
Before I found it, I posted here about 3M #4...in an attempt to get you guys to contact 3M with requests to bring back #4. You all pooh-poohed the idea and said you didn't care. The guy at 3M who was in CHARGE of what they produce and what they don't was WATCHING this forum to see what interest there was. When you didn't care, he didn't care and said no, they won't bring it back.
So untill I find something even better, the secret stays with me.
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