Bulk Eraser Duty Cycle warning & Radio Shack Bulk models
Hi guys,
I`m new to the forum but not so new to Hi-Fi and guitar/pro-sound electronics - I own/operate a very small custom build, restoration and repair of vintage gear primarily vacuum tube stuff - but recently bought an Otari MX5050 BII2 from good ol' Ebay and it was terribly packaged and boxed - arrived where none of the transport buttons worked - turned out the fold out circuit board in the back had a 1/4" hairline crack lower right corner through the mounting screw hole separating one small trace - that was the problem. Fixed with some precision scraping and very careful soldering of a 3/16" 24 gauge pre-tinned solid copper wire. Lots of other small issues mostly cosmetic (missing & incorrect screws all over the place, missing bottom legs and back rubber feet, side panels falling apart -some missing paint around head cover and the transport button white lettering and symbols for FF/Rewind & Play barely visible. Legs, Rubber bumpers/feet & side panels will be replaced - Legs & Side Panels got some raw 3/4" Solid Mahogany precision cut that I will finish in a deep darkish Red Mahogany color using bright red, brown, yellow & black wood dyes, shellac seal coat, wood grain filler mixed with dark walnut & merlot red stain - finally a semi-gloss or gloss spray lacquer (Dyes, stains and lacquer need to do some experimenting on scrap mahogany to get right mixes). Will post final before and after in separate post in correct area
But for bulk erasing and tape head demagnetizing - - the Han-D-Mag is the best by far head demagnetizer but as a handlheld tape eraser - not so much - someone here said - too small a magnetyic field - I used the smaller Radio Shack bulk eraser years ago for analog and digital tapes (home audio cassettes, 8 tracks, small reels and VHS) and work (data cassettes, data discs, floppy, 3 1/2" and even hard drives) - didn't own large reels at the time (7" & 15") - that nulk eraser - which I think was rated at 4 amps with a 1 minute on 20 minutes off duty cycle died in a basement flood. The one I bought recently (waiting for delivery) is the "Radio Shack Improved" 9 Amp version - bigger, stronger 1 min on and 40 minutes off if memory serves - was upgraded primarily for video tapes (VHS, Betamax) wider tape, more information on tape at much higher "digital video" frequencies.. I purchased this one for its more than double power rating (4 vs 9 amps). But I also wanted to point out how important it is to pay attention to those duty cycles - if you leave the expensive HanDMag or the much less expensive Radio Shack hand-helds on much beyond their 1 minute duty cycle (duty = "powered on") ands/or you don't let them rest / cool down for duty off cycle - these will either fry and become totally useless or they can degrade considerably with possible shorted windings - generating more heat in shorter duty cycle time with less effective magnetism.... For the most-part all these things are - are AC transformers with low resistance loads on the secondary windings basically creating a transformer with a short circuit on its output. The more expensive commercial bulk erasers have protective current limiting circuitry and many I think have an automatic duty cycle - where they turn themselves off at the end of a programmed duty cycle - these others are controlled by the user - and can and will literally burn up if left in the on position too long - back in the day - the UL wasn't as strict as they are today - these things would never get UL approval if they were made today - I had a cheapo radio shark head demagnetizer that almost set my apartment on fire back in 1979 - it was a 1960's model - later ones may have had some type of basic thermal bi-metal safety that opened if overheated but did not reset as reliably - so again if u didn't follow duty cycle warnings even if it didn't melt down most times it would not function after one or maybe a few overheats - not until much later did they consider more sophisticated protection circuits and by then these were made/used primarily for the video cassette or commercial ones for the data industry. I was looking to by a tape tension gauge there are dozens of sellers with brand new Sony tape tension gauges for $25-35 - took me an hour to find out that this tool was designed specifically for sony video cameras and players - won't help much with audio world - although I did pickup a pair of new commercial grade spring scales (2 lb & 10 lb) off Amazon for $20 each - perfect for the Otari 5050 series - I'll let u know how the Radio Shack 9 Amp bulk eraser works out when it comes in - and thanks for reminding me about the 3 foot distance for the on and off cycles.. BTW my Han-D-Mag I bought second hand because the seller included the same brand Magnometer - has anyone used this and if so what should an Otari set of heads, rollers, capstan read when in need of demagnetizing (BAD) and after a successful demag what should the magnometer read? (GOOD)