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Offline rbwtapeinterlink-Bob

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Testing Instruments
« on: October 13, 2007, 04:05:43 PM »
Peace and blessings to all. About a week ago, I was reading several posts and one of them mentioned the purchase of an oscilloscope. That got me to thinking that at some point I might have to measure voltage, look at square or sine waves, measure current, etc.

I am interesting in learning what basic test equipment should we have just in case. Can anyone comment on this area of interest and provide some advice regarding scope requirements in particular. Should I be looking for a 20 or 60mhz scope with what other characteristics? What about a volt/ohm meter. Is a digital prefered to an analog unit? What else would I need? Mind you, I am not thinking about real in-depth repair work, but maybe just a little. Thanks everyone.

Bob W.
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.

Offline jdcolombo

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Re: Testing Instruments
« Reply #1 on: October 13, 2007, 05:31:59 PM »
Hi Bob.

A scope is a terrific piece of test equipment, and can do many, many things.  For audio use, you don't need anything terribly fancy, since you'd probably never measure anything beyond 30kHz in the audio domain.  The MHz scopes are more for radio use - hams, for example, need a scope that will run out to 100 MHz to test their transmitting/receiving equipment in the high radio bands.  You will need at least two channels so that you can do an XY pattern for measuring head azimuth.  In addition, you'll probably want a sine wave generator to set recording levels, checking record EQ, bias and so forth.  Finally, a spring scale to check brake tension (the kind sold for grade school science classes are ideal, since they generally measure in both Newtons and grams; avoid the fish scales).

BUT - if you have a computer with a good sound card, you can get software to act as both a sine wave generator and as an audio-frequency 'scope.  Software is likely MUCH cheaper than a real scope, and for aligning a tape machine, the software is probably good enough.  I use my iMac for these functions with ToneGen (sine wave generator) and SignalScope software.  I've set the azimuth on my heads with Signal Scope, which also will read voltages and db to a set reference.  I'm sure similar software is available for the PC side, although the nice thing about the Mac is that the software guys know exactly what hardware is being used and what the specs are on it.  Can't get the computer to be a spring scale, though <grin>.

John C.
John Colombo
Savoy, IL

Offline ironbut

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Re: Testing Instruments
« Reply #2 on: October 13, 2007, 07:56:58 PM »
          Can't get the computer to be a spring scale, though <grin>.
Oh come on John,..use your imagination huh! Actually, I was going to ask you which 'scope app you were using. I'd like to get Doc or Romo's opinion on any shortcomings for computer based test software. I would think that an oscillator/attenuator could be replaced by lots of different software programs. As far as spring scales, I've got a cheapie that I got from http://scientificsonline.com/product.asp_Q_pn_E_3001000 Edmund Scientific. Remember them! I used to love getting their catalogs. Bought all kinds of stuff that I didn't really need ( what ever happened to my Kirlian Photography kit). The spring scales they have are OK but I'm planning on getting a better one. Doc suggested a Pesola . There's also the tensiometers designed for use in the yarn manufacturing industry. You can find used ones on Ebay but maybe Doc has a different type in mind ( they need to be calibrated to be really accurate). Well, thanks for the suggestion on Signalscope. I've thought about trying it a few times.
steve koto
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Offline rbwtapeinterlink-Bob

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Re: Testing Instruments
« Reply #3 on: October 14, 2007, 09:55:42 AM »
Thank you John and Steve. John I appreciate all of this great info. I guess I should have been a little more specific. One of the more important reasons I might need a scope has to do with check out my Audio Research amp and pre-amp and other components. Plus, I do want to become a little more proficient with use of the scope, so, I am looking at a 60mhz job that's compact and light weight.

John and Steve, I was not aware of the need for a spring weight to measure tension on the tape machine. That's real new news for me and something I will treasure going forward. I appreciate this info very much. I also very much appreciate the software info. My son is building me a lap top, but my desk top computer needs updating or replacement so might not do for the kind of software you mention. But it good info all the same and as resource info, I can certainly use it. Well, now I am going to have to purchase a white lab coat so that I can look the part (smile). Thanks again gentleman for taking the time to respond.

PS: John, how are you coming along with your newly acquired PR99? By the way, is that the MK l or MK ll? Have you actually begun to play tapes on it yet? I am also interested in what's happening with the Tascam machine? Thanks. You might want to send that info to my business email address at:
[email protected]

Bob W.
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.

Offline rbwtapeinterlink-Bob

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Re: Testing Instruments
« Reply #4 on: November 08, 2007, 08:34:29 AM »
My friends,
To be specific, so far I have a dual trace scope and a good volt/ohm meter. I think these will be important tools to begin maintaining my two best tape decks. These are the Otari 5050 Bll and the Tascam 32b. The Tascam is in tip top shape and has been serviced. Tape heads and electronics are superb. However, I will have to set this machine up for whatever tape I will be using to record some of my music. I have not yet gotten the Otari out of here for service. I am waiting to sell the house then get the Otari serviced.

Will I need to get a tension spring for each of my tape decks or will one good one do? My plans are to make the Tascam my "Tape Project" deck and bypass the internal pre-amp so that the "Tape Project" playback electronics can be used. That will be a real heady job and something I may not be able to do. I am sure that will require particular skills I may or may not possess. I will need to get more info on either building the unit myself or purchasing it from "Tape Project" already built. These are major concerns at this point. 

Well, I am blessed to have two such fine tape decks that can meet my musical needs once whipped into shape. Thanks guys for all of your help. As always I appreciate.

Bob W.
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.

Offline AZ_Gary

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Re: Testing Instruments
« Reply #5 on: November 09, 2007, 11:24:02 PM »
Where do I find more information about the use of the spring scales? What range do I need? Best way to do measurements?

Thanks,
Gary
Gary Marklund
Sun City, AZ - USA

Offline stellavox

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Re: Testing Instruments
« Reply #6 on: November 10, 2007, 09:56:50 AM »
If you're really into this stuff, the Sound Technology 1500/1510 Tape Recorder Test System is the way to go  - incorporates the features of many separate instruments including a voltmeter, audio generator and audio spectrum analyzer (if it has this option installed).  Sometimes comes up reaspnable on Ebay - especially if you consider it versus the price of separate instruments.   

Charles

Offline ironbut

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Re: Testing Instruments
« Reply #7 on: November 10, 2007, 10:47:55 AM »
Hey Charles, I've been keeping an eye out for one of those. Have you ever used one of the pc based scopes? I was wondering if there would be any drawbacks to using something like Signalscope http://www.faberacoustical.com/products/signalscope_pro/  for aligning heads.
steve koto
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Offline docb

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Re: Testing Instruments
« Reply #8 on: November 10, 2007, 12:01:20 PM »
So I'm over at Ed's a while back and I find he has a Sound Technology 1500 sitting on the shelf above the bench. Haven't played with it yet, but now that tapes are headed out I have to seriously get going on machines, which I have fallen terribly behind on. Hopefully that unit might come in handy.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline stellavox

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Re: Testing Instruments
« Reply #9 on: November 11, 2007, 06:41:44 AM »
Doc:
Enable the 1500's self test mode and see if it runs through to the end (have to set the audio output to 2 VRMS before doing so).  If it does finish the self test your in fine shape - if not you are in for an expensive repair. ST is up by you somewhere and still services/ugrades all their old equipment IF you have upwards of a grand to drop.

The 1500 used a special calibration tape for playback that has "synched" tones for frequency response and azimuth - also has 1Khz reference. BTW, the azimuth adjustment method is really neat AND simple (ALMOST foolproof). Tapes are still available from MRL but their "normals" are one speed/EQ. - Needed something for multi speed work, so I had them make me up a single tape for 15, 7 1/2 and even 3 3/4 with both NAB and IEC EQ for little more than the cost of one tape - BUT short reference/azimuth and only 2 sweeps per speed/EQ.

Ironbutt:
Regarding the PC-based Test Equipment, I highly recommend it HOWEVER, is makes sense only if you have a laptop which you can "tear away" from your normal operating position and bring it to your test bench.  I have "Audiotester" loaded on this old laptop but normally use it "upstairs".  Going to get a new computer for Christmas and this will end up on my workbench (along with becoming a music server).

Audiotestor is a German product that costs around $30.  The developer sends it to you via Internet and had free "trial" version.  Only have to make up/buy two sets of RCA to mini (stereo) phone plug cables (to plug into the computer's microphone and headphone jacks.  It has versatile Audio Generator, Oscilloscope and Spectrum Analyzer functions which seem to work really well - HOWEVER I found that the documentation left a lot to be desired and I had to spend a lot of time "playing with it" to get it going.  DOn't know about other products but DO recommend you get something with these functions as a minimum.  Can also do "waterfall plots" of speakers but I doubt I'll ever figure THAT out.

Turns out that the dynamic range of the spectrum analysis function depends on the "quality" of your sound card and I "lucked out" that the chips in this old IBM thinkpad 390 allow for around a 120dB dynamic range.  Plenty good enough for my needs (can see distortion products down to 0.001%!) ans it's really neat to be able to input a signal into, say, an amplifier and see the distortion products diplayed in "real time".  You could probably pick up an old 390 for $100 and for another "few bucks" for a program you're ready to go.

Unfortunately, I haven't seen much discussion in audio chat rooms about PC-based audio testing equipment so I can't suggest a place to go for more info.  If anyone out there can enlighten us (about your experiences also) PLEASE do.

Charles 

Offline ironbut

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Re: Testing Instruments
« Reply #10 on: November 11, 2007, 11:55:16 AM »
Thanks Charles, I already have some music editing software that have generators, spectrum analysis and signal inspector functions. I know what you mean about documentation. I find most of the "Pro" audio stuff is seriously lacking in the user friendly area. Once I waded in and just start to use them, I started to get the idea and that experience made learning new software a lot easier. Man, that first step can be a tough one though. It's always nice if there's a company forum and video tutorials are huge. I use a Mac so Signalscope is about the only game in town. Maybe someday I'll grow out of it, but for now, the $$$ and space savings are important.I bought a new laptop this summer when I must've thought I was rich or something so, thanks for the suggestion. The more uses I can come up with, the less I  feel like a putz.
steve koto
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Offline rbwtapeinterlink-Bob

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Re: Testing Instruments
« Reply #11 on: December 07, 2007, 07:49:28 AM »
My dear friends,
I want to thank each of you for all of the great information and suggestions here. Let me tell you what testing equipment I have, and you can tell me if I am on the right path. So far I have:

1. Dual trace oscilloscope
2. Audio oscillator
3. AC volt meter
4. AC/DC multimeter

That's it so far. Presently, I don't have the springs you gentleman talk about so I will have to get those. Do I have the most basic equipment needed to get started checking out my tape decks? Thanks for everything. I am more that thrilled I found and join this club. Everyone here is extra wonderful.
By the way, Steve how did you determine which set of springs, if you purchased more than one, to get from Edmund Scientific? Thanks.

Bob W.
« Last Edit: December 07, 2007, 08:02:57 AM by rbwtapeinterlink »
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.

Offline docb

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Re: Testing Instruments
« Reply #12 on: December 07, 2007, 09:24:57 AM »
The most common tension gauge I see in ebay is a Correx. I happen to have a rather obscure ARPO, that is essentially the same thing with the additional of nice little rotating markers around the bezel. The one I use ranges from about 100G to 1000G, just right for a Technics machine that has adjustments ranging from 140G to 900G. What range you need for your machine will be determined by the most important tool in your arsenal:

a service manual - gotta start there. There are several places you can get manuals. I don't have specifics but perhaps other folks can share some good sources.

A Tentelometer, which measures the tension on the moving tape, is a very useful piece of gear too. They are quite expensive new (as is a Correx gauge), but with the demise of videocassette they are for sale cheap on ebay all the time. Again you need to get one with a scale that is appropriate for your deck. The Tentel site has good info on the various models to help guide you to the right models to look for. Get one with the calibration weight included.

Both of these tools require some practice to get a handle on. As long as you aren't wildly changing settings while you learn the feel of these tools, you shouldn't cause any harm to your machine.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: Testing Instruments
« Reply #13 on: December 08, 2007, 01:22:28 AM »
Oddly enough, I recently got a Tentelometer (500gm) and a Correx tension gauge.  Actually, I followed Doc advice and boy, are they nice. The Tentelometer was about $30 including shipping and the Correx was maybe $2-3 more. Pretty amazing considering the Tentelometer retails for over $800! So I'm using the Correx measure the brake tension and the Tentelometer is designed specifically to measure tape tension. So, the only thing I'm actually using the spring scale for now is to check the pinch roller pressure.
Doc is exactly right about starting with a service manual. I've gotten in the habit of ordering one before I actually get the gear in house ( do wait to win the auction if that's how your getting it, this may sound silly but, I've almost jumped the gun a couple of times). Here's 2 good sources for manuals.
stereomanuals.com
www.agtannenbaum.com
I've bought some from both and they ship quickly and even if the manual is a copy, they're good copies. Don't buy the ones on popular auction sites. They're usually crazy $$$$.
steve koto
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Offline rbwtapeinterlink-Bob

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Re: Testing Instruments
« Reply #14 on: December 09, 2007, 08:06:05 PM »
Thanks guys I reall appreciate your interest and response. I recently obtained operating/owners manuals for the Otari 5050 and the Tascam 32B. So I am set as far as that goes. My Tascam 32B is in excellent shape and has be checked over, cleaned, belt replaced and returned to me in great condition. The Otar 5050 ll may have to go into the shop for service. I am still trying to determine how to tell what condition the heads are in. I have cleaned this machine up good but still have to deguass it. I have started to play some of my tapes on it and they sound great particularly the 17 & 18th century large scale choral works. The boys choirs sound awesome and in many cases I can even hear the hall effects. I have got to pick up those springs though.

I am planning on building a cart that will be wide enough to roll my Tascam 32B (2 track) and Otari 5050 ll (2 track & 4 track play) around. This way I won't have to heft a different machine into place when I have 4 track tape I want to hear. I am still in the process of developing a design. Again, thanks much guys.

Bob W.
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.