Test Equipment to Service Tape Delay

[Primus]

I recently picked up a Roland RE-201 Space Echo. Everything seems to be working OK, but it has not been serviced and I need to adjust for more feedback, which is trivial, so I might as well service it while it is open. The service manual seems fairly straightforward, but a digital multimeter is my only test equipment. Most of the tests involve providing a 1 kHz square or sine wave with -50, -48 or -24 dBm signal and then observing the output on a DMM or oscilloscope. Can anyone recommend a cheap, used, multi-function audio generator and oscilloscope or a simple audio generator for this purpose?

[Mark Hammer]

As a tape-based system, the RE-201 would require all the same sorts of checklist items as would be found on any open-reel deck or cassette deck:

1) Assure the heads and any other relevent parts are fully demagnetized and clean.

2) Assure all soft and hard parts in the tape path are clean and the pinch rollers are soft enough to have some grip.

3) Assure the tape head/s are oriented properly and are not off-axis in any way.

There's more, but the general theme of tape-machine maintenance is that: a) the tape move smoothly, b) the tape not get erased in transit, and c) the tape be close enough to the record and playback heads thatsignal is effectively laid down and sensed.  In the world of tape, what can seem like tiny distances to us can be immense gulfs to the tape and tape head.  Simply cleaning the gunk off a tape head is roughly equivalent to moving your pickups from 1" below the strings to their proper height.

None of this necessarily requires "equipment", although setting tape-head azimuth might be tricky.  It's not usually one of those things that needs adjustment, though.

[edvard]

First fret on the 2nd string is approximately 1046 Hz and run through any decent fuzz ought to get you square waves just fine. 
Seriously, there are quite a few square wave circuits available on the web. These two look easy enough:
http://www.talkingelectronics.com/html/SquareWaveOsc.html
http://www.redcircuits.com/Page74.htm

As for an oscilloscope, search ebay and craigslist. Nice new oscilloscopes are NOT cheap and for good reason.
If all you need is to see a signal trace without pinpoint accuracy, there are several oscilloscope programs for your computer that just feed from the sound card.

P.S. Listen to Mark...

[Rectangular]

you dont need a scope, I've calibrated one of these by ear. I  gave it a bright signal with lots of harmonics (approx 1000hz) and then adjusted the tape heads for the brightest sound. apparently you can also use pink noise. cheap substitutions might be radio or tv static, and for a strong frequency signal, you can try using mixer feedback, although that's completely dependent on the mixer.

also theres a trim pot inside for adjusting the maximum delay time,  VR12. adjust it to suit your tastes.

[wavley]

I have a 101 and a 501 and I regularly maintain several of my friends' echoes... 201, 301, 150.  I've kept my 101 running for 20 years and it still sounds great.

Make sure that it's clean and de-magnetized (han-d-mag!) with fresh tape and see how it sounds before you adjust it.  Make sure the rubber pinch roller's bearing is lubed you don't know how many of these I saw come into the shop because they were locking up and they the grease was all dried up and sticky.   You can clean it in dish soap and warm water, if you need a replacement then you can get one at Terry's Rubber Rollers.

Sounds like you have the service manual, but if you need it I can give you a link.  You can adjust the motor speed which will adjust delay time, also the INT trim pot will adjust the amount of feedback so you can drive it into self oscillation.  

Here is where you need a scope, but you can do it with your ears most of the time and that is for adjusting the bias if you switch tape types.  A lot of the head and mechanical alignment can be done by eye/ear but a scope and sig gen help.

I have a bench scope that is nice that I got on ebay but I also have one of these... http://www.allspectrum.com/store/product_info.php?products_id=28&osCsid=4c5d3f183a059c7834dabf90a7b92641

and one of these http://www.mcmelectronics.com/product/TENMA-72-505-/72-505

The combo makes for a nice carry around  tool box.

Let me know if you need any help, this is my area of expertise.

[Primus]

Thanks everyone for your responses. This thread is quite a gold mine...

I also want to give a special thanks to Mark Hammer, who always seems to have great feedback (no pun intended) on my delay related threads for turning me into a delay junky. Just to give some context, Mark, I've been working to turn my Deluxe Memory Man into as close approximation as possible to a tape delay by making the following changes:

1. Modify for DC power to remove AC transformer noise (done)
2. Re-house in a 1590DD (Taiwan, a 6 screw Hammond will NOT work) box (done, required sanding the circuit board down a few mm)
3. tweak the voicing by changing capacitors in the regen path using an idea for a pseudo variable capacitor I got from Skreddy (done)
4. Use soft compression by using germanium diode ladders to ground. (in progress)

At this stage, I am taking the regen path "ex vivo" to a breadboard so that I can compare it to my RE-201, once it is reconditioned. I intend to write all this up and do an A/B test so that I can give back to the community some. It is shaping up to be a very nice delay, somewhat similar to First Echo on the Moon but with more vintage mojo.

Thanks, also, to waltk for his awesome XR2206 PCB. I will be trying this guy out in the near future.

Thanks, waveley, for your suggestions. It is my understanding that getting all the mechanical aspects together is critical before dealing with any of the other calibration aspects. I've read you can buy any 1/4" tape on a spool and splice a 12' segment for a Space Echo. What's a good source for audio tape and splicing tape? The Roland replacement tapes are still available, but fairly spendy.

[wavley]

Don't buy real Roland tapes, they are old, overpriced and the last two I tried to use gummed up in half an hour.  There are lots of replacement tapes on ebay, don't use Robert L tapes, he uses BASF tape and they haven't made tape in years, once  again, gummed up in about an hour.  Now this is an extreme case because it was the middle of summer in Florida and the humidity kills tapes.  Now that I live in Virginia it is not as much of a problem. Lubricated tape is the way to go, the kind they put in carts and 8 tracks.  Currently I'm using cobalt lubricated tape and it is WONDERFUL!  When I get home I'll look and see where I got it.  There is a lot of myth and hype surrounding space echo tape, mostly generated by guys trying to sell you tape.  Some guys will tell you that 457 is the way to go while the same guys will tell you that silicone lubricated will eat your heads are selling you mastering tape that will eat your heads.  8 track tape is silicone lubed, cart tape is either Cobalt or Graphite, either is great.  US recording media has splicing tape, blocks, and de-gaussers but the tape stock they have is mastering/recording tape, meant to stick to the heads a little because big decks have big motors, but the space echo only has that puny pinch roller.  Quantegy 457 sounds really great but give it a few hours and it will start wrapping around the roller and capstan.  If you can get them to respond to you these guys have the perfect tape, it's listed as echoplex 850x http://www.cartguys.com/ctr_prices.htm#anchor973579  Tape not to try; 457, 456, 480, 490, 632, 661  all of which sound really great and they are enough to get through a session but that's about it, of course at like 8 bucks for 1200' you can reload 100 times, just have lots of extra loops pre made   Just remember that if you buy cart or 8 track tape on a reel then it is wound opposite of reel to reel tape so you might make a loop that has the back side facing the heads and freaking out because your expensive tape doesn't work, of course I don't know anybody that has done that

[Rectangular]

heed wavely's words, I've had a similar problem tracking down a decent tape to use. mastering tape (ampex, quantegy, etc) will sound good but start screeeching within an hour or two of usage.  I found that getting the right tape thickness was more important than the lubrication, but I guess both are important factors.  dont use 1.5 mil tape (thickness), try for 1.0 mil or 0.5,  these are usually long-play tapes, 2400feet or so. 

wavely:   I've got a lot of 8-tracks, I should try using that tape,  and see how smoothly it goes.  what's a cart tape ? is that the thing that radiostations used to use for commercials and songs ? I've got some of those as well.

[wavley]

Depends on how humid the environment is.  I've gotten away with non lubricated tape when it stays air conditioned.  Thickness is a big issue, it has to flow well in the tray but on a humid day thin stuff wraps around the pinch roller even faster, that said I prefer thin.  Honestly the best tape I used for years was Radio Shack Laboratory Standard, it was cheap, thin and well lubricated, but all tape eventually goes bad and now I'm left with rat shack tape tape sheds sticky brown stuff.

Radio station cart tape is what I use now, it works beautifully.  You might have trouble finding 8 track tape that is still good, my first replacement tape was spliced from Johnny Cash's Greatest Hits.  I got my 101 for $50 because it was the late 80s and nobody wanted it and it needed a tape.  I cleaned it and spliced my 8 track loop, didn't know about self oscillation yet and the intensity was cranked up to that sweet spot so I ended up with an eerie weird off speed loop of "ring of fire" that just kept going and morphing, I was in love instantly and wish I had recorded it because I'll never be able to get that again.

[wavley]

So I got a great deal on 3m 8206 Logging tape: 2x3600' reels for $26.  Quantegy is currently the maker of this and the datasheet says that it is lubricated, the current Quantegy form of this is still expensive but if it works then it means that we have current production tape that will work!!!  UPS says I will get it tomorrow, give me a few days to see if it works, biases right, and sounds good.  http://www.totalmedia.com/store/audio-1/logging-tapes-1671/1-4-tape-1227/3m-1-4-x-3600-logging-tape-on-7-plastic-reel-2353.html Everybody cross your fingers

[Rectangular]

after my batch of terrible StickyShedSyndrome from the quantegy tape I bought, Im pretty skeptical of anything from them

still, we'll wait and see. I guess its not over till the fat lady reverberates   

[wavley]

Me too, they say that they have fixed sticky shed, but we'll see.  I might have more luck from this NOS 3M stuff, but you know how tape is... I thought it was worth a $26 chance lord knows I've spent a lot more than that trying to find the right stuff.  RGMI makes some sort of logging tape they claim is equivalent but the datasheet doesn't say anything about a lubrication package so I am skeptical.  Now on further investigation it seems that the Quantegy 8206 is just old stock being sold off by reel deal pro audio until Quantegy returns with 456, 457, and GP9 all useless for echoes.  Our last hope is RGMI for current production being that ATR only makes mastering tape.

[MKULTRA]

Someone tell me how to embed a PDF document and I'll upload the Roland RE-201 service notes.

[wavley]

Got my 8206 last night in nice plastic storage cases.  Spliced it, put it in my 501... it flows well, it sounds great, the self oscillation sounds really great.  The thickness is perfect, I left it running for about two hours at high speed and no problems yet.  I'll keep you posted on my experiment because total media has 3600' reels for $13

[Primus]

Ouch! Guess that would mean I burned myself by being impatient and buying the hi-fi stuff.

In the service manual, they reference a lot of the signal measurements in dBm. Is this typical? Does anyone know the best way to measure dBm power or can i be approximated another way?

[wavley]

Ouch! Guess that would mean I burned myself by being impatient and buying the hi-fi stuff.

In the service manual, they reference a lot of the signal measurements in dBm. Is this typical? Does anyone know the best way to measure dBm power or can i be approximated another way?

Well we aren't out of the weeds yet, two hours isn't much of a test and we know for a fact that the stuff you bought works.  Ironically the Cart Guys finally emailed me back, so I guess they're still in business.

I cheat because that hand held scope that I use has a multimeter built in and gives readouts in dBm.  Sometimes I use my big scope for accuracy with my hand held for readouts.

[wavley]

Ran the 8206 for another couple of hours last night, to bad I didn't get to play guitar the whole time   I just turned it on and walked away so I could do my wife's bidding.  So far it's holding up, most non-lubricated tape would have crapped out by now, we'll see how logging tape does, but it seems to be working out.

[DougH]

Here's something you might find useful: http://www.tequipment.net/ElencoFG-500K.html

I think I'm going to pick one up at some point. I've read some good reviews of them.

[teletroy]

I'm loading some new tape in tape machine that I'm trying to get running and I'm wondering is it shiny side towards the heads are away? 

Guess I can try it both ways and just find out

[newperson]

where do you get splice tape?