Messages

1

Reel to Reel Tape Machines / Re: Biasing for Studer A807 using RMGI 468 tape

« on: March 11, 2010, 10:36:25 PM »

Thanks for the additional tip, Paul. I remember reading that same tip elsewhere (though I can't remember where. an MRL paper?).

One thing that I'm puzzled by with regard to this tip, however:

Wouldn't I be better off biasing / calibrating by using the larger voltage / db swing? My intuition tells me calibrating to a 0.2 db difference would be more susceptible to noise margins than calibrating to a 3.5 db difference.


One other question regard to calibration: The calibration process starts (in many cases) by applying a 1kHz sine wave with reference voltage of 775 mV to the input (and measuring test points / adjusting trimming pots as appropriate). What's left unsaid is whether this reference voltage is 0.775 V RMS or peak to peak. I'm assuming it's an RMS measurement.

Thanks again,
Chris

2

Reel to Reel Tape Machines / Biasing for Studer A807 using RMGI 468 tape

« on: March 08, 2010, 03:34:58 PM »

I am a newbie to R2R and am about to make my first attempt at calibrating my recently purchased Studer A807 (Mark II).

I've purchased some of the Tape Project's RMGI 468 pancakes to play around with and have read the Studer A807 Service Manual.

The bias adjustment procedure is done by 1) applying a 10kHz input signal 2) increasing the bias until the maximum output voltage is reached and 3) continuing to increase the bias until the output voltage drops by an amount (Delta U) from Max.

Delta U is tape dependent and is specified for a variety of common tapes (of the day?) in a table near the end of the chapter.

Unfortunately, RMGI 468 is not listed in this table (see attached file). How do I determine what I should use for this tape type?


Thanks in advance.

3

Reel to Reel Tape Machines / Re: How do you measure tape tension

« on: March 02, 2010, 04:21:20 PM »

Can someone please advise / lead us through the exercise of measuring tape tension WITHOUT a tentelometer?

In the section related to tape tension, my Studer A807's manual states:

  "Insert a tape tension meter between the left reel and tape tension sensor. Press the key PLAY. By means of of the trimmer 'Play' adjust to 70p +/- 2p; the distance "X" should be in the range of 56 to 58mm."

I'm pretty sure I can understand the procedure if I had a tentelometer (what are "p" units, however?). Is there another tool that will do the same job? If the answer is a spring tension gauge, how does this work?

One last question: is it possible to perform the procedure above without a tension meter altogether? i.e. Just by turning the trim pot until distance "X" is in the right range?

Thanks in advance,
Chris

4

Suggestion Box / Eva Cassidy!

« on: January 25, 2010, 09:11:11 AM »

I second the Eva Cassidy suggestion/recommendation!

Chris

5

General Discussion / Re: Any Freight / Shipping company recommendations?

« on: December 14, 2009, 09:42:05 AM »

Thanks for the very helpful information.

Chris

6

General Discussion / Any Freight / Shipping company recommendations?

« on: December 10, 2009, 09:53:46 AM »

Does anyone have any recommended carriers / shipping companies that will do all the shipping legwork for large decks (i.e. pickup / packing / crating / shipping)?

Here's where I'm coming from:

I have been on the lookout for a good deal on a top-end professional deck (i.e. Studer, etc.). Unfortunately, most of the good deals (ebay) are "pickup-only" due to the size and hassle. What I need are companies / individuals that will pickup the deck, prepare it for shipping / freight, and ship it to me (where I could pick it up at a Terminal that is local to me). Are there any companies out there that will provide the service I'm looking for?

Thanks in advance.

7

Reel to Reel Tape Machines / 5050 B2HD Service Manual

« on: December 08, 2009, 03:56:36 PM »

Does anyone know where I can get the (preferably free) MX5050 B2HD Service/Maintenance Manual ?

I am not looking for the Instruction Manual, the schematics, or Parts Lists (I have all of those). I am looking for the manual that specifies technical details (proper tape tension, adjustment screws on the head block, etc.). The Instruction Manual doesn't contain this information.

Thanks in advance,
Chris

8

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 16, 2009, 10:42:04 PM »

Thanks for the helpful advice Steve.

I cracked open my deck and reseated all the internal connectors (after applying Deoxit 5). I don't know if that was the missing ingredient but, thankfully, I'm getting some music out of both channels. I'm getting full output when in SRL (Standard Reference Level) mode but there's a level mismatch somewhere in the signal path when using the Output Level Pots.

Given that I bought an Eros Preamp earlier today, I'm satisfied enough that the transport is working and will concentrate on getting the motor controllers tuned up (replace leaky electrolytics) and the tape path working as smoothly as possible.

Chris

9

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 15, 2009, 12:15:31 PM »

I have a friend who has an alignment tape (from years ago). I was planning on using that to debug my machine's problem. The only thing holding me back is finding the time to do the testing.

Can anyone point to what the likely causes are for these issues (leaky electrolytics, blown transistors)?

To reiterate what I had said in an earlier, I plan to hardwire the head outputs to an external preamp. With that in mind:

  1) What's the likelihood that something is wrong with one of the repro heads on my deck? I assume the probability is low.
  2) What's a good wire to use for the connection between the heads and the external preamp? Shielded twisted pair? coax? Does it matter?

Chris

10

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 10, 2009, 08:22:10 PM »

Yes, you're right, the 2T/4T switch is in the Instruction Manual.

What I meant is that the switch is not shown in the schematic that I found somewhere on the web. The "Record Reproduce Amplifier; A1028.." schematic shows a generic connection to the repro heads but not the switch itself.

No big deal as Jay already answered this question. 

Incidentally, after removing the headblock and cleaning the switch and headblock connector (with contact cleaner), the source of my problem still exists. I'm not getting any output from the left channel. I'll need to dig further to find where the signal is getting dropped.

Chris

11

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 10, 2009, 03:15:54 PM »

More questions to add to my newbie list:

1) Is it a bad idea to use a "dry erase" marker to identify the path that the tape makes over the heads? I recall reading this was a helpful debugging technique for head alignment somewhere on one of the R2R guides. I can't seem to find anyone else using this approach in any of the forums, however.

2) Is the Otari's 2-Track/4-Track switch's output contained within the head block? I am assuming that I don't need to worry about the output of each individual repro head if/when I directly wire to an external preamp. I find it strange that the 2T/4T switch doesn't appear anywhere in the MX5050 schematics (I haven't found it yet)....


Prior to testing out my deck, I had done a thorough cleaning (with CL-100 cleaner).  I will clean the pots and switches with contact cleaner later tonight.

Chris

p.s. I did happen to find a toe nail stuck in one of the shielded repro heads. It might be Magic Johnson's but the burnt-in wear pattern looks more like the image of the Virgin Mary. Do you want me to send it to you? ;-)

12

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 09, 2009, 09:12:27 PM »

Thanks for the help Steve.

Your suggestion to try out the Monitor switches was the correct one (although it highlighted another problem). The fact that I was able to hear the 1kHz was an indication that I had the Source Selected (and not Tape).

Unfortunately, the left channel doesn't appear to be working (no sound, no movement on the VU meter). The right channel is working (but sounds awful).

I've got more work to do to figure out the source of the problem. Given that I intend to bypass the output electronics and connect to the repro heads directly, I'm not too concerned about the left channel issues (yet) and won't spend too much effort isolating the problem.

BTW, assuming that I will connect the repro heads to an external preamp (Erose?), is there any benefit to keeping the connection to the internal MX5050 amps intact? (i.e. for the VU meters, headphone jack, etc.). I've got to believe that by hardwiring to the tapeheads, some of the basic functionality goes away   (source/tape monitor).

Chris

p.s. My deck was apparently used at a radio station at Michigan State University and has a serial # indicating it was built in 1982. Other than that, I have no other historical info.

13

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 09, 2009, 05:47:35 PM »

Well, my impedance roller does not have a rubber roller and, frankly, doesn't appear to have ever had one (i.e. there's no left-over adhesive residue where a rubber roller might have existed). My version is a B2HD so I'd be interested in hearing from others with the same model.

As an aside, I just received a set of hubs and, finally, hooked it up to my system for the first time (a few minutes ago, literally). Unfortunately, I couldn't get it to play any music to speak of. I can hear the internally generated 1kHz Oscillator test tone (out of my speakers) but nothing when playing a tape. It looks to me like the tape is making good contact with the playback heads.

Disappointed but not daunted.

Chris

14

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 07, 2009, 12:10:30 PM »

Thanks again for the help.

The obvious conclusion is that my MX5050 version (B2HD) requires the Hub adapters.

Chris

p.s. I anticipated this answer last night and have already ordered a pair (from ebay). I'll just have to wait for them to arrive before I can test out my machine further.

15

Reel to Reel Tape Machines / Re: Otari MX5050 newbie questions

« on: November 07, 2009, 09:42:57 AM »

Thanks for the helpful responses. Sorry to be so dense but I'm still unsure how to mount 7" tapes to my machine's spindles (without falling off).

I can fit the 7" reels onto the spindles but was expecting to have some mechanism for securing/locking them to the spindles. The spindles on my machine are smooth and straight with no apparent locking mechanism. There's no mention of reel locks in the manual so I don't know what they should look like. Shouldn't there be some kind of hub (or other) that goes over the tape reel, engages the spindle, and prevents the tapes from sliding off?

I've already gone through the links and resources mentioned (analogrules.com, etc.) and didn't find this answer. I had already downloaded the B2HD manual and that, too, couldn't help.

Chris

p.s. I've attached a pic of the spindles on my machine if that helps in anyway.