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Messages - Ki Choi

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Reel to Reel Tape Machines / Re: Nagra T "stutter" issue
« on: March 31, 2012, 12:15:41 AM »
Hi Doc B:

Although I feel a little uneasy about not knowing the exact cause for the issue, it looks like you are making good progress.  When you run into a critical demo situation and your T is still sick, remember you can borrow one of mine with direct head wired to temporary RCAs that you can mount your VU meterbridge with the Tube Repro for show & tell.


Please send me an email.


Reel to Reel Tape Machines / Re: Nagra T "stutter" issue
« on: March 29, 2012, 07:00:36 PM »
Thanks Doc for your comment and maybe a judge of good beverages of adult kinds...

You should have the service manual tomorrow, and it has good illustrations of the measurement points for the capstan motor/tachometer without removing the assembly.

Reel to Reel Tape Machines / Re: Nagra T "stutter" issue
« on: March 29, 2012, 12:29:25 AM »
Actually the tacho feedback for the capstan motor might not be an encoder disc but a ring.  Either case, the tacho signals should be checked since they directly impact capstan motor.

The other possibility is that your battery is on its way out and may have already lost its charge and corrupted the RAM.  One of the members I had helped last year also had numerous issues with his T including shuttle mode problem similar to yours.  The RAM was refreshed by removing the battery for about 10 min for the capacitor to drain and reconnecting a fresh battery and powering it up to reload the firmware onto RAM and the shuttle worked properly again.

I will put a copy of the service manual CD in the mail tomorrow.

Reel to Reel Tape Machines / Re: Nagra T "stutter" issue
« on: March 28, 2012, 02:01:46 PM »
Hi Doc B:

I am a bit late in seeing your post.  One of the first thing to check would be the two signal outputs that are 90 deg out of phase from each other from the left Tachometer with a scope.  It's circuit is in 8.5-1 section.

There's also a known issue of Nagra T's Tachometer etching rubbing off over time and not producing consistent pulses for the capstan servo motor to follow.

If this is the case, your left capstan will be jerky and eventually fault out (or run away...)


Reel to Reel Tape Machines / Re: Sonorus ATR10
« on: March 20, 2012, 04:18:06 PM »
Here's small but sweet photo and write up on the latest Stereo Sound magazine in Japan that I saw last week in Kobe.


At this rate, I am holding on to two perfect Nagra Ts for future vacation home in Hawaii...

Reel to Reel Tape Machines / Re: Source for Nagra Parts, Supplies?
« on: February 06, 2012, 03:38:58 PM »

You can call Nancy at

Nagra USA
450 W Main St # B4  Gallatin, TN 37066-3193
(615) 451-4168

However, their stock level for analog tape machine parts is very low to none, unfortunately.

Only other option is to take your chances at buying parts or parts machine on eBay...


Hi GenX,

It depends on which model A80 heads you have.

For normal Studer heads, I have experienced head wear but not enough to be concerned in decreased frequency sweep performance starting after about 500 hrs with modern tapes.


Reel to Reel Tape Machines / Re: NAGRA T-Audio 30 IPS
« on: December 24, 2011, 07:36:41 PM »
Hi Hani:

Thanks for the info on the CMOS chip.  I think you are the Nagra T expert!

Happy Holidays!


instead of lurking here for more tape fixes for your illness.

If you can't help it, you are among others who feels the same way. 

Have a safe and happy holiday season.

got to go now, wife is calling.  Ki

Reel to Reel Tape Machines / Re: NAGRA T-Audio 30 IPS
« on: December 21, 2011, 12:59:35 PM »
Hi David and Joe:

Here's what you need:

Mouser #: 639-CR12600SE-T

Mfr. #: CR12600SE-T COMP-3-1 SOLDER TABS

Manufacturer: FDK Batteries (Formerly Sanyo)

Desc.: Electronic Battery 3V 1500mAh

Price: $9.65 ea.

For other Nagra T owners,

As soon as you disconnect the battery, the RAM loses all the codes and data loaded at power up and user entered values.  Sometimes it could be a good thing as Hani found out to clear out the corrupt data.  The machine will load factory defalut parameters and operational code at power up.   But if you don't want to lose the set up data, I would suggest you get a battery holder with two AA batteries and temporarily solder in parallel with the Nagra battery before removing the old battery.  You would solder in the new battery and desolder the AA batteries and you should be good to go.

Good luck!


Reel to Reel Tape Machines / Re: Help needed for Studer A810
« on: December 18, 2011, 11:26:56 PM »
Hi Hagen:

It's good that you had found the source of the problem and fixed it.  Judging from the electrolytic capacitor issues you had with spoolng motor controller, I would supect you have similar problems elsewhere.

The first area of problem would be the filter caps in the Basis boards.  Although there are many, once you get started, it goes fast.  The next one is the caps in the Power Regulator board.  I have also replaced two electolytic caps in the LED Display board.

The ones that most people miss and I found to be critical are two electrolytic caps in the head preamp board inside the headblock.  I would replace them before you do any audio work on the machine.


Reel to Reel Tape Machines / Re: Help needed for Studer A810
« on: December 16, 2011, 11:31:09 AM »
Good work Hagen.  I haven't looked into the details of the MPU version changes but now I know.  The main concern in old MPU card incompatibility with the latest firmware versions is for MPU cards (1.810.752.XX) with 07/83 or older.

Let us know how your recovery work ends up.

After you have your A810 working perfectly, you need to contact the Queen, Eilleen, and get hold of the TP tapes and hear what the fuss is all about!


Reel to Reel Tape Machines / Re: Help needed for Studer A810
« on: December 15, 2011, 04:58:40 PM »
Hi Hagen:

Based on your MPU card part number (1.810.780-00), the firmwas was had been updated.  the MPU card version came with the firmware version 40/85.

Since A810 firmware version 01/88 is the latest official version and your MPU card is somewhat old (-22 is the youngest), I suggest you stay with proven version 01/88 than to upgrade to the last version 25/91 that offers no audiophile related functionalities or default EQ data.

The last time when I checked with Audiohouse, they had 25/91 for sale but no longer stocked the 01/88 chip set.


Reel to Reel Tape Machines / Re: NAGRA T-Audio 30 IPS
« on: December 11, 2011, 04:54:17 PM »
Doc B is correct, Nagra T Audio is capable of 30 ips speed.  However, based on photos you had posted and if the legend for speed selection on your pushbutton panel matches with four diffenent settings for your Speed/EQ interface cards, your machine is configured for top speed of 15 ips (38cm/s) at A and C settings and can't do 30 ips in its current configuration.

You need the schematic to modify the Speed/EQ cards for CH1 and CH2 for A or C setting (since they are the same) to operate at 30 ips.


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