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Nagra III Rewind?


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I need some help/advice regarding my Nagra III. I made a DIY power supply from a wall wart (12VDC @ 1A) using  a 6 pin DIN and pins 2 and 5 on the accessory connector. Positive is earth/ground.

 

Works almost perfect except for rewind. I've read the manual and other relevant posts here and elsewhere but can't figure this out.

 

Again, playback, record, line in/out and the XLR all work as they should.

 

I have the function selector switch set to EXT and when I turn it to either playback option and turn the tape transport control knob to the 'ON' position it plays no issue.

 

However when I turn the On/Off knob to the left to disengage the tape and rewind it does a fast spool forward instead of rewind.

 

The fast spool button works as it should spooling the tape forward onto the take up reel.

 

When I acquired the deck it had a tape treaded and was in the ON position for who knows how long. I know that is not ideal. There is a blurb in the manual that this may affect the rewind capability. 

 

Quote

When out of use, turn the tape transport control to its mid position. In the "ON" position, when not running, there is danger of producing a flat on the capstan roller. The working surfaces of the fast rewind clutch may also suffer.

 

I don't think it is my PS being wired backwards since that would make the normal playback in reverse which is not the case. I'm guessing that I simply don't understand the mechanics....or that the working surfaces of the rewind clutch have suffered as stated in the manual.

 

I did purchase a replacement belt kit but I'm a little anxious about doing the work. It looks intimidating.

 

Any ideas?

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  • 1 month later...

Compare the picture in the service manual on page 2 with your Nagra. Consider "Operating Instructions German". So you can endure you mistakes. On the other pages there is something about the engine and the traction forces that must have tape and how to set them. Quickly everything in German, but written very sparingly. On the last pages there is again something in English.

 

https://www.nagraaudio.com/wp-content/uploads/2020/09/Bedienungsanleitung-Nagra-III-Deutsch.pdf

https://www.nagraaudio.com/product/nagra-iii/

Let's tell it like it is, my English sucks, but I hope you understand what I'm trying to say. 

As you fault whether the fault at the battery power rights. 
If not, then look in the power supply area (for example, in the area of the "small cloth socket"). 

If the error is in the power supply, read the manual (the engine is used in both English and German versions, and the troubleshooting procedure is solved).
The block diagram can also help to locate the error. 

If that doesn't help, I'll take photos of my Nagra III and upload them here and compare the cables as best I can with yours.

 

If it is a fault in the electronics, ask in this forum. 
Tape technology is a German invention, they will also find many experiences here.
Many speak English, certainly better than I do and can help you there.  

https://tonbandforum.de/

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Thank you so much for your reply TBFAN! I have uploaded a few photos of the inside of my Nagra for your diagnosis. I have not tried to use batteries due to a note written inside the battery compartment as seen in the photo. It reads: When battery operated a shorting plug MUST be used Pins 2 and 4. So if I just take a piece or wire and connect pins 2 and 4 together would that be sufficient?

 

The belts are not tight and should be replaced. I need help with that. I have some resources to follow but have not taken the time since it will take me a while to complete carefully.

 

I will look at the service manual you provided and see if I can make any sense of it. The troubleshooting at the end looks helpful.

 

Thank You again!

Kevin

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Ok this is going to be a little more difficult. 

I think someone has changed something on their Nagra. 

 

I guess judging by their location they should be able to speak perfect English and (if they haven't done so, have a look at the user manual)

(https://www.nagraaudio.com/product/nagra-iii/ scroll down to downloads )

 

First the belts: The Nagra has 3 round (!) belts:
2x 90mm x 2.5mm or 3mm
1x 64-66mm x2,5mm 

 

I can't explain the exchange exactly, but if you have some time I will make a video about how to exchange all three belts without having to readjust everything afterwards.

 

On page 15 (Electrostatic discharge) is something about a small brush ... Read this passage and compare it with your Nagra. 
 

You can find this brush on the Honywell switch for the fast rewind (this little red box, on the take-up reel)

 

 

https://museumofmagneticsoundrecording.org/images/R2R/NagraIIIManual.pdf Page 27 block diagramm. 

On the bottom of the page is the wiring of the Tuchelbuche as it should be. 
(To the left of the playback head) 

 

Contact 2+4 would be:

Ground (2) and motor stop (4)

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4 hours ago, tbfan said:

Ok this is going to be a little more difficult. 

I think someone has changed something on their Nagra. 

 

First the belts: The Nagra has 3 round (!) Belts:

 

I can't explain the exchange exactly, but if you have some time I will make a video about how to exchange all three belts without having to read just everything afterwards.

 

Great observation! Strange. This is exactly how I received it. The replacement belts I ordered are round, 3 of them. A Video of the belt installation would be INCREDIBLY helpful, thank you.

 

4 hours ago, tbfan said:

 

On page 15 (Electrostatic discharge) is something about a small brush ... Read this passage and compare it with your Nagra. 
 

You can find this brush on the Honywell switch for the fast rewind (this little red box, on the take-up reel)

OK I will investigate this and report back, thank you.

 

4 hours ago, tbfan said:

https://museumofmagneticsoundrecording.org/images/R2R/NagraIIIManual.pdf  Page 27 block diagram. 

On the bottom of the page is the wiring of the Tuchelbuche as it should be. 
(To the left of the playback head) 

 

Contact 2 + 4 would be:

Ground (2) and motor stop (4)

Yes, that seems correct. So is that standard to have to short these pins to use batteries? I prefer to use the EXT DC input for my purposes going forward.

 

 

Thank You for shedding some light on this mystery of mine and giving me something to do during this time of no work and no light at the end of the tunnel.

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New belts were installed yesterday and now I can rewind a tape, I'm so excited! It wasn't as bad as I thought but there were some moments of shouting expletives. I was not able to remove the smaller belt under the motor. I couldn't get the old one off. It seems to be in good shape however and if it becomes a problem I have a replacement.

 

I also found the electrostatic discharge wire and put that back how it should be (I hope).

 

My next challenge will be the Playback Amplifier.

 

Test mode and Record mode seem to be working fine. I get good mic and line level signal input and sound through the recording amplifier to the monitor output (phones) but upon HiFi playback there is very low output and no movement on the modulometer at the same output level on the fader (0db). I'm assuming there are out of spec components in the PB amp that need replacing. Tested at 7.5 ips NAB and 15 ips with the same results.

 

Also, FYI for anyone reading this hoping to get service on a Nagra III I did call Forrest Forbes formerly of Trew Audio and left a voice mail but never got a response.

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Well, they have a schematic and block diagram to help them find errors, but I have to say that Kudelski was very picky about what they used to build Nagra. 

We are not talking about an Uher Report or a Revox, Telefunken Studer...

 

Normally I always change electrolytic capacitors, but Nagra has electrolytic capacitors that were really only found in military applications. 

I know also no Nagra which quit the service because of broken Elkos. If you have a component tester, unsolder the suspected electrolytic capacitors, test them and replace them if they are defective, but I don't think that the electrolytic capacitors are the problem. 

 

My Nagra shows a similar behavior as theirs, probably not quite so extreme but still. This is because a tape machine must be calibrated to a specific tape, then the level is correct again. The procedure is explained in the German manual, although not as detailed as one would need it. 

Try (if you have) different tapes (sometimes one tape is no longer good). 
 
I have found that mine has problems with Agfa tape, BASF seems to suit her (especially DP26), Pyral/RMG/RTM LPR35 she also likes to. 

 

Try to find out where your Nagra came from, most of the time you can find out what kind of tape the previous owner calibrated the machine to.

Mine came from Radio Bremen or NDR, which means the machine was most likely tuned to BASF DP26. 

 

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18 hours ago, tbfan said:

Well, they have a schematic and block diagram to help them find errors

 

If you have a component tester, unsolder the suspected electrolytic capacitors, test them and replace them if they are defective, but I don't think that the electrolytic capacitors are the problem. 

 

This is because a tape machine must be calibrated to a specific tape, then the level is correct again. The procedure is explained in the German manual, although not as detailed as one would need it. 

 

Try to find out where your Nagra came from, most of the time you can find out what kind of tape the previous owner calibrated the machine to.

Mine came from Radio Bremen or NDR, which means the machine was most likely tuned to BASF DP26. 

 

You're likely correct about the tape formulation and the Nagra set up. The tape I've been using to test with was the tape it came with, looks like Scotch 150. It was from a radio station. I plan to attempt to calibrate it myself with help from the manuals and Google Translate.

 

I've hesitated to put on a new tape because I know it won't be calibrated for it. I have some Ampex, RMG and ATR stock. I also have some old Scotch that I can use and should be more period correct and also match the calibration. I did test a few different reels with it, that Scotch, BASF, and a Honeywell with the same results accross the board; good input/record levels and very low output.

 

One thing I think it really needs is a demag. The tape was threaded and the pinch roller engaged for years. The heads may be magnatized.

 

I'm also not seeing the speed stabilizing to 60Hz for the US. Both wheels spin freely and never settle, as on my turntable stroboscope. I'm using AC power so should be 60Hz.

 

Also, FYI Forrest called me within an hour or two of my post so he is still around and happy to work on your Nagra 4 series and said he could help with my playback amp if I decided to do it. $250 lab/bench fee and you get it all cleaned/lubed and set up for whatever tape you want. Not bad really.

 

Thanks again for keeping me engaged with this project!

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Okay, calibration requires instrumentation that Nagra III does not have on board. 
If they have the instruments, nothing stands in the way of the project.

 

I remembered one thing that I forgot.
On mine, the heads were so worn that they had the effect you describe. 
(If you press your finger against the tape during playback, the sound will improve if you lap the heads).

After I have refurbished the sound heads, the level differences were completely gone and the sound was crystal clear again. 

This procedure for reconditioning is called "Läppen". 

 

As for the strobe, have you read the instructions? 
There are the general conditions under which the stroboscope works. In short: Use a real light bulb and no LEDs.

It is better to check the speed with a measuring tape, everything else is inaccurate. 

 

Pressure roller (if you meant the part), a new one cost 80EUR on Ebay. 


Finally, do everything on your tape recorder that you feel comfortable with, but no more. 
If you want to do everything yourself, get a locking ring pliers and spring carriage (tape tension). 
If not, the offer sounds good and fair. 

 

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  • 2 months later...

my nagra 111 has identicakl ''loss'' on playback on monitoring output,

also on hi-fi record when in ''after'' on the b/a switch.

 seems mine =may?= have been modified????? any ideas please

its loosing about 20dB

S/N PHO 6812802

I'VE DEGAUSSED AND SCRUBBED HEADS WITH J&J COTTON BUDS WITH ISOPROPYL ALCHOHOL

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