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Cassette All discussions pertaining to cassette decks. These include general usage, recording, playback and service questions. For subjects related to tape itself, see the Cassette Tape subforum under this one. Obscure service subjects that don't quite fit go in the Help and Do It Yourself subforum.

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  #21  
Old 12-04-2017, 03:56 PM
mityooo mityooo is offline
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This is in my Onkyo mechanism.The spring plate 31 performs a brake spring function.


Whatever it is important to push down!

.
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File Type: jpg spring.jpg (38.5 KB, 23 views)
File Type: jpg spring 1.jpg (46.4 KB, 27 views)
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Last edited by mityooo; 12-04-2017 at 04:45 PM.
  #22  
Old 12-05-2017, 12:25 AM
Teo2005 Teo2005 is offline
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Thanks both of you for your help.

On my mechanism, the brakes are indeed pushed down by #31 Cassette Hold Spring as in mityooo's mechanism. The brakes are doing the job as the Reel Hubs can't be spinned easily while in STOP mode. Maybe when I reassembled the mechanism I positioned the cam in a different position and the timing of the brakes is off? I don't think so, as the cam position is determined by the 3 Mode Switches that follow the cam's profiles but I might be wrong...
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  #23  
Old 12-05-2017, 01:05 AM
mityooo mityooo is offline
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Because it is not in my hands I can only guess! In all cases the brake is the cause of the strip being released. I would deform the plate 31 for more pressure and quicker reaction. Unscrew the three screws holding the motor plate, lower it and twist it slightly. Check that the brake plate 11 moves freely while the spring 31 is released!
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I speak only Bulgarian, Russian and Spanish so do not be angry with me!

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Last edited by mityooo; 12-05-2017 at 01:12 AM.
  #24  
Old 12-05-2017, 02:17 AM
Teo2005 Teo2005 is offline
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Frustrated

Quote:
Originally Posted by mityooo View Post
Because it is not in my hands I can only guess! In all cases the brake is the cause of the strip being released. I would deform the plate 31 for more pressure and quicker reaction. Unscrew the three screws holding the motor plate, lower it and twist it slightly. Check that the brake plate 11 moves freely while the spring 31 is released!
Already tried this (lowering a bit the arm of #31 Cassette Hold Spring) for increased pressure on the brakes plate. Also rised a bit the arm of the #11 Brakes Plate (the arm that makes contact with the cam) in order to lower the Brakes Plate position and thus engage the reels earlier, but no joy
  #25  
Old 12-05-2017, 08:38 AM
Teo2005 Teo2005 is offline
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PROBLEM SOLVED!
No back tension spring or anything needed. Just to be careful!
As I said in my first post, switching through different operations (PLAY - STOP - FFWD etc) seemed like the heads assembly doing extra moves like going through PLAY mode every time, even if PLAY not selected. So I remembered I opened the CAM motor to clean the brushes and oil the shaft. It seems that I had put the motor cover wrong, i.e. rotated at 180 degrees, so the cam motor was spinning in reverse. Desoldered and inverted the wires to the cam motor and it worka flawlessy, no tape loops no extra moves

Sorry for wasting your time guys, I promise I'll be more careful in the future.
  #26  
Old 12-06-2017, 01:51 PM
Teo2005 Teo2005 is offline
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Ok, sorry to bother you guys but I have another issue...
Having a scope and a cassette recorded with 400Hz 1k 3k 10k 15k on my other deck (Sony TC-K711S) I started to check things like azimuth, tape speed etc to see how far the 2 units are one from another. Following the SM - electrical adjustemens I reached point 5 - Playback Level Calibration. Since I don't have a VTVM I hooked the oscilloscope probes to TP101 and TP201(it can measure also RMS voltages) to check if outputs are at least close to 350mV. Found out that on both test points there are oscillations of about 90kHz 70mVrms, even if PLAY is not engaged; hitting PLAY those oscillations overlap the 400Hz signal from the tape, making readings impossible as the scope can't trigger correctly (the result is a 90kHz oscillation modulated at 400Hz). Those oscillations don't appear in REC mode, only in PLAY or stand by... Also they don't show up at LINE OUT RCAs. Checked the ground wires that go from PCB to chassis, they're fine. I'm pretty lost as electronics isn't my best friend. If someone has an idea of what's goin' on...

P.S. Checked the IC101 IC201 (NE654N) and IC102 IC202(TEA0654) and they are cold, not sure if they auto oscillate. Also, as I read in other threads about "orange cap disease", should I change those ones?

Last edited by Teo2005; 12-06-2017 at 02:00 PM.
  #27  
Old 12-06-2017, 02:36 PM
mityooo mityooo is offline
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At what point does the probe "ground"? Check out the preamplifier, the out of the dolby chips, where they appear and where the 90kHz start to grow.
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This does not prevent me from not loving narrow-minded and fools with principles!

Last edited by mityooo; 12-06-2017 at 02:48 PM.
  #28  
Old 12-06-2017, 03:13 PM
Teo2005 Teo2005 is offline
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Quote:
Originally Posted by mityooo View Post
At what point does the probe "ground"? Check out the preamplifier, the out of the dolby chips, where they appear and where the 90kHz start to grow.
Signal is clean at pin 9 of IC101 (so just after the Q101 Q102 Q103 preamp) but is tainted at pin 5 of IC101 just before TP101 (L104 any clue? no reference on electrical adjustements workflow, marked as adjustable on schematic diagram)

sorry dunno what else to check...
  #29  
Old 12-07-2017, 04:47 AM
Teo2005 Teo2005 is offline
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Update: The frequency of the noise on R-channel doubles if Dolby C is selected (90kHz -> 180kHz), on the L-channel it halves (64kHz ->32kHz) roughly...
The RMS voltage remains the same.
  #30  
Old 12-07-2017, 05:36 AM
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ypsilon ypsilon is offline
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Quote:
Originally Posted by Teo2005 View Post
Ok, sorry to bother you guys but I have another issue...
Having a scope and a cassette recorded with 400Hz 1k 3k 10k 15k on my other deck (Sony TC-K711S) I started to check things like azimuth, tape speed etc to see how far the 2 units are one from another. Following the SM - electrical adjustemens I reached point 5 - Playback Level Calibration. Since I don't have a VTVM I hooked the oscilloscope probes to TP101 and TP201(it can measure also RMS voltages) to check if outputs are at least close to 350mV. Found out that on both test points there are oscillations of about 90kHz 70mVrms, even if PLAY is not engaged; hitting PLAY those oscillations overlap the 400Hz signal from the tape, making readings impossible as the scope can't trigger correctly (the result is a 90kHz oscillation modulated at 400Hz). Those oscillations don't appear in REC mode, only in PLAY or stand by... Also they don't show up at LINE OUT RCAs. Checked the ground wires that go from PCB to chassis, they're fine. I'm pretty lost as electronics isn't my best friend. If someone has an idea of what's goin' on...

P.S. Checked the IC101 IC201 (NE654N) and IC102 IC202(TEA0654) and they are cold, not sure if they auto oscillate. Also, as I read in other threads about "orange cap disease", should I change those ones?
By creating your own calibration tape and then using it to set the wrong voltages, you have most likely screwed up the calibration of your deck. E.g. the 350mV specified at the test point, only applies when the Nakamichi DA09005 series of test tapes is used. Furthermore you used the self-made tape as an azimuth tape, which is a faux pas in itś
's own right. Azimuth calibration should only be performed with a special, full track alignment cassette, and never, I repeat NEVER, with a tape recorded on another deck.
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Nakamichi BX-300E, BX-125E, BX-100E, CR-3E, Yamaha KX-493, Akai GX-F80, UC-F5, Teac V-44C, Technics RS-B565, RS-B665, Kenwood KX-400. On the workbench: Sony TC-K22, TC-K33, Akai CS-34D, Nakamichi BX-150E, Cassette Deck 2.
  #31  
Old 12-07-2017, 06:39 AM
Teo2005 Teo2005 is offline
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Quote:
Originally Posted by ypsilon View Post
By creating your own calibration tape and then using it to set the wrong voltages, you have most likely screwed up the calibration of your deck. E.g. the 350mV specified at the test point, only applies when the Nakamichi DA09005 series of test tapes is used. Furthermore you used the self-made tape as an azimuth tape, which is a faux pas in itś
's own right. Azimuth calibration should only be performed with a special, full track alignment cassette, and never, I repeat NEVER, with a tape recorded on another deck.
As stated in a previous post, I did the cassette to see haw far the other deck (Sony) is from this one. Didn't tampered with adjustments, measuring is different from modifying.
Also I fail to see how azimuth or play speed is related to this issue, if I'm blind please explain

Last edited by Teo2005; 12-07-2017 at 06:44 AM.
  #32  
Old 12-07-2017, 12:00 PM
bohelcho bohelcho is online now
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Get better prepared for the jobs you plan before you start

Quote:
Originally Posted by Teo2005 View Post
As stated in a previous post, I did the cassette to see haw far the other deck (Sony) is from this one. Didn't tampered with adjustments, measuring is different from modifying.
Also I fail to see how azimuth or play speed is related to this issue, if I'm blind please explain
Having adopted this approach (playing a 'calibration' cassette recorded on a consumer grade deck for test purposes), without touching the adjustments is simply a waste of time. Reading your post it was not clear to me what exactly the results of this exercises are.
The better way would be to use commercial test cassettes (there are plenty of them on eBay, but beware, most of them are at least 3 decades old and used. However, there is a member here who makes calibration cassettes of the same quality as the industry standard, on virgin premium tape, and his calibration tapes are very reliable!).
You should further be aware that there are certain differences between the calibration tapes used by Nakamichi and the generally accepted cal tapes made by Teac, Abex, etc.
If you do not dispose over the required equipment listed at the very beginning of the SM you are at risk to end up with unfaithful and misleading results (even if you have not touched the internal adjustments).
And one more thing: without a VTVM (or maybe better a true RMS sensitive AC meter designed specially for audio applications) you can practically do nothing.
As azimuth and speed adjustments are concerned, here you will need again specialized equipment if you want to be sharp on the specs.
Azimuth: you need a Dolby level calibration tape (the one made by Nakamichi), and a 15 kHz tape at -20 dB also recorded across the whole tape width (single track mono). With these two, as you say you have an oscilloscope, azimuth alignment should not be a problem. The 15 kHz tape must be used with the VTVM, though.
Tape speed is done with a calibration tape containing a 3 kHz signal at -10 dB (again full track) and a frequency counter. The procedure on the BX-125 is clearly described in the SM and does not deviate from that with other belt driven transports.
Excuse me if I am telling you things you already know. I prefer the 'old school approach'. There have been numerous attempts to do cassette deck calibration by other means differing from the SM or a generally approved method, and all these are far, far from accurate.
However, the choice what to do is yours.
You have asked for help, we're doing what we can.

Regards
Nick
  #33  
Old 12-07-2017, 01:06 PM
Teo2005 Teo2005 is offline
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Nick, I appreciate all you've said, all are sound things, no debate on that. The help I was asked for is in #26 post, so correct me if i'm wrong but again I fail to see how using a cassette recorded on another machine (for comparison purposes) can generate noise or auto oscillation at test points, even if it's not playing (in idle state)... Again, I don't (refraining to use bold) underestimate the genuine (either professional or consumer grade) test tapes, I have an idea of the equipment used to make them and why certain features (full track for example) are used, but that's not the point. Sorry for inconvenience, if any.

Regards,
Teo

Last edited by Teo2005; 12-07-2017 at 01:08 PM.
  #34  
Old 12-07-2017, 02:15 PM
bohelcho bohelcho is online now
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@Teo: No inconvenience whatsoever. I was trying to show you "the right way"(lol!).
As I mentioned before, there have been many cases where younger members (especially newcomers) have tried to cut corners, believing the methods suggested by them are superior to the 'traditional' approach. Mostly, these have failed.
My point has always been: Follow the SM as close as you can, although SMs are normally written for service personnel (and the majority Tapeheads are not).
The good news is that we at TapeHeads Net are generally friendly people, trying to help one another (with some exceptions, of course, where there are certain members using acid tongue and acting in not the best manner).
Misunderstandings are not excluded. In the end everything goes fine!
Sorry if I have been rude.

Regards
Nick
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