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Tape drive troubleshooting


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#1 Zerock OFFLINE  

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Posted Wed Aug 8, 2018 9:26 AM

I have an official TI program recorder that doesn't appear to be working correctly. I've had it apart and cleaned it thoroughly before testing it. I've also tested all the pins on my interface cable. I think my problem is with playback, since it doesn't seem to matter what volume setting I use, I hear the same volume low hum either from the speaker or with headphones. I would assume that if playback were working then I would hear different volumes of tape noise.

 

Regardless, I don't have a prerecorded audio cassette to test my hypothesis with. I do know the TI-99 is putting out a signal when recording (tested on my PC). What things should I check to identify and perhaps fix this problem?



#2 sparkdrummer OFFLINE  

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Posted Thu Aug 9, 2018 2:44 AM

Try inserting a scracth tape into the recorder and cycle the record play buttons several times. Why? - When record is enabled part of the switch circuitry cuts the audio while recording. If the switch is dirty sometimes when you return to play mode the audio stays cut. This has happened on several of my recorders and doing the cycle trick has brought them back. Hopefully this all that's wrong with your deck. 



#3 Zerock OFFLINE  

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Posted Thu Aug 9, 2018 5:39 AM

So just take one of my blank tapes and play with the buttons? Seems easy enough if it works. Think it's better to change between play/record in rapid succession or to run for a while and then switch?



#4 sparkdrummer OFFLINE  

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Posted Thu Aug 9, 2018 5:48 AM

Yes, try cycling both buttons as quickly as you can to try and clean the switch up a bit. I hope it fixes your issue. 



#5 sparkdrummer OFFLINE  

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Posted Thu Aug 9, 2018 5:54 AM

I forgot one other thing - cycle the pause/play switch too. 



#6 Zerock OFFLINE  

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Posted Thu Aug 16, 2018 5:38 AM

So, after much fiddling and opening up the cassette player to inspect the switch, I finally got it to play. Now, I'm still having read errors, and I have some other possible causes I'd like to investigate.

 

The first most obvious problem could be the volume and tone settings. The manual says to position them so that the marker is in the "middle" position. I've noticed this isn't actually the middle of the wheel's range of motion. I assume this is actually a medium-high setting as one would expect to need when using a cassette drive. How much fiddling about is expected to try and find the right setting? I never grew up using tapes, so I have nothing by which to judge how sensitive things should be.

 

Next, I'm using a 90-minute tape when the manual says to use 30- or 60-minute ones. Does this actually matter? I have noticed that there's a specific spot near the beginning of the tape where the cassette's plastic chassis actually moves inside the player. The tape then moves slower than it's supposed to for a moment before returning to its original position and resuming normally. I haven't looked hard enough to see if there is a bigger pattern. Is this a sign of a problem with the player or with the tape?



#7 sparkdrummer OFFLINE  

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Posted Thu Aug 16, 2018 7:13 AM

TI recorder right?

 

The markings on a TI recorder are pretty good. I recommend putting tone on max treble and volume at about 8. Be sure the heads are clean. If you have a head demagnetizer I would use that. The TI-99/4A is looking for a signal from the recorder of about 1 volt AC. If you have a VOM, put it inline with the lead going to the computer and adjust the volume control to read about 1 volt.

 

As an aside - I was checking one of my TI recorders and had no output - after cycling the pause/play a bunch of times now it works.



#8 Zerock OFFLINE  

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Posted Thu Aug 16, 2018 7:52 AM

By "about 8" do you mean with respect to the full range of motion or to marker visibility?



#9 sparkdrummer OFFLINE  

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Posted Thu Aug 16, 2018 8:03 AM

Marker visability - Volume -8, Tone - 10. The TI like treble.

 

By the way - C-90 tapes were frowned upon because there is a claim that they can stretch, which of course can effect the recorded data. I've used 90's with no issues, but if you put a ton programs on them fast forwarding and rewinding and stopping I suppose could cause some stretch. DO NOT USE a C-120!

 

Are you trying to load tapes recorded elsewhere? If so, sometimes you've got to fool with them a bit to get to load.  



#10 Zerock OFFLINE  

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Posted Thu Aug 16, 2018 3:35 PM

I think the player itself might be having issues. I just ran a test, recording a program to a tape then playing it back over headphones. On the first play, the sound was loud and clear, but the volume was gradually fluctuating. On the second playback (and subsequent ones), it was faint.



#11 sparkdrummer OFFLINE  

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Posted Thu Aug 16, 2018 5:36 PM

Are the volume and tone controls scratchy sounding when moved back and forth? If so, run them back and forth fully a bunch of times until you hear the "scratch" clearing up. Cleaning all the switches/controls with a good quality cleaner would ideal though.

 

Did you clean the heads?

 

Using a good quality tape "regular" bias tape?



#12 HOME AUTOMATION OFFLINE  

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Posted Fri Aug 17, 2018 5:21 AM

I used to be rather successful at restoring functions to compact cassette units ...longer playing cassettes contain thinner tape owing in part to less ferric oxide coating having been applied to the tape ...resulting in lower amplitude and otherwise compromised performance ...I prefer chromium oxide formulations(CrO2). The play/record multi-switch is often a problem on older units if their use has been infrequent. Noise in the potentiometers (knobs) is from the same source I imagine ...oxidation on contact surfaces. Tuner and control cleaner spray combined with smooth and rapid cycle operation of the switch or shaft through it's full travel several hundred times can be an effective start-up procedure. On most mechanisms it is possible to press record than press stop but do not release stop than begin rapid(not frenzied) cycling of the record switch while keeping the stop switch in the down position. Yes, max. treble ...because low-end units use a high-cut filter, distorting the the relation between the two original frequencies' relative amplitude linearity ...and perhaps even key-stoning the square wave somewhat.

 

With regard to: "I hear the same volume low hum either from the speaker or with headphones". The case may be that the main filtering capacitor in the power supply may have "dried out" internally ...allowing 60Hz. fluctuations from the A.C. to enter the system. I don't think the console would appreciate such distortion. Using batteries would be a simple way to eliminate this. I would attempt to assess the waveform directly if you can upload a sample! :idea:


Edited by HOME AUTOMATION, Fri Aug 17, 2018 5:49 AM.


#13 twoodland ONLINE  

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Posted Tue Sep 11, 2018 10:46 AM

I used to be rather successful at restoring functions to compact cassette units ...longer playing cassettes contain thinner tape owing in part to less ferric oxide coating having been applied to the tape ...resulting in lower amplitude and otherwise compromised performance ...I prefer chromium oxide formulations(CrO2). The play/record multi-switch is often a problem on older units if their use has been infrequent. Noise in the potentiometers (knobs) is from the same source I imagine ...oxidation on contact surfaces. Tuner and control cleaner spray combined with smooth and rapid cycle operation of the switch or shaft through it's full travel several hundred times can be an effective start-up procedure. On most mechanisms it is possible to press record than press stop but do not release stop than begin rapid(not frenzied) cycling of the record switch while keeping the stop switch in the down position. Yes, max. treble ...because low-end units use a high-cut filter, distorting the the relation between the two original frequencies' relative amplitude linearity ...and perhaps even key-stoning the square wave somewhat.

 

With regard to: "I hear the same volume low hum either from the speaker or with headphones". The case may be that the main filtering capacitor in the power supply may have "dried out" internally ...allowing 60Hz. fluctuations from the A.C. to enter the system. I don't think the console would appreciate such distortion. Using batteries would be a simple way to eliminate this. I would attempt to assess the waveform directly if you can upload a sample! :idea:

 

The program recorder has a 6V DC power jack input left of the ear/spk jack.  This may eliminate the hum that you are hearing without having to use batteries.  The only thing is, I can't recall if the center post is positive or negative... (The manual does not refer to this power input at all).






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