SL-2401 Betamax Problem


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SL-2401 Betamax Problem

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signsofrain
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Apr 29, 2009, 1:33 PM

Post #1 of 12 (9870 views)
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SL-2401 Betamax Problem	Can't Post

Hi Everyone,

I recently acquired an old (circa 1983) Betamax deck, and I'm looking to get it working to play some old family tapes. It's a Sony SL-2401 and the problem seems to be that it thinks it has a tape in it. (The "Tape Inserted" icon on the front panel is illuminated, and the deck will happily play, pause, fast forward, etc, though there's nothing in there)

Here's what happens:

When the deck is turned on, the semi-transparent gear you see just to the right the gear with the toothed belt on it spins quite fast, to no apparent effect. Then one of the little plastic bits that turn the tape spools rotates for awhile, followed by some mechanical movement I can't see beneath the tape-holder assembly. Sorry I can't be more specific about what these parts are... I don't know much about VCRs.

Then the tape icon lights up on the front panel. Pretty much the same thing happens when I press the "Eject" button.

If I try to insert a tape, it will go partway in but no further. There is a small sensor switch that detects the tape's initial insertion, which I tested with my multimeter. It works fine.

Basically, since I don't know much about VCRs, I don't know what these symptoms could mean, and I hesitate to start disassembling this thing without knowing that I'll be able to put it back together.

I hope there's a resident expert who can help me! If you need additional photos, or video, or anything, just let me know.

Thanks!

(This post was edited by signsofrain on Apr 29, 2009, 1:33 PM)

jts1957
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May 3, 2009, 6:24 AM

Post #2 of 12 (9856 views)
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Re: [signsofrain] SL-2401 Betamax Problem [In reply to]	Can't Post

1) I'm assuming that (as pictured) unit is fully threaded, and that pressing "eject" does NOT result in it unthreading.
2) You don't say the ribbed (toothed) belt (and it's pulleys) spin. (I'm presuming = No)

Are you familiar with how a plastic gear or pulley is "press fit" onto a motor's metal shaft to spin as one? Over time the plastic develops a crack so that metal shaft and plastic no longer turn as one (motor's metal shaft "spins" but the plastic gear/pulley does not).

If you take the loading assembly apart, you'll find that that is most likely the case here. Small Gear, Loading: Part # 3-679-114-00. No doubt = No Longer Available. Carefully gluing is the usual solution now.

(P.S. - I had always thought that "threading" could only occur with cassette basket in "down" position)

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Location: Far, Far Away

Dillon123450
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Jun 4, 2009, 1:20 AM

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Re: [signsofrain] SL-2401 Betamax Problem [In reply to]	Can't Post

Hi Guys, Dillon from Trace Electronics Repair here.
I have just finished tackling one of these Sony SL-2401 units and the problem seems to be as described in this thread. Here ios What I did:
As you can see in this thread picture, the Beta machine is stuck in play mode ( all the tape mechanisms are up around the drum (servo) assy and did not return to it's home position on the last eject function. It is apparent here that the small black gear connected to the bottom of the shaft the drives this entire tape assy is busted. These mechanisms need to be manually returned to their home position while the gear assy is removed and while the Beta tape is removed. Sony really goofed on the design here..with having way too much stress and way too many components being driven by suach a small wheeny girly- man gear.
I used a 2 compound 5 minute epoxy on my gear. Note that as the black gear split up the side, the tooth gap opened up slightly started to bind on upon a full rotation of the gear. I had to secure the assy with a small clamp to put pressure on the gear as it dried so that the tooth gap closed up. I am really crossing my fimgers on this.
Dillon, Trace Electronics, Barrie, Ontario, Ca

Dillon123450
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Jun 4, 2009, 2:44 PM

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Re: [jts1957] SL-2401 Betamax Problem [In reply to]	Can't Post

Hello fellow Expert:
I have successfully repaired that small black gear as described in my previous post. I am not sure how long it will last though as is with anything that is repaired or rebuilt as opposed to replaced (gear).
Upon assemblying my unit and doing a few tests, I am noticing that the drum assy (servo) in not spinning up to its required rpm that is required in playback mode (actually no sign of movement at all), also, the take up spool is not gathering the tape. What possible causes am I looking at here? I have fixed a few VCR's in my day but this beta unit takes the cake. Any helpful information here would be appreciated!
Thanks, Dillon
Trace Electronics, Barrie, ON, Canada

(This post was edited by Dillon123450 on Jun 4, 2009, 2:52 PM)

jts1957
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Jun 4, 2009, 8:15 PM

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Re: [Dillon123450] SL-2401 Betamax Problem [In reply to]	Can't Post

Gear = Glue, just like I mentioned! Wink

Let's start at the beginning, so we know we're both on the same page...
1) Does unit Power On? - And STAY On?;
2) Does unit accept a cassette into the front and lower it into machine? And STAY On?;
3) Does tape from cassette "load" around cylinder? And STAY On?;
4) Does unit "try" to go into mode (FF/REW/Play) selected (should click, at least), but the unit "senses" there's something not right, And unit then takes it back to "stop?"
5) Have you tried with a "dummy" tape - so as to see what moves, what amount of torque, etc.?

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Location: Far, Far Away

Dillon123450
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Jun 4, 2009, 10:06 PM

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Re: [jts1957] SL-2401 Betamax Problem [In reply to]	Can't Post

Hi HT, Yes, The gear fix worked like a charm!.. Thanks!
Ok, Noe to answer your questions...
1) Yes, The unit powers upand stays on. No problem.
2)Yes, Accepts tape, Loads it into the machine ans stays on.
3)Tape loads up around the cylinder and stays on.
4) Here I can FF, and rew. no problem. There is no activity at all with the drum or head assy at this time not spinning. As soon as I press play, everything appears to work fine--except the tape starts to jam up in the capstan area and does not go inside the tape (take-up), and the drum is still not spinning. All the motor and solenoid activity appears to be ok and functional. ( I have to FF or REW in order to retract the tape so that is doesn't get busted and caught up inside the unit).
I do not have a dummy tape (beta) but will continue to work the issue. I will also check torque ( the unit was sitting for a while so I will check for sticky components.
So..if you can think of anything...would love your input.

Thanks,Dillon, Barrie, ON

Dillon123450
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Jun 16, 2009, 9:50 PM

Post #7 of 12 (9778 views)
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Re: [jts1957] SL-2401 Betamax Problem [In reply to]	Can't Post

Hi JTS,
At what point in the sequence of loading events should the drum spin up to its required RPM? After tape is loaded? as soom is power is turned on on the betamax unit?
The drum on my unit is not spinning at all and I am about to go right to the control pcb to troubleshoot the drum circuirty. Could this problem be due to a sensor?
Any thoughts? Would love to know.

Thanks, Dillon. Trace Electronics.

jts1957
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Jun 17, 2009, 1:51 AM

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Re: [Dillon123450] SL-2401 Betamax Problem [In reply to]	Can't Post

Been too long. I don't recall. Sorry. (For sure when you hit "Play." Smile

)

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Location: Far, Far Away

denonjapan
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Jul 23, 2009, 4:07 AM

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Re: [signsofrain] SL-2401 Betamax Problem [In reply to]	Can't Post

signsofrain! LOOK WHAT YOU DID! ALL THESE PEOPLE OVER THIS ACQUIRED 1993 OLD CIRCA....NO LONGER AVAILABLE parts are now in heaven.

denonjapan
made in japan

Barry777
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Jan 16, 2010, 10:29 PM

Post #10 of 12 (9396 views)
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Re: [Dillon123450] SL-2401 Betamax Problem [In reply to]	Can't Post

Hi Dillon,

I'm having a similar problem with a Sony SL-HF600. Most of these consumer Beta machines share fairly similar-looking mechanisms and probably also have fairly similar circuitry. I can fast forward and rewind just fine, but get no capstan or drum rotation at all when I go to Play mode. I get a click, and the pinch roller momentarily engages against the capstan until the machine finds out there's no drum or capstan activity, then it retracts the capstan and won't do anything else until I eject and reinsert the tape.

I'm thinking more in terms of power supply problems, since I have two dead things at the same time. With no schematic or service manual, I did just a few quick voltmeter checks here and there. I get +5V, and plus and minus 15 volts at certain points on the PS board, but can't be sure other terminals are supposed to be energized by other circuits sending "turn on" signals to the power supply board. I'm not getting hardly any voltages on the system control board except a +5V at a few of the IC pins. This tells me that the computer stuff is being fed, but there are no drive voltages for the drum or capstan, as the chips controlling them aren't getting anything except computer power, and nothing to pass on to the drum and capstan motors. That whole board is basically dead except for that occasional +5 volts here and there.

My next step will be to recap the power supply, as the electrolytics have reached the end of their expected life and I've already fixed a few machines by simply recapping the power supply. These problems were all servo lock related, and the capstan and drum drive circuits place the greatest demand on the wimpy switching-type power supply. Sure would like to have the service manual, it would make the troubleshooting much more efficient.

Another possibility is a failed mode switch, which is probably buried deep in the mechanism - but would be another reason that more than one thing is dead, as it can make more circuits at once. Just in case you don't know, the mode switch is controlled entirely by physical movements in the mechanism. If it gets dirty or fails, it will still move when triggered by the mechanism, but of course won't make the required electrical connections.

Another Beta machine I have loses servo lock about every 14 seconds, until the unit warms up and then it's fine. This is a sure sign of aging power supply caps. If you're like me (and it seems so), you want to get right into the complicated stuff, when the trouble is actually in a simpler area. But I would say recap the power supply as a first step - the machine surely needs it anyway, so you're not really wasting your time or money if that's not the trouble. From my experience, low cap/high volt units (such as 1 uF at 50 volts) are usually the ones most likely to be bad. I very seldom see a bad high cap/low volt unit, like 6800 uf at 35 or even 63 volts.

Good luck!
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Barry Fone - VCR Repair hobbyist and professional FAA Repair Station Avionics Bench Technician (top level). TEST EQUIPMENT: (4) Sencore VC93 VCR Analyzers, (11) Tentel gauges, Sencore VA48 and (2) VA62 Video Analyzers, Sigma Electronics TSG-375 NTSC/SMPTE Video Generator, several VCR Alignment Tapes, plus countless Oscilloscopes, Frequency Counters, Wow and Flutter Meters, Distortion Analyzers, Vectorscope, 136-channel Logic Analyzer, Signature Analyzer . . . . VIDEO GEAR: (6) JVC BR-S822U's, (3) JVC BR-7000 series, (3) JVC BR-S500U, (2) JVC BR-S800U, JVC GR-800U and (2) GR-860U Editing Controllers, Sony FXE-100 Video Switcher/Effects Generator, (5) Time Code Generator/Readers, (1) Sony SLO-1800 (Beta), (2) Alesis ADAT-XT, (1) Sony DXC-1200 TV Camera, Pioneer VP-1000 Laser Disc Player plus many consumer grade Beta and VHS VCR's. Passionate electronics enthusiast since 1973...most anything except computers. Check out my collection at www.barrys8trackrepair.com/MyVideoGear.html

Barry777
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Jan 17, 2010, 4:00 AM

Post #11 of 12 (9391 views)
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Re: [Dillon123450] SL-2401 Betamax Problem [In reply to]	Can't Post

Dillon,

I'm happy to announce that I recapped the power supply, and now the drum and capstan are happily spinning and the entire VCR is working great. As mentioned before, the large value caps (3300 and 10,000 uF) were fine, which is good because I don't carry many of the larger values in stock. I have to keep reminding myself to always recap the power supply before getting too crazy with troubleshooting :-)

If you're doing much work on older electronic equipment, it's almost imperative to buy up at least 100 of every value of electrolytics from below 1 uF up to about 470 uF. You can find large lots cheap on eBay, which is how I acquired my stock. Usually, 50 volt values will cover most applications, though you'll find a few 63 volt caps here and there. And of course, it's okay to replace any value lower than 50 volts with standard 50 volt caps. Only the electrolytics routinely fail from age, all other types hold up great over the years.

Hopefully, this will be the trouble with yours too - easy fix as long as you love to solder! A cheap solder sucker from Radio Shack works great for removing the old ones - it's basically a standard soldering iron with a vacuum bulb attached. Squeeze the bulb, heat the connection and suddently release the bulb - it sucks the old solder right up and allows easy removal of the old part. Be sure to blow out the bulb into a glass or metal container every single time, or you'll eventually blow solder on the PC board. I learned quickly not to use the ashtray as a receptacle for expelled solder - ashes go everywhere! Good luck man -
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Barry Fone - VCR Repair hobbyist and professional FAA Repair Station Avionics Bench Technician (top level). TEST EQUIPMENT: (4) Sencore VC93 VCR Analyzers, (11) Tentel gauges, Sencore VA48 and (2) VA62 Video Analyzers, Sigma Electronics TSG-375 NTSC/SMPTE Video Generator, several VCR Alignment Tapes, plus countless Oscilloscopes, Frequency Counters, Wow and Flutter Meters, Distortion Analyzers, Vectorscope, 136-channel Logic Analyzer, Signature Analyzer . . . . VIDEO GEAR: (6) JVC BR-S822U's, (3) JVC BR-7000 series, (3) JVC BR-S500U, (2) JVC BR-S800U, JVC GR-800U and (2) GR-860U Editing Controllers, Sony FXE-100 Video Switcher/Effects Generator, (5) Time Code Generator/Readers, (1) Sony SLO-1800 (Beta), (2) Alesis ADAT-XT, (1) Sony DXC-1200 TV Camera, Pioneer VP-1000 Laser Disc Player plus many consumer grade Beta and VHS VCR's. Passionate electronics enthusiast since 1973...most anything except computers. Check out my collection at www.barrys8trackrepair.com/MyVideoGear.html

Shown
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Jul 6, 2010, 8:16 AM

Post #12 of 12 (9053 views)
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Re: [Barry777] SL-2401 Betamax Problem [In reply to]	Can't Post

Nice information dude!! thanks for sharing. I apprenticed for your good work.

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