View Full Version : Has anyone here worked on early Betamax VCRs?


ChrisW6ATV
01-17-2012, 09:26 PM
Hello-

I am working on an early Sony Beta VCR (SL-8200) for a friend, and I have hit a potentially tough problem. The symptom is, the tape will not move when Play is pressed, but FF and Rewind are OK (or should be fine once I replace their idlers/tires). Play uses a part called a Forward Idler that includes a plastic multi-section cylinder with a spring in the top section and a rubber tire around the middle section. The idler is driven by a belt from below; all of the belts are new. The rubber tire contacts the take-up reel. Between the middle and top/bottom sections of the cylinder are pieces of material that seem to act as a clutch with the pressure from the spring in the top. The Sony test/repair procedure (from my original Sony service manual) is "test the torque in Play mode; below a certain number, replace the Forward Idler". The part is no longer available (no surprise there!). Its tire looks good as opposed to the FF/Rew ones, but I will probably replace it anyway if possible.

My questions are: Have you seen and repaired this problem in any SL-6200/6300/7200/7300/8200 Sony VCRs, and if so, how? Lacking a new idler, do you have a suggestion about maybe replacing or improving the clutch material if in fact it is bad? Thanks.

tvtimeisfun
01-18-2012, 07:08 AM
Hello that machine is a boat anchor I have a couple of top loaders setting on my front porch I am not sure if they would have the parts you need.. I believe you could find those parts somewhere maybe somebody has nos parts good luck...

maxhifi
01-18-2012, 09:16 AM
there is a product called rubber re-nu i think by MG chemicals. I bought a tin of it 20 years ago and have plenty left. If the idler isn't too far gone that'll get it going.

ChrisW6ATV
01-22-2012, 01:57 AM
Thank you both for the notes. TVtime, if I do not have success with replacing the tires on these idlers, I may get in contact with you for a possible part from one of your units if they are otherwise not going to be used/restored.

ChrisW6ATV
02-11-2012, 04:27 PM
I have replaced all of the tires and FF/rewind are fine. Play is still bad, for a different reason: The capstan motor does not turn. My service manual is actually for the SL-7200 (one-hour-only version of this machine), so I am ordering a Photofact manual for this model.

ChrisW6ATV
02-15-2012, 10:32 PM
I got the manual and looked online for the motor. Other owners have had the same motor freeze, so I took this one apart and added a drop of oil, then exercised it, now it turns nicely. I am going to put it back in and see what I get.

ChrisW6ATV
02-16-2012, 12:01 AM
I reinstalled the motor, and the machine plays and records well in both speeds.

tvtimeisfun
02-16-2012, 06:37 AM
Hello congrats on fixxing your machine hope it last awhile good luck..Timothy

ChrisW6ATV
02-19-2012, 06:21 PM
Thanks, Timothy. The machine has some trouble locking onto signals recorded on older tapes (the motor/servo system "hunts"), but it seems fine with its own recordings, so I am doing a few more tests.

ChrisW6ATV
02-19-2012, 07:16 PM
Well, it is not a new/old issue, or this VCR/other VCRs issue, but an X1/X2 (Beta I/Beta II speeds) problem. It locks onto the BI one-hour recordings perfectly every time but has problems with BII recordings, even the ones it just made itself. Now, I need to start figuring out the motor servo control system, apparently. Anyone here have any hints or tips? Thanks.

Electronic M
02-19-2012, 09:13 PM
look at the speed switch and what parts it connects into circuit exclusively for the beta II speed odds are it is one of the parts that is only used for beta II.

ChrisW6ATV
02-19-2012, 10:54 PM
Thanks for the suggestion, Tom. There is a speed switch but it is only for recording; the play speed is set automatically (as with all VCRs I know of). The servo circuits do possibly have sections that are dedicated to each speed that I will look at. Also, a few things I have found online point to bad tantalum capacitors in those circuits. I already checked the electrolytics and tantalums in some of the circuits and replaced one bad tantalum (with no improvement), but now I will check them again more closely and also look for more servo circuits I may have not yet checked. (They are spread over at least two boards that I have checked so far.)

ChrisW6ATV
02-22-2012, 11:50 PM
I checked the boards again and found several tantalum caps that have high ESR. I am going to replace them and see if it helps.

Retrovert
03-05-2012, 12:37 AM
there is a product called rubber re-nu i think by MG chemicals. I bought a tin of it 20 years ago and have plenty left. If the idler isn't too far gone that'll get it going.

Not to reactive a dormant thread, but I found this posting and dug out some information on the product. The product is indeed from MG Chemicals (http://www.mgchemicals.com) but it is called Rubber Renue (http://www.mgchemicals.com/products/408a.html). It is described as:
Rejuvinates and conditions rubber. Apply with a cloth, brush, or swab to bring belts, platens, rollers, and rubber parts back to life.

Zero residue
Fast dry
Removes oxidation film
100% Ozone safe


The MSDS says it contains: Xylenes 70-90% and Methyl salicyate 10-30%. Xylene (en.wikipedia.org/wiki/Xylene) is a common solvent; it's like toluene. Methyl salicyate (en.wikipedia.org/wiki/Methyl_salicylate) is Oil of Wintergreen, and is the active ingredient in the electric shaving cleaner/lubricants sold in an aerosol can.

Another product that I dug out is called Fedron (http://www.federalmining.com/fedron.html) from Federal Mining & Manufacturing Company (http://www.federalmining.com/). It is described as:
FEDRON is a clear liquid, blended of highly refined pure chemicals, specially formulated for cleaning rubber, metal, Teflon, silicon, and similar materials. FEDRON cleans and revitalizes, making your investment last longer.

The MSDS (https://www2.itap.purdue.edu/msds/docs/9255.pdf) lists: Xylol 40-50%, Ethyl Acetate (http://en.wikipedia.org/wiki/Ethyl_acetate) 5-10%, Methanol 1-3%, Ethanol 40-50%, Methyl isobutyl ketone 1-5%. Ethyl Acetate and Methyl isobutyl ketone are used as solvents as in nail polish remover.

I have no direct experience with either one.

ChrisW6ATV
03-05-2012, 10:31 PM
Thanks, Retrovert. I am still working on this VCR, but I did buy replacements for all of the rubber components except the pinch roller. I also got a second of the same model VCR, and I am going to replace all of its rubber parts and relubricate it before I work further on the first one. The second machine worked OK in both speeds when I got it (except for standard symptoms of old belts and tires), so I hope to use it to help troubleshoot the first one.

tvcollector
03-06-2012, 05:28 AM
old leaky caps on the servo board will cause playback issues, usually off speed playback which will cause tracking lines to go up or down the screen, with wow and flutter.. Adjusting the pot switches may help, but that's not a fix..

ChrisW6ATV
03-06-2012, 11:11 PM
Thanks, tvcollector. I did replace all the low-value tantalum caps on both servo boards and did the servo electrical alignments without a change in the behavior. Surprising, though, I can put in the one servo board from the second machine and then the (first) VCR definitely works better (servo lock on BII tapes most of the time rather than just occasionally), but it is not solved. Are you referring to tantalums or others? I hope to put in some good time on these machines in the next few days.

tvcollector
03-07-2012, 03:17 AM
I think the most problematics are the electrolytic caps.. I know that's the issue with the SL-5000 models...

ChrisW6ATV
03-08-2012, 01:16 AM
OK. I did test all of those and they were good on my meter.