Toshiba M-9485C VCR

[mike_drz]

Re: Toshiba M-9485C VCR

Here are a few more pics from the dungeon. That pcb with the sheild is labeled reel.

[mike_drz]

Re: Toshiba M-9485C VCR

Here are a few more pics from the dungeon. That pcb with the sheild is labeled reel.

[mike_drz]

Re: Toshiba M-9485C VCR

I've replaced all caps on the main board and the front panel. The picture got a bit better, but the vfd still has the same issue, now it's brighter though. I think it's a multiplexing issue, something with the driver IC.

[mike_drz]

Re: Toshiba M-9485C VCR

I'm back, today I'm working on a board called "video ccd". It was on the video controller board in a can, and almost all the caps on it were bad. I've attached some pics of the board below.

One problem I'm having is with the surface mount stuff, I measured C421 as a short in circuit. I took it out and it measured infinite resistance, and 40 pF. I can't read the color code on it, but it looks like either brown black gold, or red black gold.

Are they supposed to measure as open with an ohm meter?

[budm]

Re: Toshiba M-9485C VCR

The cap may be connected in parallel with other component that may have low resistance. So what is the resistance reading do you get that shown as shorts, < 1 Ohm?

[mike_drz]

Re: Toshiba M-9485C VCR

The cap may be connected in parallel with other component that may have low resistance. So what is the resistance reading do you get that shown as shorts, < 1 Ohm?

3 ohms or so. Yes I think you're right, there are a lot of inductors in that part of the circuit. The coils measure a similar resistance. Do does anybody happen to know how to read the color code on these caps? Would it be 10 or 20 pF or something like that?

[mike_drz]

Re: Toshiba M-9485C VCR

After reading the whole post, I have learned more about this topic. Thank you so much.

Hi Horence, I'm glad you enjoy the posts! These machines really are quite complicated. I spent a week just on all the mechanical parts, to get all the gears, cams, servos and belts working.

I'm glad there is still some knowledgeable techs out there when it comes to VCR's. I'll post some more pics for anybody who wants to follow along. I've already spent 75 bucks on this machine. I know you all think I'm crazy, but it has sentimental value. It's also a great learning experience, both with mechanical and electronics skills.

[R_J]

Re: Toshiba M-9485C VCR

The style are called melf or mini melf (NO not milf) I believe its the same color code as the resistors. I have never seen a bad one. looks like L404 could be accross C421

[mike_drz]

Re: Toshiba M-9485C VCR

The style are called melf or mini melf (NO not milf) I believe its the same color code as the resistors. I have never seen a bad one. looks like L404 could be accross C421

Hey RJ, thanks. I'll still call them milfs now that you brought it up. haha I appreciate all your help. I couldn't have done some of the work without your help.

I've got the head off, and am going to look at the motor drive. I already took apart and greased the capstan bearings and idler motors.

The head has a lost of oxidization around it because a tape was left in there for years. I want to make sure nothing got in there.

All in all the pictures been getting a lot better with all the re capping. It's still a little lite and gets washed out with very white scenes.

[R_J]

Re: Toshiba M-9485C VCR

The drum motor uses sealed bearings, nothing to lube. careful with the upper drum the heads are very fragile

[mike_drz]

Re: Toshiba M-9485C VCR

The drum motor uses sealed bearings, nothing to lube. careful with the upper drum the heads are very fragile

Thanks, I think a stray solder blob fell in there when i was clean the top. Don't want it to spin up before checking. It wont mess up the clearance or rip the wires off if I just take the top off right?

[mike_drz]

Re: Toshiba M-9485C VCR

I got the head apart today. There was a bunch of the tap rust stuff everywhere. I cleaned it out from around the heads with a wooden toothpick, and super fine tiny painters brush.

RJ I need your advice on this one, the magnet wire that's coiled around the drum has come loose in spots, and comes out. I'm pretty sure it should be glued down. Is it okay to use a bit of thin CA, or is epoxy better? I don't want to make it too heavy and throw off the balance.

[R_J]

Re: Toshiba M-9485C VCR

I don't know why you took the drum motor apart but I wish you luck getting it assembled and timed properly. I don't think a bit of glue will affect the balance much.

[mike_drz]

Re: Toshiba M-9485C VCR

I don't know why you took the drum motor apart but I wish you luck getting it assembled and timed properly. I don't think a bit of glue will affect the balance much.

Thanks, I couldn't get it apart without taking that collar off, to get it all apart. I marked everything, but we'll have to see if it still works after. That orange tape rust got everywhere.

[mike_drz]

Re: Toshiba M-9485C VCR

RJ, yep you called it. I put it back together on the marks the grub screws left on the shaft. Must still be a bit off though, I guess I create more fun times.

It plays but it crinkles the tape and cuts out, it also sounds like the motor is changing speeds sometimes. Is the only way to fix it trail and error changing the set screws?

[R_J]

Re: Toshiba M-9485C VCR

The drum itself should not cause the tape to crinkle, it would cause the head switching point to be out or to have a very poor picture. try and see where the tape is being crinkled in the tape path. What else did you remove or adjust?
On the lower part of the drum there is a machined groove, the tape should be riding just above it. make sure the drum is mounted properly to the chassis

[mike_drz]

Re: Toshiba M-9485C VCR

The drum itself should not cause the tape to crinkle, it would cause the head switching point to be out or to have a very poor picture. try and see where the tape is being crinkled in the tape path. What else did you remove or adjust?

I changed the idler tire too, everything else was the same. I adjusted the tape path just now, it plays okay for a bit and then starts to grind on the tape again. The envelope on the scope is no where near what it was before. It's not catching on any guide posts or anything. It enters straight, and starts to crinkle when leaving the drum. The back tension and everything else are the same.

Would the switching point show up on the scope as being off?

[mike_drz]

Re: Toshiba M-9485C VCR

I took some scope shots, The switch is at 2v/div @ 10 mS, Envelope is 20 mv/div @2ms. CTL is 0.5 volt DC, 2H is 5 volt DC.

The shots didn't come out super well, because of the frame rate.

[R_J]

Re: Toshiba M-9485C VCR

The head switching will show up at the bottom of the screen, We usually used a tv or monitor with the vertical size reduced so we could see where the switching was taking place It should be around 6 lines up from the vertical pulse. If the sw pulse is too low it will switch in the vertical pulse causing the picture to jump, if its too high it would show up in the picture, that all

You should have found what was causing the problem before adjusting the tape path.
What all did you remove besides the drum assembly? It should have just droped back in and maybe only minor adjustments would have been needed. If the drum was not assembled properly it would have shown up as a very poor or no picture but the tape itself would still run smooth.

[mike_drz]

Re: Toshiba M-9485C VCR

The head switching will show up at the bottom of the screen, We usually used a tv or monitor with the vertical size reduced so we could see where the switching was taking place It should be around 6 lines up from the vertical pulse. If the sw pulse is too low it will switch in the vertical pulse causing the picture to jump, if its too high it would show up in the picture, that all

You should have found what was causing the problem before adjusting the tape path.
What all did you remove besides the drum assembly? It should have just droped back in and maybe only minor adjustments would have been needed. If the drum was not assembled properly it would have shown up as a very poor or no picture but the tape itself would still run smooth.

Thanks RJ, the drum assembly is all slotted with guide pegs etc, it can't go in wrong. Thanks for all the tips, very valuable info. Yeah the picture is quite crappy, and does cut in and out. There are some lines too, but I'm using a small cheap monitor, so I can't tell right now.

The tape sounds like it's almost making a grinding noise against the drum, and the drum slows down. A few seconds later, it'll run smoother, with just the crunchy tape sound. Not very good at all, I swear I didn't touch the tape path until I heard that grinding noise and saw the tape starting to fold. I looked all around first, and couldn't see it getting folding on any of the posts or guides.