What's wrong with my VCR? It won't do anything.

[digicube]

I was cleaning my SVHS Mitsubishi HS-U748, then it malfunctioned. It won't do anything; play, fast forward or rewind. I've attached a video what happens when I press play, rewind or fast forward.

Attached is the service manual.

[hech54]

Has it ever functioned normally without the lid/top cover on?

[digicube]

I have never operated it with the lid cover off.

[hech54]

Put the lid back on and see if it works. VCRs(all of them?) have sensors that shut them down when bright light gets in.

[digicube]

It still doesn't work with the lid cover on. Could it be a belt issue?

[mazinz]

Did you happen to use any sort of compressed air on your vcr? If you did leave it off for a full 3-4 days and the try it again and it should work. If you used no compressed air then disregard this

[digicube]

No I don't use compressed air since it can be expensive. I use electric duster or hand squished air blower. This VCR is clean so there was no need, I just cleaned the heads and roller.

This VCR is a Turbodrive. I heard high speed rewind/ff is bad, so I have a feeling it could be a loose belt or broken gear. Or the mode switch just needs a cleaning.

[davexnet]

I have this VCR also, I've never seen these symptoms.
On mine, the VCR lacks strength when FF or RW, and often slows down and stops before the end of the tape. Because of this
I have opened it and removed the chassis for closer examination.

The mode switch is that big black wheel you see in your video, upper right sitting under the sideways motor .
I don't know whether my problem is related to yours or not. I do have a copy of the service manual and can post it here
if you need it.

[digicube]

The big black wheel is a mode switch? I thought mode switch are small. The service manual would be helpful. Please post it here. Thanks.

I'm would like to clean the mode switch.

[davexnet]

I agree with you about the mode switch, I was expecting something small on the underside of the chassis, as seen in the many repair
videos on Youtube, but I couldn't find anything. (If you find something let me know)

Here is the manual

[digicube]

According to the service manual on page 8, the mode switch is small and on the underside of the chassis.

[davexnet]

According to the service manual on page 8, the mode switch is small and on the underside of the chassis.

Are you looking at figure 2-13 "mode position unit" on page 8? I saw that also, it's a fixed block, no moving parts and no electrical
connections. Best I could do was clean the outside. That parts seems to be measuring the position of the big black wheel,
mentioned earlier, and relaying an optical signal to some sensors below the chassis on the main board.

[digicube]

Yes figure 2-13. So it seems the mode switch on this VCR is different from the usual mode switch. I've successfully removed the chassis.

I've circled the mode switch and the mode switch sensors (4)

[davexnet]

Yes the two sensors at the bottom are the reel table sensors and the one in the middle is for the end of tape light (I think)
Not much you can do with them. Regarding that big black wheel, make sure its edges are clean as that can affect the associated sensor.
Good luck with it, let me know if you find anything interesting

[digicube]

This is what one person I asked said. "I could see the tape loading mechanism working, but it didn't appear that take up reel was winding the tape in. Perhaps the tape sensor doesn't detect any movement of the supply and take up reel, so it immediately goes into shut down?"

So it seems something is up with the supply and take up reel.

Maybe a capacitor has gone bad in the capstan motor assembly.

The VCR will repeat this tape loading action if I reset it with a tape inside. It's like a self-test that it needs to pass.

[digicube]

Wow I just found out Turbodrive decks don't have mode switches.

PHILIPS TURBO DECK
Alan J. Roberts describes the main features of the Philips Turbo VCR
deck mechanism and provides notes on general servicing and some points
that can cause confusion
#1 Intro
The Philips Turbo VCR mechanism has been around for a number of years
and has proved to be efficient and reliable. The wind/rewind speed is
very fast, hence its name. A unique feature is the absence of a mode
switch. Replacement parts are usually supplied as kits, so that all
associated gears or levers are replaced at the same time, ensuring a
reliable repair.

[digicube]

Welp looks like the more I tinker with it, the worse it gets. I think I've messed up the mode position and since it uses optical sensors, I don't know how to align it.

2 SVHS VCRs to the landfill.

[davexnet]

Did you pull out that big black wheel? I did this myself once but there is either something on the underside that lines up
or there is an arrow - I remember seeing something when I put it back. Looking at the manual figure 2-18-2 suggests there is
a hole to look for

[digicube]

No. I pulled out the capstan motor. It auto shuts off even when I detached the chassis, so I think the problem lies on the main PCB.

[digicube]

What is the device she's using called? https://youtu.be/PQhQzR2TQKk?t=307

[JVRaines]

It's a transistor tester.
https://www.amazon.com/Mega328-Transistor-Resistor-Capacitor-Mosfet/dp/B01H6QKVOU

[jagabo]

Transistor (etc.) tester.
https://www.amazon.com/Mega328-Transistor-Resistor-Capacitor-Mosfet/dp/B01H6QKVOU/

too late...