Fisher recieves power, doesnt turn on?

MistertheMan · #1 08-06-2021, 08:59 PM

I recently purchased a Fisher Studio-Standard Stereo VCR (model no. FVH-830, mostly likely manufactured in 1985), and have been going through hoops to fix every problem present. A melted drive belt was replaced as well as a circuit wire reattached from the faceplate.

When plugged in, no noises are made from inside the machine, but the display screen lights up in full, with all numbers showing an '8'. Neither power on or off lights function when powered on, switching to power on changes nothing and pushing a cassette into the basket doesn't trigger a response either. While an orange socket appears to be open next to the tape drum (best visible in the 4th image), there are no signs of other open sockets or dangling wires.

I'm at my wits end and am completely unsure of the next steps to take but will continue to work on it!

latreche34 · #2 08-06-2021, 09:51 PM

Unless you are repairing it for a museum display or collection purposes It's not worth time and money even for a skilled technician given the quality of playback you would get from an ancien machine like that, A low end VCR from late 90's will perfom equaly or better than that beast assuming it is in perfect condition, which is not.

Dougmc · #3 08-07-2021, 07:59 PM

8888 maybe cause the clock is not set.
Open the door on bottom make sure it's not switched to timer mode.
If not that and u don't have a schematic look up the data on the stk pack in the power supply
Make sure the voltages are there.
Not much more info without a schematic.
Doug

MistertheMan · #4 08-07-2021, 11:20 PM

The manual states that when first plugged in, the display should show a blinking '12:00'. Instead it just shows '88:88' without blinking. The power on/off/timer buttons on the left is set to off, setting it to timer doesn't change it from displaying all '8's. In fact, the left front face circuit board does not receive any power, period. (the circuits for the faceplate are split in 2, left side is for everything under the cassette slot and the power/timer buttons, the right side has the display and everything else to the right of the cassette slot).
I don't have a schematic but I do have the owners manual in full, readable condition.
And the STK pack reads 'STK5431ST', and its by Sanyo. I'm unable to find any information about that specific pack online.

Dougmc · #5 08-08-2021, 06:36 AM

https://www.datasheetarchive.com/STK5431-datasheet.html
When u open one of these it may list another ic but look at the spec
Sheet it has other numbers
.
So it looks 15v, 12v, 9.5v 5.1v...
It's possible not all voltages are there as its need a switch
Voltage to turn it on completely.
I would assume the 5v should be there and not low.
Also clean ,no bad capacitors.
So start there, looks like pin 1 for 5v.

Dougmc · #6 08-08-2021, 06:50 AM

https://www.repairfaq.org/sam/vcrreg.htm
Little more info

MistertheMan · #7 08-08-2021, 07:08 AM

Would you happen to have an image of what I should be looking for? its not often I mess around with specific parts on a circuit board and there are a few boards close to the power supply.

Dougmc · #8 08-08-2021, 09:21 AM

In your picture 5 it's mounted on that aluminum heat sink.
Next to the power transformer.
Carefull probing it as you can short two pins together.
Looks like that power supply is on its own circuit board.
There is a connector on it just probe it and see what voltages you get.
If you have a oscilloscope you can check for tipple, ac voltage on the
DC voltages.
Be carefull about the 120v ac coming into the unit.

MistertheMan · #9 08-08-2021, 12:06 PM

While I dont have a oscilloscope, I do have a multimeter which I was able to read ~120v coming off the 2 prongs from the plug that go into power board A (which is the one the transformer is on). Im unsure if theres something else I should be attempting to get the voltage from on either power circuit board.

MistertheMan · #10 08-08-2021, 12:24 PM

I took a picture specifically of the power supply area just to give a better view.
Heat sink on the left, STK pack is attached to both the heat sink and Power Board B at the bottom of the picture.
Power Board A is to the right and has wires connecting it to Power Board B, as well as having the transformer attached to it. The 2 prongs i tested are near the back (top of the pic) and go to the AC in. Theres also an AC out (yes, this vcr can apparently power something external) going to Power Board A. Lastly there are wires strewed down to the brackets keeping the transformer in place.
Hope this gives a better image of what im looking at!

Dougmc · #11 08-08-2021, 03:31 PM

Having flash on would help.
To the left on that picture is a couple wires screwed to that metal ,hopefully that is ground then probe those
5 or 6 pin connectors near the stk pack see what voltages you have.
I can't read the reference numbers on those connectors picture is not sharp enough

MistertheMan · #12 08-08-2021, 08:26 PM

I had turned the flash off in the picture due to having flash on making the picture darker/lower quality. I shined a lamp inside for this one. I just took the multimeter and probed the pins going from power board A to B (more specifically, 04 and 05 on the bottom right of the pic on board B to 01, 02, and 03 on the right on board A). The currents seem to vary, but mostly stay around 14.

Dougmc · #13 08-08-2021, 08:42 PM

We need to know what the 5v is .
My best guess the top pin on the stk pack is pin 1 for 5v. This is the power for the ics
If it's low or has ac on the DC 5v could cause your problem.
U might do searches on the web for a schematic.
It would help us both greatly

MistertheMan · #14 08-08-2021, 08:59 PM

I was able to get a reading of ~40 by using the top pin of the STK pack and pin 1 (the far left pin) of connector 05 on power board B.
As for schematics, it looks like physical service and troubleshooting manuals exist for the FVH-830, but none that are free. I do have the owners manual but doubt itd be any use in this case.

Dougmc · #15 08-09-2021, 06:15 PM

Not getting anywhere.
Maybe pull the front cover there is a large ic near the display
Look up the data sheet see what pins are ground and what pin is b+ 5v.
And measure there.
Also before u pull the front off look for a little hole on the faceplate some may of had
A reset button ,long shot.
Maybe post what area you live maybe someone close by is willing to help
U learn..most of us started like u.
Also search web for ham vests in your state.
1 a month in different parts of the state.
I go
To the ones that have a flea market, may find cheap test equipment along
With help.some may give u something