2024-11-24 - Fixing a Sony SLV-815 VCR
--------------------------------------

A while ago, I got a Sony SLV-815 VCR that was in very bad
shape[0]. The most glaring issue was the power supply, in which the
capacitors had leaked so badly that it was even visible from outside
the power supply. A sane person would have just thrown the VCR away
at that point (maybe after stealing parts of the mechanism to use as
spare parts for VCRs with the same mechanism), but I'm crazy, so I
decided to have a go at it.

General Notes on Disassembly
----------------------------

First off, note that some of the disassembly pictures were actually
taken after I was done because I hadn't taken any pictures when I
first disassembled the VCR. I cannot guarantee that everything was
put together exactly the way it was supposed to be because, again,
I didn't take proper pictures in the beginning.

The sides of the SLV-815 are decorated with panels made of pressed
wood that first have to be removed by unscrewing a screw and then
sliding them back[1]. There is then one more screw on each side
before the cover can be removed, exposing the inside[2]. Note that
there is a screw missing from the main circuit board in that picture
(in the middle on the far side). That's because I took this picture
after I was actually done, and I had forgotten to put the screw back
in. The front panel is only held on by several clips, so it can be
removed fairly easily[3].

Power Supply
------------

WARNING: Fixing power supplies is dangerous, please don't kill
yourself. Read up on safely discharging power supply capacitors before
attempting any repairs.

There is a small plastic piece covering part of the power supply, which
is held on by plastic clips. This needs to be removed in order to take
out the power supply[4]. The power supply unit itself is held on by a
few screws. There is also a large metal piece covering the mechanism,
as seen in [2], which also is screwed onto the power supply. Once these
have been removed, the entire unit can be removed from the case and the
cables removed from their sockets. The capacitors had leaked so badly
that some of the damage was even visible outside the power supply[5].

In order to get to the actual power supply board, a metal piece
has to be removed that is clipped onto the metal cage. The board
is then soldered onto the metal cage, so it has to be desoldered
first[6]. The mains input can be removed from the cage as well[7], but
I just desoldered the wires because that made it easier to work on the
board. Note that both of these images were taken after repairing the
power supply. I also don't actually know if the clear plastic piece
in [6] is supposed to go there, but that's the only place where it
fit properly.

The original state of the power supply was pretty nasty[8][9][10], so
I first desoldered all capacitors and scrubbed the entire board with
isopropyl alcohol several times. I also desoldered the transformer
and the secondary circuit board so I could clean those properly. I
learned later that it probably would have been better to just use water
(ideally deionized) and let the board dry afterwards because isopropyl
alcohol isn't ideal for removing capacitor electrolyte. The board
definitely wasn't perfectly clean after washing it with isopropyl
alcohol, so I hope that it isn't destroyed later by the remaining
traces of electrolyte. However, I had already replaced all the
capacitors when I learned about that, so I didn't want to wash it
with water anymore.

I replaced all the capacitors with new ones even though some actually
seemed to be fine still. In particular, the ones on the primary side
seemed okay, but I decided to just replace all of them while I was at
it. The main filter capacitor was supposed to be 135uF, but I replaced
it with 150uF because 135uF was difficult to find (people who know
more about electronics than me said that this change shouldn't matter
too much for this specific use-case). I later looked at the service
manual that I found online, and it specifically mentioned that this
capacitor could be 135uF or 150uF.

NOTE (added 2024-12-06): I don't want to go into any details on how
to choose proper replacement capacitors because there are much better
resources online already. This also isn't supposed to be a guide to
repairing power supplies since, again, there are much better
resources available already. The main purpose of this is to document
what I did in case anyone finds it interesting. The most important
part is that the voltage and temperature ratings must be the same or
higher on the replacement capacitors. The capacitance should be
exactly the same, unless you really know what you are doing and know
for sure that a different capacitance is fine in a particular spot.
It also is important to use low ESR capacitors, at least on the
secondary side, although I've heard that too low ESR can also cause
problems. I've also heard that it can actually be a bad idea to use
low ESR capacitors on the primary side, although I didn't have any
problems with it in this case. As I said, please consult other
resources if you want to learn about this properly.

The final result can be seen in [11], although I later added some
silicone glue to hold the main filter capacitor in place properly
without damaging any pads/traces because of its weight. Note that you
specifically need to use neutral cure silicone glue because other types
release acid and can damage the circuit board[12]. The electrolyte
had also damaged the solder mask on the board, but luckily no traces
were damaged, so I just cleaned away the flaky solder mask and added
some UV solder mask[13].

I didn't solder the power supply board back to the metal cage at
first so I could access it more easily in case anything else was
damaged still. I'll come back to that later, after describing the
other repairs I had to perform.

Two Other Circuit Boards
------------------------

After seeing what state the power supply was in, I decided to look
at the other boards in the VCR to check if there were any more leaky
capacitors. In order to get to the main board, first the display
board at the front has to be flipped up. On one side, it is attached
to another board with a connector that has to be opened[14], on the
other side a screw has to be unscrewed[15]. In [14], you can also see
a 5.5V/0.22F supercapacitor which I replaced. The original had also
leaked quite badly[16]. The display board can then be flipped up[17].

The main board has several screws and a clip holding it in place[18]
(the clip is at the letter E on the side). When the screws have
been removed and the clip is pushed to the side, the entire board
can be flipped up[19]. There are two plastic clips attaching it to
the hinges[20]. If you want, you can push those clips through the holes
and remove the main board completely[21]. I did this in order to make
working on it easier, but all the things I ended up doing wouldn't have
been any more difficult if I had just left the main board connected
to the rest of the VCR.

Most of the boards didn't have any leaky capacitors, but there was one
that was in very bad shape. In [22], it is the third board from the
right (note that the picture was taken after I had already replaced
the capacitors). The white plastic part on top is only held on by
four clips. [23] shows the board in its original state. It isn't very
clear in the picture, but several capacitors (especially the large
pink ones) had leaked quite badly. I removed all the capacitors,
cleaned the board thoroughly with isopropyl alcohol, and soldered
in new capacitors[24]. The other side of the board had been damaged
quite badly by the electrolyte, so I had to repair two traces[25]
(I scraped away the solder mask and soldered on thin magnet wire). Of
course, I verified with a multimeter that there was continuity and
that there were no short circuits between neighboring traces. I
also scraped away the solder mask on some other traces, partially
because it was somewhat damaged from the electrolyte, and partially
to check if the traces below were damaged. After verifying that all
the traces were good, I covered them all in UV solder mask[26] (yes,
I know that one pad is nearly gone, but there was still enough of it
left to solder on the capacitor).

There was also one pad that was ripped off completely[27]. It probably
would have been perfectly fine to just use some magnet wire to
connect the trace to the capacitor leg which belonged in that hole,
but I decided to try something different. I cut out a small piece
of copper foil (I think it was 0.1mm thick), poked a hole in it, and
attached it using UV solder mask[28]. I then covered it in solder and
connected it to the trace[29]. I think it would have been better to
cut out a small "leg" on one side to connect it to the trace because
it was kind of difficult to get a good connection this way.

Power Supply (Again)
--------------------

When I was done with those boards, I could finally put everything
back together and test if the VCR actually worked. Surprisingly,
it did! Well, sort of at least...

When I first plugged it in, it turned on, although I didn't try
to play a tape yet. However, if I unplugged it and then plugged it
back in, it didn't turn on anymore. If I left it for several hours,
it turned on again. This behavior made me think that maybe there was
a bad resistor in the power supply that was supposed to discharge
some capacitors. I don't know enough about electronics to say how
much sense that theory makes, but I decided to go ahead and test all
the resistors. Before long, I found at least one resistor that was
completely open. I decided to replace three resistors that were all
a bit sketchy[30]. [31] shows the new resistors (they're the shiny
ones), and [32] shows the same spot with two of them covered by a
large resistor that I had to desolder to get at them.

Once I had replaced these resistors, the VCR always turned on, but
there was still a problem. The head drum only sometimes spun up,
other times, it wouldn't move at all. I eventually determined that
the 9V power supply wasn't working properly. Testing this is kind of
dangerous because you have to probe around on the live power supply,
so only do this if you know how to not electrocute yourself. One
small note here is that the testing has to be done when the VCR is
turned on. Only some power rails are always on, others are supposed
to be off as long as the VCR is off, so probing around while it is
off won't help much.

After following several rabbit holes, I eventually noticed that
there was a fairly low resistance between the ground and enable pin
of the 9V voltage regulator (IC204 in [33]), and this resistance was
still low when I tested it out of circuit, so I determined that the
regulator itself must have been bad. My theory is that it worked a
few times "by accident", maybe because the short-circuit was
temporarily interrupted by the heat when all the components warmed
up, but I have no idea what exactly happened. Anyhow, I had to
somehow get a replacement for a Sharp PQ09RF11 voltage regulator (at
least I'm pretty sure that was its model number - this was a while
ago, and I forgot to write anything down). I couldn't find an exact
replacement, but there was a seller offering a pack of 20 PQ09RF21's.
The PQ09RF21 is 2 amp instead of 1 amp, but otherwise very similar
(the electrical characteristics described in the datasheets weren't
identical, but I hoped that it wouldn't matter too much). I went
ahead and bought those PQ09RF21's and replaced the PQ09RF11 with
it[34][35]. On a totally unrelated note, let me know if anyone needs
19 PQ09RF21's...

Once that was done, the power supply finally seemed to be working
perfectly. Note that I did replace one capacitor on the circuit board
underneath the mechanism because it had a high ESR value, but I don't
think this was actually necessary[36][37] (the Kemet capacitor under
the copper piece is the replacement). If I remember correctly, I did
that before I figured out that the actual problem was the 9V regulator,
so I was just sort of stabbing around in the dark and looking for bad
capacitors anywhere near the head motor.

Putting the power supply together again is a bit annoying because
there are a few clips that have to be attached to various components to
push them against heat sinks[38]. There is also a plastic cover that
I forgot at first[39]. The circuit board can then be soldered to the
metal cage again and the metal protector attached to the bottom[40].

Mechanism
---------

The mechanism on this VCR was actually in decent condition, but I
still decided to have a closer look at it. I wrote another article on
a Sony SLV-E9, which uses the same mechanism[41], so I won't repeat
all of that here, I'll just mention a few special parts.

Note: I realized later that it's possible to just remove the bottom
cover of the VCR to get at the mechanism, so most of this work would
have been unnecessary, but by then I was already done[53][54].

The most important part is that there's a hidden screw that has to be
removed in order to remove the mechanism. The circuit board between
the front panel and the mechanism has a connector on the right and
a screw on the left, which have to be removed/opened first[42]. The
board is then only held on by several plastic clips (there are also
several cables connected to it, but those don't need to be unplugged
in order to access the hidden screw). Once the board is out of the way,
the hidden screw behind it can be accessed[43].

In order to remove the mechanism, the loading mechanism first has to
be removed, but that's very similar to the SLV-E9, so I won't repeat
that here. The main difference is that the SLV-815 has a big metal
plate covering the mechanism that first has to be removed, and there
are more cables that have to be unplugged. It also is necessary to
unscrew the head preamp before the mechanism can be removed (or at
least I think it's the head preamp - the metal box with three cable
bundles plugged into it, as seen in [2]). There are also two ribbon
cables going from the circuit board underneath the mechanism to the
main board, which have to be unplugged (in my experience, it's easier
to flip the main board up and unplug them from there than to unplug
them from the mechanism side - or at least it's easier to plug them
back in that way in the end). When the mechanism has been removed from
the VCR, the circuit board underneath still has to be removed from the
mechanism. It is only screwed on, but there is a cable bundle going
from a connector on the circuit board to the head motor. I found that
it was best to unplug that before pulling the circuit board up because
the infrared sensors for sensing tape ends prevent the circuit board
from being tilted very much while pulling it out. Other than that,
there isn't too much to mention. I didn't take any proper pictures,
so I can't really explain much more. If you need to take one of these
VCRs apart, just make sure to take good pictures beforehand so you
know how everything was put together.

The infamous "blue gear" wasn't completely broken, but there was a
small crack in it already, so I went ahead and replaced it (see [41]
for a description of that). There are obvious signs that it's an old
device. For instance, the path for the tape guides was cracked in
many places. In one place, the plastic had even come off the metal a
bit[44]. I should probably glue that down at some point so it doesn't
end up blocking the threading arm.

To my horror, I discovered that the VCR suddenly didn't pull back the
tape properly when ejecting. At first, I suspected the reel sensors
that are supposed to sense if the reels are turning. I cleaned the
infrared sensors underneath the mechanism[45] and the reflective parts
inside the reels[46][47] (note that these are not the tape end sensors
that I mentioned earlier, those are at the sides of the mechanism,
at the height of the tape).

At first, I thought that had fixed it, but it seems to have just
been random because the problem came back and the tape wouldn't even
play anymore (the capstan turned, but the reels didn't - luckily, the
VCR noticed that before too much of the tape was pulled out). I then
noticed that the tension arm wasn't attached properly anymore[48].
It's supposed to be held down by a plastic clip, and I had probably
somehow caused it to come loose while playing around with the
mechanism. However, fixing that still didn't change anything.

Luckily, I have a cheater cassette, which is just a regular cassette
with as much as possible cut out[49] and the holes on the left
and right side taped shut so the tape end sensors think there's a
tape inside[50] (yes, I know I could have cut everything out much
more nicely, but I was in a hurry when I made it). This allowed me
to observe what was happening with the gears between the reels. I
decided to compare it with the SLV-E9 since that was already working
at this point. Eventually, I realized that I had just made a stupid
mistake. I had taken out most of the gears just out of curiosity,
but I had accidentally forgotten to put back a washer[51] (it can be
seen on the metal bar behind the gear that is lying on top of the
other gears). Without that washer, the gear could get stuck at the
bottom when it was actually supposed to be pushed up. If I remember
correctly, eject actually worked properly in this case since the reel
on the left (supply-side) was always connected with the driving gear,
but play didn't work because both reels were connected to the driving
gear instead of just the takeup reel.

However, after fixing this, it still didn't work properly (if I
remember correctly, play worked again, but now the tape wasn't pulled
back properly on eject again). It was then that I realized I had made
another stupid mistake. When greasing the mechanism, I had decided
to grease all the gears around the clutch assembly as well because
"it won't hurt, I guess". This was a bad idea because the grease
caused the gear in the middle to move more slowly[52]. This gear is
supposed to move to the left or right depending on which reel it's
supposed to be turning, so it didn't move to the supply-side reel
quickly enough to pull back the tape when ejecting. After removing
the grease as best as I could, everything started working properly.

The moral of the story is that you shouldn't grease gears that aren't
supposed to be greased, unless you really know what you're doing.

One last thing I did was to replace the motor coupling in the loading
mechanism, but that's also described in [41].

UPDATE (2025-01-30): I had this VCR open for so long that I completely
forgot to put back one piece. There's supposed to be a metal cover over
the front part of the mechanism that has to be screwed on before putting
the front panel back on[55]. I only noticed that because I found the
metal cover lying around and wondered where it had come from.

Conclusion
----------

There were several moments during this endeavour when I was very
close to giving up. I'm glad that I didn't, though, because it would
have been a pity to put all that work in just to have a non-working
VCR. Now I just need to figure out what to do with it because I have
plenty of working VCRs already...


[0] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/slv-815.jpg
[1] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/wood_side.jpg
[2] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/inside.jpg
[3] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/front_panel.jpg
[4] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_disassembly.jpg
[5] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_leak.jpg
[6] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_soldered.jpg
[7] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_mains_input.jpg
[8] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_orig1.jpg
[9] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_orig2.jpg
[10] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_back.jpg
[11] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_recapped.jpg
[12] https://electronics.stackexchange.com/questions/18525/what-kind-of-glue-should-i-use-for-pcb-mounted-components-to-avoid-vibrations/18533#18533
[13] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_back_recapped.jpg
[14] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/display_board_connection.jpg
[15] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/display_board_screw.jpg
[16] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/display_board_capacitor.jpg
[17] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/display_board_flipped.jpg
[18] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/main_board.jpg
[19] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/main_board_flipped.jpg
[20] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/main_board_clips.jpg
[21] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/main_board_removed.jpg
[22] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/extra_boards_holder.jpg
[23] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board.jpg
[24] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_recapped.jpg
[25] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_traces.jpg
[26] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_traces_covered.jpg
[27] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_pad.jpg
[28] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_pad_copper.jpg
[29] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/hf9_board_pad_fixed.jpg
[30] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_resistors_orig.jpg
[31] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_resistors1.jpg
[32] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_resistors2.jpg
[33] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_9v.jpg
[34] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_9v_replacement.jpg
[35] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_9v_replacement_soldered.jpg
[36] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/unnecessarily_replaced1.jpg
[37] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/unnecessarily_replaced2.jpg
[38] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_metal_clips.jpg
[39] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_plastic_cover.jpg
[40] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/powersupply_metal_cover.jpg
[41] gopher://lumidify.org/0/phlog/2024-11-24-sony-slv-e9.txt
[42] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/panel_board.jpg
[43] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/mechanism_hidden_screw.jpg
[44] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/plastic_crack.jpg
[45] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/reel_sensors1.jpg
[46] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/reel_sensors2.jpg
[47] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/reel_sensors3.jpg
[48] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/tension_arm.jpg
[49] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/cheater1.jpg
[50] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/cheater2.jpg
[51] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/clutch_washer.jpg
[52] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/clutch_grease.jpg
[53] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/bottom_cover.jpg
[54] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/bottom_open.jpg
[55] gopher://lumidify.org/I/phlog/2024-11-24-sony-slv-815/metal_cover.jpg