Items Covered This Month
- Akai VS-G425EA VCR.
- Teac MV1440 Televideo.
- Philips 14GR1224/75R TV set.
- Sony DVP-S735 DVD player.
Some years ago, I gave my mum a Teac Televideo (MV1440) for her
birthday. It was perfect for her little bedroom and she could lie in there and
watch her recorded soapies to her heart’s content.
Recently, to everyone’s surprise and relief, my son actually
got a job as a warehouse assistant. This was fine until one day the ancient
warehouse roller door decided to jam in the open position.
Unfortunately, the earliest anyone could replace the door was
the following week, which meant the warehouse had to be left open to the world.
The consternation about security concerns this caused management was enormous
until my son, who had just learnt about overtime, put his hand up to become
nightwatchman. This appealed no end to the management who eagerly agreed to this
My son quickly went home to get some essentials, like a six
pack (of light ale) and his Walkman. He also persuaded his granny to lend him
her prize Televideo – to get through the wee small hours.
He arrived back at the warehouse, unloaded his van and
proceeded to build a little nest in one corner of the warehouse which was in a
good position to view the broken garage entrance. The TEAC was placed precisely
on top of an old oil drum but unfortunately the reception was lousy with the
indoor aerial. Apparently, he was fiddling with the aerial in an attempt to
improve the reception when the accident happened.
The way he tells it, it was the set that had deliberately
committed hari-kari. The way I saw it, he had pulled the lead too hard and the
set fell off the oil drum and landed very heavily on its back on the concrete.
He brought it to me the next day, sheepishly pleading: "Please fix Gran’s telly
. . . and please don’t tell her anything".
Well, I took it to the workshop but as soon as I had removed
the back, I could see that the set was a write-off. The neck of the tube had
broken and the motherboard was cracked. What could I do? I went around to a
rival TV repair shop whose main line of business was buying, restoring and
selling secondhand TVs.
I’m on good terms with them and so I asked if by any chance
they had a Teac MV1440 in stock. We went down into their warehouse and had a
rummage. The only thing they had was an MV1480 MK II, which is a later model,
but it did have some faults. Apart from being filthy and having the front flap
missing, the set worked a bit. There was no sound and a washed-out snowy picture
on-air. The video was also working but there was just a snowstorm on playback.
However, this all worked to my advantage in the price negotiations.
Back at the workshop, I started with the video playback, which
turned out to be very dirty heads. A careful wipe of the heads axially with a
lint-free material and oil-free acetone cleaned them thoroughly. The sound fault
was more difficult to find but in the end turned out to be an intermittently
open-circuit loudspeaker. All I was left with was the snowy off-air
First, I checked the aerial socket and for continuity to the
extremely small Murata tuner. I then checked that the set was able to tune in
all the stations on VHF and UHF, which it did – albeit slightly snowy. I then
checked the RF AGC (it was about 6.5V) and found that the AGC control in the
separate equally small IF module also worked but adjusting this didn’t clear the
Although I had the service manual for this model, the circuit
is not drawn for the tuner or IF modules which are just shown as block diagrams.
I was faced with a dilemma – was the tuner faulty or was it the IF module or
both? I was satisfied that all the voltages into both were correct. The big
downer in this progress was that the tuner alone had a trade price exceeding
$108 and the IF unit over $172.
To narrow things down, I connected another tuner in place of
the original and found that the picture was more or less the same after
retuning, which to my mind eliminated the tuner. I then removed the IF module
and examined it. It consisted of an IC, several coils and ceramic filters, and
several surface-mounted components, including three transistors. I checked the
transistors and this revealed that the SAW filter driver (or first IF
transistor) was open circuit.
Unfortunately, I didn’t know its type number, so I had to try a
different approach. I looked through a pile of scrapped TVs and videos,
searching for a similar surface-mounted transistor which was performing the same
function. I eventually found one in the IF stage of a Hitachi video and swapped
them over. And that did it – after retuning and readjusting the AGC control, I
could finally tune in perfect pictures.
A bit of "Nifti" cleaner and some polish cleaned the rest of
the set up nicely. Finally, I checked that the old remote control worked the
newer model which it did.
Granny was surprised to get back a different set but found that
the new one gave a better picture. As for my son, he’s traded the repair for a
few months of lawn mowing and other domestic duties.
A crook Akai VCR
Mr Jones brought in his Akai VS-G425EA video, complaining that
it was chewing up his tapes. Unfortunately, he didn’t bring in any of his tapes;
nor was he clear what he was doing when the tapes got damaged.
Fortunately, I have a large box of ruined tapes for such
occasions. I removed the covers, put a tape in and it immediately laced up
against the drum and played OK. It could also fast forward and rewind but was
intermittently slow in bringing the tape back into the housing. It would also
sometimes leave tape loose on top of the deck so that when you pressed eject,
the cassette door would close, leaving the tape outside to get all "scrunched"
My immediate assumption was that the idler reel was faulty and
sticking and not providing sufficient torque to pull the tape in whenever the
mechanism unlaced the video heads. I removed the whole deck which is very easy
these days – undo five screws and pull three assorted plugs and sockets and it’s
out (after you have removed the front escutcheon, of course). I removed the reel
roller, examined it closely but could find nothing wrong to the eye. I put a new
one in just in case and replaced the belt as well.
Unfortunately, they made no difference. The reels were running
free, with no hindrance, so the problem had to be elsewhere.
My eye now moved onto the next suspect, the mode select switch.
This VCR isn’t very old and looks new with little wear. Mr Jones is an old age
pensioner but doesn’t watch many video movies, so why would you expect trouble
with a fully encapsulated rotary switch underneath the deck?
Yeah, well I wish someone would tell me because replacing it
fixed the problem completely. In fact, before I did that, I lightly squirted it
with CRC 2-26 and that also fixed it. I then opened up the switch to have a good
look inside. It looked immaculate, nice and clean with a transparent layer of
light switching grease to protect the metal surfaces.
Despite all this, apparently the contacts had gone high
resistance, hence its early demise. Cleaning and re-lubricating them will work
for a while, but clients demand much more these days!
Over the years, I have seen many Philips GRI-AX chassis TVs. By
and large, they have been an excellent series of models which have performed
well and have been mostly easy to fix – that is, until recently!
Mr Sorensen’s 11-year old 14GR1224/75R was dead and he sensibly
brought it in because it is a lightweight and it’s always easier to bring the
set to the workshop rather than vice versa.
The set was slightly corroded inside but consistent with its
age, and it didn’t take long to work out that the flyback transformer and line
output transistor were both cactus. Both were replaced and the set left on soak
test for several days before Mr Sorensen came to pick it up.
As is my policy on all TV repairs, if there are any dry joints
in the set (and which set doesn’t have any?), I set to work and resolder them.
The GRI-AX is very prone to dry joints, especially around I7020 and the line
output stages, but after a thorough soak test, I was very confident that all
would be well.
But it was not to be. Three weeks later he brought it back in,
saying it was dead again. I lent him another set and had another go at it.
Intermittent problems with this model are invariably due to the SCR crowbar
current switching on prematurely. By measuring the voltage across C2660, or more
conveniently from the anode of the SCR6641 to ground, which should be 97V, you
can then adjust VR3625 until the SCR fires – theoretically at about 101V or
If it is less than this, I change zener diode ZD6640 from 30V
to 33V, or even higher if necessary, and then repeat the adjustment. When
satisfied it is firing at the correct point, I then reset the voltage for 97V or
The other thing that should be done is to replace C2523 with a
new 10μF capacitor and also replace C2542
and L5524. With all that done, I was feeling bullet-proof but this set only
worked for another day before it died again and stayed dead.
I was so glad it had happened in
the workshop and not back
at Mr Sorensen’s house. And I was even happier that it was now permanently dead
because this gave me a better chance to nail the problem properly.
I soon found that the remote control could switch the set on
from standby, after which the red LED would go out. There would then be a
"wimpish" noise from the set as it tried to come on, before ultimately
It was time for some voltage measurements. The full 97V was
available right to the collector of the line output transistor (TR7528) but the
9V startup voltage was way down at about 6V. Using an oscilloscope, you could
see the correct waveform start to build up all the way from pin 26 of IC7020,
through TR7521, TR7523 and TR7528 – but it would always collapse almost
The set is designed to start with 9V and then have the 12V take
over from the flyback transformer via D6542. I had already replaced the flyback
transformer (T5530) and the line output transistor (TR7528), so now I fitted a
new IC7020 into a freshly soldered 28-pin IC socket. This made absolutely no
difference so I then swapped the chassis with one from another nearly identical
set that was also in for repair but the main chassis still refused to fire up
properly. Grasping at straws, I next desoldered the sound output IC
(IC7103), as this is often troublesome and can provide an unacceptable load when
the set is attempting to start. This still made no difference.
Finally, I connected an external power supply to the cathode of
D6635 and wound it up to 10V before switching the set on. Bingo! – it fired up.
I then removed the external power supply and the set remained on. Next, I
switched the set to standby and then on again and it still worked. I repeated
this many times until suddenly it wouldn’t start again unless an external power
supply was connected to the 9V start-up rail.
What was going on? My assumption was that this rail was too low
for a successful startup sequence but after installing new diodes (D6635 and
D6632) and several new electrolytic capacitors and getting nowhere, I decided to
try a different tack. It was time for the hot and cold treatment, so I began by
hitting the usual suspects with freezer to see if this would pinpoint the
Now, I might add at this point that when the set did start on
its own, the 9V rail was actually closer to 10V. It definitely wasn’t low, so I
couldn’t help feeling this was a red herring. Anyway, it was while I was
alternately freezing and heating components near the rear of the flyback
transformer that I noticed the problem suddenly become more critical – like a
doctor or dentist finding a sore spot on your body or mouth.
Anyway, it seemed to me that the culprit was D6624. My circuit
showed this to be a 4.3V zener diode but in actuality it was an 1N4148. I then
realised I was looking at the wrong circuit diagram because in fact the set was
GRI-AX version 2. I replaced the diode anyway and a few others nearby but the
trail was becoming cold again.
More soak testing was required before the fault re-occurred two
days later and I repeated the hot and cold treatment. By now, I was beginning to
realise that if the line drive signal was insufficient on startup, the set would
not turn fully on. This might also be due to a lack of gain in transistors
TR7521 and TR7523.
I replaced the latter first with a BC547C, the original being a
BC337-40, but it made no difference. By now the set was again in one of its
"let’s play dead" modes. I then replaced TR7521 (a BC368) with another BC547C,
making sure that I bent the base lead around the collector lead to fit the leads
in the correct holes.
This time the set switched on perfectly. I measured the old
transistor to find its collector-emitter junction was very leaky. I was
delighted to have at last found a real faulty part and left the set to soak test
with repeated on/off switching for the next week before returning it to Mr
Sunk by friendly fire
A good friend of mine is an Australian of German extraction and
is a fine technician, working for the local Sony agency. An English client
brought his Sony DVP-S735D DVD player in, complaining that the disk drawer
wouldn’t open. My friend showed him how to open it by pushing a lever underneath
to release the drawer. The client did this but when he put the DVD back in, the
drawer jammed shut again.
My friend finally booked the unit in and examined it in the
workshop. First, he noticed that without a disk in it, the drawer would open and
close by itself quite normally and without duress. However, when the DVD was put
in, the drawer jammed. The DVD played perfectly and did all the trick functions
– it just wouldn’t release the disk.
My friend removed the covers from the machine and tried to see
what was happening. He could see the disk go in OK, the spindle locking magnets
clamp in position and the laser focusing as the disk started to spin. All was
fine, until he hit eject. The spindle locking magnets opened but instead of
releasing the disk, the DVD was being held by the top magnet and was preventing
the door from opening.
It looked as though this particular DVD was magnetic! He tried
half a dozen other DVDs and CDs and none of them gave any problem – it was just
this particular DVD.
And the name of the movie on this DVD? – it was "U-571". Talk
about being sunk by friendly fire!
Now, I thought this was a damn good story – but there is a
twist. My friend went home that night after fixing it and thought about it. In
the end, he just couldn’t believe that the DVD disk could be magnetic – it
stretches one’s credibility just too far. So the next day he went back to the
set and re-examined the facts.
The DVD player could play any other DVD/CD except "U-571". What
about trying it in another player? He did that and found that it would play on
other machines, thus exploding his original theory – almost every other player
uses the same magnetic clutch mechanism. So why wouldn’t "U-571" play on the
Very careful examination under a magnifying glass showed there
was a very fine film of "gunk" on both the DVD disk and the metal plate it was
sticking to. The two surfaces were almost analogous to a 2-part epoxy glue. By
cleaning both surfaces very carefully, he was able to then play "U-571" on the
Sony machine without it sticking to the magnetic metal plate.
So I guess the answer is obvious – always keep it clean!