Satellite Workshop 08
The customer who visited me last week was a dog owner and his dog, it
appears, was partial to remote control handsets. This time it was a
handset for an old Uniden UST7007. Since Uniden pulled out of the
U.K., it has been almost impossible to obtain these. I didn't bother
to look through the usual suppliers' catalogues but, instead, checked
my diary. I remembered receiving a call from a company back in 1992.
Sure enough, I found my notes. Alex Hoyle of "Trackdown Consultants"
claims to be able to find or repair almost any make of handset -- and
his prices aren't bad either.
I gave Alex a call and yesterday the handset arrived. It was second
hand (apparently) but in good, clean, working condition. The dog
lover didn't know how lucky he was.
If you have a stock of old handsets (or new) you might like to
contact Alex at http://trackdown.co.uk. He won't necessarily buy up
your old junk but, if somebody enquires about a handset which you
have, he will get in touch. Of course, if you need a
handset, give him a call. He tells me he has about ninety percent
success rate in either finding a handset or repairing the old one.
You might like to make a note of the telephone number before you give
this issue to your grannie!
I had a strange request from a customer who owns a Nokia SAT1700 MkI.
He's one of those enthusiasts who like to flick through every channel
on every satellite in the sky. They seem to be most thrilled by those
pictures which can barely be discerned through the sparklies. "Look!"
they cry. "I can receive Bonzok TV from outer Mongolatia!" Then they
will fiddle with the video bandwidth, audio bandwidth and tuning
controls to try to minimise the sparklies which so excited them in
the first place.
Anyway, I digress; the request was to "improve the threshold." At
first I was about to refer him to the builder next door, thinking
that his doorstep was crumbling. However, it was his tuner threshold
which he wanted to lower. I think that the SAT1700 tuner has a
threshold of around 6dB but he wanted it to be better than that. A
quick call to Nokia Technical department elicited the information
that it was not Nokia's design philosophy to provide upgrades and
that a new receiver was the answer. Maybe I asked the wrong question
or phrased it badly because when I asked the same question of
Davenham Satellites I was told that the tuner in a SAT2202 (order
code 55-31755-03) had a slightly lower threshold and was a direct
replacement.
The new tuner was not cheap but my customer seemed happy to pay any
price to improve his receiver. Next day he called me to thank me and
to announce that he could almost receive pictures from
sixty degrees West. Well, I think I'll just stick to "Discovery" and
"CNN." The excitement of owning a motorised system and
almost be able to receive foreign stations might be bad
for my health.
Regular readers will know that I become cross about the way that
owners treat their satellite receivers. The most popular installation
method appears to be to place the receiver on top of a hot video
recorder in a so-called "Hi-Fi cabinet." Put newspapers on top, close
the doors and simmer gently for at least six months. Oh, and
never use the Standby button!
This method never fails to make the receiver go faulty within
the guarantee period . It seems criminal to me that the
customers who abuse their equipment get a free repair and those who
look after it suffer a large bill after a year or more.
On this occasion, the owner suffered what I believe was poetic
justice. his SRD520 lasted precisely thirteen months definitely
unlucky for him! When I collected it from his house I saw that the
ubiquitous "Hi-Fi cabinet" was placed against a radiator! Was it
still under guarantee, he asked. I refrained from giving the answer
which, I felt he deserved. With great restraint I asked if he'd taken
out the extended warranty option. No? Oh, what a shame! (Yuk
yuk).
Back at the workshop I had the cover off the receiver in an instant.
Inside, everything was black. The picture quality was abysmal with
video level extremely low and only the occasional sync pulse. I felt
that I was on a loser. Even if I found the main fault, there would be
others. To make matters worse, another dealer had apparently "mended
the power supply" some time after purchase. Instead of the
recommended 47k resistors rated at 350 volts, some idiot had fitted a
pair of five watt elephant size things. These had clearly been arcing
so my first job was to remove them and to fit the correct types. I
tend to buy them in kit form from Telepart in Wolverhampton or from
Davenham Satellites. Other companies stock a kit but I prefer these
suppliers because their kit is comprehensive and comes with
instructions.
With an oscilloscope I tracked down the main signal loss to C6 a 10 F
near the video level trimmer. Renewing this got the picture locked
but there were interference lines and the picture was not sharp. To
cut a long story short, if you get one like this, measure all the
biasing resistors at the front end, before the filter and clamp
circuit, and replace any electrolytics which are discoloured or
measure low in value. Also, make sure that the customer has not set
the video bandwidth to "wide" in the menu!
This receiver was returned to the customer with a recommendation that
he knock the back out of his "Hi-Fi cabinet" and turn the radiator
off. Even with the new components, I doubted that the receiver would
be reliable but it would be an impossibly expensive task to replace
every electrolytic and resistor on the board!
I wonder how many times I've seen "goes off when hot" on a fault
report? Often it's the picture or sound which "goes off", not the
receiver itself. This time it really was the receiver, although it
actually went to standby not what I would call "off."
In a previous report I mentioned an SRD510 which flashed red and
green LEDs alternately when plugged into the mains. The fault was
caused by carbonised glue forming a short circuit across the standby
switch. Luckily, I remembered this, because the cause of this SRD510
going into standby after four hours warm-up was exactly the same
carbonised glue across the standby button solder joints. When I
mentioned the first, I thought it was a one-off. Having had two in
the same month, I'm beginning to wonder!
A local dealer brought me a PRD800 which he had attempted to repair.
He had apparently fitted a standard power supply kit but the receiver
simply "ticked." Then he fitted another kit, but one which he'd made
up "from the spares box." Several components had gone bang and the
circuit board had black streaks. I quoted him a silly price but he
agreed so I was committed to repair his damage. The first problem was
that he'd removed three solder pads and used pieces of insulated wire
to make the connection. This was not the single-core teflon-coated
"Kynar" which I use (order code 143-378 from Farnell) but
multi-strand mains wire!
The other obvious problem was that in place of R2, 100k/2Watt, he'd
fitted a ceramic-bodied 1 Ohm resistor! Needless to say, the TEA2018
had not survived 240 volts and nor had several other components. I
replaced all the electrolytics and semiconductors, plus the resistors
which were open-circuit.
After repairing the broken tracks and measuring for shorts and opens
I plugged in and switched on. It ticked.
A friend came in at that point and I decided to take a break and make
a pot of tea. While I did that, my friend peered intently at the
board on my workbench.
"Careless, today, aren't we?" he remarked.
Now you have to appreciate that my friend has a streak of sarcasm and
loves to pick fault with my work, although he can't solder for
toffee.
"Big solder splash, there."
I looked and he was right, although exaggerating. In the middle of
the board was a tiny blob of solder which straddled a surface mount
capacitor. However, it wasn't mine. It had the appearance of dry,
grey powder. I've seen it before as a result of careless use of a
pump-action solder sucker. I don't have one, relying on solder wick
and an electrically operated pump suction iron, neither of which
create dry powder balls. Clearly this was a problem caused by the
dealer. Removal of the offending short had the PRD800 up and running
in an instant. My friend drank his tea and gloated, before wandering
off to annoy someone else with his cleverness.
Since last I wrote about Grundig spares availability, things have
improved. A card flap for a GRD150 arrived next day from Willow Vale
the sort of service that other suppliers dream about! However, a very
dead GRD250 arrived in the workshop, today, with a cryptic note from
the customer that said "Lightning Damage." Although the unit would
light up, I could get no menu or picture on screen. Lack of activity
around IC4 led me to suspect this beast. The service manual told me
to fit "IC4 Emulator Upgrade Kit."
A call to Willow Vale elicited no information. It was not listed.
Being somewhat naughty, I rang a young man in the Grundig design
department to check. He was most helpful but had no part numbers and
suggested I ring Rugby spares department, which I did. Grundig, being
the careful organisation that it is, put me through to "Customer
Relations" instead. (It must be my northern accent that does it! I
get treated as if I'm 15 instead of 51) A nice lady took down details
of what I wanted and promised "someone would ring me back." Normally
I take this promise like "the cheque's in the post" but, just fifteen
minutes later, a gentleman did call me and told me to
look in the Service Manual for the part number. Red face! There it
was in black and white.
Back to Willow Vale with the part number. Not listed. Oh dear! The
young lady promised to ring me back after she had spoken
to Rugby. Sure enough, a fax has just arrived with the price and
ordering details. It's very gratifying when people keep promises! Now
I can quote my customer for the repair.
In a previous report I mentioned Terry who runs "Tardis
Electronics."
Desperately in need of an Eprom to replace a defunct one in a D2Mac
decoder, I rang Terry because I remembered seeing some in his shop.
He was in a bit of a state because, on the previous day, three
enormouse warehouses next door had burned to the ground! (It even
made Sky News) Luckily, Terry had been there to make sure that the
firemen kept his shop roof nice and wet. Now all he has to do is mop
up a few puddles. Sure enough he was able to send me a used but
erased Eprom at a very reasonable cost. He has everything from the
very old 2708 to a more recent 27C512. A pity he has no Megabit
Eproms but you can't have everything, even in a Tardis! (01270
763029. 8am till 6pm except Sundays).