This old receiver gave sterling performance in its day but is barely
worth spending money on nowadays since it's not "Astra 1D
compatible."
Some customers have more money than sense, however, (luckily for me!)
and the nice old lady merely grinned at my suggestion to "use it as a
door stop" while handing me a crisp fifty pound note.
Armed with this incentive, I decided that the SRD4 was worth saving
and connected it up to see the fault myself. The symptom was two test
bars and the words "no signal" on the TV screen. There was no sound
or picture on any channel, although the LNB voltage measured
correctly. I've known this fault to be caused by a broken "F"
connector solder joint and also by a dead PNP transistor TP71 but
each of these faults results in no LNB voltage.
The next most common cause is the SDA3202 I.C. which handles the
frequency synthesis for the tuner. Located below the board, behind a
metal screening can, it's a surface mount device which requires some
patience to remove successfully unless you have the proper equipment.
Luckily, I have the equipment AND I still have quite a few of these
I.C.s in stock, although the device is now obsolete. However, you can
rob one from an old Ferguson BSB receiver or order one from
SatCure.
A quick check of the voltages around this I.C. convinced me that it
really was the cause of the fault so I fitted a new device. This
produced a picture that was far from perfect. Unfortunately, once the
electrolytics in an old receiver have cooled down, they seem to "give
up the ghost". Severe picture interference usually results and this
seldom disappears when the receiver warms up again. The only answer
is to replace the electrolytics and, in the case of this SRD4, I had
to fit a dozen new capacitors before the picture quality was
acceptable. I think I earned my fifty quid!
For some reason, I have a lot more trouble with these than the
average Pace or Amstrad. Even though the receiver is inherently more
reliable (or was during the guarantee period) the faults which are
occurring now seem to be ones which are difficult to trace. Perhaps
that's because most of the signal processing is performed by a single
"Application Specific Integrated Circuit" which is a 64 pin surface
mount device.
Anyway, the receiver which came to me on Christmas Day (yes, people
really need to watch satellite TV that badly!) was
"stuck in standby". It would light up but did not respond to button
presses. This was tricky.
I checked the power supply voltages then "jumped in with both feet"
and replaced the microcontroller and associated crystal. I was
clutching at straws and I was wrong. It had to be something on the
I2C data bus. Maybe the EEprom? Wait a minute! The tuner is also
connected to the data bus. As I looked across to the tuner, I spotted
a crack which had propagated from the tuner securing lugs across two
adjacent tracks. Repairing these effected a complete cure. The pub
owner's wife was impressed by my speedy service. Her husband was less
impressed with my invoice but he still drew me a pint.
Christmas time always brings some curious faults and some curious
people, too. In walked a fellow who was wearing a red coat with hood
and sported a snow-white beard. Out of his sack he pulled a
PRD800.
"Just on me way t't' school" he mumbled. "Gotta give out t' presents
t't' kids you know. Darn satellite won't tune above 11.573. All I get
is snow. Missing me Eurosport. Faulty fuse, I'll bet. Bung us another
one in, ta."
With that, he shuffled outside into the snow and vanished.
Sure enough, there were no programmes above a certain frequency. I
thought at first that the power supply might be switching my
Universal LNB to "high band" but there was no sign of interference on
the supply rails. Unconvinced, I fitted a new tuner and it made no
difference at all. I monitored the tuning voltage which, above a
certain frequency, switched from 1.6 volts to 4.8 volts and stayed
there. This could not be caused by anything other than the "Nicky"
I.C. so I replaced that and was rewarded with normal operation at
last.
The customer had thoughtfully put his name on the label but no
telephone number. Maybe I could get it from Directory Enquiries? He
sounded local. Unfortunately, the operator had no listing for "Mr S.
Claws".
Two of these arrived from a local dealer with precisely the same
symptoms: "intermittent 'motor error' and broken diagonal lines
swimming around the picture." It didn't take me long to see that the
top of C263 was bulging. This is a 1000 F/63v capacitor which
supplies the positioner board voltage in the 508-IP and supplies the
Dolby board in the MSS1000. Replacement with an Ultra High
Reliability type is recommended and that is what I used. The original
interference disappeared but in its place were more diagonal lines
with soft edges. I fitted the complete RELKIT10 without curing the
fault and was close to jumping up and down on it when a customer
walked in with an Amstrad receiver.
"Think me LNB's dud but can you just check this fer me to be certain,
ta?"
Obligingly, I disconnected the MSS508 and connected his Amstrad. It
worked perfectly but, curiously, there on the screen was precisely
the same interference! (Picture of light bulb above head). I had been
using my Pace-Link system to download the MSS508 memory contents and
the computer monitor was next to my TV. The interference lines were
coming from that!
A whole hour had been wasted! Thank goodness this
customer had arrived when he did.
"Why weren't you here an hour ago?" I demanded, grinning.
"Sorry," he said sheepishly. "Had to do the shopping fer the
missus."
With that he grabbed his receiver, slapped a fiver on the counter and
ran.
"Oh," I began. "I didn't mean...."
Too late. He had gone without hearing my apology. Darn! Now I would
have to spend his fiver.
Every once in a while I have a visit from my rival repairman,
Wossname, who has a shop up Church Street. He used to come more often
until I stopped giving him cups of tea. Now he appears only if a
receiver has him well and truly stumped and his customer is
threatening legal action.
"Blue screen, no signal" he announced as he handed me a Prima circuit
board assembly. He knows I hate it when people bring me unprotected
boards like this so he does it on purpose. The problem is that the
assembly is very easily damaged by static electricity or by knocks
and I much prefer to have a complete unit protected by its case.
"Saves taking the screws out" he grinned. "Keeps the cost down,
too."
"Leave it with me." I can't work while he looks over my shoulder.
"Busy are we? OK, see yah later."
There was plenty of evidence of his meddling. Brown flux everywhere
hiding a multitude of dry joints. I cleaned the board and tidied the
soldering before testing it. Sure enough, most channels gave just a
blue screen. Now, the "factory reset" does not alter the individual
channel tuning on this model but it can sometimes clear corrupted
bytes in the EEprom which is a 24C16. I pressed the handset button
sequence: MENU [0] STORE [>] [<] and
the receiver immediately gave good pictures and sound. Too easy. The
EEprom was actually quite hot to the touch, although the 5 volt
supply was correct. I decided to change it as a precaution.
As an excuse to charge more, I took a preprogrammed 24C32 and fitted
that to give 250 channels instead of 125. It wouldn't do to
undercharge old Wossname!