What's your component removal system?

[ppppenguin]

Is this the stuff: http://uk.rs-online.com/web/c/tools/sold...4294967294&applied-dimensions=4294966007

[Herald1360]

I've found that however "good" the solder wick is, it works even better if you run a flux pen along the bit you're just about to use!

Even using professional standard solder removal gear, you can still f*** up a pad/track from time to time. Wirewrap wire and dabs of hot melt glue to hold it in place on long runs can fix almost anything, though......

[Murphyv310]

Hi.
I suppose we all have our own ways of working and we get comfortable in the way we tackle a job, I doubt any of us has never lifted print and then had to make a repair.
The advantage of working for big companies like when I worked for Sony, there is an abundance of good quality equipment. microscopes, de-soldering pumps, hot air rework soldering equipment and of course a good sized bench and lighting which helps with not making mistakes in the first place.
My bench tends to get messy when I work, when I finish a job its cleaned and washed down and all components are either binned if duff and new ones returned into stock.
One other thing is don't get cold as you can loose concentration.

[Terry]

It's nice to know that common sense has prevailed and you are now following the same procedures as everybody else - plus, of course, that you've found them much easier than you anticipated! Don't forget that most techniques you will find described here were developed for two good reasons: simplicity and reliability. Nobody does anything the hard way unless there is a very good reason for it!

I think you referred somewhere to the difficulties of tracing out the circuit from the component side of the board. A tip that can work with early hand assembled boards is that the better the quality of board that is used, the more translucent it is so a bright light shone through from the underside can be useful.

Unfortunately, when flow soldering became popular, a solder resist was printed over the copper side of the board so that the copper was only exposed at the joints and this resist is, of course, opaque!

As an aside to this, our Brown Brothers* rep asked me to look into their showrooms during the 1969 Trade Shows and cast my eye over a Russian TV they had on display there. I wasn't over enamoured by the performance but quickly had the back off. The cabinet had a bit of an old fashioned appearance to it but inside was a revelation - a vertical chassis in the style which hadn't been used in the UK for nearly 10 years plus the rather odd sight of Russian resistors mounted on a UHF tuner which was very obviously the product of AB Electronics in South Wales!

What really grabbed my attention, though, was the colour of the PCBs mounted in that vertical chassis - the material was uniformly black!

After that, I was escorted to a taxi - prepaid, of course! - which took me on to the West End where the major manufacturers had their shows.

I left the retail trade a month later and have no idea if any of those Russians TVs were sold on the UK market - they wouldn't have been much use until after the 3-channel 625 line service was introduced in November - but I somehow doubt it ...

* A large UK wholesaler to a variety of trades.

[Nowhere-Man]

I have had to force myself to get on with this so I will respond to comments and tips a bit later.
I replaced the parts and it was successful although I had an incident where two wires came off the output transformer. Fortunately I did have a couple of pics and these helped.
I tested my track connection because I had to be much quicker solldering to avoid peeling. I tested the radio and really I seem to have made no difference to performance although it was still wise to replace the components. I look on it as a learning curve. Very fiddly work carefully removing old components, cleaning the board and wary you don't make things worse.
My plan now is to not rush into a quick fix but first test all the tracks and the brittle connections. Study the design and schematic. After all this is the band problem isn't solved I will simply trace the HT to switches.
If I had screwed up on this I'd have been gutted but hopefully I'll keep learning.

[Nowhere-Man]

Thanks for the tips and comments. I am able to take components out if it seems if I take my time but a magnifier would help and flux.
I was pressured when it became clear two output transformer wires had come off but I had taken a couple of reference pics weeks ago. After careful comparison I soldered back the wires. As to fitting components it was fiddly and demanding some patience.
As Miguel stated the legs of components in these Soviet.boards can snap really easy so I can check for that. The sixties seems fairly modern but for a PCB board that's a long time ago. I am not sure how East German vintage radio compared with West German production but I guess the producers would have expected them to last till the eighties at best.

[Cardigan]

Is this the stuff: http://uk.rs-online.com/web/c/tools/sold...4294967294&applied-dimensions=4294966007

Yes, that's the stuff. I tend to buy the tins of ten unless I have a specific job in hand.

[Nowhere-Man]

I serviced the output transformer today. There is a 4700 picofarad capacitor mounted on its board and the manufacturers should have insulated the leads. The lugs are not stiff so the capacitor can easily creep in or out and short to another lug. On that transformer board are some hefty voltages. I changed the odd wire and cleaned the board. Next stage I guess is to test the tracks, try and trace the circuit and search for any dry joints or brittle leads.
The main thing is to learn new stuff. Till a few weeks ago I had zero understanding of boards or experience with piano buttons or FM. Sometimes I ask if it's worth the effort but at least it's a learning curve.
One thing I am curious over. Is there an average DC voltage to the secondary of an output transformer? I know it's AC induction but what would be the max and min voltages?

[ppppenguin]

A DC voltmeter should read zero across the secondary of an output transformer. Or any transformer for that matter. The AC waveform should be equally above and below zero.

[pwdrive]

As Jeffery has said.

Also when trying to learning circuits and configurations one of the best things you can do is to start with some basic theory, learn about voltage and current behavior with resistance, reactance and impedance, ohms law formula is your friend here as it can be applied to all those three, just change the term, eg: I = V/R, I = V/X, I = V/Z

Lawrence.