Radio & Record player repairs by novices.

[jonnybear]

Looking a some posts, (it seems to me I may be wrong), some repairers seem to have a fixation that every capacitor, every resistor in a old piece of equipment needs replacement, just because their digital meter tells them that a resistor measures 5%-10% difference in value to the markings is faulty. Lots of old components had 10-20% tolerance anyway, so may be perfectly OK.
When repairing any piece of equipment, the first thing to do is take a good look at the circuitry with a service sheet, get familiar with it, then take as many photos as is necessary from all angles,(may save a lot of heart ache). Before tearing in removing component willy nilly check the main items ie SMOOTHING ELECTROLYTIC, filter/coupling waxies, ceramics & micas are normally OK. only ever change one component at a time, as you will find yourself connecting components to the wrong points, and going in ever decreasing circles. If there are several components going to one point it is better to remove all the solder and remove faulty item and replace without resoldering the joint just twist wire end as original, there may be another faulty component going to the same point later in the refurb, solder joint only when confident all components going to it is OK, otherwise soldering and unsoldering a 50 year old connection will finish in snapping it off. well I hope it helps the learner (novice) not intended for the professional repairer.
John

[Peter.N.]

I was in the trade for 50 years and still only believe in changing what is necessary, some components have an extremely long life evidenced by the fact that you can plug in a 50 year old radio or TV and providing it has been stored somewhere dry there is every chance that it will still work, there are many pre war sets that will still plug and play.

It depends of course what you want from a restoration, many want to restore the set to pristine condition in which case more work is often required but if you only want to get it working my philosophy is plug it in and see what happens - but be ready to unplug it promptly if necessary!

Peter

[jonnybear]

Hi Peter
I have also been in the trade since 1961,started my apprenticeship in Exmouth.
I only put in this post as a guide for the novice, as looking at some of the threads, they seem to create a fault that is not there to start with, Doing blanket repairs without really knowing what the components do is a very hit and miss type of repair in my eyes, and in some cases could be fatal. That is where the old Practical Wireless magazines came into there own they were very informative, pity they are not around today, though it would be a good idea for a novice to pick up some old copies from ebay or the like, would help them understand things more.

John

[G8HQP Dave]

Yes, here and on some audio forums we get the plaintive cry "I recapped my old amp/receiver/preamp and now it doesn't work. Help!". It can be difficult to explain to a novice that fault-tracing where half the components have been changed is much harder than finding a single fault on untouched circuitry or debugging a prototype. Often the perpetrator doesn't know how to use a meter so can't even reliably report voltage readings to us.

[Station X]

The problem is that old record players have become "trendy". They are bought by people who, like the original purchasers, just want to play records on them. Seeing the auto changer mechanism working may fascinate them, but they have no knowledge of how the mechanism actually works or even in some cases how to use it. The operation of the amplifier is an even bigger mystery to them. At least you can see how the auto changer mechanism works, but all you can see with an amplifier is whether the valves light up or whether smoke comes out.

So they buy a record player, preferably a Dansette because they mistakenly think that they're the best. The player is advertised as "serviced", which often means it's just been wiped over with a damp cloth, Then they find that their pride and joy doesn't work. The seller doesn't want to know, "it was OK when it left me guv, blame The Post Office for dropping it". They look for a repairer, but can't find one, so after a bit of Googling they end up on these forums.

When they get here they don't do any searching. If they did they find this excellent thread put together by Darren UK:-

https://www.vintage-radio.net/forum/...ad.php?t=75401

So we get the same old questions. Does it need a new needle, should I change the valves, can I add another speaker and make it stereo? We give the same old replies. Don't plug it in without making some checks. Clean off the old grease and relubricate. Touch the wires going to the cartridge and see if you get a buzz. No you can't play stereo records with that cartridge/stylus.

If the problem is more serious it's very difficult to advise them. They don't know what a volt, amp, ohm, capacitor or resistor is. They don't know how to use a meter or how to solder in a new component.

We advise them to measure the HT voltage on pin 2, But wait a minute, which is pin 2? What does HT mean? Where should the other meter lead be connected to? Which way round should the leads be connected? Which sockets on the meter should the leads be connected to. What range should be used. Should the player be switched on? Whoa! Is the mains lead the right way round on a live chassis player? I get a reading of 3. 3 what?

We advise replacing C3. Member Googles "C3", but can't find anyone who sells it. No. C3 is a component designation. You need a 0.05uF cap, sorry I mean 0.047uF, sorry I mean 47nF Should I get a red one or a yellow one? Does it matter which way round I connect it? So it goes on. Everything has to be explained at a very basic level.

Some of these record player users develop an interest in vintage gear and gain the knowledge and expertise to repair it. I suspect most of them just become disillusioned and sell the player on to someone else who then joins the forums......

I know we all have to start somewhere, but the place to start is with a bit of reading of theory etc. In these days of the internet it's much easier to say to complete strangers "It doesn't work, what's wrong, how do I fix it?

[dave walsh]

I think all of these excellent posts [from very experienced people] give a fair and balanced description of the law of unforseen consequences ie when you seek to be open and helpfull and generous to other enthusiasts [Forum members excell at this as I've experienced] difficulties can arise!

Graham gives the overview and his last sentence pretty much sums it all up in one go. It may actually be as much about attitude and application as anything else. I've very little technical ability but I was on the Forum for quite a while before actually making any enquiries. It is true that I already had some basic electrical knowledge from my school days but when I pick up any other sort of interest, whether technical or otherwise, the first thing I do is some basic reading around the subject. This is because I don't like to be completely clueless. It's one thing to get stuck and then benefit from a step by step guide [as often happens] but you need some primary knowledge to function and this is more readily available than ever nowadays, at the press of the very same buttons!

Graham is right though, we do now live in a culture of instant gratification and quick resource to the Internet so there is a bit of a "disconnect" [no pun intended] in perception that will lead to these kind of problems. I've never really believed that "A little learning is a bad thing" but perhaps the wholesale replacement of capacitors trend is a newer version of the classic Trade stories I read where the customer [oblivious] confidently assures the engineer [expert] that it must be a valve at fault.
Dave W

[Nickthedentist]

Very true, Dave.

Newcomers often seem to ask "could it be a bad [sic] cap?", presumably in part because a lot of modern equipment fails because of faulty electrolytic capacitors, and this is widely propagated on the net.

I'm certainly not a "change everything" kind of person, but freely admit to blitzing sets of Hunts wax/paper caps. However, I'm a careful worker and capable of finding my mistakes should I make one.

Nick.

[G8HQP Dave]

The sad thing is, if they succeed in getting their Dansette to work it will then proceed to damage all their irreplaceable vinyl! Fortunately, their other turntable may be a £50 USB one so they won't notice the damage.

[Peter.N.]

Originally Posted by jonnybear

Hi Peter
I have also been in the trade since 1961,started my apprenticeship in Exmouth.
I only put in this post as a guide for the novice, as looking at some of the threads, they seem to create a fault that is not there to start with, Doing blanket repairs without really knowing what the components do is a very hit and miss type of repair in my eyes, and in some cases could be fatal. That is where the old Practical Wireless magazines came into there own they were very informative, pity they are not around today, though it would be a good idea for a novice to pick up some old copies from ebay or the like, would help them understand things more

Hi John

I started in Kent in 1954, we have only been here since 1970. I would agree with your thoughts, even when doing repairs you have to be careful not to disturb anything other than the bit you are working on otherwise you end up with unrelated faults which can cost time and money. Also fitting components to tag boards 'properly' in some of the very old stuff can cause problems, I just snip off the old component and solder the ends of the new one on, if you can solder properly they are not going to come off.

Peter

[jonnybear]

Hi Peter
So you have to wait another 6 years to be accepted as a local then.
John

[paulsherwin]

Most of the record player people are impossible to help, as Graham implies.

It's noticeable that most people opposing blanket recapping seem to be retired professional service engineers with many years of experience. The problem is that the world has changed since they learnt their stuff. If you were tracing a fault in a 1955 valve radio in 1970, it didn't make sense to change all the capacitors, as most of them would have been perfectly OK. 40 years on and things are very different - every single domestic grade waxie or mouldseal is going to be leaky by now, and there's no point in trying to identify the bad ones because they'll all be bad.

It's certainly true that low value ceramic and mica caps are usually fine, and I try to point that out to newbies when advising them, but there's often a fundamental lack of understanding of what a capacitor is never mind what the different construction types are.

I also advise people to leave resistors alone as they rarely affect operation significantly unless hugely out of tolerance. Sort out the cap related problems first, get the thing working, then go through and check the circuit voltages. If any are out measure the resistors.

[cmjones01]

There's also the important point that it's a good idea to test the equipment briefly after replacing each suspect component. If it works the same or better, you've probably done it right. If it's got worse, you know where the mistake is likely to be!

Chris

[Lucien Nunes]

There is an interesting comparison between this and electronic organ repair by novices. Electronic organs are generally in surplus now as ever fewer people are able to play them, so dozens of low-end models are scrapped daily, after failing to sell at £0.99. However there are still a few people interested in acquiring and playing them but they often find some part of their newly acquired thrift store bargain doesn't work. Again, typically they are not electronically skilled, just interest in the music.

However, an electronic organ, especially a decent one from the 60's-70's heyday of home organs, is some orders of magnitude more complex than a record player. The would-be amateur repairman hears crackling, or the A#'s are too quiet, or the saxophone doesn't work, and he takes the back off.... to run headlong into 100 DIL IC's including custom mask-programmed 40-pin jobs, 1000 transistors, 2000 electrolytics. There was a time when it was sufficient to guide them to the loose 80-pin connector or dirty stop contact, or advise how to refit the pedalboard so that the keys actually hit the switches. But now, all those thousands of caps are coming to the end of their life, the custom LSI IC's are failing with odd symptoms and all sorts of maladies are creeping in that even the careful, conscientious novice cannot hope to diagnose easily.

Luckily, there are still some trustworthy stock faults that anyone reasonable with a soldering iron can fix without complex troubleshooting. On another forum, I was repeatedly handing out advice to change 4016 4x1 CMOS analogue switches on a particular model as they are all going. Dad's Wurlitzer has had half a dozen of its 50-odd 4016s changed. Plus of course all the basics, reservoir & smoothing caps etc but these are rather more of a challenge on an organ than an RP as there might be three power supply chassis totalling 60 electrolytics. For the same reason, shotgun repair by replacing everything suspect is not always a sensible way forward; there might be 1000 caps past their best but do you want to change all those just on the offchance that one of them is responsible for the poor tone quality?

Sadly, when enterprising organ-rescuers find that their 99p bargain is going to cost £750 to bring up to spec, it tends to bite the dust there and then. Luckily, RP's are now being spared that fate!

[Michael Maurice]

I get phone calls everyday, "my TV has gone wrong its a small job, just changing some capacitors....." Oh no it isn't!

Regarding vintage record players, amplifiers etc I tend to replace all hunts, mouldseals, waxies etc. I check and replace if necessary any resistors that are going high say in the anode load circuit.

I also replace grid leak resistors as they will start to be going high in value.

Transistor amplifiers are left alone unless they need repairing, which is not very often.

[Tim]

Hi all.

I do tend to replace all waxies I find(98% of then are leaky anyway) but usually end up doing all anyway, as most of my repairs are for other people so I don't want the set coming back a few months later with another fault. I always check "that" capacitor as a matter of course. I don't think I have ever found a Hunts moldseal that WASN't faulty in some way, so those are usually replaced on sight as well. It's not because I don't know what I'm doing, it's the benefit of experience!

I also check electrolytics.

In my experience those resistors most likely to change in value are those that have a high voltage across them, and are high in value to start with( so screen grid resistors, audio triode anodes etc)--these tend to go even higher or O/C. Faulty de coupling capacitors can also stress resistors.
Very occasionally one may find output valve cathode resistors go LOW in value. I do test the important ones but generally I leave resistors alone unless voltage measurements or dynamic tests reveal them to be faulty.


Remember, we were ALL novices once!