Discussion in 'Tuners' started by steveUK, Aug 10, 2018.
I'm looking for a source for service data for the Tandberg 3001A tuner if anyone can help please?
HiFi Engine has the TPT30001 which I understand is identical except for the color finish it has.
Screw HiFi Engine, they got all their Tandberg stuff from Njord's site anyway and you don't need to register to access his.
Steve, this is the known manual covering the 3001 and 3001A. The changes in early to late 3001 are relatively decently documented, and the differences between the late 3001 and all 3001A's are not vast. There's an extra transistor on one of the tuning system boards to beef up supply and some other smaller changes. You can certainly service the A version using that manual (have done so many many times).
IIRC there are also some bulletins that are worth reading, and some tech's widely circulated copy is out there with a few scribbled notes (including his description of that added transistor, which the factory tacked in place on the rear of the board before they got the boards revised to provide an actual location for it later. I can probably pull that other stuff together, I have it all somewhere.
Are you going to go at one of these yourself, or having one done by another tech? Feel free to bounce questions off me either way... haven't done one for months and months but at this point I pretty much have it down pat. They will present with some unusual issues now and then though, so always opportunity to learn more.
The part about learning is spot on
Thanks John. Yes I always do all of my own serving and restorations. Been an electronics engineer since doing an apprenticeship in the early 70s. Saying that, I have to ask for verbal help on many occasions - as you well know! The so called 'techs' in the UK are very few and far between. Most 'repairers' work out of TV repair shops and are the sort who send you your set back with screws missing, wrong screws fitted, scratches and the original fault untouched! There are some proper vintage hifi techs but knowing the good ones is the thing. But anyway, nothing has yet stumped me even if it sometimes takes months to get a set working.
Fortunately the usual presets and programming problems do not appear to be present, maybe someone has fitted a new battery and maybe even new switches. Saying that, it is a pristine unit so maybe somehow the presets have just survived. The only problem I'm noticing as yet is what appears to be backlash in the tuning meters/tuning. That is to say, you can wobble the tuning knob and the meters do not respond, but turn it in one direction and they pick up eventually. Maybe a slack tuning string or dried, hard grease on the tuner. The tuning knob doesn't 'spin' anyway. I only got it yesterday and haven't even taken the top off yet, so a lot to learn. Are the bulbs easy to change? mine don't work, but maybe it's a loose connection or PS fault. Anyway, I've ordered four bulbs from a German supplier in readiness. The muting control is very stiff, so hopefully a spray with Servisol contact cleaner will sort that out. I'd like some rosewood side panels for it - anyone?
The programming procedure is a bit weird, although very simple when understood. I saw your procedure in another thread John. It's a bit disconcerting pressing a preset button and hearing the station jump to that one instead of the one you're trying to preset! I have made a mental note to write the procedure up with all its foibles and slip a printed version into the user manual for future reference should I forget.
Photos to follow.
Update. Having gone back to the tuner since last night (UK time here!), the presets have not kept their memory, so clearly the battery needs changing. They do keep their memory so long as the set is switched on, that was what fooled me. So the preset switches appear to be ok, just the battery.
I have little to contribute, except the knob thing. I have the 3001 and 3011A. Both need serious help, far beyond my skills. I can't even use them. Both knobs were totally frozen, wouldn't turn at all.
In both models, the tuning string wraps around an oddly shaped "pulley" in the front-center of the unit — both pulleys were seized. I dripped some oil into the pulley's bearing (being careful to get none on the string) and that freed it. Now the knobs spin freely — the needles even glide smoothly from end to end, with just one light twist of the knob to start them. It was very satisfying to fix it! Hope this helps.
But the tuners still don't work. The 3001 sometimes decides to function properly for minute or two, and gets my hopes up before crapping out again. The sound is awesome — not a word I use casually.
Does anyone know the ampere hour rating of the battery? This one is clearly leaking and totally shot. It's highly unlikely that the same physical style battery will be available hence I will have to buy an alternative design. There's tubular ones with wire ends that I could use but I want to get the correct A/hr rating.
AK member par excellence JDurbin located the correct battery and can provide them — or at least he used to. Ask him.
I had a Yamaha T-7 and they just soldered a normal AAA size battery onto the circuit board, could have been the Energizer Bunny for all I know. I don't know enough to say if the A/hr rating really matters, but the physical shape certainly does (this is the first time I've even seen the term "A/hr", which shows how little I know).
Thanks, I know John, that's partly why I ask the question, he's already on this thread.
The physical size or shape of the battery doesn't really matter so long as there's room to fit it in. There's plenty of room in the 3001a. But nonetheless if there's a 'preferred ' replacement it would be nice to know, especially wrt the A/hr rating.
I've located a direct replacement battery: https://www.ebay.co.uk/itm/Varta-1-V150H-2P-Central-Heating-Timer-Battery-V100R/392045818698
I took the tuner apart in order to get at the battery solder terminals and in doing so discovered all of those stiff wire connectors that make connections between PCBs. On examination they showed signs of corrosion (darkening) and worst of all there were traces of a stubborn greasy substance that clearly couldn't have being doing me any favour wrt reliable connections. Presumably this was some kind of electrical grease/lubricant that was applied at the time of manufacture but has long since dried up. I used a fibre glass pen to shine up the pins and applied Servisol Super 10 contact cleaner to the sockets.
I have managed to free up the stiff tuning situation by applying Si lube using a wire 'dropper' to the relevant bearings of pulleys etc. It's still won't spin from one end to the other, but I'm happy with it how it is. The one thing outstanding now is that backlash in the tuning. With the unit apart I can now see what is happening - to an extent. There is slack between the tuner's plastic drive 'disc' and its shaft/gearing. If you move the tuning knob in one direction it picks up and continues to rotate the actual tuner fine, no problems. If you stop and turn it the other way, then there is a backlash of a few degrees before the tuner itself begins to rotate in the opposite direction. Similarly if you wobble the tuning knob the tuner is unresponsive, you have to turn it in one direction for a few degrees for it to pick up, take up the backlash. But I cannot see how to tighten the coupling between the plastic drive disc and the metal shaft that it sits on. Maybe the drive disc is a push fit onto the shaft and the plastic has deformed with time or something causing it to be slack? Dunno. Help.
The pulley is split as we’ve discussed offline. On a 3001A that usually means someone has ham-handedly forced it to turn against abnormal resistance caused by a jammed gearbox shaft.
No lube should be used ANYWHERE near the tuning gearbox. Ok on the small black pulleys at the end of the dial cord path but using it on the gearbox will ultimately destroy it.
I’ve sent the info on how to address the gearbox issues, trust based on our previous discussions on other units that you can get thru that without further destroying it. I don’t cite those repair details widely though as the repair is delicate, no spare parts exist, and in the wrong hands the failure of this particular repair usually renders the tuner completely unusable. Keep that in mind if you decide to post your own repair results here.
BTW that dark crud is not factory. Someone has been inside this tuner doing stupid stuff. Do however look very hard for cracked solder which was probably what made them start packing junk into the connectors in the first place. Almost every 3000-series component will suffer from cracked solder somewhere, starting at the board connectors.
You’ve found the correct battery. Caveat to replacing that with the same part is that it will inevitably leak again in the future. I replace them too but knowing that it’ll need to be watched and eventually replaced again. I really need to devise a better, remote located replacement battery installation so that any leakage does not damage that tuning system board and so batteries can be replaced without having to dismantle the tuning system boards - that’s a fairly invasive process.
As I had pondered, and what John was sure of, the black plastic tuning pulley is split. Looking at it closely under a strong light I could just about see a hairline crack in the end of the tapered 'cone' section. The crack could be seen to open more if I rocked the tuning knob back and forth. Even then, we're only talking a few thou, doesn't seem much, although clearly it's enough to cause backlash. I first thought about applying twin pack epoxy to the crack to repair it, but as it was already 'open', albeit by just a few thou, then although that would hopefully stop it from splitting further, it probably would not cure the backlash. So I decided to apply a copper wire tourniquet around the end of the pulley to close up that split. I got a decent length of thinnish copper wire, bent it into a 'U' shape, passed it over the end of the cone section and tightened it with a pair of pliers. The end section of the pulley on which it sits is quite small, perhaps a millimetre or two. So there's a danger of the loop slipping off the end of the pulley as you tighten it. Fortuitously, the lamp PCB sits within a millimetre of the end of the pulley, so I found that by pressing the PCB against the end of the pulley, it stopped the wire tourniquet from falling off as I tightened it. Once on nice and tight, I tested it and the backlash had gone, the wire tourniquet was a success. However, I figured that the chances of the wire staying in place or remaining good and tight were not so good, so I added a fillet of epoxy around the wire to hold it in place and stop it coming loose. Applying the epoxy was an intricate, delicate job that was done with a small jeweler's screwdriver. Given the small size of the gap between the end of the pulley and the lamp PCB, it was inevitable that during the process epoxy would end up bridging it - and it did. I removed this using a small plastic epoxy spatula and a jeweler's screwdriver. Then just to make sure, I placed a length of Scotch magic tape in the gap that I will remove after the epoxy has fully hardened.
I now need to sort out the tuning knob assembly itself that is being pulled to one side like the leaning tower of Pisa by the pressure of the tuning cord. I'm thinking that the white nylon moulding in which the tuning knob shaft sits is split, and this is also causing the tuning assembly to be stiff in operation. So I'll dismantle that maybe tomorrow and report back.
Many thanks to John who has been giving me valuable help and advice behind the scenes - as always!
John, in simple terms couldn't that be a battery and receptacle fitted to the back of the tuner? Eg an AA size battery and holder? Ok it wouldn't look original but in this case doesn't need become more important than beauty?
Yes it could. Could also with some slight tweaking be a coin cell in a holder, with some minor tweaks so it doesn't get charging current from the tuner.
I wouldn't put it on the outside probably, not that hard to remove the bottom cover to get to it. Just needs to land somewhere where leaking doesn't reach boards or corrode stuff around it. The factory solution gives you different outcomes based on how it's stored; normal horizontal means you get drips that eat the galvanized bottom cover finish, the other way maximizes the amount of damage it can do on the solder side of that board. On end gives you other results.
The white bushing the tuning shaft turns in just needs to be unscrewed and rotated 180 degrees and screwed back in. Those don't split but they do wear at an angle due to the dial cord tension. You can get another 10 years or better out of the unworn side, after that it'll either be 1) someone else's problem, or 2) time for a bushing resleeve/replacement. This happens on all 3001/3001A/3011/3011A but I have not met one yet that has both directions worn, so...
BTW that view with the wire twist also shows in good detail the two metal gears that need to be pinned together, as well as the fragile nylon gear. Can also see the two screws that have to be removed (actually it's three, now that I think of it) that you have to remove in order to get the gearbox removed. Hopefully your pulley repair still allows the pulley to be removed. I don't think I mentioned it, but you want the entire steel front subframe removed from the chassis at that point. Means removing some screws that anchor the switches and nuts for the other controls, and unsolder a couple of meter wire jumpers, but it's way easier to get to and work on the tuning parts once that assembly is off the tuner. Tandberg was clever enough to allow that, the whole dial string/pulley/tuning mechanism comes off 100% in place attached to that steel frame.
Thanks John, I'll report back in due course.
I turned the white nylon tuning control bushing through 180 degrees and the assembly it is now properly at right angles to the chassis instead of being pulled inwards as it was previously - thanks John!
I've a hunch that the tuning cord is/was generally too tight on mine. I loosed it a tad by extending the cord a little by letting it through it's brass retaining crimp. Now, although it's still not possible to spin the tuning from end to end, it does carry on travelling a little on its own impetus given a good spin. That probably means that the gearbox shaft is, as John strongly suggests, split. However the fix for this is not for the faint hearted, it requires the gearbox to be dismantled with lots of trips and risks. John has kindly given me a good run down on how to do it, but given that the tuning action is now very acceptable (do I really need to spin from end to end?) I'm presently pondering on whether to proceed with dismantling the gearbox or leave it as it is, which is perfectly adequate for my needs. A bad mistake could render the whole tuner useless. So, I'm presently pondering my next move..
On the battery replacement - I used a large low voltage memory cap there instead. I don't have exact details om hand, as it was done many years ago. The cap is a better long term solution (in my opinion) as it should never need replacement (compared to re-chargeable batteries). On testing, I think it held the stations for maybe 1-2 weeks, but again, this is from memory. You are looking for a unit rated at like 0.1 to 1 Farads (not uF).
Good idea but as you allude to, there's a degree of personal choice here as not everyone would be happy with 1 - 2 weeks ability to hold stations.
I think you answered your own question. There's nothing to ponder.
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