Board Pics!

Ok, so it's not nearly as nice as a real picture, but the scans are not bad either. The boards really look much better than that, especially when you can see the shiny tin plating.

Output Board, Initial Review

Here's the bad news. My digital Pentax has given up the ghost. I dropped it in Boston and it's been barely alive ever since. It's now officially unusable. This means no assembly pics, but I may do some scans of the board.

I've de-populated the original (i.e. ruined) as fast as I could, and compared the two boards.

Here's the objective review:

The prototype is really really good. The multipath output needs to move about a third of a millimeter. Otherwise mechanically it's a really good match for the original. Not only that, it's really a beautiful piece of copper, tin and fiberglass. It's not perfect though. Here are the issues I've found so far:

• The fixed L and R outputs. Fortunately you can cross the resistors that go to them very easily.
  
• One of the scope outputs has the last trace on the wrong side. Fixable with electrical tape.
  
• The holes for the switch are really really tight. I had to use a pair of Robo Grips to finish seating them. I probably could have avoided using solder. :)
  
• I broke the capacitor. I'm replacing it with a 0.1uF metal film. I hope that's good enough! :) It's the right physical size anyway. :) The original one says 250 one one line and then underneath it u 1.
  

These are not show stopper issues, specially if you weren't going to use the scope outputs.

The one show stopper I do have is that the 100 watt soldering gun I have doesn't come even close to putting out enough heat to solder on the Cardas jacks. Tomorrow I'm off to Radio Shack for a 150/250 watt soldering iron. If that doesn't work, I'm screwed, because I am not about to buy a solder pot for this thing!

I'm making fixes to the design, but I am only going to make another run if there is significant interest. Otherwise, this run of six boards is all there will be.

The Wick and Me...

I have prototype boards! Because these are in fact prototypes, I have to take some different steps than hopefully anyone else will. In order to properly guage any differences between the prototype and the original, I have to completely de-populate the original, removing every single part so I can take the two empty boards and put one over the other to accurately see at any differences in the two. Those of you who purchase any of these will be able to get by with just pulling off the Molex connectors, switch and cap.

I have eye-balled them so far and they look really really good. There may be some slight variations in the scope outputs which I will have to correct, but so far, if all you wanted was audio outs, it looks pretty good. :)

Oh, and the Cardas connectors fit MARVELOUSLY! :) I'm very very happy with the way they snap in.


Erik

Prototyping...

The board design is off to the factory, should have it back by Friday.

I'm happy to say that some major improvements were made before it was submitted. The ground plane was broken into 2 sections, one for the audio and one for the multipath and scope outputs.

The traces and resistor locations were optimized even more, giving the fixed outputs the shortest, most isolated trace paths possible. The VARIABEL [sic, "inside" joke, which is itself a bad pun] outputs also have very good trace routing, but maybe a tiny bit less optimal.

The original board kept clearances of about 0.050" around the audio signal traces, this board will have 0.100" clearances, significantly shorter traces, as well as a massive grounds in a star-like configuration. This, along with Cardas jacks (which I understand were originally designed for Jeff Rowland Design) should make this about the best output boards you can put in a Tandberg tuner, short of re-designing how the boards connected to each other. There is also, as I mentioned before, a special feature for multiple cable addicts which I will show you once the boards are back.

The sad part is, I'll probably be selling my extras on e-bay before I ever get to hear the benefits myself. This is because it will be a couple of weeks before the power supply rebuild is complete.

More when the parts start to arrive!

Pics, sort of!

For those of you wondering what the boards I'm making will look like, here is a 3D model created by PCB 123 Layout from Sunstone. The software is among the best that I have used in the free or try before you buy category. It turns out that Sunstone is the parent company for Express PCB, which also has a free PCB layout package. Frankly, it's easier to use, but I went with this one in order to be able to order boards with more features, like 2.5 oz. copper, silver plating, etc.

One of the biggest problems with this software is that it doesn't treat corners as an entity. And that means if you don't like how a trace is routed, you seem to have to delete the whole trace and start from scratch. Oh well, the price I pay for my hobby. Also, please note that the quality of the image is poor, which is based in part on the 3D rendering, and in part on the fact that it's a cut of a screen shot, so don't judge me by the jagged edges. :) 

So where is the progress?

The Tandberg 3001 FM Tuner refurbish project is continuing, sometimes at the expense of my studies, but the output board and the power supply are moving forward.

The Output Board
I received the Cardas output jacks Friday which means I was able to finish laying out the board with accurate device footprints. I will probably order a prototype run of the board this Wednesday, when you may see me selling the extras on E-bay if they fit.

I've also ordered all of the parts for it as well, which is just Vishay Mil-Spec Metal Film ultra low noise resistors. Everything else I will be pulling off the original board.

The Power Supply
When I bought the Tandberg 3001 tuner, I was informed something smoked, and when I took the cover off and found that in the power supply at least one cap had expanded beyond it's normal physical dimensions as well as a carbonized trimmer pot. In addition, I read in a Yahoo FM Tuner group that the power resistors were standard cement types, and sure enough mine were too.

As most of you know, electrolytic caps do have a limited shelf life, and are often the first to go in electronics gear, often taking out other components around them. So for the PS, I ordered abox full of Panasonic FM and FC capacitors, Kiwame Carbon Film and Vishay Metal Oxide resistors, new trimmer pots, and bags full of Panasonic Metal Film caps to use for bypassing. There will probably be a need for new transistors as well, but taking each one out and testing it would not be easy. Instead I will replace all the caps first, and then see if I can diagnose any bad transistors. After this, I will replace the trimmer pots, and power resistors.

Ok, before anyone starts, there is just no space in this thing for the fancy Solen/Auralcap/Multicap bypass caps that are all the rage so don't even start with me. If you aren't going to get hot without those, scroll down and droll at the CJ Power supply mods, then come back to this project. :) Maybe when I start making power supply boards for the 3001 from scratch we can discuss these. :) Just kidding, there's no way I have time for this with work and school. However, if you are a well-heeled devotee of the 3001 and really want a custom built power supply board with some seriously upgraded capabilities and components, send me a note. :) Maybe I can make a bunch of them at once.

Ok, so why not some Black Gate caps? Mostly, they have too long of a burn in time which starts over when you turn the unit off. According to what I read, it takes days for their electrolyte to become fully saturated and for you to get the full BG experience. With a vintage piece of gear like this with notorious overheating problems I just felt that BG's would not be worth the cost of ownership. I'm not going to leave it turned on for more than a day or weekend at a time. Besides, the Panasonic FM's are really really good compared to what was in there originally when this tuner was dominating the FM tuner ratings. Lastly, frankly, I need to see if this tuner ever turns on again. The power supply smoking may have ruined it, in which case spending a couple of hundred bucks on PS caps would be a complete waste.


On Progress and Humility
FYI, this tuner is going to rock when I am done, but honestly, if I had to design this tuner from scratch, there is NO way I could come close to the achievements Mr. Tandberg made to Audio, so I want to take a moment and express my gratitude at being able to in a small way connect with the work he and his engineers did in the 80s.

However, it is also true that many things have changed since then, so it is likely that Mr. Tandberg himself would have made improvements in several areas if he were still around. To begin with, double sided circuit boards are much cheaper in both production and prototype quantities. This is one major reason why I will make the amount of imrpovement in the output board that I will. It's worth going over because much that applies to it can apply to many re-builds of vintage equipment. The original board was single sided, forcing the ground plane had to share space with the audio traces. Because my version is double sided I can put down a massive ground plane on one side, with the signal traces on the other, which gives me better spacing which should lead to lower crosstalk and lower noise than the originals. The other reason this version will be better are the connectors. Rhodium over silver over brass will beat tin over plastic almost every time. As I noted above, I'm using very low noise Vishay resistors on the board as well. Lastly, I'm adding a surprise to the board specifically for that rare breed, the FM and cable junkie. He's not an average audiophile, nor is he an average cable head either. This species of audiophile still tries to find an FM station worth listening to AND he's a cable junkie. A very rare combination, usually found around Boston or LA or Chicago. But I won't say more until the boards are back. :)

The next place where things have gotten better than the Tandberg (and frankly, MY) days is in the size and quality of components. Electrolytic capacitors as well as power resistors have made major improvements in their quality as well as their size. A half watt or 5 watt resistor is much smaller than it used to be. Also, you can find some very high power resistors in metal film versions, which can take 30 watts in the space of a TO-220 case. High power, high stability and low noise in small packages. Sadly I can't use them without redesigning the power supply board (hah!) so I'm going to have to "settle" for some Kiwame's and Metal Oxides. But still, they are SO much smaller than their originals it's almost hard to use them. Two watt 1.2 Ohm Metal Oxide resistors are so small these days it may be difficult to put them in the place where the 2 1/2" long resistor went originally.

Also, we now have the ability to get very low inductance electrolytic capacitors in smaller packages than what Mr. Tandberg used as "standard." I'm talking about the Panasonic FM series here. They are smaller, have something like half the impedance of most other low inductance electrolytics when compared to Nichicon low impedance types. The one bit of a drag is that I can only find them with values up to 50V, so you have to step down to Panasonic FC types to get 63V caps. Not a big deal if you can apply some under-the-board metalized polyester film caps to make up for this small shortcoming.

My point to all of this is that I think if Mr. Tandberg had been succesful, and was still around, I think he would be designing with:

• Double sided boards
• Smaller, higher quaility components which....
• Would let him get enough space for things like metal film resistors with heat sinks, bypass caps, larger ground planes and traces, along with holes in the board for the transistor and resistor heat sinks.
  

One of the things I've noticed about the 3001 is that I don't think I have ever owned a component so full of parts. I think this tuner has more parts than all of my other audio components put together. Putting together this many parts, on so many circuit boards using single sided technology in a low profile design really was an amazing bit of work. If I were to do the industrial design for gear like this I would have used a card cage design, and have made it twice as tall. This is closer to what Revox did during the same era, making their products easy to service but looking a bit like ham radios or toasters by comparison.

When I post again I'll put pictures of the insides of the Tandberg 3001 so you can see what I'm talking about when I say "full of parts."

Maybe I should change the name...

of this blog, because I'm so far away from working on power conditioning that it's almost not funny. Instead I've been busy working on my own mini-system, finding ways to improve it one way or another. I've been looking for a good vintage tuner and DAC to put into my CJ/Sumo/Monitor Audio system, and came across at Tandberg 3001 at Goodwins for $275. Now, if you are any sort of FM fan at all you know that a 3001 doesn't sell for less than $700 anywhere unless there is something wrong with it.

So, I went to Goodwin's and got the answer. Aparently this unit came out of some well heeled accumulator (as opposed to collector) of audio gear. The output board was "cracked" and parts in the power supply "assumed their gaseous state." So, I offered him $200 and walked out with it.

Here is a picture of the output board. It's not really as bad as described. The problem is two fold. It seems like a previous owner used really high pressure connectors and pushed so hard on the RCA jacks that it pulled the tabs and the copper off the PCB on the back. The other problem is that these jacks are just tin and plastic.

So, I am left with a couple of choices, I could scrape off some solder mask, and add big gobs of solder, and stick it back in, and start working on the power supply OR I could make a new PCB board sized for Cardas RCA jacks. Well, if you've followed my blog at all, you know which of these two choices I'm going to take. :)

The mechanical drawing of the original board has been completed, now I'm debating which PCB manufacturer to go with. I like the software that Express PCB offers, but I may want options, like thicker copper traces, or gold plating in case I find others who would like to upgrade their Tandberg 3001 or 3001A boards.