Audio stage restored and tested. Blaupunkt Sultan 24300 restoration pt.2
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- Опубликовано: 6 сен 2024
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The first stage of the restoration - the power supply section - was a success, so now it's time to move on to the audio stage. This is my normal progression and will establish a stable audio stage to allow us to determine whether the radio is working at all.
The interesting thing about this radio is the fact that it uses a single tube - the ECL86 - for the entire audio stage. This tube includes a triode, which is used as a preamp stage, as well as a pentode to do the power amplification. Quite a useful tube, although it tends to need more regular replacement due to its high workload in the radio.
Let's see how we get along.
Hope you enjoy the video.
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Manuel. I always learn something new with each of your videos. Thanks for explaining why these radios occasionally have a 1,000 volt rated capacitor. The first time I saw that I considered it to be an error on the schematic….not so as you explained .
👍
That works a treat Manuel... now the dial string 😄
Yes, the dial string … actually, this one seems quite straightforward 😊
Because I do so much restoration work for my own clients, and have a considerable backlog, I simply don't have the time for the finer cosmetic touches, like turning a radial cap into an axial one. But I can certainly appreciate your great attention to detail. I see that the ECL86 has indeed "bit the dust". These "combo tubes" always seem to be more failure prone than their single stage counterparts. It's much the same issue that I have with the SABA Continental (Freiburg) with its dual ELL80 output tubes. Those too are drying up. Another failure prone tube that's prone to leakage and noisy operation. I've thought of making up a PCB with sockets wired to take 4 EL95's as replacements. There was an adapter made, that plugs into the original tube socket, but it won't fit in the SABA.
The SABA is super packed, so I can see why adapting the tubes would be difficult.
The time I’m able to dedicate to these radios is purely because it’s a hobby. I can understand that some of the details would be impossible if I was doing this as a profession. The ultimate objective is the same: getting these to work again 👍
Keep up the great work!! I like the capacitor approach, especially when you have the right capacitor but it's radial and you need an axial. This is a good workaround and looks good too!
👍
Quick note, when you have a burned and exposed resistor, you can often take measurements from either end to the exposed middle and get an idea of what half the value might have been even if the resistor measures open.
Good point
Manuel Two points I would like to point out about watching your videos:
1. Your desire to restored to original both in performance and under chassis appearance,
I/E your capacitor housing trick.
2. Your detail oriented videos become a reference source for others restoring vintage sets.
Thanks. 🙏
The same PCB is probably also used for a stereo version as there appears to be an empty place for another ECL86 tube.
Makes sense
Manuel, THANK YOU for making videos where things are repaired and cherished. This is SO important in todays world where we are surrounded by the opposite. 73 OM
You are very welcome 🙏
Great viewing as always!
👍
Just a thought, you could 3-D print end caps for the capacitors you put inside the heat-shrink tubing. I’m thinking they would also be inside the tubing, and would also act as guides for the leads. You could probably even print entire enclosures if you wanted to.
With 3D printed parts from his favorite sponsor PCBwhatever? 😂
Now while your idea certainly is feasible, I ask myself where this ordeal will end. To each his own, but at this degree of striving for autenticity one should gut the old caps and use miniature or even SMD electrolytics to restuff them to preserve a 99% original look. Because just plainly looking at the facts, one has to remember that the original caps were not hand made to begin with. They were already mass produced. So strictly speaking his hand made and most of all hand labelled ones are actually much more out of place than new axial ones could be. And if you were opting for radial caps, if you just bend the negative lead back and put transparent heat shrink on, you would have the axial mounting shape and a mass production looking labelling. But why all of this? After all he is using these red radial film caps and splaying out their leads to replace the old axial paper caps. That mounting sticks out as much as a radial cap with the leads splayed out would...
Could, but not really necessary.
I have a 1960 Blaupunkt that functions well, but the dial slips. all pullies are free, and I lubed the bearings in the tuner. All is free, but the tuning knob still slips. Life is easier, now that I`m concentrating on Toy Model Trains.
😊
Looking good so far. I think people sometimes get confused with watts as so many solid state manufacturers claim ridiculous high numbers, which they really never meet in the real world. I find "Tube Watts' are quite different to the solid state claims. 1 to 1.5 watts in a table top with the original speakers is heaps. It sounds like nothing compared to 50, or 100 watts claimed be modern manufacturers, but it really is comparing apples with oranges.
True 😊
The only real difference between tube and transistor watts takes place at the overload point of the amplifier. Most transistor amps clip very cleanly, with clear "flat topping" of the waveform, where tube amps used in radios will gradually distort until pushed well into overload., This kind of "clipping" is more tolerable to the ears, but in my opinion, it would be better to just design the audio system to have sufficient loudness capability without ever approaching the clipping point regardless of the topology used. The best sounding tube radios I have all use push pull output stages that produce higher power and lower distortion than the single ended types. They all sound better too.
👍
👍
Thanks
C733 was in almost inappropriate angle.
😁
😂
@@electronicsoldandnew And of course, I was only talking about how to install components.
BTW, even the model name of this radio is a bit questionable, I mean in a sense of some kind of cultural appropriation.
Just out of curiosity will you be testing the dud ECL86 on your valve tester to find if the triode or the pentode is at fault? If the pentode part is still good is it it worth keeping for adhoc projects?
I may do that.
There is no real sense in keeping a dead tube around other than for fooling around with. Yes, the ECL86 is expensive, but the 14,5V heater PCL86 are still rather cheap. And they are drop in replacements if you can provide the higher heater voltage (f.ex. voltage doubling 6,3V to 12,6V which is close enough). And if you want to base something on the pentode section of an ECL86, you can use a EL41 or EL80. These are the pentodes that the pentode section of the ECL86 was roughly based off of.
But all these tubes are getting rare and expensive. So for any project with significant use or life span, you should avoid the ECL86 or opt to rewire existing circuits to use 1/2 ECC83 and EL84. There is even a project for adapters to make up an ECL86 by either stacking a ECC83 and a EL84 on top of each other or in a side by side adapter, much like the ones that were made for the ELL80 using two EL95.
I have one of these sultan radios that I got from my uncle awhile back that I'd like to have repaired . Can you provide this service ?
Afraid not. I live on the island of Madeira 😊
I miss the pile of cotton swabs.
😂