Comments for page: Eico Cortina 3070

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Posted by Jacob B October 13, 2020 - 09:00 am
Hi again Steve.

I swapped those caps and also applied new thermal paste under those transistors.

Sadly, the cap replacement did not resolve my issue. I am still getting no output through the speakers at all, not even noise. As mentioned before, I can still get some audio if I use the tape out and attach a blue tooth speaker.

It appears that something that affects both channels must be broken. The caps were definitely leaking bad so replacing them was worth the effort either way.


Posted by Steve L. October 07, 2020 - 04:26 pm
Hi Jacob, Actually, when I said, "and it's mate, C5," I was referring to the 2000uF cap which is the output coupling cap in the right channel (not related to C305). C6 is the output coupling cap in the left channel. So I was saying it would be best to replace both C5 and C6 with a 4700uF value. Yes, C5 could be the issue you're trying to fix. I trust you've checked the fuses. They often blow when there's a problem in one of the power amps. In any case, I'll be happy to help if the cap replacement doesn't fix it.

Posted by Jacob B October 07, 2020 - 02:46 pm
Hi Steve. Thanks for the prompt reply!
When you say C5, you are referring to C305 correct?
My C6 cap is blown and leaking which I am hoping is what caused the output to stop working. I still get photo output through the tape output which I have hooked up to a Bluetooth speaker temporarily. Hoping replacing the C6 cap does the trick!

Posted by Steve L. October 06, 2020 - 07:18 pm
Hi Jacob, As covered above in the "Low Frequency Stability Problem" section, I found that C6 (and it's mate, C5) need to be increased to 4700uF to avoid a large peak in the low frequency response. I would make those low-ESR and long life types if possible. A quick look at Mouser shows Vishay MAL202190062E3 ($4.57) would work. It has a 5000 hour rating. No special ESR is featured but the typical value is given as 0.079ohms, which seems good. Let us know how it goes if you get a chance.

Posted by Jacob B October 06, 2020 - 06:40 pm
Hello. I need to replace C6. Any input on what to replace this with? Will any bipolar 2000uF 25V cap work?

Posted by Steve L. September 24, 2020 - 06:31 pm
Hi Mike, Congratulations on restoring the 3070! Glad you brought the output bias current down to a good value. Yes, paralleling R307 with fixed values is a perfectly acceptable way to do that.

That is an amazing price for the Kuman tester. I see that it was originally an open source project and from the 450 ratings on Amazon, there have been a large number of satisfied customers.

It's great that your first solid state project went well and you can enjoy that "space-age" transistor sound :) When I used that term in the article in 2011, it was meant tongue-in-cheek, since the space-age had become dim history in the U.S. But now, with the advent of SpaceX and others, the space-age has come back. Who'd have thought that we would ever see a vertical rocket landing, like they used to depict in old movies?

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