Comments for page: Eico Cortina 3070

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Posted by Walt N. November 21, 2021 - 12:13 pm
Replacing Q201.
The 2N5089 has a different lead configuration than the original EICO transistor. I want to make sure that I'm not screwing up before I apply power as I have replaced the original because I remember the noise from "back in the day" when I had one of these.

Posted by Steve L. November 12, 2021 - 02:01 pm
Hi Walt, Yes indeed, all Reader Comment sections on are active. We are notified whenever there is a post and endeavor to answer asap. By the way, your browser page may need to be refreshed to see a new posting.

And yes, you should replace C5 and C6 even without the transistor replacements. The issues they fix are independent of the transistor changes. To measure Iq, put the DMM probes across R12 (or R14) for the left channel and R11 (or R13) for the right channel. Since those resistors are 1.0 ohm, the current in amperes will be read directly in volts. For example, if the DMM reads 0.033V, that indicates 0.033A = 33mA. Cheers

Posted by Walt N. November 12, 2021 - 01:34 pm
I hope this may still work. I'm no more than a hobbyist. I am about to order new electrolytics for my recently acquired 3070.
1. Should I order 4700uF caps for C6 even if I don't replace the transistors? Will it hurt?
2. Assuming I do replace them, I have no idea how to calculate or measure Iq once the pots and resistors are installed. Can anyone help me here? I DO have a good meter and a scope.

Posted by Steve L. October 02, 2021 - 04:41 pm
I'm posting here a PDF file containing the interesting email exchange I just had with reader Ryan W., with his kind permission. It covers his debugging of the Cortina 3070 he had modified according to the article. Enjoy but note that it's about 5MB: W thread on debugging the Cortina 3070.pdf

Posted by Ryan September 28, 2021 - 08:04 pm
Thanks Steve, I went ahead and emailed you to follow up.

Posted by Steve L. September 25, 2021 - 10:27 pm
Hi Ryan, Thank you for your kind comments. Sorry you're experiencing very low output levels with both phono and aux sources. First, please make sure that the Tape and Loudness rocker switches are OFF, the Speakers rotary switch is set to Main and the speakers are connected to the Main output terminals. Also, I assume you are applying audio to both channels and BOTH channels can only produce very low output levels, right?

Regarding your questions:
1. The 4007 rectifiers will be fine for CR1,2,3 and 4.
2. The cleaning you described should be okay with respect to this issue.
3. You are quite right that in the "Summary of Modifications" on page-2 of the article, the bootstrap caps item should have said "C303--both channels" but had a typo which made it "302" instead. Sorry about that and thank you for reporting it! Will get it corrected. (The bootstrap discussion on page-1 correctly mentions C303.)

I will be happy to help troubleshoot the level problem--you can email me at the address given on the About page, accessible with the About button near the top of the Tronola Home page. The first steps after checking the items mentioned above would be to check the power supply voltages and then the DC circuit voltages. Eico has written some of those voltages in rectangles on the schematic. If this is really affecting both channels, one would expect to find something wrong which affects both and that points to the power supply. Best Wishes

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