Posted by
Max H |
February 23, 2012 - 12:52 pm | |
I plan to replace all electrolytics in both tuner and amp. Like you I'll get a full set of transistors for both channels, just to be on the safe side. It's a shame the little ones on the driver board will no longer say RCA on them, but at least it should be functional!
To be honest, the reason the amp has sat so long, is I am a bit embarassed by how it got damaged in the first place.
When I was still in high school, I was frequency sweep testing a speaker, and decided that more power was needed. Why not put my recently re-capped EICO in mono, and parallel the speaker outputs? It worked very briefly, then fuses blew, and goodbye EICO. I knew enough about electronics even then to know it was a bad idea, but I thought hey, you can parallel a Dynaco ST-70, this thing should be able to handle it too! I realized there was some risk involved, but assumed that worst case I'd blow the fuses.
New fuses did nothing, and now the voltage measurements were all off. At the time I was more interested in tube amplifiers, so the EICO was put into storage.
The tuner stayed part of my system for years after, but eventually it stopped working properly, and was replaced by a Pioneer. I'll worry about the tuner once the amplifier is working.
I have experienced what you are talking about with small electolytic coupling capacitors. The worst device I have ever worked on for this problem, is a Phase Linear 4000 preamplifier. It must have 100 1uF capacitors in it, and nearly all of them on the verge of failure. I replaced them one at a time, and gave up on it for the time being. Some day it will be a rebuild project too, but for now I am appreciating the more minimalist EICO. |
Posted by
Steve L. |
February 23, 2012 - 08:20 am | |
Hi Max, Yeah, what would we do without the Net? Ironic that the pinnacle of modern technology is such a boon to supporting vintage audio.
On the channel with the good output transistors, one would suspect the drivers, of course.
In the tuner, the German sourcing is reminiscent of the vacuum tube HFT9X series, in which the RF tuner was a cast-aluminum module, made in Germany. The one time I ventured inside, I found an amazing a 3D sculpture of components. I tip-toed back the way I came... :)
I have found that the larger Eico electrolytic caps are pretty reliable, though filter caps might need to be reformed. Sadly, those little 2uF caps (and similar) are a different story. Those are among the few components that I replace en masse. Ceramics should be fine. |
Posted by
Max H |
February 23, 2012 - 01:56 am | |
Dug out the EICO. On one channel, both output transistors are shorted. Other side blows the fuse, but the output transistors test okay. Going to order parts before I continue to troubleshoot, but thankfully the design is simple enough there's only so many things which could be wrong.
Took the cover off the tuner. Electrolytic filter caps have a date code of 1967. Tuner is interesting - the RF and IF sections are made in Germany, and with only the multiplex board and power supply made by EICO. Tons of capacitors to replace, mostly axial 2uF electrolytics on the multiplex board.
Glad you got the transistors from Surplus Sales - isn't the internet great? |
Posted by
Steve L. |
February 22, 2012 - 07:26 pm | |
Hi Max, That is a great find! Thank you so much for posting about Surplus Sales of Nebraska. I just ordered ten units for myself. Have dealt with them in the past but didn't look there searching for the transistors. Google didn't find them at the time, either.
It's neat that your great-uncle bought your amp and tuner new. Glad that you're going to save it. By the way, there is a Summary of Modifications on page-2, in case you didn't see it and want to make sure you have all the parts (for the things you choose to do).
And yeah, those vacuum tube amps don't get any awards for efficiency. But at least in the winter, when the heat is on, you can be consoled by the fact that 100% of the energy goes into heating the house. One might carp that electric heat is more expensive than fuel-based heat but at least the energy doesn't go to waste. (Of course, summer is a different story!) |
Posted by
Max H |
February 22, 2012 - 04:50 pm | |
Just ordered 10 units of real RCA 40312 from surplus sales for $1.50 each, plus shipping... their min. order is now $10. I should be able to get a pair out of ten units, hopefully same date code. |
Posted by
Max H |
February 22, 2012 - 04:34 pm | |
Hi Steve,
Thank you for your response! I never really thought of the Cortina as classic, but you may have changed my mind! I have the matching FM tuner for my Cortina as well, and the pair made a nice compact hi-fi setup. I rescued the pair from my dad's uncle (who bought them new) in the early 1990s, changed all of the large electrolytic capacitors, and used them for a while before the accident. I was actually searching for info on the tuner when I stumbled across your website.
I found that surplus sales of nebraska has the RCA 40312 for a very nice price, provided I can make their minimum order, etc. I was planning to make an order to Mouser for another project anyway, so adding the other components to fix up the EICOs will have a very low incremental cost.
http://www.surplussales.com/semiconductors/Transistors-SCR-3.html
An additional motivaiton for this project is that the recent increases in the cost of electrical energy motivated me to acquire a plug-in watt meter, of the type used to measure power use of appliances. Apparently my all tube hi-fi setup uses almost 450 Watts just to sit idle! At current electricity rates and with how often I use the stereo, that translates into about $6 per month, or $75 per year. Considering the trouble I've gone to to change all the lights in my house to CFL, and other means to reduce energy consumption, it seems appropriate to revive the EICO for non-critical music listening.
I will add a comment once I've made some progress. Thank you for the excellent website.
Best Regards
Max |
|