Eros 1 refresh...

[gstew]

I just purchased a used Eros 1 off EBay, this one:

www.ebay.com/itm/167227941754?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=twqQBWzxQkq&sssrc=4429486&ssuid=LSNq8YkQR3u&var=&widget_ver=artemis&media=SMS

My 2nd, I also have an Eros 2 I purchased in '18, assembled in '19. Best phono stage I have here among several commercial & DIY ones including the Seduction I built in the early 2000s... & later modified to use 6N1P tubes with a separate filament transformer & some slight circuit value changes as recommended in response to my inquiry about those tubes.

1st, it was sold by someone other than the builder, only testing being powered on & tubes light... & no manual. Many, many thanks Ms Eileen for fast purchase & access to the Eros 1 manual so I can check it out before trying it in my 2nd setup.

2nd, I plan to rework it somewhat & possibly do some upgrades. I especially want to incorporate non-magnetic terminal strips (if I have enough left or can source them) & brass hardware, as I do for all my DIY builds.

I also want to redo the amplifying circuitry & incorporate the Eros 2 active loads & biasing servo board. Can I purchase one? I am a long time DIY'er, so expect I can source the parts to populate it, but if there are some that can be hard to find, can I order them too?

3rd, in that rework, is there anything recommended?

TY!

Greg Stewart

 

[Paul Birkeland]

This Eros you've bought is a tape head Eros, not a turntable Eros. 

The Eros 2 PC board was built with the intention of bolting into and working properly in the Eros 2.  The Eros 1 has the signal split up side-to-side with a lot of space between the channels, and the Eros 2 active load board isn't going to integrate very well into an Eros 1. 

We do still manufacture the C4S boards that go into the Eros 1, and I suspect you could order a pair of those from Eileen for not a ton of coin, but a lot of the rest of the parts that went on that board have been superseded in our inventory when we went to Eros 2, so you may want to source most of the resistors/caps/transistors/diodes in there. 

If you are rebuilding this into a phono Eros, you could order 10 of each of the EQ caps at Mouser and hand match some tight tolerance pairs, that would be a nice upgrade. 

 

[gstew]

Interesting.

& that explains why after a cursory look at it (just received it yesterday), it seemed to have a higher component count in the active circuitry than my Ero 2 & had a switch (which I first guessed was output shorting muting, but after a 2nd look could see was selecting different filtering.)

Ok. Unless anyone desperately wants to trade a phono Eros for this tape head one, I'll continue with my plan with some modifications.

I've confirmed the schematics for the PSU board & Shunt Regulator boards are virtually the same between the Eros 1 & 2, except the Eros 1 uses either a 6CG7 as the regulator output device (per the schematic... including of course being wired for the 6.3V filament) or a 12BH7 (per the parts list)... & 2.2uF caps added across the 220R resistors in the output voltage setting divider.

If this unit is wired for a 6CG7, any reason to retain it in that configuration versus rewiring it to the Ero 2 12AU7 configuration (except that I have a few nearly unused 6CG7s sitting around with no other current use for them)?

& unless you can confirm these two boards should be the same between the Ero 1 phono & tape head versions, I'll check the component values on the boards here to confirm that match.

Also, should the plate load / servo boards be the same between the phono & tape head versions

& my next steps would be to strip it down, refresh the soldering on the boards, add the 2.2uF caps to the regulator board, install the replacement terminal strips, source the active circuitry components, & proceed with the refresh starting with step 1 of the instructions & either performing or confirming each step as I go.

Does that sound about right?

& MANY THANKS for identifying this & all your assistance!

Greg in Mississippi

 

[Paul Birkeland]

The Eros 1 tape and Eros 1 phono C4S boards are not populated with the same parts. 

We ended up using the 12BH7 for the Eros 1 shunt regulator, but I can't remember why it was that over the 12BH7 (it could be related to availability or possibly heater current). The 12AU7 works fine in that position and is a bit more abundant. 

 

[gstew]

Paul,

Again, thanks for the great & very useful info!

Getting back to this finally, some questions...

- The .01uF, .03uF, & 2.2uF metalized polypropylene caps are Panasonic ECWF(A) series, correct? Definitely will hand match the RIAA caps, thanks for the suggestion!

- The various 1/8W metal film resistors are Vishay/Dale CMF55 series, correct? Also what PPM, 50 or 100?

I'm sourcing the various electrolytic caps from Digikey or Mouser, the.larger film caps from Parts Express, & will ordered the various other resistors, silicon, & boards through BH.

I should have any hardware I need either on the unit or on hand.

Anything else I should have asked that I didn't?

Thanks!

Greg

 

[Paul Birkeland]

Oh man, the Eros goes so dang far back that those will be questions that are somewhat hard to answer.  I wouldn't stress too much about about resistor PPM in our kits, as they don't really get all that hot (the EQ resistors themselves dissipate nearly no heat) and the tolerance is so tight relative to measurable dB of deviation from the RIAA EQ that it's mostly a wash.  CMF55, RN55D, etc. are all really nice parts. 

https://www.mouser.com/ProductDetail/YAGEO/CFR2WSJT-52-47K?qs=sGAEpiMZZMsPqMdJzcrNwjRWpSA1Ui8vz8y1rbkmcFEQHeH1uVYTWw%3D%3D

I think I'd go with those for the 47K plate loads if you're doing a Mouser order.  2W carbon films can be hard to find and go in and out of stock frequently, but they are in good supply at the moment.

 

[gstew]

Paul,

Again thanks for all your assistance!

Orders in to BH & for more terminal strips.

Again, thx!

Greg in Mississippi

 

[Paul Birkeland]

I don't think there's anything super productive to be done with that information.  There are very, very few changes electrically between the Eros 1 and Eros 2.

 

[Paul Birkeland]

I'm available at pb(at)Bottlehead(dot)com.