Eico AF-4 stereo SET EL84 amp

Eico AF-4 stereo SEP EL84 amp

I have a hard time resisting even low end Eico tube gear, especially with this classic "look".

Found this dusty little guy , an Eico AF-4 integrated stereo amp.

I brought the amp into my "Abandoned tube amp" rescue shelter and took these images to document the process of rehab

Barn found, and in total original as-built condition. I even found one crappy obvious soldier joint that the builder did poorly. In the end more than 20 bad connections

Before I try to power it up, I'll get the schematic and try to validate the wiring. Doesn't look too bad, real long leads, longer than I would use

Pictures of inside the Eico AF-4 tube amp

Underneath component side




I am starting to appreciate single ended amplifiers because it is allot easier to find TWO great output tubes instead of a matched quad


many a lonely night this amp sat quietly waiting for its life to begin again

a sleeping beauty


silently waiting for technical Prince Charming

This is meant to encourage you

my HF85 looked pretty much like that.
I've gutted it and am remaking it to a point.

Saw that little Eico on CL and thought about calling on it but as is I have more than enough projects lined up to last a while.

Can't wait to see what you do with it.

After basic cleanup

Here it is after a basic clean up. Big surprise are the two-tone color knobs. The brass plate polished up well with Simichrome polish.

I did get the schematic and build manual (shout out to Mark)

This is nothing but elbow grease so far

After a overnight soak failed to remove the guck on the knobs, I used my wife's sonic cleaner on them but still not 100%

De-Oxit is good for metal too

love that original patina

I have a complete set(5) of J/J tubes on order for fifty-five bucks

Love those SET amps, easy on the wallet

My first obvious kit restore experience; grounds are especially suspect

I checked out the build against the manual and pictures of known working amps and the guy J.B. Webster got it right. I will not remove his name tag!

I did spend 20 minutes hovering over the chassis and validating solder joints with my Weller.

AF-4 recapped

Here is the AF-4 all recapped.

The two 50uf 50v e-caps tested bad as well as both 10uf 6v e-caps. The disc caps were rock solid but I changed those to film caps. I've had those mallory's waiting for a project

I used .022 Mallory film caps to replace the ceramic disc .025 caps. I hope thats okay?

I also replaced the broken fuse holder.

I did check all resistors for out of spec and I am going to replace two 130ohm 2 watt resistors because they are just at margin

I found my label maker


While I had my head in the electronics I did notice that this amp had been touched in the past

Two big resistors had been changed with the metal oxide ones in the pictures

That implies excessive heat in the circuit.

Then as I was comparing the wiring with a picture from Radio Museum I noticed the darkening of the PT paper and that some wires from the PT had darkened (lets not say scorched), so I lost a night of sleep worrying about that. Is the PT okay?

The PT windings ohm out okay but I have not applied power to anything yet

And check the connectors out. The two on the left are speaker connects left/right. The plug on the right is EXACTLY like the speaker plugs but instead of the 8ohm connection for a speaker, that is B+, yes, 200+ volt B+. and the speaker plug fits into the voltage plug perfectly

Personally, I find this description kind of hard to comprehend, but the author does weave an intricate technical thread that makes me feel for the main components

I guess its ready to apply power but I wish I had the skills to variac it and bring it up correctly

Hello!

Thanks for posting! Looks like a great project. Robert

You sure haven't wasted any time getting it cleaned up and restored. Now we're going to need a listening report. Nice job. Wish I would find something like this. However, I have a couple pairs of the Roberts/Akai R2R SE amps, so I guess this should fire me up to work on those.

Thanks for sharing.
John

nerdorama said:

You sure haven't wasted any time getting it cleaned up and restored. Now we're going to need a listening report. Nice job. Wish I would find something like this. However, I have a couple pairs of the Roberts/Akai R2R SE amps, so I guess this should fire me up to work on those.

Thanks for sharing.
John

Click to expand...

Thanks, I will report on the performance as soon as I get the nerve to fire it up.

I recently posted on the my own Roberts 990 conversion? That went well and they sound great

I am a total amateur OJT when it comes to electronics

what a great transformation.
From a junkyard dog to a shining example of
tubularity Eico style.
good job Omegaman.
Hope it sounds good as it looks.

Great work and great amp, Congratulations!

I powered it up.

IT WORKS GREAT! What a satisfying success!

I need to re-de-oxit the controls but it is really a sweet sounding amp

I have not done full function testing but with AUX it works

smooth Hi fidelity sound in both channels though one channel is a little louder than the other. Not a little louder, but kicks in audible at different level potentiometer positions

I am very relieved the transformers still have life

I have to make up speaker cables for it and listen to it for a couple of days

Maybe I will take it in for a professional final checkup. It might be worth the effort

Re-capping WORKS! Should be good for another 50 years

ahhh...this is what it's all about

ch imbalance is likely vol/tone pot tracking. just a guess.

I have been auditioning this sweet little Eico AF-4 SE amp for a week now and it sounds true, lifelike and faithful.

I am impressed with this amp and it has made me aware of the quality of SE amplification

I got the amp with no tubes so I bought a full brand new set of JJ tubes

I also loaded up some Fisher 7189 tubes I had in stock which added a new level of output power

I also learned about volume pots.

I heard some mis-match volume from one channel but only at lower volume settings, it matched at higher setting, so I measured the volume pot ohm reading on each stereo half of the pot with the volume set at 0, 1, 2, 3..etc up to max vol and the two pots did NOT show equal (or close) ohm readings in some positions

It was not matched at common lower volume settings but matched at higher vol settings 6 or 7 (+/- 5%)

If I could get a new pot I would replace it

I might also swap the volume pot with the tone pot as the parts list says they are both 1M ohm dual pots

or just leave the battle scared resurrected survivor alone and play the dang thing

One thing I also learned was the phrase "Normal Listening levels".

I just got a HFT-90 tuner to match with this amp

LONG LIVE VINTAGE! VINTAGE RULES THE PAST!

There's my listening stool

And check out the speaker connectors



I got those metal 4-prong perfect connectors from the remains of a discarded cable while
converting a Roberts/Akai to two mono-blocks.

A fellow AK'er who just happened to be doing the same Akai conversion donated the second matching connector

I also covered the power out socket and went crazy with the label maker

A new non-polarized AC power cord marked for transformer side

That AF-4 cleaned up like a miracle. I would have not believe possible.

SE sound is an awaking due to the simplicity of design leaves little to murk up the audio path. I gotten PP amps to sound about as good as SE, but requires careful design.

Hi super job on the AF-4, i agree with Sony6060 SE sound is an awaking.
the clean up you did was an eye operner. i would not have thought it would have cleand up that nice. i might have even passed on it my self. good job

i have been working a heathkit aa-201 se amp i picked up. it did not need all the attention yours did but it had some bugs. i got it running but still has a small hum.

but the sound is amazing this is the first se amp i have owned or even heard.


good job and happy listing

P.S. i hope that is your foot stool in the pic not your listening seat. lol
Don P

The listening stool is rated at 350 man pounds and can withstand a kinetic force of 40 Jules. Designed by Kelly Johnson, built by the Lockheed Skunk Works and sold by Sears, at least thats what the guy on Craigslist told me

Arizona preserves electronics very well.

Added an Eico HFT-90 tuner

Got this Eico HFT-90 from a fellow AK'er on BT.
Nice to have the matching tuner
Not stereo, but MPX out and I have an adapter

Works, including ultra cool exclamation point tuning indicator. Glows brighter as you tune in

No output from the audio, just the multiplex so I'll have to put it in the shop for service. The 6C4 tube measured DEAD. I had a spare but no difference

The volume does not change the volume of the multiplex output, maybe thats normal

Case on the AF-4, a 4, case on the tuner, a 9

Very nice case that exactly matches my AF-4 amp. Maybe a case swap will put the best case on the most important component, the amp.