Topic: Aerco MP-2 preamp - Part 2

[audBall]

Anyone out there still running their mp2? I ran mine for the Greek shows and was real happy with the results. Curious about what the potential smallest external batteries out there might be. I've been running the Talentcell 12V/6000mah for a few years and a single charge gets many, many hours with the preamp - far more than necessary for a single show. I was thinking about trying the 3000mah version as it's a bit smaller. 4.1x2.5x1 in vs 5.7x3.5x1.1 in

Looks like they have a triangular (toblerone?) shaped one rated 2600 mah that's approx. 4x2 in.
https://www.amazon.com/dp/B09SLQD7D1

Any other options out there?

[fanofjam]

I know that you’re looking for a different suggestion..  but I always used the 9v DVD style batteries when I ran an Aerco. Worked great.
The only multi voltage batteries that I have are Tekkeon, and I know that those are considered “old”  and that there are much better multi voltage batteries these days.
Not much help, but I know that Aerco rocks!!

The old Tekkeon's are indeed old, but I personally don't think there's anything better.  I keep recycling my original model Tekkeon batteries with four new 18650 cells and I'll use these until the day I die.  They're so solid and so convenient for what I use them for and since I can keep getting 18650's I'll just keep on refurbing my Tekkeons with 18650 x 4 forever.  That's the 3300 version of the Tekkeon, not the larger capacity 3450 that use 6 x 18650.  Those old 3300 version Tekkeons are like a VW bug.  They're basic and simple on the inside and sooo easy to rebuild, but the 3450's are a pain in the ass.

[audBall]

My old Tekkeon knock-off was a beast and ran forever. The Talentcells also use the 18650s as well, correct? I bet they could be refurb'd in a similar fashion.

[goodcooker]

I got back the Aerco that I sold in 2019. Thanks Jon!

I forgot how small these things really are.

The batteries have been removed and it works just fine on an external, so I'm just going to leave it that way for now.

Looks like it needs new RCA output jacks. One of them is a loose connection to the plug like it's a half mm smaller. I remember having some trouble with this when I had this same one before but chalked it up to the cables I was using. It looks like a relatively simple repair - the jacks just have a couple hex nuts on each side of the case but the soldered connections are like nothing I've ever seen before with the grounds soldered to a piece of copper foil on the case that's right on the edge of the right side RCA jack panel mount nut and a split that goes directly to the 1/8 jack. Small, weird and difficult, but doable.

There's some sort of opamp/IC in there that I never noticed before. It looks like a lot of 8 pin socketed ICs and a search of the numbers turned up an Analog Devices similar part that the description says nothing about audio other than to mention it's often used in radar and telemetry devices. Part number - Maxim NAX 427 - GPA 0626.

[Gutbucket]

It may just be a physical contact connection between the RCA's and foil that has the grounds soldered to it, in which case you might only need to re-solder the center signal wires to the new RCAs. Jerry may have done it that way simply because its easier to solder to the foil because it's less of a heat sink than the jack bodies.  Otherwise you can probably eliminate the foil and run the grounds straight to the RCA bodies.  Only other reason I can think of for it is if the foil helps screen RFI from making its way in around the jacks if the there is a small gap.  Is the case metal? I can't remember.  If so that might explain why the entire thing isn't lined with copper foil.  Hope that helps.

[rigpimp]

I would re-solder the center pin and only on the channel showing intermittent connectivity.  If it is both channels then I would unscrew both jacks and rub the metal bare between the foil and the case.  The copper/case union may be oxidizing.

The foil was probably easier to solder too and he did not wrap around the unit since the last thing you would want in an audio unit (to prevent rf interference) would be a copper loop.  (think antenna)

[goodcooker]

It may just be a physical contact connection between the RCA's and foil that has the grounds soldered to it, in which case you might only need to re-solder the center signal wires to the new RCAs. Jerry may have done it that way simply because its easier to solder to the foil because it's less of a heat sink than the jack bodies.  Otherwise you can probably eliminate the foil and run the grounds straight to the RCA bodies.  Only other reason I can think of for it is if the foil helps screen RFI from making its way in around the jacks if the there is a small gap.  Is the case metal? I can't remember.  If so that might explain why the entire thing isn't lined with copper foil.  Hope that helps.

I think all these things are likely true. I ordered some very similar new RCA jacks so I think if I can't actually leave that right channel back panel mounting nut in place with the solder still on it I'll at least be able to screw the new one into the same spot and reflow a little solder onto it. Guess I'll be able to tell once I start taking it apart. Yes, the case is cast aluminum.

I would re-solder the center pin and only on the channel showing intermittent connectivity.  If it is both channels then I would unscrew both jacks and rub the metal bare between the foil and the case.  The copper/case union may be oxidizing.

The foil was probably easier to solder too and he did not wrap around the unit since the last thing you would want in an audio unit (to prevent rf interference) would be a copper loop.  (think antenna)

The bad connection is the barrel of the right female RCA being an off size. It's too small and every RCA plug I've put on it slides off real easily. It's not an electrical problem. Every manufacturer has some tolerance and mine's just not the right size. This has always been a problem with this unit - in the past I would gently squeeze my RCA plugs to get them to grip a little better.

The copper piece in the pic is just around the RCAs I'm assuming it's just a common ground.

[audBall]

Just a guess, but it appears the RCA jacks were swapped out with gold at some point, the foil grounding was changed, and silicon added. Here's a photo of two below, 20-70 dB on the left, 5-30 dB on the right. The one on the left has the same chip as yours shown. I've also had one of the tiny hex nuts loosen allowing the RCA jack the jiggle somewhat. Interestingly, I found a small profile IKEA wrench to fit inside almost perfectly to re-tighten, although I'm always afraid my hands are going to slip. The reason for the tape on the right is the XLR connectors are flip-flopped and someone added the tape as a buffer between the prongs and the case. The transformers are slightly different heights as well, taller on the left.

What's your gain range?

[rigpimp]

The bad connection is the barrel of the right female RCA being an off size. It's too small and every RCA plug I've put on it slides off real easily. It's not an electrical problem. Every manufacturer has some tolerance and mine's just not the right size. This has always been a problem with this unit - in the past I would gently squeeze my RCA plugs to get them to grip a little better.

The copper piece in the pic is just around the RCAs I'm assuming it's just a common ground.

In that case, I would yank out the RCAs and swap them out entirely.  I would re-terminate the ground the way they are in the two pics that Horus posted.



^^ Man, works of art right there

[goodcooker]

Those look a lot cleaner inside than mine. Mine has lots of hot glue that's been flowed over the gain pots and also that upper circuit board.

Gain range is 0-60. 0-50 on the left knob in 10dB steps and 0-10 on the right knob in 2 dB steps.

[goodcooker]

Rather than monkey around with a bespoke piece of gear that can no longer be fixed by the maker/designer I decided since it's working just fine as is (except for not having internal batteries any longer) I went a different path and made new output cables. I used the Deadbolt RCA connectors from Sewell (screw terminal not ideal and I'll probably keep looking for another good fit) and they fit great.

At some point when my eye doctor gets my prescription under control I may do some work to this thing but for now my eyesight it too bad to do fine work even with a magnifier light on my solder station.

[audBall]

That sounds like a good solution for now. Please keep us posted.

Long live this little beast!

[spyder9]

The original RCAs were weak on my Aerco too.  I ran it by Jerry on what to buy and he recommended the ones below from Rean (Neutrik).  I ordered a pair of these from Dale Pro Audio back in 2011.   They fit perfectly in the Aerco.  I even soldered them myself.   Too easy.   Been a happy camper ever since.

Black

https://www.markertek.com/product/nys367bk/rean-nys367-0-gold-plated-rca-phone-chassis-mount-socket-black?gclid=EAIaIQobChMI6NiO7ey0gAMVXKVaBR1KFwoKEAQYASABEgKvGvD_BwE

Red

https://www.markertek.com/product/nys367rd/rean-nys367-2-gold-plated-rca-phone-chassis-mount-socket-red?gclid=EAIaIQobChMI6NiO7ey0gAMVXKVaBR1KFwoKEAQYBCABEgJJjfD_BwE

[goodcooker]

I think my Aerco is bricked. Can't get it to do anything.

Which is weird since I didn't do anything to it. I was thinking about those RCA repairs and decided to pass for now. Found a screw locking Switchcraft connector in my pile of parts so I was going to make a new power cable for it and try it out into the SD Mixpre6 to get a comp at Vince Herman tomorrow night and nothing.

Battery is good, cable is good, connector is good all checked with a meter.

I've only run it once since I got it back. This sucks.

[aaronji]

I am sorry to hear that. Maybe something minor that can be repaired, hopefully. I haven't run my Aerco in quite some time, but, honestly, I will never sell it. Jerry made it for me and it is a bonafide piece of taper history. Probably the only piece of gear I own that I wouldn't part with (it would need to be pretty dire before I ditched the 4015s, though).

Fingers crossed for you!