Another Electro Voice Interface D Restoration Thread

[JustinCase]

MCM Fan you are going to love those speakers. Trust me. I found my pair this summer and got the foams ordered and done. I love these things. I've yet to find a genre of music that doesn't shine with these things. Listening to them right now. I won't ever be selling these. For me they are in that league - "forever speakers". They only move on when the owner is deceased. That's how I got them- the brother in law of the deceased put them up... the wife wanted them outta the house... taking up too much space. Other than situations like that I don't know why someone would ever sell a pair.

 

[MCM_Fan]

MCM Fan you are going to love those speakers. Trust me. I found my pair this summer and got the foams ordered and done. I love these things. I've yet to find a genre of music that doesn't shine with these things. Listening to them right now. I won't ever be selling these. For me they are in that league - "forever speakers". They only move on when the owner is deceased. That's how I got them- the brother in law of the deceased put them up... the wife wanted them outta the house... taking up too much space. Other than situations like that I don't know why someone would ever sell a pair.

Thanks, I can't wait to hear them! Still looking for a replacement for the missing woofer.

 

[Mircea Popa]

Hi everybody, this is my first post here but I've been following with great pleasure your forum. Learned a lot and bought my equipment based on your advice and opinions! Thanks a lot!
Anyway, I am the proud owner of the Interface D's that I've been using without the EQ. Recently I found on ebay.de an Intreface A EQ which I modified to an D EQ based on the attached schematic found on another forum. The guy posting it said he got it from EV! As you can see on the schematic, there is a table with the resistor values for A's , B&C's and D's. So hope this will help!

 

[soundmotor]

After looking at the schematic I'd wager replacing the signal path electrolytic & power supply caps with fresh ones wouldn't hurt either.

 

[MCM_Fan]

Hi everybody, this is my first post here but I've been following with great pleasure your forum. Learned a lot and bought my equipment based on your advice and opinions! Thanks a lot!
Anyway, I am the proud owner of the Interface D's that I've been using without the EQ. Recently I found on ebay.de an Intreface A EQ which I modified to an D EQ based on the attached schematic found on another forum. The guy posting it said he got it from EV! As you can see on the schematic, there is a table with the resistor values for A's , B&C's and D's. So hope this will help!

Thanks for posting that. I've downloaded a copy for my archives.

The table in the schematic confirms the values of the replacement resistors I mentioned in post #4 of this thread (13K and 220K). So, now we have confirmation of those values from both an original Interface D EQ PCB and an original schematic. Time to order some resistors!

 

[MCM_Fan]

After looking at the schematic I'd wager replacing the signal path electrolytic & power supply caps with fresh ones wouldn't hurt either.

And here's where the schematics and the actual PCBs diverge (ever so slightly).

Both the schematics and my original Interface B EQ PCB have 100uF 100V and a pair of 100uF 16V electrolytic caps on the PS. So, that part is easy enough.

However, the other five electrolytics vary slightly between what's on the actual PCB and what's shown in the schematic. The schematic shows all five to be 5uF 15V, but the PCB (both my Interface B EQ and the Interface D EQ pictured in post 4) have 4.7uF 25V caps in these locations. Probably not a big deal as these are probably 20% tolerance caps and a higher voltage rating never hurt anything.

I'll probably go ahead and order the caps when I order the resistors and swap them all out at the same time.

 

[soundmotor]

The schematic shows all five to be 5uF 15V, but the PCB (both my Interface B EQ and the Interface D EQ pictured in post 4) have 4.7uF 25V caps in these locations. Probably not a big deal as these are probably 20% tolerance caps and a higher voltage rating never hurt anything.

Exactly, they should be within tolerance. Being at the stated value is preferable when they are part of a filter but I can't recall seeing that for line-level signal. If you truly want to get in the spirit of pooge'ing, bypass any signal path electrolytics with HQ films. Heck, why stop there? Get low-ESR ones for the PS, and no, gut the PS entirely and replace with a low-Z regulated supply, and, and, yeah, Yeah, YEAH....!

/howard dean scream

Sorry, I always get a bit carried away with mods.

 

[MCM_Fan]

Exactly, they should be within tolerance. Being at the stated value is preferable when they are part of a filter but I can't recall seeing that for line-level signal. If you truly want to get in the spirit of pooge'ing, bypass any signal path electrolytics with HQ films. Heck, why stop there? Get low-ESR ones for the PS, and no, gut the PS entirely and replace with a low-Z regulated supply, and, and, yeah, Yeah, YEAH....!

/howard dean scream

Sorry, I always get a bit carried away with mods.

The PS caps shouldn't be a problem. Lots of options there. I usually go with some low ESR caps rated at 105C. The originals are Nippon Chemicon 100uF 100V, 85C and Illinois Capacitor 100uF, 16V, 85C. Just plain, ordinary general purpose eletrolytics. Anything I put in here will be better than the originals and nearly 40 years newer.

The signal path caps are another story. They are axial lead polarized electrolytics - Illinois Capacitor EXA series, nothing special. There are plenty of options in general purpose axial lead electrolytics, but it seems like audio grade electrolytics only come with radial leads. I thought about film caps, but they are huge compared to the original electrolytics, so mounting and installation might be an issue.

So, I can go with standard axial lead electrolytics, perhaps bypass them with small film caps, or go with audio grade electrolytics (Elna Silmic II, Nichicon Muse, etc.) in radial lead and make them fit. Shouldn't be an issue, they are quite small in this value (4.7uF, 25V).

Thoughts/recommendations?

 

[soundmotor]

Thoughts/recommendations?

Your comment that anything would be an improvement over the 40YO ones in there is the real money shot IMO.

That said, I would likely spring for one of the "approved" audio upgrades you listed, perhaps even 100nF bypassed.

 

[MCM_Fan]

Your comment that anything would be an improvement over the 40YO ones in there is the real money shot IMO.

That said, I would likely spring for one of the "approved" audio upgrades you listed, perhaps even 100nF bypassed.

What about 10nF bypass caps on the 4.7uF electrolytics?

I have a bunch of the little 0.01uF Vishay Roderstein MKP 1837 metalized polypropylene film caps on hand. I bought them when PartsConnexion was having a sale. I needed a few for bypassing some crossover caps in my JB L36 Decades, but bought more than I needed so I'd have some on have for future projects. I've only used them to bypass other film caps in crossovers. I've never tried using them to byass electrolytics.

 

[soundmotor]

What about 10nF bypass caps on the 4.7uF electrolytics?

I have a bunch of the little 0.01uF Vishay Roderstein MKP 1837 metalized polypropylene film caps on hand. I bought them when PartsConnexion was having a sale. I needed a few for bypassing some crossover caps in my JB L36 Decades, but bought more than I needed so I'd have some on have for future projects. I've only used them to bypass other film caps in crossovers. I've never tried using them to byass electrolytics.

I used 100nF because I had about several hundred Wimas onhand. It was solely for convenience rather than optimal or... with forethought. I'd use the .01uF in place of the .1uF if I had them and likely sleep well. It isn't like anything will explode and crater your home if you do.

 

[MCM_Fan]

I used 100nF because I had about several hundred Wimas onhand. It was solely for convenience rather than optimal or... with forethought. I'd use the .01uF in place of the .1uF if I had them and likely sleep well. It isn't like anything will explode and crater your home if you do.

The Elna Silimic IIs in 4.7uF 25V are only $0.20 each. So, using those in combination with the .01uF MKP1837s I have on hand seems like a slam dunk. As you say, it can't hurt anything.

 

[soundmotor]

...and badass speakers BTW. Can't wait to see the final result.

 

[MCM_Fan]

OK, I'm going to order the caps today, and would like to order the resistors at the same time from the same source to save on shipping. Anything special I should look for here? The originals look to be 1/4W, 2% carbon film resistors - nothing special. The two 13K ohm resistors (R8 and R224) are in the signal path, while the two 220K ohm resistors (R10 and R226) are shunted to ground.

What about the diodes in the PS bridge rectifier? Should I upgrade these while I'm swapping out the PS caps? If so, what should I use?

 

[MCM_Fan]

I haven't made any real progress on these since I started this thread two and a half months ago, but I had a breakthrough today. I found an EVM 12S with a torn cone on eBay at a favorable price. I pulled the trigger and arranged with the seller to ship it directly to GordonW, the SpeakerFixer, to recone and refoam it and make it into a proper Interface D woofer. I'll also be sending GordonW the original woofer shown in my first reply for the same recone and refoam treatment.

With two soon-to-be functional woofers, I was inspired to order the parts to convert the Interface B EQ into an Interface D EQ. I went with the Takman Metal Film (REY) resistors from Parts Connexion and also ordered Elna Silmic II caps to replace the eight 40-year old electrolytic caps in the EQ. Total parts cost: $9.10. Hopefully, I'll have a fully reworked Interface D EQ ready and waiting when the reconed woofers return from GordonW.

I'll also start taking things apart and will get the info and photos of the VMRs PeterSchut requested. While I have things apart, I'll also take a look at the crossovers. I don't remember much about them, other than that they were INCREDIBLY dusty after sitting unused in the previous owner's unfinished basement for over 20 years.

I'll probably order some replacement grill cloth, but it's too cold and damp to work with paints, finishes and adhesives this time of year. I don't have a dedicated workshop, so I have to do all my cabinet and finish work in the garage with the overhead door open. So, I'll probably have to wait until late Spring or early Summer to dive into the cabinet work. But, hopefully well before then, I will have some fully functional, if somewhat cosmetically challenged, Electro Voice Interface D speakers to listen to.

 

[MCM_Fan]

@PeterSchut - here's the photo of the back of one of the VMRs you requested. They both look the same and have the same part number.

I'll have to borrow a meter from the lab at work to measure the DC resistance.

 

[MCM_Fan]

And, for future reference, he's a "before" photo of one of the crossovers:

Little bit dusty. There were also spiderwebs, a few dead bugs and some mice droppings inside both cabinets. The good news is none of the critters seemed to have chewed on anything. So, hopefully this is mostly going to be an exercise in cleaning everything up and repainting the bases.

I'll definitely replace the one electrolytic cap in each crossover. Any reason I should consider replacing the instructors or resistors. I may do the resistors, maybe spring for some fancy Mills resistors, but I'm always leery of replacing inductors for fear of altering the DCR of the circuit.

 

[Brad Muller]

I think I recently saw somebody selling one of these somewhere.

 

[MCM_Fan]

I think I recently saw somebody selling one of these somewhere.

One of what, Interface D speaker, equalizer, woofer or VMR?

 

[MCM_Fan]

Could one of you Interface D owners please do me a favor and snap a close up photo of one of the badges on your grills and post it in this thread?

Mine didn't come with badges. The badges I've seen in photos are from a distance, but they definitely look different than the standard EV badges. Eventually, when I get to the point of redoing the grills, I'd like to add the badges for the sake of authenticity.