SAE 2800 equalizer info sought

dogwan

dogwan

Dogwan
Anyone using?
Have service manual or schematics?

Just picked up a nice clean unit as "parts or repair... does not power up".

Got it home and 1st thing I checked was fuse. Instead of 1/8 (.125) amp it had a 1/4 (.25) amp fuse. Looked good but tested dead. Closest to spec I had was a 1/5 (.20) and put that it.
Hit power and no LED but did hear relay click.*
I pulled fuse and put Ammeter in-line and under power it's drawing about 240mA (0.24A). That would explain the larger fuse.

Have not tested for sound or function yet. The fact that it's drawing about 2x the current of the stock fuse rating tells me it's not too healthy. At least it's not shorting or drawing an insane amount of current. Looks like I will need to tear into this unit before using.

Hard to find any info on the SAE 2800. There is a person selling a "rebuild service" on eBay for about $230 and that posting has the only nudie shots I've been able to find. Looks like about 6 quad op-amps are involved in the circuit. I do see there are a few handfuls of electrolytics that probably should be replaced. Hopefully any significant problems are in the power supply or the electrolytic caps.

I'm hoping I can get this beauty back to her former glory. Apparently, this was the EQ to have back in the day from what I've read. I have seen two different MSRP of $550 and $700 in 1978 dollars. That explains why they are pretty rare.

Any help of info is greatly appreciated.

* in searching for schematics I found a couple references to a service bulletin about LED power modification, so maybe LED is burnt due to not having the correction done?


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lol, that is some EQ. If you had a thermal camera, you could possibly find what is getting hot. Otherwise, use the good old finger.
 
Better get a gallon of Deox-it Faderlube..:biggrin: All those sliders a probably scratchy /dirty.
 
I have one in for repair now but haven't touched it yet. I do know it has one broken slider. Musicparts has the schematic, etc for it.

Craig
 
Ohh! you did good! this is the one all right!. I have the SAE 2100 pre-amp, which has only 2 frequencies and are commun to channels A and B.
Not a tech here but, i would still try it out on a cheap test system?.
There are lots of OPAMPS in there so one or more could be thirsty for power...
Good luck with that SAE, it's a niiice piece!.
(If you find the SAE 2100 or, SAE 1800 service manuals, there are lots of similarities to help you).
 
Well, got her open and even without schematics I could run a quick test on PS. Luckily there are labels indicating the + and - 15v legs as well as a 26v leg. There is also a 48v relay. Getting no voltage on the 26v leg. On the bi-polar 15v legs I am getting negative voltage only...no positive voltage. This is netting about 1vdc only across the +Vs and -Vs pins of the opamps. The relay doesn't activate like I thought (it must have been the sound of the power switch).

I don't see any signs of hackery so that's good.

I did notice that a couple of the pins of the relay have solder bridges between them. It looks intentional, but I can't tell yet if that is stock or someone tried to bypass the relay?

Also, right off the bat I noticed on the PS board there is a Jfet that has the GDS labelling that doesn't match the component datasheet. Wouldn't surprise me if it's a mis-print on the board as the part and solder pads look original.

I did find schematics online, but it will cost me $20 for a reprint for schematics only. Since this is from the late 70's I gotta think someone in our hobby has them and wants to share.

20200703_103053.jpg

20200703_103046.jpg
 
If you're not going to pop for the schematic I will but you'll have to give me any PSE schematics you have.:)

Craig
 
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llwhtt said:
If you're not going to pop for the schematic I will but you'll to give any PSE schematics you have.:)

Craig
Click to expand...

Hahaha, there are no PSE schematics! Seriously. I've talked to Dean Klinefelter on the phone and if he has them, he's not releasing them.

Looks like the SAE schems are available here a little cheaper....
https://www.stereomanuals.com/man/r...2e4vHM7EdaV3-k-KarzhBKCBtS9bEzM_bW7tkpIh-BGm4

In all seriousness, I'm not morally opposed to paying for the docs, or someone monetizing them. But, for hobbyists like us where we're likely only going to use them once and we're trying to restore these cost effectively I am willing to take my time. I once paid an exorbitant price to someone in the UK for a really poor scan of a Hitachi IA-1000 service manual. It was almost useless. Then a month later someone posted a really clean professional scan on HifiEngine. Oh well.
 
I usually use Musicparts as they are a download and pretty good copies. I'll go ahead and get it. PM me with email address.

Craig
 
dogwan said:
Well, got her open and even without schematics I could run a quick test on PS. Luckily there are labels indicating the + and - 15v legs as well as a 26v leg. There is also a 48v relay. Getting no voltage on the 26v leg. On the bi-polar 15v legs I am getting negative voltage only...no positive voltage. This is netting about 1vdc only across the +Vs and -Vs pins of the opamps. The relay doesn't activate like I thought (it must have been the sound of the power switch).

I don't see any signs of hackery so that's good.

I did notice that a couple of the pins of the relay have solder bridges between them. It looks intentional, but I can't tell yet if that is stock or someone tried to bypass the relay?

Also, right off the bat I noticed on the PS board there is a Jfet that has the GDS labelling that doesn't match the component datasheet. Wouldn't surprise me if it's a mis-print on the board as the part and solder pads look original.

I did find schematics online, but it will cost me $20 for a reprint for schematics only. Since this is from the late 70's I gotta think someone in our hobby has them and wants to share.

View attachment 1915806

View attachment 1915807
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I think it’s probably more like SAE labeled the board with what they originally started with and changed to something else later on. Seen this a lot on their stuff.
 
hamrules said:
I think it’s probably more like SAE labeled the board with what they originally started with and changed to something else later on. Seen this a lot on their stuff.
Click to expand...

Hmmm, maybe. I'll have to pull the transistor and if it's still good I can read what legs are which (pinout). It does concern me that the holes are labeled differently than the corresponding pinout of the existing transistor and even if they changed parts the Gate, Drain, and Source leads should still go to the same through-holes.
 
How are you doing on this? It might be an OpAmp that has shorted. Hope you get the issue isolated and the unit repaired.

I used a 2800 in the 90's. I'll never let the 180 go as I use is all the time when transferring old tape recordings. The 180 is half of the 2800 and more compact but without the clip indicators.
 
safebet said:
How are you doing on this? It might be an OpAmp that has shorted. Hope you get the issue isolated and the unit repaired.

I used a 2800 in the 90's. I'll never let the 180 go as I use is all the time when transferring old tape recordings. The 180 is half of the 2800 and more compact but without the clip indicators.
Click to expand...

This is likely to be a back-burner project for a bit. Now that I've determined the PS section is shot I need to order some parts. My priority project right now is finding a job before I start spending money on parts. I probably shouldn't have even spent money on picking up the 2800, but could not resist when I saw it.
 
dogwan said:
This is likely to be a back-burner project for a bit. Now that I've determined the PS section is shot I need to order some parts. My priority project right now is finding a job before I start spending money on parts. I probably shouldn't have even spent money on picking up the 2800, but could not resist when I saw it.
Click to expand...

Anything new on the this SAE 2800?
 
dogwan said:
Well, got her open and even without schematics I could run a quick test on PS. Luckily there are labels indicating the + and - 15v legs as well as a 26v leg. There is also a 48v relay. Getting no voltage on the 26v leg. On the bi-polar 15v legs I am getting negative voltage only...no positive voltage. This is netting about 1vdc only across the +Vs and -Vs pins of the opamps. The relay doesn't activate like I thought (it must have been the sound of the power switch).

I don't see any signs of hackery so that's good.

I did notice that a couple of the pins of the relay have solder bridges between them. It looks intentional, but I can't tell yet if that is stock or someone tried to bypass the relay?

Also, right off the bat I noticed on the PS board there is a Jfet that has the GDS labelling that doesn't match the component datasheet. Wouldn't surprise me if it's a mis-print on the board as the part and solder pads look original.

I did find schematics online, but it will cost me $20 for a reprint for schematics only. Since this is from the late 70's I gotta think someone in our hobby has them and wants to share.

View attachment 1915806

View attachment 1915807
Click to expand...

I have one of these that I repaired and upgraded. The relay is for muting the outputs on power up. You should hear a click about 5 seconds after power up. Hopefully the IC's were not damaged if the power sully is bad.
 
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Drummerboy2 said:
Anything new on the this SAE 2800?
Click to expand...

Unfortunately no progress on my unit. I was actually thinking I might put together a Mouser order soon and at least replace all the transistors in the power supply. I haven't worked since January so I am being extremely frugal.
 
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