SAE 2200 Rebuild

[sabrefencer]

The 330k ohm was great for getting QC at or above 1v, but pushed DC offset too high. So I tried a few more combinations.

Dropped the 330k ohm (R27/R29, R28/R30) to 240k ohms, and kept the 2.0M trimmers in place. This brought maximum QC down to about 950mV and lowered DC offset to 20 to 25mV. Better on the DC offset than the 330k, but not really much different from where I started today with the 220k and 2.2M fixed combination.

Next, I pulled the 2.M trimmers and put the 2.2M fixed back and kept the 240k resistors. This gave me the following: ChA: QC=995mV, DC offset = 16mV, and for ChB: QC = 975mV, and DC offset = 20mV. This is slightly better than when I had the 220k resistors and the 2.2M fixed, so I think I am done for now. Very close to the 1.0v target on QC on both channels, and DC offset at half the max spec. I think that is as close as I'm going to get it.

By the way, all of the measurements I have been taking were with line voltage set at 120v through a Variac. My wall voltage is 122v and sometimes 123v. When plugged directly into the wall QC on ChA is slightly above 1.0v, and ChB is 992mV. I think the elusive (unpublished/guestimated) goal for QC of 1.0vDC has been achieved.

Time to do one more bias check and put the covers back on.

What do you think?

 

[hamrules]

Sorry keep forgetting you have 68ohm resistor's in those locations.

 

[sabrefencer]

Bias set to 1.158vDC on both channels. Covers are back on. Will let it be for a while. Transformer hum is still there (not coming out of the speakers), but I did notice that the hum diminished when I put the amp under load during distortion testing. That tells me that I just need to turn it up

Next up, a 2400L, that will generate more questions as I put together my parts order.
Thanks to Craig @llwhtt and @hamrules for your help.

 

[Leonardo9342]

Good evening, I have a power supply problem with my SAE 2200.
I live in Italy and I have a SAE 2200 non-export model so "120 V. 50/60 HZ AC."
In Italy the current is "240 v 50/60 HZ AC." and I would need to modify the transformer or buy a power supply specifically to use it.
What do you recommend?

As a stupid person, I connected the SAE2200 to the power supply and to the preamplifier and the lights turned on and moved a little and I could hear the music at a low volume.
Do you think I have broken something? Should I also change the power supply?
I would need some help to get it working again.
Thank you all!

 

[darwinwandle]

It is amazing you didn't blow a fuse or circuit breaker. Most likely you fried the transformer. You can do tests with all fuses out and unplugged and test input to output windings with an ohm meter. Connect one meter lead to input prong and other meter lead to each output winding and see if they are open circuit. Then test each secondary to see if they are shorted or each winding is still isolated.

 

[darwinwandle]

Bias set to 1.158vDC on both channels. Covers are back on. Will let it be for a while. Transformer hum is still there (not coming out of the speakers), but I did notice that the hum diminished when I put the amp under load during distortion testing. That tells me that I just need to turn it up

Next up, a 2400L, that will generate more questions as I put together my parts order.
Thanks to Craig @llwhtt and @hamrules for your help.

If you can get some transformer shellac from an electric motor rebuilder and determine the type (ask him thinner he uses) thin the shellac and expose the transformer windings best you can and pour it in moving the amp in all positions to get it to leak into windings. If he doesn't know type of shellac Krylon is one of the biggest manufacturers of motor and transformer sealants. The 2 best thinners are Toluene and Xylene available at Home Depot. Toluene is water accepting and Xylene is petroleum distillate not water absorbing either should work with Krylon products one just thins and penetrates better without dissolving other paints and glues. Toluene is less damaging to existing parts rubbers paint glue and electronic components Xylene can eat into a lot of items even wire plastic insulation. If in a pinch use Varathane Polyeurathane from Home Depot and thin with Toluene. If you pour it in and plug in transformer switch it on for a second or 2 a few times to get the windings to vibrate it into the cracks and gaps. unplug it and stuff some rags in where it is leaking out. Put in a really warm place to evaporate thinner out and if it has all visibly disappeared where you poured it in pour in a bit more not thinned out. Let it dry really hard 2 days in warm place then plug it in and see if you stopped the windings from vibrating. If not best to take transformer out and if you don't think you can fill it up take it to an electric motor re-winder and get them to put it in their dip tank. And, then their heat chamber. Only do all this after you have made sure you don't have any electronic ground loops between the inputs and speaker outputs and the chassis grounds. I have connected a jumper wire from amp chassis to 3rd prong in a wall outlet and to pre amp and amp to get rid of electronic hum.




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[shooters68]

Hello everyone, I'm revisiting this very interesting post to get some information, I also own an SAE2200, I read on this thread that some bulletins have been released regarding some electronic updates on this power amplifier, do you know where I can find them?

I also read that James Buongiorno has released a file with all the components to modernize the Sae 2200, I looked for it everywhere but I couldn't find it, can you help me?

 

[llwhtt]

I have the Service Manual with bulletins, start a conversation with me and include your email.

Not heard of the JB 2200 update but I sure am interested, I'm going to start my search.

Craig

 

[hamrules]

There’s an old thread in groups.io that I think might be what’s being talked about here. It’s titled “completely lost”.