Comments on: Adjusting an SAE A202 Amplifier DC Offset

By: David Aldridge

David Aldridge — Fri, 16 Oct 2020 19:59:59 +0000

Hello. Maybe someone can shed some light on a issue here. I have a full SAE rack system. Two 502 amps running in mono mode. Recently one of the led displays is only reading one direction. Bad connector? I haven’t been in it yet. Why I ask.
Thanks in advance. David

By: peter

peter — Wed, 07 Oct 2020 01:12:52 +0000

I just acquired a SAE P102 pre amp & a AES AS02 Amp. I have a receiver and I can get the pre amp to acquire the signal and the bars move up & down, but I cannot get the speaker to put out any sound. The middle light and the 2 speaker lights come on the AS02 fine (comes out of standby mode). Could a fuse still be blown (it is ceramic and I am new to amps- cant see if its blown). Also wondering why a small plastic piece is preventing the unit from being taken out of stereo mode also. Any help would be appreciated.

By: Keith Neufeld

Keith Neufeld — Mon, 14 Sep 2020 15:31:17 +0000

Brian, I believe the click on channel selection is the relay. I suspect a problem in the power amp stage. A service tech experienced in component-level repair of transistor circuits should be able to fix this for you … and of course, they’re getting harder to find.

By: Brian

Brian — Mon, 01 Jun 2020 02:49:18 +0000

Hello,

Was gifted a second hand A202 that I used with some smaller dj speakers. The sound, to me, was fantastic. One day I was using it and volume just cut off completely. A relative took it to get repaired, and it came back with the same problem. Unit powers up, clicks when making channel selection, and meter responds to input sound, but no sound coming out.

Do you think this could be a blown transformer, a malfunction of the relay function mentioned in the top post, or a dc issue? Would it be super expensive to get this repaired?

Thank you

By: Donald

Donald — Wed, 26 Feb 2020 23:10:52 +0000

Is the SAE A202 considered a 2 channel amp or 4 channel amp?
If 2 channel amp that would be 100w x 2 right?
If 4 channel amp that would be 100w x 4 right?

By: Daniel

Daniel — Sun, 28 Jan 2018 06:51:11 +0000

I bought a A502 from a second hand shop and it would not fire up. Long story short, I replaced a transistor and a resistor in the safety circuit. Seems the resistor value that is published in the schematics I have is wrong too and I read a lot of people do repeat repairs because of it. I also saw oily residue all over the amp so I figured the caps were done after 30 years. I did a full recap and replaced 52 caps in total, including the main caps. The amp lives again. I have the schematics but I do not have any of the procedures used to calibrate the amp. I looked at your A202 post regarding DC offset and observed 4mv of offset on my amp. The strange thing is if I move the pot to adjust offset it increases and then settles back down to 4mv no matter what position the pot is in. It is almost as though this thing is auto adjusting back down to 4mv. I see there are test hoops soldered onto the main board. I imagine there is a formal procedure to align this amp. Do you have the documented procedures?

By: Mohan Siribaddana

Mohan Siribaddana — Sat, 08 Jan 2011 02:23:49 +0000

Hi Keith,

I have Classe Model 20 pre-amp which has been coupled with Marantz MA500 Mono-blocks. Recently while listening to music, the pre-amp went into protection mode while green led indicator was blinking. I immediately switched it off and allowed it to rest for some time. Also, I checked the associated equipment and cables, I did not find any faults.

After a long rest, the Classe pre-amp was switched on again, It started to work normally for 4-5 minutes and later again went into protection mode. However, the green led light indicator was continuously blinking without the amp getting into steady state.

I contacted the Classe Canada, they informed me that this abnormal behavior of the amp was more likely to be due to DC offset.

Kindly let me know how I should get over the problem. Classe was nice enough to send me the schematics for the discontinued Classe Model 20.

If you want the schematics, how can I upload it to you for your kind perusal.

Cheers

By: Keith Neufeld

Keith Neufeld — Sun, 05 Sep 2010 20:26:52 +0000

Sam, if the offset trimmers aren’t working, I don’t know what to suggest!

I just emailed Jim at Jim’s SAE site to see about buying a copy of his A202 service manual. If it has schematics, I’ll have a look and see whether that generates any new ideas.

By: Sam

Sam — Wed, 01 Sep 2010 02:47:30 +0000

Hi Keith: I have a dusty old A202 that plays fine but heats up badly causing the caps to become noisy. The bias adjustment is clearly labeled. Do you know the test points and the correct reading? I measured the DC offset at 150 mV and 50 mV respectively, which is too high. The DC offset trimmers do not seem to have an effect on these figures. Any ideas and advice would be greatly appreciated. Thanks, Sam.

By: Keith Neufeld

Keith Neufeld — Sat, 10 Apr 2010 12:40:22 +0000

Jason, you’ll need a separate preamplifier to plug between your stereo’s line outs and the amplifier or an “impedance converter” (may go by other names) to connect between the stereo’s speaker outs and the amplifier.

I’d recommend changing out to a separate preamp, because you’re probably already missing the bass by the time you get out the speaker outputs and the SAE amp won’t put it back in.