Hello All;
There is a lot of knowledge here that I hope to tap just a bit of.
Short story: I bought an SAE 2400L on the recomendation of a friend as “one of the greatest sounding amplifiers.”
The one I bought had a failed channel so I took it to a “guru” in a real audio electronics business. I asked that it be completely restored ie anything that would or could normally be suspect for an amp of its age be replaced.
As requested it came back with an AudioPrecision dyno sheet and from all angles it looked to be perfect. New power supply caps, output transistors and a bag full of other little goodies.
It played for about 20 minutes on my JBL 4435’s in my office then dropped a channel, bofore I could get to it, burning embers literally poured out of the bottom of it. Sad indeed.
Six months later it is still in the shop that repaired it.
The reason I ask if it may be possible that it is unrepairable is summed up in three stories I will keep as short as possible.
First I had another friend who went through the same thing with a repair guy somewhere in California. Sent his SAE 2400L amp in with a prepay, got a note that it was done and a request for payment, payment sent, another note that it had blown up on the bench and he was going to re-repair it, delay delay then no response and in the end he paid someont to steal the amp from him. 🙁
Second my friend who recomend I buy one said, later that one thing he remembered was that if you cycled the power off and back on just once rapidly like a power glitch that would start the fireworks show in his 2400L’s and in for repair they sould go. That’s less than comforting.
Third and possibly unrelated: In a converstation with one of the Crown repair facilities about a stack of Techron badged M600’s I have that I want to cycle through for rebuild I was asked to identify the input board because apparently the newer faster output transisters don’t always play well in older amps. The earliest boards in combination with the newer output transisters after rebuild can apparently occilate and be very difficult to track down and eliminate.
Fortunately all mine are the later boards.
With all this in mind, is it possible that these old SAE’s just can’t be made to behave?
I always thought SAE products were robust and reliable but a mains power glitch or a person switching it off and back on leading to repeated and certain destruction seems to indicate a possible design issue no?
I am not looking to identify or throw the shop under the buss. I liked what I heard before the fireworks but don’t know if I should just lick my wounds and move on.
I honestly appreciate any thoughts and help in the matter.
Thank you.
Barry.
There is a lot of knowledge here that I hope to tap just a bit of.
Short story: I bought an SAE 2400L on the recomendation of a friend as “one of the greatest sounding amplifiers.”
The one I bought had a failed channel so I took it to a “guru” in a real audio electronics business. I asked that it be completely restored ie anything that would or could normally be suspect for an amp of its age be replaced.
As requested it came back with an AudioPrecision dyno sheet and from all angles it looked to be perfect. New power supply caps, output transistors and a bag full of other little goodies.
It played for about 20 minutes on my JBL 4435’s in my office then dropped a channel, bofore I could get to it, burning embers literally poured out of the bottom of it. Sad indeed.
Six months later it is still in the shop that repaired it.
The reason I ask if it may be possible that it is unrepairable is summed up in three stories I will keep as short as possible.
First I had another friend who went through the same thing with a repair guy somewhere in California. Sent his SAE 2400L amp in with a prepay, got a note that it was done and a request for payment, payment sent, another note that it had blown up on the bench and he was going to re-repair it, delay delay then no response and in the end he paid someont to steal the amp from him. 🙁
Second my friend who recomend I buy one said, later that one thing he remembered was that if you cycled the power off and back on just once rapidly like a power glitch that would start the fireworks show in his 2400L’s and in for repair they sould go. That’s less than comforting.
Third and possibly unrelated: In a converstation with one of the Crown repair facilities about a stack of Techron badged M600’s I have that I want to cycle through for rebuild I was asked to identify the input board because apparently the newer faster output transisters don’t always play well in older amps. The earliest boards in combination with the newer output transisters after rebuild can apparently occilate and be very difficult to track down and eliminate.
Fortunately all mine are the later boards.
With all this in mind, is it possible that these old SAE’s just can’t be made to behave?
I always thought SAE products were robust and reliable but a mains power glitch or a person switching it off and back on leading to repeated and certain destruction seems to indicate a possible design issue no?
I am not looking to identify or throw the shop under the buss. I liked what I heard before the fireworks but don’t know if I should just lick my wounds and move on.
I honestly appreciate any thoughts and help in the matter.
Thank you.
Barry.
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A sad tale indeed. I suspect some of the PCB's inside contributed to the the embers you described. As these are often unique to a paticular model of amplifier they may be impossible to obtain new, however eventually one may be sourced from another amp. Hence the delays.
Your repair shop sounds like a competent business - just ask them.
I had a pair of SAE 2600 amps. They drove cutting machines for several years in a vinyl mastering business before I owned them. Both had lost backlight globes but had not required any repairs. Seems to me SAE are well made.
Good luck with yours.
Your repair shop sounds like a competent business - just ask them.
I had a pair of SAE 2600 amps. They drove cutting machines for several years in a vinyl mastering business before I owned them. Both had lost backlight globes but had not required any repairs. Seems to me SAE are well made.
Good luck with yours.
Hi Barry
Sorry to hear about the issues with your SAE2400L.
I believe your SAE was marginally stable after repair.
The symptoms are like you described, the amp blows up after a few minutes of play or it blows up when you switch OFF and then ON it immediately.
With vintages like SAE, the repair is much more involved than simply replacing transistors with newer ones because doing that will lead to instability.
One needs to re-calibrate the amplifier to ensure it's stable.
If this is my amplifier, I will discard the totem pole output and convert that to a conventional one ie. a single driver driving two power transistors in parallel.
Actually, I would rather double the number of power transistors if the heatsink can accommodate. That would be a total of eight transistors, four on either side.
The amp will at least stay alive when the speaker dips to 4 ohms.
Regards
Mike
Sorry to hear about the issues with your SAE2400L.
I believe your SAE was marginally stable after repair.
The symptoms are like you described, the amp blows up after a few minutes of play or it blows up when you switch OFF and then ON it immediately.
With vintages like SAE, the repair is much more involved than simply replacing transistors with newer ones because doing that will lead to instability.
One needs to re-calibrate the amplifier to ensure it's stable.
If this is my amplifier, I will discard the totem pole output and convert that to a conventional one ie. a single driver driving two power transistors in parallel.
Actually, I would rather double the number of power transistors if the heatsink can accommodate. That would be a total of eight transistors, four on either side.
The amp will at least stay alive when the speaker dips to 4 ohms.
Regards
Mike
Maybe try and find a schematic for the 2300, those use the same quantity of outputs, but in parallel. Not sure about the rest of the circuits, rail voltage, etc.
I use my 2300 with 4ohm (Magnepan) speakers.
I use my 2300 with 4ohm (Magnepan) speakers.
Thank you All;
I have a 2300 that has a 30 seconds on fault that makes a channel weak and distorted. I have not sent it in based on the outcome of the 2400.
I printed out an enlarged shematic of both the 2300 and 2400 but I haven’t looked at them for a few months, I will have another look but electronics at this level are currently beyond me.
I hope the shop will take the time to attempt to make it run.
Thank you all again.
Barry.
I have a 2300 that has a 30 seconds on fault that makes a channel weak and distorted. I have not sent it in based on the outcome of the 2400.
I printed out an enlarged shematic of both the 2300 and 2400 but I haven’t looked at them for a few months, I will have another look but electronics at this level are currently beyond me.
I hope the shop will take the time to attempt to make it run.
Thank you all again.
Barry.
I work on a lot of SAE, GAS and SUMO. Some of them are a PITA to work on because of the mechanics but all of the circuitry is similar. I've done several strip and start over rebuilds, MK31B, 2400, 2600 and just finished a MKIIICM. I've never had any problems with using modern parts and haven't had any returns either. This isn't rocket surgery!
Barry, I think we've talked on the phone about these amps.
Craig
Barry, I think we've talked on the phone about these amps.
Craig
I hope Craig is able to help you out.
But, back in the 70's, when SAE amps weren't yet 'vintage', I worked in a repair shop. Even then, our management had (before I even got there) refused to take them in for repair since they tended to go up in smoke with relatively little provocation and would keep coming back for re-repair. I don't know whether it was all models or just a few, but the had that 'rep' even back then.
But, back in the 70's, when SAE amps weren't yet 'vintage', I worked in a repair shop. Even then, our management had (before I even got there) refused to take them in for repair since they tended to go up in smoke with relatively little provocation and would keep coming back for re-repair. I don't know whether it was all models or just a few, but the had that 'rep' even back then.
In this family of amplifiers the only ones I've seen that have the "gone up in flames" syndrome are the GAS amplifiers, Ampzilla IIa and Son of Ampzilla, that used the Fairchild FT317 and 417 transistors. It seems every time I get one either they've been replaced already or are bad. The drive boards get scorched in a few places as the resistors burn up. I don't know if it is poorly chosen parts or defective parts. Maybe I've been lucky so far.
Craig
Craig
Hi Craig,
I also have an SAE 2400L that needs repair work and been having a difficult time finding a shop that can do the repair work. Any suggestions for a shop in the LOS Angeles area?
I'm rebuilding a 2400L at the moment. I'm in the high desert if that's close enough. PM if you want to discuss it.
Craig
Craig
Music1980,
I replied to your PM yesterday a few times but nothing is showing up. As for the filters capacitors Mouser has a couple that will do nicely.
DCM173080CC2B or 36DA183F100CC2A
Craig
I replied to your PM yesterday a few times but nothing is showing up. As for the filters capacitors Mouser has a couple that will do nicely.
DCM173080CC2B or 36DA183F100CC2A
Craig
somebody have schematic from SAE 2400 ?
Im not believe ... cant repair this amps
Professional Power Amplifier BGW 750B/C from 1978 or older one 750A from 1974 no problem to fix
I cant believe 1978 SAE 2400 impossibile to repair HI-FI Amp and work stable
please upload schematic
Im not believe ... cant repair this amps
Professional Power Amplifier BGW 750B/C from 1978 or older one 750A from 1974 no problem to fix
I cant believe 1978 SAE 2400 impossibile to repair HI-FI Amp and work stable
please upload schematic
SAE 2400 - Manual - Solid State Stereo Power Amplifier - HiFi Engine
Get an account and get a schematic...
Get an account and get a schematic...
That 2400 is in my shop now, filter capacitors, output transistors, small electrolytics is all that was replaced. Now there is one dead channel, new outputs are shorted along with several more parts on the drive boards. Now why did this all happen? I removed the heatsink assy. from the mother board to find rock hard thermal goop on the bias transistors. It was obvious that this portion of the amplifier was NOT serviced. PLUS the shop used thermal pads on the output transistor, no problem I use them too, BUT I don't use thermal compound with them. Boards are stripped and are being rebuilt with new available parts. It will live again AND last.
Craig
Craig