Just installed new the fuses in my speakers, and connect the amp straight to the speakers, before that I was using a amplifier selector box, so far the amp is not blowing anything, maybe the amplifier selector was causing all the trouble
This SAE amp is a virtual clone of the Acurus A250 amp. Picture of stock Acurus A250 board and schematic for the A250 is attached. Its obvious the same person/company designed these two boards. In fact, these appear to be amp modules and even the heat sinks, bolt patterns for the covers, etc, look identical. It'd be interesting to find out who, Mondial or SAE or some other company designed these boards.
The layout of the board is just about identical between the two. The input is a cascoded complimentary diff with active current sources, and the location of all of these components is identical between the Acurus and SAE boards. Mondial did install a bias adjustment circuit and pot. Mondial also has their thermal switch in the same place as the SAE amp only Mondial used a TO-220 style flat plastic pkg'd switch there versus the round thermal switch and subsequent cut-out in the board to accommodate the height of the switch for the SAE. Funny, none of the Acurus amps ever used an inductor in the output like the SAE has, but one of the old Acurus A250 schematics has an inductor hand drawn into it on the input. Mondial integrated the output zobel onto the board, where SAE had it hanging off of the binding posts. So it appears that the Mondial Acurus boards are updated versions of the older SAE design if I had to guess anyway....
I know that the Acurus A250 showed up sometime around late 1991 or early 1992. I have no knowledge of the vintage of the SAE A205 amp.
The layout of the board is just about identical between the two. The input is a cascoded complimentary diff with active current sources, and the location of all of these components is identical between the Acurus and SAE boards. Mondial did install a bias adjustment circuit and pot. Mondial also has their thermal switch in the same place as the SAE amp only Mondial used a TO-220 style flat plastic pkg'd switch there versus the round thermal switch and subsequent cut-out in the board to accommodate the height of the switch for the SAE. Funny, none of the Acurus amps ever used an inductor in the output like the SAE has, but one of the old Acurus A250 schematics has an inductor hand drawn into it on the input. Mondial integrated the output zobel onto the board, where SAE had it hanging off of the binding posts. So it appears that the Mondial Acurus boards are updated versions of the older SAE design if I had to guess anyway....
I know that the Acurus A250 showed up sometime around late 1991 or early 1992. I have no knowledge of the vintage of the SAE A205 amp.
It was built after 1988.
he company we know as SAE was
sold to DAK in 1988. Dak very famous for their catalogs
According to some websites the designer was Andrew Hefley
Is it possible to change the Toshiba output transistors to Mosfets ?
he company we know as SAE was
sold to DAK in 1988. Dak very famous for their catalogs
According to some websites the designer was Andrew Hefley
Is it possible to change the Toshiba output transistors to Mosfets ?
Looking at the schematic from post 1, I would guess vrery nice sound out of that old beast.
Only that two capacitors (C90 and C91) worries me but could be I'm wrong.
I would give it a try in verry high quality surrounding, good source, speakers... cables included, before any desidion about tweaking.
My feeling tels me you will be pleasantly supprised 😉
Only that two capacitors (C90 and C91) worries me but could be I'm wrong.
I would give it a try in verry high quality surrounding, good source, speakers... cables included, before any desidion about tweaking.
My feeling tels me you will be pleasantly supprised 😉
Not a simple change, and why would you want to? I mean if you want an amp with mosfet outputs then buy an amp that was designed to use mosfets. There are many many good mosfet amps on the market. If you do not have the capability to do this work yourself as a hobby side project then paying someone else is going to be very labor intensive and expensive. Any reputable tech would charge you a kilobuck or more to redesign and rebuild this amp into a tested and stable mosfet output amp and then you'd have an amp worth $100 - $200........
I could almost see redesigning the amp if it were in a mega buck high end chassis, like say a Krell KSA chassis with massive heatsinks and faceplate, but this is a low budget chassis with low budget heatsinks and low budget parts inside.
The schematic in Post #1 is in no way related to this amplifier. Your 1st big clue is the fact that the amp schematic in Post #1 uses sixteen 3281/1302 output transistors per channel. The SAE A205 amp that is pictured in post #1 only uses eight 3281/1302 output transistors per channel.
The Acurus schematic I attached in Post #43 is about as close as you're going to get to viewing this SAE A205 amp, but it should be about 98% accurate.
The earliest versions of the Acurus amps used 1 watt rated TO-92L MPSW92/42's for Q6,Q7,Q13,Q14. Later versions used the 1 watt rated ZTX657/757 combo in that location as shown in the schematic I posted. I see that this SAE amp used the MPSW 1watt parts on one side and standard 625mW rated MPS parts on the opposite polarity and then used heatsinks due to the lower wattage rating. I guess their supplier was out of the MPSW parts.
I see 1988 date codes on the primary capacitors in the amp shown in the 1st post and 1990 date codes on the primary capacitors of the amp shown later by the OP. Based on this I would surmise these amps were built late 80's and into the early 90's as the OP suggests in post #44. This aligns with the timeline of the Acurus amps that came out in the early 90's and used an upgraded version of this same board and circuit.
I see 1988 date codes on the primary capacitors in the amp shown in the 1st post and 1990 date codes on the primary capacitors of the amp shown later by the OP. Based on this I would surmise these amps were built late 80's and into the early 90's as the OP suggests in post #44. This aligns with the timeline of the Acurus amps that came out in the early 90's and used an upgraded version of this same board and circuit.
+1 @Chamberman.
I've worked with one of the earliest Acurus A250 where the PCB's came with a fixed resistor instead of a BIAS-pot, about 620-680ohms if my memory is correct.
Looking at the pictures on page 2, I'll bet the A250-schematic besides form small minutes as posted by @Chamberman would be almost identical to the SAE.
The 90's Acurus amplifier lineup are quite easy to make a decent performer with a few mods, I'll bet the SAE would benefit the same by the looks.
Regards
I've worked with one of the earliest Acurus A250 where the PCB's came with a fixed resistor instead of a BIAS-pot, about 620-680ohms if my memory is correct.
Looking at the pictures on page 2, I'll bet the A250-schematic besides form small minutes as posted by @Chamberman would be almost identical to the SAE.
The 90's Acurus amplifier lineup are quite easy to make a decent performer with a few mods, I'll bet the SAE would benefit the same by the looks.
Regards
Pretty much the only thing to do is a recap it with good quality parts ?
What about removing the resistors for the bias and installing pots, what do you think the bias number are ?
What about removing the resistors for the bias and installing pots, what do you think the bias number are ?
Installing a bias pot into the bias control transistor voltage divider network shouldn't be a problem. You can look at the Acurus schematic posted above to see how it's done. The Acurus A250 which uses the same heatsink but is running +/- 90vdc on the rails will bias at a max of 10mV as measured across one of the emitter resistors. However, Mondial spec'd it at like 5mV. If you're running really inefficient speakers then 10mV may be too high and overheat the stock heatsinks.
What is your final opinion for the A205 ?
Should spend money is a full restoration or move on to something better?
Should spend money is a full restoration or move on to something better?
Be aware that R20 in the Acurus schematic BIAS-network states 10Kohm. This is a mistake, and original 1Kohm is used here.
I'd say that you should listen to it and decide if its worth spending money on. The sound character isn't likely to change much with a standard recap unless there's something terribly awry.
Oh and the 100W Class A is ridiculous. The 100W/200W switch just selects a different tap on the transformer primary winding to give a lower DC rail voltage in 100W mode. This doesn't alter the output stage bias at all so the amount of Class A output power (which is negligible) is unchanged in either mode. The 100W mode will be good for operating the amp into low impedances and help to keep from overheating the small heatsinks. It would've been ideal if SAE had set the amp up to be operated in BTL mono mode with the switch put in 100W mode and the lower rails it would probably have allowed safe operation in mono mode with 4 ohm loads, but they didn't do that.
After a lot of digging around on the internet I think I have a reasonable idea of the lineage of this SAE amp and how it relates to the Acurus A250. Morris Kessler the creator of SAE also created ATI in the early 90's. ATI has built a lot of other manufacturers equipment, i.e. B&K, Adcom, Crestron, etc. It appears that the Acurus product line was built through the 90's by ATI in California. It sounds like a portion of the Aragon product line was also built by ATI during the same period. I found a few mentions of this manufacturing relationship in various forms out there. Morris Kessler sold SAE to Giorgio Moroder in 1988 and a year later Moroder sold the company to DAK who of course went bankrupt in the early 90's. Not too long after that ATI came into existence. My assumption is that the SAE 205 was probably the last amp design before SAE was sold and as such Kessler carried it in concept to the new company he created (ATI) with him. It was still produced through the early 90's however as the SAE A205. The Acurus A250 was mildly redesigned, the heatsinks appear to be slightly taller than the SAE205 and of course the board was mildly updated and modernized and the rear panel layout of the amp was altered for the better but at its core its essentially the same amp design from the SAE days.
thanks for all the info, is a keeper now, can you comment on the Toshiba outputs transistors ? are those any good ?
Toshiba 1302/3281 are used in a wide range of amplifiers and in most cases I've seen they still perform flawlessly after many years of music, including my own amplifier witch is daily run quite hard with a same transistors.
Let them be if they are OK
Let them be if they are OK
