They are running a business not a charity. They have all the design and setup costs amortised over ONE unit. It is not like knocking out hundreds or thousands of the same design in one go where those design/setup costs are divided by 100 or 1000.
yeah there are a few haters, but I have been running mine for a few years now without any issues.
But what is also funny is the continuous "they are unreliable", but when you actaully look at Counterpoint amps in context, most are 20+ years old before they go wrong, I had one that was made in 87 and only died a couple of years ago due to my stupidity. What other consumer electronics last 20+ years? Not computers, cellphones, cars (you think a Tesla or a Prius will still run in 20 years?) even kitchen appliances are hard pushed at that point....
And of course the IRFP240 is significantly better rated.....
This amplifier has been sitting in my shop since August without a solution. Too bad I've got many hours into restoring the main PCB, only to find out that the power transformer has a faulty winding.
If anyone is parting out an SA100, please let me know. I need a power transformer.
If anyone is parting out an SA100, please let me know. I need a power transformer.
I got a power transformer manufactured by a company in Poland. So now I'm doing the power up testing and it looks like I got a defective Nichicon capacitor! The one at right labeled C5 is in parallel with the one labeled C53 to its left. When I reached 50% line voltage on the variac, C5 started to vent. These are the DC filament smoothing caps. It was a royal PITA to get to the solder side of the PCB because there is no removable bottom plate. The whole board has to be disconnected from the MOSFETs, jacks, etc, to flip it up for solder side access. Super frustrated! Been waiting 7 months to get a transformer for this, and now this happens. This is a negative profit repair. It's become a personal challenge, as it is way over budget and now coming out of my personal time.
You should replace both caps - the other one will fail soon...
And since you have the board out, I recommend replacing BR2 (that also fails), mounting it on flying leads with the rectifier bolted to the chassis floor for heatsinking. That way it has a chance of actually meeting its current rating
2 hours later, I have replaced both capacitors with high voltage caps. In tracing out the paths, I found out they go to the rectifier on the 270V winding. No wonder the originals were exploded too! I'm baffled as to how this amplifier ever worked.
So I've traced the real 8 V DC supply and put in the appropriate caps.
Powered up the system slowly, eventually getting to full line voltage.
We have no filaments though. I have proper voltages at the Drain terminals of the MOSFETs (not installed yet), but no filament and no bias voltage. And, no voltage powering the 555 timer.
Given the torn up nature of the PCB traces having been eaten away by corrosion from the original exploded caps, I can only deduce that the through hole plating is gone and we've no continuity between solder and component side.
I cuss at the folks that designed this amp with no removable bottom plate! I've deal with more broken wires from flipping this PCB out for soldering. Every time I remove it, some other wire breaks off. The bias transistor wires have completely broken the pads on the PCB so I had to install headers and solder from below to make connections.
Not sure where the break in the filament supply bus is, but it's under one of the 6800uF caps most likely. Lacking a PCB layout drawing, it's a guessing game as to which traces on top need to be jumpered to which traces on bottom side.
Over 10 hours labor on this, not including online searching for a transformer!!
(And on the transformer, the one I got from Poland is about an inch too big to fit inside the chassis. Somehow they read my 115mm limit as 150mm because that's the transformer I received. I'm running it external to the chassis at the moment. They're going to make me a smaller transformer, but we first want to get temperature readings from this one with the amp running. Obviously, that's going to take a while due to no filaments).
So I've traced the real 8 V DC supply and put in the appropriate caps.
Powered up the system slowly, eventually getting to full line voltage.
We have no filaments though. I have proper voltages at the Drain terminals of the MOSFETs (not installed yet), but no filament and no bias voltage. And, no voltage powering the 555 timer.
Given the torn up nature of the PCB traces having been eaten away by corrosion from the original exploded caps, I can only deduce that the through hole plating is gone and we've no continuity between solder and component side.
I cuss at the folks that designed this amp with no removable bottom plate! I've deal with more broken wires from flipping this PCB out for soldering. Every time I remove it, some other wire breaks off. The bias transistor wires have completely broken the pads on the PCB so I had to install headers and solder from below to make connections.
Not sure where the break in the filament supply bus is, but it's under one of the 6800uF caps most likely. Lacking a PCB layout drawing, it's a guessing game as to which traces on top need to be jumpered to which traces on bottom side.
Over 10 hours labor on this, not including online searching for a transformer!!
(And on the transformer, the one I got from Poland is about an inch too big to fit inside the chassis. Somehow they read my 115mm limit as 150mm because that's the transformer I received. I'm running it external to the chassis at the moment. They're going to make me a smaller transformer, but we first want to get temperature readings from this one with the amp running. Obviously, that's going to take a while due to no filaments).
I ran a jumper from bridge rectifier negative to pin 4 of one of the 6DJ8s and now I've got filament voltage.
Also found out the 555 timer Vcc pin is at ground and the whole thing runs -9V below chassis reference.
After about a minute, I heard the relays click and I've got -1.3V on the gate pins. Next step is to install the MOSFETs and start testing and fine tuning the bias.
Also found out the 555 timer Vcc pin is at ground and the whole thing runs -9V below chassis reference.
After about a minute, I heard the relays click and I've got -1.3V on the gate pins. Next step is to install the MOSFETs and start testing and fine tuning the bias.
This is like EVERY power supply ever made. No need to exaggerate. C30 is too big for the 6CA4 rectifier diode though. This has a negative impact on the life expectancy of the 6CA4 but shouldn't affect the cap.
Remember this cap and all of the other parts in the box are now 30+ years old. So failures at turn-on (when stresses are maximized) are, sadly, to be expected.
ampexperts said:
After about a minute, I heard the relays click and I've got -1.3V on the gate pins. Next step is to install the MOSFETs and start testing and fine tuning the bias.
I suggest you adjust VR1 (the bias pots) to a minimum voltage on the gates. The IRF MOSFETS have a low gate threshold voltage. Can't recall if you have replace them at all in this repair
After about a minute, I heard the relays click and I've got -1.3V on the gate pins. Next step is to install the MOSFETs and start testing and fine tuning the bias.
I suggest you adjust VR1 (the bias pots) to a minimum voltage on the gates. The IRF MOSFETS have a low gate threshold voltage. Can't recall if you have replace them at all in this repair
My earlier notes said something around 1.1 volts on the gates (referenced to the source).
The other thing I am re checking is the pinouts on the Hitachi devices compared to the ISC brand devices.. they appear the same according to these data sheets..
The other thing I am re checking is the pinouts on the Hitachi devices compared to the ISC brand devices.. they appear the same according to these data sheets..
On the P junction, it will only adjust down to -1.164v. The N junction gate reads -0.2V.
I had the thought that maybe the offset adjustment was off, but that only causes the N junction to go to zero when I get the P junction to be -1.1v.
I'll recheck that I did the mods correctly, but failing that, it looks like this amplifier takes the record for fighting me at ever turn.
I had the thought that maybe the offset adjustment was off, but that only causes the N junction to go to zero when I get the P junction to be -1.1v.
I'll recheck that I did the mods correctly, but failing that, it looks like this amplifier takes the record for fighting me at ever turn.
Well this is what I got in both channels.. MOSFETs not installed yet. Maybe I should retest the four zeners, R14/15.
The best I'm able to do after adjusting the offset and cranking the bias pots full CCW, is -0.95 n P junction and + 0.95 on N junction.
I can't find the four zeners mentioned on the schematic. They don't exist on this particular board s/n 21H11.
I can't find the four zeners mentioned on the schematic. They don't exist on this particular board s/n 21H11.