Sorry for the delay. I am travelling for the day job.
There is nothing simple left to do. I could direct you to the appropriate test point table and get you to measure the dc test points.
But, this preamplifier is difficult to work on and is quite complex.
If this is your first time under the hood of a piece of equipment, then this unit is definitely not the place to start.
Send me a private message and we can discuss what your options are
There is nothing simple left to do. I could direct you to the appropriate test point table and get you to measure the dc test points.
But, this preamplifier is difficult to work on and is quite complex.
If this is your first time under the hood of a piece of equipment, then this unit is definitely not the place to start.
Send me a private message and we can discuss what your options are
Thanks I appreciate the help. I only have experience with simple electronics and even then I'm really only a "Parts Changer" - I did speak with the local vintage Mcintosh repair guy and he said he'd take a look at it so I'll probably start there.
I've worked on one of these before for a client. I went backwards from the output with a scope, looking for the test signal, then forwards from the input jack, looking for the place the signal stopped.
It stopped at a black piece of plastic that looked like the cap for a container of mechanical pencil lead, cylindrical. No part number or anything, and it wasn't a capacitor. Went to unsolder it, and the cap came off in my hand, almost full of heatsink grease. It was covering up the input JFET that Counterpoint tried so desperately to hide in their flagship ""All Tube" (signal path anyway) preamp. Replaced it with a new JFET, and music happened.
I suggest starting with those first, as I have indeed seen one fail, and, it might be the cheapest part to replace in that unit 🙂
Don't get me wrong, it sounded great when we got it playing!
It stopped at a black piece of plastic that looked like the cap for a container of mechanical pencil lead, cylindrical. No part number or anything, and it wasn't a capacitor. Went to unsolder it, and the cap came off in my hand, almost full of heatsink grease. It was covering up the input JFET that Counterpoint tried so desperately to hide in their flagship ""All Tube" (signal path anyway) preamp. Replaced it with a new JFET, and music happened.
I suggest starting with those first, as I have indeed seen one fail, and, it might be the cheapest part to replace in that unit 🙂
Don't get me wrong, it sounded great when we got it playing!
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They weren't trying to hide the JFET - it is clearly mentioned in their promotional literature of the time.
The plastic cover is to keep air currents away from it so that its temperature is more stable.
There are components placed under the PCB for the same reason
The plastic cover is to keep air currents away from it so that its temperature is more stable.
There are components placed under the PCB for the same reason
Was this issue ever resolved? Just wondering if the guy ever checked the "Monitor" points with a meter or scope? I see there is "Pre RIAA" check point just to see if the signal is even getting to that point. If all the Green Lights are on its got to be something simple if its related to both channels.
Hi The issue has NOT been resolved. After trying all the basic troubleshooting and since I don't have scope and skills to use one, I've decided to try and find a tech that can repair it. I did try replacing the tubes in the phono section and still not working (previous tubes were hand marked with their locations) Tubes do light up and all leds on phono board are green.
Regardless I've really been enjoying the line stage and have been listening to it daily with HD streaming and CDS. Really fantastic. I almost hate to send it out but I'm really curious to hear the phono.
Regardless I've really been enjoying the line stage and have been listening to it daily with HD streaming and CDS. Really fantastic. I almost hate to send it out but I'm really curious to hear the phono.
@JXLSTUDIO if both channels are not getting any sound it's not a circuit but most likely a connector or switch position. How do you have your switches for the Phono section set on the front panel? Should be at 47k for MM and Phono for output. You can also set the TAPE SEND switch to Phono and see if you are getting anything on that output from the back of the preamp.
I have a SA-1000 that had the Phono input cutting out on both channels. After looking the pcb with a magnifying glass I saw that where the input switch selector when into the PCB there was some cracked traces and I had to do some pcb trace rework to fix it properly. Yours is different but still worth to look it over very carefully with the unit powered off. Voltage measurement may have to be taken to see if all the proper voltages are getting to where they should.
Like I said, it has to be something not set right. Please check the output with switches set to how I said. If you are getting sound out of the tape send then its something else not set right.
I have a SA-1000 that had the Phono input cutting out on both channels. After looking the pcb with a magnifying glass I saw that where the input switch selector when into the PCB there was some cracked traces and I had to do some pcb trace rework to fix it properly. Yours is different but still worth to look it over very carefully with the unit powered off. Voltage measurement may have to be taken to see if all the proper voltages are getting to where they should.
Like I said, it has to be something not set right. Please check the output with switches set to how I said. If you are getting sound out of the tape send then its something else not set right.
@Drummerboy2 I have tried the input set on the main PCB board for MM and the front knob as phono input. I also just tried the Tape SEND back to my other amp as per your suggestion and everything is still a NO GO. I've also tried MC and many many other combinations. Like I said the line stage works stellar. I could see it being a fail near or at the input selector as it's both channels. It's a bit out of my league as there are three boards- front, main (suspended) and back with fragile looking connections and I'm wondering if it would take an experienced tech to move and check them correctly. Thanks for your info about the input Selector.
If you have the complete schematic, a decent tech could signal trace the problem down in a few minutes.
Most likely, given the symptoms, is signal relay K6 at the phono output that is not working.
Or other bad connections, etc. that result in the same effect.
Most likely, given the symptoms, is signal relay K6 at the phono output that is not working.
Or other bad connections, etc. that result in the same effect.
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Per rayma about the K6 relay, does the RED LED come on for K6 when switched to Phono? As you go through the switch settings each LED should like up when you select that input you want.
Yes, even if the K6 LED lights normally, the K6 relay may still not actuate properly.
So then you measure the voltage directly across the K6 relay coil contacts to see if it gets power.
Then if it does, ohm across the switch contacts to see if they close properly.
But if both channels are out, probably K6 is not getting any power due to a problem in the control circuit.
So then you measure the voltage directly across the K6 relay coil contacts to see if it gets power.
Then if it does, ohm across the switch contacts to see if they close properly.
But if both channels are out, probably K6 is not getting any power due to a problem in the control circuit.
Watch out - - HIGH VOLTAGE!
And a slip of the probe can do extreme damage to the circuit.
Working on this unit is for experienced technicians only.
And a slip of the probe can do extreme damage to the circuit.
Working on this unit is for experienced technicians only.
There should be some clicking when you select the Phono Section if the relay is working.
that is true but he doesn't have much experience in this type on measuring points. I'm more worried he may slip and cause another or hurt himself.
It's very likely that an inexperienced person would make a mistake and damage themselves, or the circuitry,
working on this very complicated, high voltage unit. I would not, and have not, recommended him doing this.
He said he would find a tech to work on it in post #29. All we have done here is discuss the problem.
working on this very complicated, high voltage unit. I would not, and have not, recommended him doing this.
He said he would find a tech to work on it in post #29. All we have done here is discuss the problem.
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