Thanks All! No worries, I'm familiar with high voltage and my limitations. I'll just check the K6 LED again.
I could not find a K6 LED with my own eyes or in the Service & Owner's manuals. Not sure if it has a different number. That said, I did hear a relay click for all the input stage settings and the tape send settings. The phono/input/Tape 1 selection knob is seperate and goes thru a long shaft to a pot on the back PCB board and does not seem to have an associated relays or if it does have them I can't find it.
Attachments
K6 relay will be where R23 is, the K6 relay should be to the right of R23. That LED to the right of R23 and above K6 relay should be lit when you select the Phono section "Tape Send" switch.
Hi,
I purchased this piece from JXLstudio and I can confirm that I cannot get any signal from the phono input.
I set both internal switches to MC and inserted the shorting plugs to the MM inputs.
The jumpers for the buffered outputs were both set to disable.
I inserted all the tubes in the correct tube sockets per the board and the manual.
I set the main output switch to phono.
Tape Send was set to Disable.
Turned the preamp on and it initialized and then the LED went solid amber.
All of the green LEDs on the board were lit per the photo previously posted.
I unmuted the preamp and the Ready LED lit up and the red “UNMUTE” LED on the input board came on.
No signal heard as I turned the volume across the full range.
I switched the main output to Line and set the selector to CD and the preamp passed a signal in both channels.
I switched the main output to Tape and the preamp passed signal in both channels.
I don’t know where the K6 LED is located, but above the row of relays on the input board, the corresponding LEDs all seemed to work as I changed the input selector.
When I set the Tape Send switch to phono, TS Phono lit up. When I set it to Line, both the TS Line and TS Phono lit up.
That’s the only strange behavior I could see inside the preamp.
So where can I find the K6 LED?
I purchased this piece from JXLstudio and I can confirm that I cannot get any signal from the phono input.
I set both internal switches to MC and inserted the shorting plugs to the MM inputs.
The jumpers for the buffered outputs were both set to disable.
I inserted all the tubes in the correct tube sockets per the board and the manual.
I set the main output switch to phono.
Tape Send was set to Disable.
Turned the preamp on and it initialized and then the LED went solid amber.
All of the green LEDs on the board were lit per the photo previously posted.
I unmuted the preamp and the Ready LED lit up and the red “UNMUTE” LED on the input board came on.
No signal heard as I turned the volume across the full range.
I switched the main output to Line and set the selector to CD and the preamp passed a signal in both channels.
I switched the main output to Tape and the preamp passed signal in both channels.
I don’t know where the K6 LED is located, but above the row of relays on the input board, the corresponding LEDs all seemed to work as I changed the input selector.
When I set the Tape Send switch to phono, TS Phono lit up. When I set it to Line, both the TS Line and TS Phono lit up.
That’s the only strange behavior I could see inside the preamp.
So where can I find the K6 LED?
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I also connected a headphone amp to the Tape Send output. I was able to get sound from the linestage, but not the phono.
https://www.diyaudio.com/community/attachments/img_8876-jpg.1196763/
There are jacks on the board PRE RIAA Monitor , is signal there or not ?
There are jacks on the board PRE RIAA Monitor , is signal there or not ?
While looking at those jacks, I noticed that Q4 and Q104 are both missing. Could this be the root cause?
Does anyone know a good source for them? Or a suitable replacement?
https://www.mouser.com/ProductDetail/InterFET/P1087?qs=OxRSArmBDfw4K1CdF692eQ==
Will this work?
https://www.mouser.com/ProductDetail/InterFET/P1087?qs=OxRSArmBDfw4K1CdF692eQ==
Will this work?
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It appears to be the same part, but I couldn't get a good hit on the noted QFP1087 in the schematic. I'm also not sure if something like a J74 might not be a better substitute, or if there are others that would be better suited.
I did mention about him checking the RIAA Test point and if he had signal there in post #27. Never got an answer. If he would have checked that and depending on what he saw we would have gotten our answer if the signal was even making it there.
Nice find! well if you can get the parts to put in there you will have a very nice Phono section with a nice linestage. 🙂 I can't remember if Mike Elliott had a mod for these transistor inputs. I know he did remove the Mosfet on the output of the Tubes in his SA-1000 preamp. Most likely it would be the same as on the SA-3000 preamp since the SA-3000 and SA-5000 phono section are very close in design and input stages.
Here’s what the old Alta Vista site said about the SA5000 phono:
There are two ways the SA-5000 can be modified to use MC stepup transformers:
1. For The Fellow That Knows What He Wants: The original MC step-up JFET is removed from the input stage and replaced with a pair of MC transformers. The MM inputs remain available for MM use. Not only does the flexibility of the preamp remain unchanged, there is an additional benefit even when listening to MM cartridges! This is because even when in MM mode, the SA-5000's MC JFET is connected from the tube cathode to ground. It's biased fully "on" and "looks like" a pure resistance to the phono tube, but as we know, using the very best-sounding resistors is important in an audio product and that JFET in the tube's cathode circuit is not a great-sounding resistor. By installing an MC transformer and removing the MC JFET, both the MC and the MM inputs benefit. THIS IS THE BEST-SOUNDING CHOICE!
2. For The Man Who Is Afraid To Commit: If you know you will not be using an MM cartridge, we can keep the existing MC input jacks and their associated JFET step up circuitry. But we take the MM jacks and connect then to a pair of MC transformers. Both sets of inputs become MC inputs, and both are available for use (using the internal MC/MM switch to select between them). One set provides gain via a JFET, and one via the new transformers. However please note that unlike the option above, the original MC JFET which is located between the input tube's cathode and ground in classic cascode fashion is not removed. When the SA-5000 is in MC mode, the MC cartridge signal is connected to the JFET which provides low-noise signal gain, driving the tube through its cathode. But even when we select the MM (new tranformer-driven MC inputs) that JFET is still in the tube's cathode. It is biased on so hard that it looks like a resistor so it should not color the sound . . . but you can still hear the its subtle "JFET-y" sound: a slight brightening, a slight grain and mist on the treble.
There are two ways the SA-5000 can be modified to use MC stepup transformers:
1. For The Fellow That Knows What He Wants: The original MC step-up JFET is removed from the input stage and replaced with a pair of MC transformers. The MM inputs remain available for MM use. Not only does the flexibility of the preamp remain unchanged, there is an additional benefit even when listening to MM cartridges! This is because even when in MM mode, the SA-5000's MC JFET is connected from the tube cathode to ground. It's biased fully "on" and "looks like" a pure resistance to the phono tube, but as we know, using the very best-sounding resistors is important in an audio product and that JFET in the tube's cathode circuit is not a great-sounding resistor. By installing an MC transformer and removing the MC JFET, both the MC and the MM inputs benefit. THIS IS THE BEST-SOUNDING CHOICE!
2. For The Man Who Is Afraid To Commit: If you know you will not be using an MM cartridge, we can keep the existing MC input jacks and their associated JFET step up circuitry. But we take the MM jacks and connect then to a pair of MC transformers. Both sets of inputs become MC inputs, and both are available for use (using the internal MC/MM switch to select between them). One set provides gain via a JFET, and one via the new transformers. However please note that unlike the option above, the original MC JFET which is located between the input tube's cathode and ground in classic cascode fashion is not removed. When the SA-5000 is in MC mode, the MC cartridge signal is connected to the JFET which provides low-noise signal gain, driving the tube through its cathode. But even when we select the MM (new tranformer-driven MC inputs) that JFET is still in the tube's cathode. It is biased on so hard that it looks like a resistor so it should not color the sound . . . but you can still hear the its subtle "JFET-y" sound: a slight brightening, a slight grain and mist on the treble.
Not that JFET is missing , it's the one in the second stage. And are not the same
Anyway I would not modify the circuit so easily , only after much listening and thinking . Even if you remove one JFET the whole thing is full of transistors and buffers because it is what it is - hybrid
Anyway I would not modify the circuit so easily , only after much listening and thinking . Even if you remove one JFET the whole thing is full of transistors and buffers because it is what it is - hybrid
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Agreed…I posted that because the topic of eliminating the JFETs was mentioned as something Alta Vista did with their mods. I just posted what the old site had listed for SA5000 phono mods.
I’m definitely looking to find the correct part to bring the phono stage back to life.
I’m definitely looking to find the correct part to bring the phono stage back to life.
Looks like someone who had this preamp before was going to do something in the front end of the phono stage. I did also ask him in a PM IF the phono section ever worked before he bought it. He said he go it at an Estate sale of a passing Audiophile.
"Agreed…I posted that because the topic of eliminating the JFETs was mentioned as something Alta Vista did with their mods. I just posted what the old site had listed for SA5000 phono mods."
Yes, that's what it was the SUT mod. Just get the preamp back into proper working order. I only mention the mods because with the transistors removed it triggered some memories about those transistors being removed for a Mod. I just couldn't remember which mod.
Yes, that's what it was the SUT mod. Just get the preamp back into proper working order. I only mention the mods because with the transistors removed it triggered some memories about those transistors being removed for a Mod. I just couldn't remember which mod.
I wonder if something like a 2SK170 would work in place of the QP1087. I did find a P1087 that Fairchild made. If you can get some info on the SA-3000 preamp service manual, I bet these Jfet's are the same since they are used the same way in both the SA-3000 and SA-5000.
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