Hi!
I’ve been using a recently acquired JVC AX-V1050PTN receiver a lot lately as my main amplifier since I like JVCs from that period and I’m also a huge fan of the last superDigifine series 🙂
However, I’m beginning to see signs that it doesn’t operate as intended regarding the heat emitted from it. It doesn’t malfunction in any other way but the voltage measured in the power amps(s) is +/-52V which I now believe is the voltage it should use only when needed... Look at the cropped parts from the diagram below:
JVC is quite secretive about this part in the SM but from what I gather the +-B should be around +/-30V in the “idle or low volume” mode and then rising to +/-52V when the signal level indicates it’s needed and the temperature is below a certain value.
All this based on the schematic below:
Does anyone have any thoughts or experience with this circuit how it should behave?
Edit: the bias has been adjusted according to the SM but still with a +-52V circuit voltage.
Regards
Per
I’ve been using a recently acquired JVC AX-V1050PTN receiver a lot lately as my main amplifier since I like JVCs from that period and I’m also a huge fan of the last superDigifine series 🙂
However, I’m beginning to see signs that it doesn’t operate as intended regarding the heat emitted from it. It doesn’t malfunction in any other way but the voltage measured in the power amps(s) is +/-52V which I now believe is the voltage it should use only when needed... Look at the cropped parts from the diagram below:
JVC is quite secretive about this part in the SM but from what I gather the +-B should be around +/-30V in the “idle or low volume” mode and then rising to +/-52V when the signal level indicates it’s needed and the temperature is below a certain value.
All this based on the schematic below:
Does anyone have any thoughts or experience with this circuit how it should behave?
Edit: the bias has been adjusted according to the SM but still with a +-52V circuit voltage.
Regards
Per
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I would really like to help you but I don't have time to devote to it.
just like you I love this generation at JVC and I am looking for this model to go with my Xl-z1010.
Nevertheless, I would be surprised if jvc used two different voltages in this way.
In my opinion it is more like the "power on demand" from NAD Proton, the two voltages are present permanently but the higher voltage is only activated in case of demand and only on the last two stages.
On the other hand, if you tell me that you find the highest voltage on the final stage while the amp is idling, then yes, I think there is a problem.
Many extremely competent people on this forum and with more time than me will be able to give you REAL help.
Good luck, I will follow this with interest.
just like you I love this generation at JVC and I am looking for this model to go with my Xl-z1010.
Nevertheless, I would be surprised if jvc used two different voltages in this way.
In my opinion it is more like the "power on demand" from NAD Proton, the two voltages are present permanently but the higher voltage is only activated in case of demand and only on the last two stages.
On the other hand, if you tell me that you find the highest voltage on the final stage while the amp is idling, then yes, I think there is a problem.
Many extremely competent people on this forum and with more time than me will be able to give you REAL help.
Good luck, I will follow this with interest.
Thanks for your insights so far, I'm thinking that this might also be the other way around, like as long as the amp is operating under a certain temperature the voltage stays at the highest level but if the temperature is getting critical the voltage is lowered unless a signal is present, not totally logic and more like a protection circuit than super A - at least in the way JVC describes it...
Also, the voltage values in this schematic doesn't fully correlate to my measured values - mine are all lower by a certain percentage. I guess that's due to my model being a European version with a little lower output power compared to the other variants...
For example, my "high" rectified B+- voltage is 44.5V compared to 52.5V in the SM and the "low" rectified B+- voltage is 30V compared to stated 35V.
As a side note, the capacitors in this one looks to be of rather high quality (ELNA) still measuring good regarding capacity and ESR - haven't found a bad behaving cap yet in this amp - not even in the hot areas around the PS 😉
However, I do have some deviations from the values stated in the SM, I thought C1251 was to blame for this but it appears OK:
The circuit around C1251 appears to be the signal detection circuit feed to pin.5 of IC651 (see first post).
I have -0.12V at that point with no signal present. Not sure what to make of that since the circuit after IC651 -> Q1212 (also in first post)
is a bit difficult for me to follow 😉
Edit: Also attaching a more complete schematic with the yellow path for this signal detection:
/Per
Also, the voltage values in this schematic doesn't fully correlate to my measured values - mine are all lower by a certain percentage. I guess that's due to my model being a European version with a little lower output power compared to the other variants...
For example, my "high" rectified B+- voltage is 44.5V compared to 52.5V in the SM and the "low" rectified B+- voltage is 30V compared to stated 35V.
As a side note, the capacitors in this one looks to be of rather high quality (ELNA) still measuring good regarding capacity and ESR - haven't found a bad behaving cap yet in this amp - not even in the hot areas around the PS 😉
However, I do have some deviations from the values stated in the SM, I thought C1251 was to blame for this but it appears OK:
The circuit around C1251 appears to be the signal detection circuit feed to pin.5 of IC651 (see first post).
I have -0.12V at that point with no signal present. Not sure what to make of that since the circuit after IC651 -> Q1212 (also in first post)
is a bit difficult for me to follow 😉
Edit: Also attaching a more complete schematic with the yellow path for this signal detection:
/Per
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Update: the more I look at this the more the IC651 circuitry looks like a protection circuit which sole purpose is to lower the whole amps voltage when either of two conditions are met, (too) high temperature or too much output from the main amp...anyone agree to that?
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