you or your technician can contact PL directly and ask for said
as I wrote - meter is there to be eye pleaser, and for what's written in #4 of my post above
procedure is to set amplifier correctly and then set needle meter to mark intended position
I agree, contact PL directly. These amps aren't exactly simple to set the bias on. You set the bias of each quad of the front stage, then each quad of the output stage adjusting for Absolute and differential offset on each channel as you go along. The biasing procedure should include checking the bias of the VAS stage.
So a quick check without sending the amp out would be to check the differential DC offset and the absolute DC offset in millivolts (mV). Actually, this is good knowledge to have. There are two offsets. Differential and Absolute. To check differential offset, using a multimeter set to volts or mV you take the pos lead and touch the pos binding post. Neg lead to the neg binding post. This will give you the differential offset. this is the DC voltage that your speaker will see. You should have less than 100mV.
For the absolute offset, you touch one lead to one of the binding posts. Then touch the other lead to a grounding point. I believe these amps have a external ground connection post on the back. That would be a good spot. I believe this is signal ground.
This is the offset of one phase of the amplifier. Each channel has two phases. Positive (pos binding post) and negative (neg binding post) Your speaker will not see this offset. It should be below say 200mV. Test the pos against Gnd, then do the neg against ground.
You cannot hurt anything doing this test and it doesn't require you opening the chassis. Now the bias can be finicky so I definitely recommend sending it out for that if you think it needs it.
Regarding the heatsink temp, if the room is hot, that will make the amp pretty much untouchable.
Circling back to DC offset, differential DC offset is a good test to do on any new amp or as routine maintenance. This can save your speakers... I almost hooked up an amp with 10v DC offset... I think that would have sent my tweeters to the heavens real quickly...
So a quick check without sending the amp out would be to check the differential DC offset and the absolute DC offset in millivolts (mV). Actually, this is good knowledge to have. There are two offsets. Differential and Absolute. To check differential offset, using a multimeter set to volts or mV you take the pos lead and touch the pos binding post. Neg lead to the neg binding post. This will give you the differential offset. this is the DC voltage that your speaker will see. You should have less than 100mV.
For the absolute offset, you touch one lead to one of the binding posts. Then touch the other lead to a grounding point. I believe these amps have a external ground connection post on the back. That would be a good spot. I believe this is signal ground.
This is the offset of one phase of the amplifier. Each channel has two phases. Positive (pos binding post) and negative (neg binding post) Your speaker will not see this offset. It should be below say 200mV. Test the pos against Gnd, then do the neg against ground.
You cannot hurt anything doing this test and it doesn't require you opening the chassis. Now the bias can be finicky so I definitely recommend sending it out for that if you think it needs it.
Regarding the heatsink temp, if the room is hot, that will make the amp pretty much untouchable.
Circling back to DC offset, differential DC offset is a good test to do on any new amp or as routine maintenance. This can save your speakers... I almost hooked up an amp with 10v DC offset... I think that would have sent my tweeters to the heavens real quickly...
Hello everyone, I'm still stuck with my mono blocks, my technician noticed overheating at 85 degrees Celsius, he changed the resistors but the j109 mosfet transistors also need to be changed, and he can't find any, he tried equivalents but it doesn't work, distortion and bad sound, so I'm looking for these 2 transistors which are exhausted or another solution. Don't ask me for too many details because I'm just the person in distress at not being able to listen to music since September but not an electronics specialis
J109 mosfet? That part doesn't exist on the .8 series that I know of. For the signal path related stuff, you have the 2sk170/j74 (JFETs), then 313/2013 (mosfets), then your standard 240/9240 mosfets for the output stage.
If you used a J109 JFET in place of the K170 on the UGS, I would think that will throw your DC offset and bias for the VAS stage way off.
Prakit on this forum may have the 313/2013 mosfets but I agree with 6L6 above. Contact PL.
If you used a J109 JFET in place of the K170 on the UGS, I would think that will throw your DC offset and bias for the VAS stage way off.
Prakit on this forum may have the 313/2013 mosfets but I agree with 6L6 above. Contact PL.
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hello thank you, there were j109s in my amps, it's not the 8 series but the Xa.60. maybe it's not normal anymore
Thank you for your intervention, that's what my technician told me, I'll ask him again on Monday. he didn't invent it, or maybe I misunderstood or maybe these amps bought second hand were "tinkered with". How to know what the original components are without a diagram. he tells me that if he doesn't find it he will have to make pairings, I'm just a listener, that's beyond my skills
yes they are indeed j109s, the welds are original and it is also engraved on the card which is a good idea,
as good an idea as putting humor in the user manual, other brands are sad and serious
as good an idea as putting humor in the user manual, other brands are sad and serious
that can be 2SJ109, not J109
7 legged critter, practically 2pcs of 2SJ74 in one case
7 legged critter, practically 2pcs of 2SJ74 in one case
hello yes error of understanding of the neophyte that I am, it is indeed 2SJ109. All that remains is to find some, my repairman tells me he throws them away regularly with old amps. now he will probably keep them