Hi,
I recently purchased two of these off eBay...well actually won them with a lowball bid..i was hoping for some help as I cannot get the seller to answer my question.
These were purchased to use in a Parasound HCA500 chassis...the amp was fried by a friend i loaned it to..i was going to put these modules in the chassis and rebuild a power supply from scratch...no problems or questions there...
What i am needing help with is there is a trim poton the board that i am unsure of howto adjust...i dont even know what it is for to be honest...i have asked the seller over and over how this is to be adjusted and i am getting nowhere...if i spoke Chinese i sink tings my go diffelently...
Can anyone help me with this trim pot...what do i do with it, where do i check the circuit to make the proper adjustments and what am i looking for?
Thanks in advance, heres the sales page:
Classic NAIM 140 Nap Mono Audio Power Amplifier Kit 1PC | eBay
Jeff
I recently purchased two of these off eBay...well actually won them with a lowball bid..i was hoping for some help as I cannot get the seller to answer my question.
These were purchased to use in a Parasound HCA500 chassis...the amp was fried by a friend i loaned it to..i was going to put these modules in the chassis and rebuild a power supply from scratch...no problems or questions there...
What i am needing help with is there is a trim poton the board that i am unsure of howto adjust...i dont even know what it is for to be honest...i have asked the seller over and over how this is to be adjusted and i am getting nowhere...if i spoke Chinese i sink tings my go diffelently...
Can anyone help me with this trim pot...what do i do with it, where do i check the circuit to make the proper adjustments and what am i looking for?
Thanks in advance, heres the sales page:
Classic NAIM 140 Nap Mono Audio Power Amplifier Kit 1PC | eBay
Jeff
Here is another seller who actually has a schematicof the same board it appers
2pcs x NAP-140 Classic NAIM CLONE Audio Power Amplifier Assembled with Sanken Tr | eBay
2pcs x NAP-140 Classic NAIM CLONE Audio Power Amplifier Assembled with Sanken Tr | eBay
Did you check out this thread http://www.diyaudio.com/forums/solid-state/112453-nap-140-clone-amp-kit-ebay.html
Its for adjusting the bias
Its for adjusting the bias
Ok, i checked the thread above...i talks about setting the bias but does not go into details of HOW to set the bias...the extant of my amp building experience has been chip amps and tune amps, i habe never set the bias on a transistor based amp like this...can someone tell me exactly how to do it? Where doi take my measurements from? The thread above recommends a bias of 38mA per output transistor...how doi measure this, where do I connect my ammeter?
Thanks,
Jeff
Thanks,
Jeff
I read that thread along time ago but someone did explain how to set the bias in there. You have to disconnect the positive rail of the power supply and connect your meter inline like a fuse. I cant remember the rest of the details but its in there. Just do a search.
Trim pot in this board is to adjust bias.
Simply using a multimeter to measure voltage drop i.e. Vre on R29 or R30 i.e. Re (seems maybe it is because too weak in schematic picture), then calculate by idle current = Vre / Re.
Origianl NAP140, is saying with idle current running on about 80mA per last output transistor.
Simply using a multimeter to measure voltage drop i.e. Vre on R29 or R30 i.e. Re (seems maybe it is because too weak in schematic picture), then calculate by idle current = Vre / Re.
Origianl NAP140, is saying with idle current running on about 80mA per last output transistor.
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If i were to upgrade any of the stock components on this kit, which would offer the best bang for the buck?
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