Hello,
I have just received 2 Denon 4400a monoblocks seconhand. I purchased them both second hand and seperately from 2 different sellers.
I thought it might be a good idea to take the cases off and look inside both of them and when I opened them up, to my surprise, they were slightly different inside.
One of them looks as though it has the original Denon circular transformer (part number: 2339577008) and the other has a square looking transformer (part number: 8B-DJW-624-01 TAM M 0124) and also smells a bit "smokey" inside.
I wanted to return them to original condition-perhalps the smokey smell is a result of the modification?
Where could I source a suitable transformer for this? When I google the original part number (2339577008), Im unable to find one.
Also, concidering that they are a bit old, is it worth changing the capacitors in them? or anything else for that matter?
Im a bit of a noob when it comes to such things but i have a "friend of a friend" who could carry out any any electrical work.
IMG20200603151217 — ImgBB
IMG20200603151204 — ImgBB
IMG20200603151156 — ImgBB
IMG20200603151145 — ImgBB
IMG20200603151056 — ImgBB
https://ibb.co/vdDTnx7
https://ibb.co/XJ9THYn
https://ibb.co/L5yHjrZ
https://ibb.co/Mpb9jJR
https://ibb.co/n3HNRMq
Many thanks,
Charles
I have just received 2 Denon 4400a monoblocks seconhand. I purchased them both second hand and seperately from 2 different sellers.
I thought it might be a good idea to take the cases off and look inside both of them and when I opened them up, to my surprise, they were slightly different inside.
One of them looks as though it has the original Denon circular transformer (part number: 2339577008) and the other has a square looking transformer (part number: 8B-DJW-624-01 TAM M 0124) and also smells a bit "smokey" inside.
I wanted to return them to original condition-perhalps the smokey smell is a result of the modification?
Where could I source a suitable transformer for this? When I google the original part number (2339577008), Im unable to find one.
Also, concidering that they are a bit old, is it worth changing the capacitors in them? or anything else for that matter?
Im a bit of a noob when it comes to such things but i have a "friend of a friend" who could carry out any any electrical work.
IMG20200603151217 — ImgBB
IMG20200603151204 — ImgBB
IMG20200603151156 — ImgBB
IMG20200603151145 — ImgBB
IMG20200603151056 — ImgBB
https://ibb.co/vdDTnx7
https://ibb.co/XJ9THYn
https://ibb.co/L5yHjrZ
https://ibb.co/Mpb9jJR
https://ibb.co/n3HNRMq
Many thanks,
Charles
Last edited:
I suspect its an underpowered replacement transformer, found the service manual here: Denon POA-4400 - Manual - Monaural Power Amplifier - HiFi Engine
There are 8A fuses on the output of the +/-72V supply board, and its rated for 250W into 4 ohms which requires 8Arms out, so 12A peak from each rail, which
The transformer has 52-0-52 secondary and an aux secondary of 19-0-19, and probably needs to be 500VA or so ideally (somewhat less for 8 ohm use).
There's no indication of anything but the toroidal part in the manual.
Can you disconnect the secondaries and measure the actual voltages from the quesionable transformer to see if its a good voltage match?
There are 8A fuses on the output of the +/-72V supply board, and its rated for 250W into 4 ohms which requires 8Arms out, so 12A peak from each rail, which
The transformer has 52-0-52 secondary and an aux secondary of 19-0-19, and probably needs to be 500VA or so ideally (somewhat less for 8 ohm use).
There's no indication of anything but the toroidal part in the manual.
Can you disconnect the secondaries and measure the actual voltages from the quesionable transformer to see if its a good voltage match?
Thank you Mark. As of yet, I havnt powered any of the units on or tested them-Im awaiting the delievery of some speaker cables and a network streamer. Im currently in the process of upgrading my music system from a very basic AV receiver to hi-fi components.
To say that im a noob when it comes to such things would be an understatement! I thought that I could find a suitable replacement on the internet and switch them over.
I thought that being as the two amps were visually different, that getting them back to original spec/performing maintenence would be a good place to start-after all, if one of a pair of monoblocks has a different transformer, wouldnt this affect the sound into one channel?
My father has a multimeter. Im not sure how to meassure the actual voltage but im willing to learn!
Thanks, Charles
To say that im a noob when it comes to such things would be an understatement! I thought that I could find a suitable replacement on the internet and switch them over.
I thought that being as the two amps were visually different, that getting them back to original spec/performing maintenence would be a good place to start-after all, if one of a pair of monoblocks has a different transformer, wouldnt this affect the sound into one channel?
My father has a multimeter. Im not sure how to meassure the actual voltage but im willing to learn!
Thanks, Charles
Well first of all be safe - if not familiar with working with mains equipment I would recommend adopting a suitably paranoid method of making measurements:
1) unplug from the wall
2) set up the measurements with the meter (use clip-on probesso you are then completely hands-free). Check your work, in particular don't leave a multimeter in current mode if measuring a voltage (bad things happen).
3) plug in and power up to take measurement, no touching the internals or meter probes.
4) switch off and unplug to set up for next measurement.
Laborious but safe. An isolation transformer can make things a lot easier if you can afford one.
Most problems people have with probing live is when holding pointy probes - slips are common leading to damage. Clip-on probes are much to be prefered, especially if they are long and properly insulated to a suitable class - makes live probing much less risky and makes the safe method described above possible.
When there's a mains section in an opened enclusure, it may be possible to screen it off from straying hands using an insulating sheet of plastic - this makes working live much safer - a physical barrier is much better than just relying on
remembering what's dangerous.
In any high-power electronics there's a risk of a short leading to a big fat spark - eye protection is a great idea.
1) unplug from the wall
2) set up the measurements with the meter (use clip-on probesso you are then completely hands-free). Check your work, in particular don't leave a multimeter in current mode if measuring a voltage (bad things happen).
3) plug in and power up to take measurement, no touching the internals or meter probes.
4) switch off and unplug to set up for next measurement.
Laborious but safe. An isolation transformer can make things a lot easier if you can afford one.
Most problems people have with probing live is when holding pointy probes - slips are common leading to damage. Clip-on probes are much to be prefered, especially if they are long and properly insulated to a suitable class - makes live probing much less risky and makes the safe method described above possible.
When there's a mains section in an opened enclusure, it may be possible to screen it off from straying hands using an insulating sheet of plastic - this makes working live much safer - a physical barrier is much better than just relying on
remembering what's dangerous.
In any high-power electronics there's a risk of a short leading to a big fat spark - eye protection is a great idea.