One of my Zen Lights has died!

[Zero Cool]

Got home tonight and wanted to put on some music and relax and flipped on the Zen lights and one bank of bulbs light up brighter then the other bank and faster! i flipped it off and waited a sec and flipped it on again and one bank of three bulbs just lights up bright immediately. So I am assuming one channel has died? I will have to crack it open tomorrow and investigate.




Zc

 

[ziggyr]

Check that the bias for that bank has not collapsed or shifted for some reason.

 

[Zero Cool]

I had noticed that bank always glowed ever so slightly brighter. But these were built by the Great Oz himself so who was I to ever question it LOL! I have never cracked em open so this will give me a chance to peek inside.

Zc

 

[ziggyr]

Have you measured the bias voltage for both channels? If there is a significant voltage difference, one bank will not be the same in brightness to the other.

 

[Zero Cool]

I will have to bring it to my shop tomorrow to work on it.

 

[Zero Cool]

N.P. should I remove the screws from the top or the bottom of the heatsink to open? IE will the top panel come off by itself if I remove the wood screws on the left side and the machine screws from the heatsink on the right side.

or should I remove the wood screws on the left side and the machine screws from the bottom of the heatsink and try and pull the top and heatsink off as one piece??

Not sure how it is connected inside if it makes a difference??


Zc

 

[Zen Mod]

hope NP is remembering those details ......

in a meantime , few pics can't hurt

 

[Zero Cool]

Here is a pic!

 

[Zen Mod]

underside and more detailed , please

I know that amp and that pic , already



looking at that , all I can tell is - unscrew these top 5 screws and see where that leads you

 

[Zero Cool]

Papa's artwork

 

[Zero Cool]

Lost a Mosfet...IRFP-040 I am going to have to order one most likely. I am checking my parts stock but that doesn't sound familiar...

 

[Zen Mod]

just replace those IRFP240 and re-check the bias

 

[Zen Mod]

I have specified the IRFP240 MOSFET transistor in Figure 5, but a wide range of similar N channel devices will work fine. The best performance is obtained with the IRFP040 or IRFP044, but unfortunately they seem very difficult to get. An in-between alternative is the IRFP140. When substituting other MOSFETs, the Gate to Source pin operating voltage becomes an important consideration. We will want a Drain voltage of about 12 to 15 volts, and if the Vgs of the MOSFET chosen is very different from about 4 volts, you will need to adjust the value of R1. Decreasing R1 will raise the Drain voltage, and of course increasing R1 will lower the Drain voltage.

 

[Zero Cool]

Hmm well I do have IRFP140 and 240 devices. but then in doesn't match the other device. I am using these Balanced as mono blocks so If i change one I really should change all 4 to match. I am going to see if I can find some 040's first.

 

[Zero Cool]

I have mapped out the schematic and verified is is basically figure 15 of the zen light article. some of the values are just slightly different but mine are the 3 bulb 40 watt versions so that may account for some of the differences.

 

[Zen Mod]

keep us informed

if not ..... ya know the drill - safe disposal , shipping on you ........

 

[moe29]

If i remember right, those IRFP 040s were hard to find when the article was written...

Maybe Nelson has a few still floating around his shop?

That is a beautiful amp! How cool is it to have a Pass 1-Off?

 

[Zero Cool]

Well i did send papa an email. Im hoping he has one as i have really come to love these.

 

[Zen Mod]

luckily , he is happy , while making Greedy Boyz happy

 

[Zero Cool]

I bought some IRFP044N's which look to be the closest I can find. I'm still hoping to find someone with one or two of these they would be willing to part with.

The thing that bothers me is that I don't know WHY it failed? I can find nothing wrong with the circuit. all parts seem to be within tolerance. I need to observe voltages at turn on and turn off to see if there is maybe a spike that is causing problems. The heatsinks do run very very warm. and I am running these with a 4 ohm load. So maybe im pushing the limits of what these can do?