| Illusus |
I just finished wiring up my first channel (monoblock) in a mock up chassis.
I have a couple issues.
1) I brought it up slowly with a variac, everything went fine. I measured all the voltages, let it cook for an hour and remeasured. The drain of Q1 is set at 24.6V, most of the other voltages are close to what is called upon by the manual, but I read nothing accross R1 or R0 ( I set the range in the right place on my dmm, I always check x3). All the voltages that the manual states at 4V are closer to 3V. Any problems here?
2) I know this thing is supposed to run hot, but I'm a little worried, I read ~88C(180F) at idle (near Q2&Q5 transistors, Q1 is cool), not much difference under load. That seems a bit hot to me. Should I take out R1? I don't mind less output, my speakers are 96db efficient. Sonic effects of this course of action?
3)I get turn on/off bump and lots of it, I don't plan to turn these off often but I don't want to risk damage to my speakers(I'm using a test pair first). Is this common? should I incorporate some type of turn off/on relay(not familiar with the how to)?
Sonically - it's fantastic, as far as I can tell from listening to one channel on test speakers. |
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| Panelhead |
Try turning down the bias. 88C is way to hot. Also, recheck those voltages.
With 96 db speakers your power needs are low. The 20 watt version will be fine.
George |
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| JasonL |
i have 2 of these also im making into a stereo block soon though il have it finnished when i get them shipped from storage to here : O ) il be following this thread to watch : O )
Got any picture's ? |
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| kilowattski |
| The heat sinks should be rated at .3 degrees C/watt or better. It sounds like your heat sinks are undersized. The Zen V4 is very, very ineffiecient and at 25 to 30 watts output the heatsink will need to dissipate over 100 watts of heat. |
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| Nelson Pass |
You should be reading some fraction of a volt across R0, R1.
This sounds like something is wrong there, and too much
current is flowing through the circuit. |
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| Illusus |
thanks for your replies so far...
- no pics yet, the chassis is far from done. Basically, it's just a heatsink on a board right now.
- the heatsinks are fairly large, about 10"x 8", 1/2" thick plate with 1" tall fins. I thought they would be close adequate.
- I also think there is a problem there, but what? I was meticulous with assembly, triple checked everything. Maybe it's a bad part, or I destroyed something with my soldering iron(I doubt the latter though, I'm careful, quick and well practiced with it). May I get a strong hint where to look?
Tonight I'm going to fire up the second channel, we'll see if I made the same mistake twice. |
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| Nelson Pass |
Like I said, if you have 0 volts across r0,r1 that is
probably because they are shorted or bypassed,
otherwise there wouln't be any heat. |
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| Illusus |
Ok, I found the problem...It was me!! :D I'm soo embarrased, I guess even triple checking is not always enough....oh, I suppose you want to know what I did. I have the board upside down in relation to the manual- R0,R1 became R15 and R14. I now read .72 across that gap.
I realized this when I was measuring the other channel, this time I looked at the value not the position on board, the first time I had the manual open on that page so I just glanced at it. I feel so dumb right now(especially after telling everybody how careful I am. :rolleyes: ) |
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| Illusus |
| I removed R1, the highest temp so far has been 62C, 42 above ambient. Obviously the heatsink is not adequate for the higher output. I'm happy for now, I would have been happy with 5W, 20 is a bonus. |
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| pro |
I think 62°C is still too high.
My V4 works at 46°C with 1.3A bias and 56°C with 2.4A bias with an ambient temperature of 20°C. The DC rail is 44V reg.
If you don't need much power, you can try to lower the reg. rail changing the value of the zener diodes.
Otherwise you need bigger heatsink.
Ciao. |
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| Illusus |
| Yes. I'm looking for different heatsinks now. It's not the size that is the problem with mine, it's the lack of surface area, the fins are very thick, making it more like a billet of aluminium than a heatsink. I'll post a pic sometime. |
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| Panelhead |
| quote: | Originally posted by Illusus
Yes. I'm looking for different heatsinks now. It's not the size that is the problem with mine, it's the lack of surface area, the fins are very thick, making it more like a billet of aluminium than a heatsink. I'll post a pic sometime. |
Mine ran at 65 - 66C for a long time with no problems. I think it will live a long time at 72C.
The 1" fins are the problem, they need to be 2 - 3 inches to really dump the heat. These units pull some real power and generate it as heat.
The nice thing is being a mosfet, it kind of corrects itself for the high temp. A bipolar would run off if uncorrected and heated up like that.
George |
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| Illusus |
will there be any negative consequences from laying the large output cap parallel to the board? Also, any problems with placing the transistors a couple inches away from the board?
These deviations would help make my chassis design cleaner. |
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| Stabist |
| Well I have transistors in my Zen on wires - around 10-15cm long ones - no problems at all .. |
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