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V9 troubleshooting: SOLVED, some remarks and questions...
V9 troubleshooting: SOLVED, some remarks and questions...
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Old 23rd April 2012, 04:23 PM   #1
Billy60300 is offline Billy60300  France
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Join Date: Jan 2011
Location: in a small town called Senlis, north of Paris
Default V9 troubleshooting: SOLVED, some remarks and questions...

Hi all

I finaly got the V9 to work and here are a few tricks which I am sure will help:

Everything is working fine.
The origin of my trouble was, it makes me rather ashamed of myself: just one soldering MISSING ! I had checked ten times and did not see it before the 11th time ! too obvious !

Now may I make a few remarks:

1) for troubleshooting: this will be very helpful for those who want to make the V9
- minimum VCC is 40 V, under there seems to be not enough to et the Mosfets to move (there are 4 in series).
- the V9 being absolutely modular, checking each stage separately plays the trick absolutely and easily.
-a problem seen on one stage may originate from another
- The design is good (happy) and there is no need to question it ! this I say for the average reader who is used to bullsh designs and will eventually come to thinking this because he will perhaps have missed a wrong solding point !

2) now about distortion, I found out:
- replacing IRF140 by ALF08N16V (cheap, got it from Farnell) improves enormously the signal shape even after 20 khz, a square is a square, with slightly rounded corners but a square still. At 1 khz it is perfect. IRFP 044 not better than IRF140. BEWARE/ THE WIRING OF THIS BUGGER IS DIFFERENT FROM THE IRF FAMILY: IT IS GSD INSTEAD OF GDS !!!
- the low frequency limit was very poor with C4 (from Q3/Q5 region) at the 220 uf you advised. To get some 30 Hz I had to increase to 1000uf ! my question is: is the low limit defined by the 220uf*1.5K (C4-R10) ? or am I again here in a mistake ? the alternative would be to increase the 1,5K to say 10K ?
In V2 I read, the R10 from neg Out to Gnd is 1000 Ohms, in V9 and others it is 100 Ohms. Why not 1000 in V9 to increase input impedance ? in another way, what is the rule of thumb to choose this value ?

3) generally saying, replace dissipators by standard computer fanned ones. If they are copper, they keep Temp at less than 40C with no noise AND they are very cheap indeed (about 25 Euros). Avoid aluminium ones, they are not good enough.
have a good time.
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Old 23rd April 2012, 07:04 PM   #2
vdi_nenna is offline vdi_nenna  United States
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Location: PA, USA
V9 troubleshooting: SOLVED, some remarks and questions... Send a message via Yahoo to vdi_nenna
Congradulations! Nice work!

Like I said, I had the same problem. I found it by wiggling parts and watching the meter.

I believe, in the end, the problem was a cold solder. A loose resistor near Q5.
How do you like the sound?

I build, therefore I am.
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Old 24th April 2012, 06:37 AM   #3
Billy60300 is offline Billy60300  France
diyAudio Member
Join Date: Jan 2011
Location: in a small town called Senlis, north of Paris
Hi Vince
Before connecting it, I want to be sure and to see a good result on the scope. I still have some questions about my work. I have to connect the negative feedbacks and to see what kind of a buffer the input will need. I am ready to build a BOZ or equivalent.
Then the whole thing will need to survive a one day connection with no signal and then another day with a full size signal. If the house does not go on fire then I will put it in its box and connect the speakers (Horn system with Fostex 206, high sensitivity and by Jove very good). My Zen V9 must beat on the quality side my current triode set, this is going to be difficult but possible.
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