Retired:Symmetrical FET

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Gustav,

Boards and transformers arrived this morning and I populated this afternoon. Beautiful boards as always, a pleasure to work on. Well done.

I'll post pics when I finish it off in the next week or so.

NF.
 
Hi there,

I just build my second unit after totally killed the first after connecting the front PCB the wrong way. After trying to remove the angled connection, I damaged the PCB. So I ordered a second one, which I got ready to go.

It doesn't work as expected, one channel does not give any sound, although the meter is corresponding.

I have got 2 pcs of NPD5566, which I got from China. What would an appropriate replacement for that? I can't get no answer, beside the bf245 in this thread. I'm not really sure, if they are working.

I think, something in the output section seems not to work. May the output transformer is not giving the signal, cause I built adapter-pcb for edcor xs 1100.  On the IC, the current seems to be fine, I'm not getting through the schematic where to look else or how to measure, if the transformer is working. Should I get an audoi signal at the outputs, when the transformers are removed?

Thanks, it is getting frustrating.

 
mike76 said:
Hi there,

I just build my second unit after totally killed the first after connecting the front PCB the wrong way. After trying to remove the angled connection, I damaged the PCB. So I ordered a second one, which I got ready to go.

It doesn't work as expected, one channel does not give any sound, although the meter is corresponding.

I have got 2 pcs of NPD5566, which I got from China. What would an appropriate replacement for that? I can't get no answer, beside the bf245 in this thread. I'm not really sure, if they are working.

I think, something in the output section seems not to work. May the output transformer is not giving the signal, cause I built adapter-pcb for edcor xs 1100.  On the IC, the current seems to be fine, I'm not getting through the schematic where to look else or how to measure, if the transformer is working. Should I get an audoi signal at the outputs, when the transformers are removed?

Thanks, it is getting frustrating.

For trouble shooting, try to isolate some of the issues you are asking about to things that can be checked or solved by comparing with the working channel.

- Should I get audio signal at the output when the transformers are removed?
- Is your adaptor working?

After that, you should be able to check voltages on the ICs and transistors on the working channel and compare to the non-working.

I would agree, your problem is in the output. If the NPD5566 you have were not working (pretty unlikely both would be bad, and on the same channel), you would not be getting any action on the meter.

Also - did you check the build guide/notice one set of pads on the dual gang pots need to be jumped if you use those?

Hope thats a start.

Gustav
 
Hi guys, Im starting this project soon, my board is on the way . Thankyou Gustav for all this effort  :)

Will a single 3.6Kohm  VU meter work on this project ok? 
 
Greg S. said:
Gustav said:
mike76 said:
Also - did you check the build guide/notice one set of pads on the dual gang pots need to be jumped if you use those?

Might you please explain your Post Gustav?

Greg, I think, Gustav means that the middle row of  the pot pads has no function and doesn't have to be connected.

I did not do this, but I used wires with connectors, which I want to remove to See, if something is wrong here. Unfortunately, my soldering Station is not working anymore, the new  one should arrive soon. Thanks for your suggestions, Gustav. I will try it soon.
 
After checking the transistors and IC, they seem to have the same values. But I have noticed a difference at the Transformers: without connected audioinput and pots, I have about 12 kOhm between pin 3 and 4 and between pin 3 and 5 in the left channel, but not in the right channel. That leads me to the conclusion, that I may should check the Transformers adapter of the channel that doesnt work.

Edit: After sending an audiosignal through the device, again without pots and frontpcb, I've got a signal (very weak) on both channels, one of them are about 6-8 dbfs louder than the other one. As soon as I got the new soldering station, I will remove and check the transformers.
 
So, this is getting really weird  :eek:

I switched the + and - outputs at the xlr/jack combo. I used an mono jack to my patchbay. Suddenly I could here both channels. The strange thing is, that I could here both channels even I didn't switched the device on! That was heavily distorted and quieter. If I switched it on, the signal was getting louder. But lacking of something, I would say bass (was a drumtrack). But I didn't have any pots, the frontpcb, etc. connected. Just the pure device.

Then I prepared two symmetrical jacks and connected them correctly (tip =hot, blue=cold) to the pcb. There again barely something to hear and heavily distorted.

I'm a bit confused and don't get the clue behind this. Is it possbile, that a not properly output transfomer can cause such a behaviour? But then both of them has to be wrong connected, which I can't  imagine.

Very confused, very very.
 
After days of reading, checking and measuring, I finally brought this unit to life :)

After accidently made one 4R3 glow like a lamp because of the  wrong direction of an IC after changng. Some parts had to be changed after that and I learned my lesson well :)

I think there were two errors: on the one output transformer was one wire disconnected from the pins, don't know why. And I traced a lack of voltage on the input stage to the npd5566, I think it was cold soldering thing on one of the resistors.

However, it is working, everything seems fine. Now I need to calibrate this and although I know where to calibrate, I would appreciate some advice. I read the 1178 manual, but I am not able to measure in dbm, so if there is an other solution, that would be fine.

Gustav said:
I just did some work on the assembly guide, and Ill do a small calibration guide.
...
Gustav

Didn't find that anywhere, may in the assembly guide, but it is not linked anymore on your website?

Thanks for your help and patience ;)
 
Fired mine up last night. All the voltages check out. Just waiting for my release pot to arrive then I'll calibrate and see how this sucker sounds :)
 
Nick Franklin said:
Fired mine up last night. All the voltages check out. Just waiting for my release pot to arrive then I'll calibrate and see how this sucker sounds :)

You could set a fixed release to get you going :)

Hope it works out.

Gustav
 
I thought about it,  but I'm happy to wait :)

I'll post some pics when I'm done.

Gustav said:
Nick Franklin said:
Fired mine up last night. All the voltages check out. Just waiting for my release pot to arrive then I'll calibrate and see how this sucker sounds :)

You could set a fixed release to get you going :)

Hope it works out.

Gustav
 
i think i have bought the wrong power transformer, i need one with 2x18v ,  not the single 18v one i have here?

20150529_125642_zps6c8hq6me.jpg
 
Also, I would run it on 15V (2 x 15V), based on the feedback from builders.

Gustav
 
Thankyou very much gentlemen :)

would this be far more suited? It's got great dimensions too!

http://au.rs-online.com/web/p/toroidal-transformers/6718943/
 
Gustav said:
Also, I would run it on 15V (2 x 15V), based on the feedback from builders.

Gustav

Anything else need to change on the board to use an input voltage of +15/-15vdc?
 

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